Renewable Energy Education Modules

Transcription

Renewable Energy
Education Modules
R E N E WAB L E E N E R G Y
T R AI N I N G C E N TE R
Solar Energy
Micro Hydroelectric
Wood Gasification & Biofuels
Fuel Cells
http://retc.morrisville.edu
Renewable Energy Outline: We have provided a large amount of information (maybe too much), but you can explore these topics at the level you feel is most appropriate for your students. We assumed that these topics could be presented to a wide range of students (ages and types of courses); therefore, we have provided depth and detail that will help you become an expert. Please adapt the content to your teaching style and format. We are very interested in your feedback. These modules are living/evolving, and we will update them based upon on your experiences and the feedback you provide to us and make revision/updates available to you. These are listed in order of presentation at the Oswegatchie 2009 workshop. 1. The Solar Resource (PowerPoint presentation with annotated slides) a. Introduction to the solar resource and influences on solar gain i. Latitude ii. Cloud cover iii. Declination b. Converting power to energy c. Introduction to the solar pathfinder d. Overview of solar energy systems 2. Solar Pathfinder Module (laboratory exercise) a. Measuring the solar resource b. Accounting for shade losses c. Estimating yearly energy 3. Power of the Sun (movie quizzes) a. Power of the Sun questions and answer key b. The Silicon Solar Cell questions and answer key 4. Micro Hydroelectricity (PowerPoint presentation with annotated slides) a. The hydrologic cycle b. Micro hydro system overview c. Measuring flow and head d. Power to energy e. Comparison to wind 5. Micro hydro module (laboratory exercise) a. Building a clinometer b. Measuring head and distance c. Developing a stream profile diagram d. Measuring flow in larger streams e. Calculating power and energy 6. Biofuel Resources ‐ Overview – (PowerPoint presentation with annotated slides) a. U.S. Energy sources b. Biomass defined c. Bioenergy defined d. Biomass energy sources/supply e. Biomass conversion processes/pathways (general) 7. Wood Gasification – (PowerPoint presentation with annotated slides) a. Renewable fuel resources: Wood/biomass b. Utilization of wood resources: sustainability c. What is gasification? d. Gasification applications: past, present, future e. Optional topics/concepts: themodynamics, efficiency, energy density 8. Woodgas Camp Stove – (Activity/lab/experiment(s)) a. Brief overview of gasification b. Build a working camp stove c. Utilize the heat (boil water, toast marshmallows, etc.) 9. Principles of Fuel Cells (PowerPoint presentation with annotated slides) a. Batteries vs. Fuel Cells: storage vs. conversion devices b. General overview of fuel cell types c. Introduction to Dr. Schmidt’s fuel cell/”gas battery” experiment (lab activity) d. Relationship of the “gas battery” fuel cell effect to PEM fuel cells 10. “Discovering the principle of the fuel cell at home or in school” laboratory experiment by Dr. Martin Schmidt. (lab manual) a. History b. Instructions for conducting the experiment(s) c. An interpretation of each step in the process, including linking the principle from the experiment with today’s commercial fuel cells Summary of Comments on Slide 1
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Author: Presenter
Subject: Presentation Notes Date: 6/18/2009 9:05:06 AM
The solar resource lecture is designed to give teachers a resource for instruction on measuring solar energy
and the factors influencing solar gain in different locations. This also serves as an introduction to important
tools necessary to measure the solar resource. Though some information on solar energy systems is
provided, the focus is on the solar resource.
The Solar Resource
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Overview
• Overview of the solar resource in the U.S.
• Features impacting solar irradiance
» Latitude, cloud cover, seasonality
• Converting power to energy
• Tools to measure solar energy and shading
• An overview of solar energy systems
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If you had to guess, which nation has the most solar modules installed? Perhaps surprisingly, Germany is, by
far, has the most solar PV systems installed (nearly ½ of the total installed systems). Spain is also very high.
Though Solar cells were invented in NY (Bell Laboratories in NJ), we have dropped the ball on installing PV
systems.
Have you heard that NY does not have a good enough solar resource? Germany must have a fantastic solar
resource…
Solar PV
World PV market in 2007, 2826 MW total
Rest of EU
6%
Rest of
world
8%
USA
8%
Germany
47%
Japan
8%
Spain
23%
Solarbuzz LLC.
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This map compares incoming solar energy throughout the year in the United States and Germany. Blue and
violet have the lowest amount of solar energy each year and oranges and reds have the highest amount of
solar energy. In the United States, you can see that the Southwest has the best solar resource. However, if
you compare NY and Germany, the very best solar resource in Germany is worse than the very worst area of
New York.
It is interesting to note that Germany is about 2.5 times the size of New York. In Germany, approximately
3,000 MW of solar PV is installed. The entire United States has only 200 MW installed (and only 15 MW in
NY).
So Germany must be sunny, right?
Class Discussion: Should the U.S. install more solar PV systems? Why? Why not? How did Germany install so
much PV? Lead the class to think of public policy differences, social and political support, government
subsidies, etc.
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Determining the solar resource of a given area is dependent upon many factors. Some of these factors
include orientation, latitude, and regional air currents. To understand these impacts, we will do some energy
conversions to convert solar power to electrical energy.
Measuring the solar resource
•
•
•
•
•
Magnetic declination
Solar pathways
Solar math (power to energy)
Latitude and curvature
Air currents
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Recall that the Earth axis is on a 23.5 degree tilt. This “wobbles” throughout the year such that the sun’s rays
are directly striking different parts of the Earth at different times of the year. During winter in the northern
hemisphere, day length and solar intensity is greatest in the southern hemisphere. Conversely, during the
summer months we are tilted toward the sun (which gives us in the northern hemisphere longer, warmer
days). The “stopping” points at which the Earth “wobbles” are known as the Tropics of Cancer and Capricorn
(23.5 degrees N and S latitude, respectively).
What impacts solar gain each day?
Latitude (winter solstice)
3/30/2009
http://dcweather.blogspot.com/2005/12/winter-time-in-washington_21.html
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As you gaze toward the sky throughout the year, the sun appears to travel across the sky from East to West
throughout the day, and from South to North (and back) throughout the year. During the Winter Solstice,
the sun is at the lowest angle in the northern hemisphere. This give us a short day length and low solar
intensity. During the Equinox periods, the equator is aligned with the sun. During the summer solstice, the
tropic of Cancer is aligned with the sun, giving us our longest solar day and the highest solar intensity.
Because the Sun is to our south throughout the year, solar modules should be oriented toward solar south
to capture the most insolation.
Sun Path – New York
Summer Solstice
Equinox
Winter Solstice
E
N
S
W
This angle should be equal to your latitude
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Author: Presenter
Finding solar south is a bit of a challenge, however. True north and south (the location of the physical top
and bottom of the Earth) do not align with magnetic north and south (where our compass would suggest
north and south are located). A magnetic field is generated from circulating molten nickel and iron in the
Earth’s outer core. This circulation is not directly aligned with the physical “true” north and south poles.
Magnetic north can be quite different from true north depending upon where you are on the Earth’s
surface. The difference between the two is known as magnetic declination.
Magnetic Declination
http://sos.noaa.gov/images/Land/magnetic_declination.jpg
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In New York, Magnetic declination can range from 10° to over 15° West. This means that orienting solar
panels according to your compass without correcting for magnetic declination would result in up to a 15°
error (which has serious efficiency consequences).
http://www.ngdc.noaa.gov/geomag/icons/us_d_contour.jpg
True south and declination
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Many compasses allow you to easily make corrections for declination. Maps are often drafted using true
north, but give a declination so that one may make the necessary corrections. Magnetic declination changes
through time as the molten nickel/iron circulate and flow. This change can be dramatic depending upon
where you live.
This NOAA website allows you to enter your zip code and determine your current declination. The
declination for Morrisville State College is 12°48’ W. By following the directions on your compass, you can
make a correction that allows you to locate true north (and more importantly for us, true south).
Declination corrections
Magnetic
M
tic North
N th
True North
12°48’ W
http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp
True South
4/3/2009
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Author: Presenter
One neat tool that allows you to map the sun’s path across the sky can be found at the University of
Oregon Solar Radiation Monitoring Laboratory (SRML) website (http://solardat.uoregon.edu/
SunChartProgram.html). This allows you to enter your zip code and some other general information. From
this it will map out the solar path for your location throughout the year.
As you can see from this map for Morrisville, NY, during the summer solstice (June 21), the sun rises before
5 AM and does not set until after 7 PM. At its highest point, the sun is approximately 70° from the south
horizon. In December, the sun is only up from 7:30AM until 4:30 PM and rises only 28° off of the horizon.
Try it for your town!
Solar Angles by month in Morrisville
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Aside from solar period and solar elevation, latitude also affects incoming solar intensity. Because the Earth
is a sphere, an area perpendicular to the length of a sun ray strikes a disproportionally larger area the
further you get from the equator. In other words, if a cross-sectional area of light 1 square meter in size hits
near the equator, it will be absorbed by 1 square meter of the earth’s surface. That same cross-sectional
area of sunlight may be intercepted by 2 or 4 square meters closer to the poles.
This means that the earth receives less solar energy per square meter of surface area in locations closer to
the poles. These low-energy rays are known as “oblique” rays.
What impacts solar gain each day?
3/30/2009
http://www.hort.purdue.edu/newcrop/tropical/lecture_02/04m.jpg
• Latitude
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Author: Presenter
These data come from the weather station at Morrisville State College. Power has units of Watts. Power can
be thought of as instantaneous solar intensity. Solar power is measured in Watts per square meter per day.
You will notice that we receive more intense sunlight during the summer months (May-August) than we do
in the winter months (Nov – Feb). This is to be expected.
If we are interested in the incoming solar energy, we must calculate this from incoming solar power.
Morrisville’s Solar Resource
Month
Mean W/m2/day
January
63.8
February
98.8
March
140.9
April
182.1
May
220.5
June
231.5
July
224.2
August
203.0
September
159.6
October
101.0
November
59.3
December
44.7
3/30/2009
kWh/m2/day
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Author: Presenter
Because we are interested in energy, we must multiply power by time. In this case, there are 24 hours per
day. So I multiply my average daily power by the number of hours in a day. This will give me units of watthours (watts * hours). Since we are more comfortable talking about kWh (kilowatt-hours), we must divide
this value by 1000, as there are 1,000 Wh in one kWh. If we do that for each month, we can get average
yearly energy from the sun.
Month
Mean W/m2/day
January
63.8
February
98.8
March
140.9
April
182.1
May
220.5
June
231.5
July
224.2
August
203.0
September
159.6
October
101.0
November
59.3
December
44.7
3/30/2009
kWh/m2/day
kWh/m2/day =
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Author: Presenter
You will notice that energy follows the same relationship that power does throughout the year; more solar
energy is found in the summer than in the winter. Note that there is a 500% increase in solar energy during
June as compared to December. (Remember the tilt of the Earth’s axis in summer?).
Our yearly average power is 144 W/m2/day and our yearly average energy is 3.5 kWh/m2/day. Remember
that map we looked at previously? Well, it said we should expect between 3 and 4 kWh/m2/day in New
York. From our weather station data, this seems to be spot-on.
Month
Mean W/m2/day
kWh/m2/day
January
63.8
1.5
February
98.8
2.4
March
140.9
3.4
April
182.1
4.4
May
220.5
5.3
June
231.5
5.6
July
224.2
5.4
August
203.0
4.9
September
159.6
3.8
October
101.0
2.4
November
59.3
1.4
December
44.7
1.1
3/30/2009
kWh/m2/day =
§ 24 Hrs ·§ 1 kWh ·
¸¸¨
W/m 2 /day¨¨
¸
© Day ¹© 1000 Wh ¹
Yearly mean power?
• 144.1 W/m2/day
Yearly mean energy?
• 3.5 kWh/m2/day
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Author: Presenter
If we graph this in a scatter plot (solar energy per square meter per day by month), it becomes very clear
that our best solar energy months are in fact in the summer.
Solar energy throughout the year
MSC weather station data
6
5
3
kWh/m2/day
4
2
1
0
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug Sep
Oct
Nov
Dec
Solar Energy
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Author: Presenter
If we need yearly energy estimates, we simply take our daily solar energy and multiply that by the number
of days in a year (365). Now that we know the map data are accurate (or at least they seem to be), we can
compare different cities. Here are two examples that have widely different solar energy per day. Notice how
much more solar energy can be captured per unit area in sunny California vs. NY. It is this calculation that
has led people to believe that NY does not have a good enough solar resource to invest in solar modules.
This is ridicules! Remember what Germany has done… there is no excuse for us not to install solar modules.
However, this has not yet answered our question about why the solar energy map looks like it does. Let’s
take another look at it.
How does central NY compare?
• Average of solar energy throughout the year is
3.5 kWh/m2/day.
» This is 1277.5 kWh/m2/year (365 days * 3.5 per
day)
» Albany has a daily average of 4.3 kWh/m2/day
(1569.5 kWh/m2/year)
» San Diego has 7.3 kWh/m2/day (2664.5
kWh/m2/year)
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Author: Presenter
The data are correct, but it still seems funny. Why isn’t there a strong decrease in solar energy with respect
to increasing latitude?
Where are the deserts in the United States? Where are the rain forests in the United States? Why did they
form there? How did they form in those areas?
Solar energy
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Author: Presenter
One issue that greatly impacts regional solar insolation gain has to do with topography and regional winds.
Let’s look at a place like the Rocky Mountains. West of the Rocky Mountains is the Pacific Ocean. As winds
blow from the West to the East, they pick up moisture. As the winds race toward the Rockies and rise in
altitude, cooler temperatures that have less energy induce cloud formation. Once enough moisture has
collected and the temperatures are cool enough, we get precipitation on the Western flanks of the Rockies.
This leaves very dry air to race down the eastern side of the mountains. This warm, dry air is known as a
“rain shadow” and is responsible for the formation of many deserts.
Cloud cover
3/30/2009
How does this impact solar energy gain? Well, if we tried to put a solar panel on the western side of this
mountain, how many cloudless days would you expect in a year? What about on the eastern side of the
mountain?
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http://www.colorado.edu/geography/class_homepages/geog_3251_sum08/07_rainshadow.jpg
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Author: Presenter
Cloud formation is not just a regional phenomenon. This is also a global phenomenon. Warm moist air
moving toward the equator from the Tropics rises due to an increased energy state. As the warm air reaches
the upper atmosphere, it cools and the moisture condenses (forming clouds). Rising air produces a “low
pressure” situation. Cool air travels in the atmosphere from the equator toward the Tropics. Because the air
loses energy, air molecules become spaced closer together, increasing air density. Heavier, cool air sinks at
the Tropics (high pressure systems) and replaces the warm air moving toward the equator. This conveyor
belt of air movement is known as a “Hadley Cell.” There are several large cells of air currents that travel in
this way (Ferrel Cells and Polar cells, for example).
Air Cells
As you can see this causes formation of rain forests near the equator (warm, moist air) and deserts at the
Tropics (warm, dry air). This is one of the reasons that solar cells might not function at a high level in
tropical forests, though at first thought it seems like it should!
http://www.earlham.edu/~biol/desert/hadley.JPG
Low pressure
3/30/2009
Rain Forests
(cloudy)
Deserts
(sunny)
High pressure
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Author: Presenter
From this map you can see that global solar energy is influenced largely by latitude. Notice that the poles
receive far less solar energy than the equator. Notice that the average solar energy at the equator is less
than the solar energy gain at the Tropics (think clouds, rainforests, and deserts from Hadley Cells).
It is also striking that the southern hemisphere has a much more clearly defined decreases in solar energy as
you get further from the equator. Why would this be? Well, look where the land masses and oceans are. The
southern hemisphere is mostly water! The northern hemisphere has many land masses that influence
climate and solar gain on a regional basis. Remember “rain shadows”? You can see the influences of rain
shadows in the western U.S. , western S. America, and Asia. You can also see influences of seasonal rains in
places like SE China.
http://earth-www.larc.nasa.gov
Global Solar Energy
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Author: Presenter
This is a fun question to play with. If you assume that it costs $10,000 to install a solar energy PV system on
a house anywhere in the United States, who pays more for the electricity that is generated from it? If we
know that places like NY receive less solar energy than somewhere like Nevada, we know that the same
system can create more electricity per year in Nevada than NY. This means that the system will pay for itself
much faster in Nevada than NY (more energy produced for the same system cost). This again has led
people to say that solar systems should not be installed in NY. Though it might be more expensive to install
solar energy in NY, remember what Germany has done…
Solar energy systems
• If you assume that systems costs are
comparable in NY and southern California,
which location has more expensive solar
energy?
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Author: Presenter
The Solar Pathfinder is one tool available for us to estimate the year-round solar resource in a single site
visit. These can be purchased for approximately $300, or you can rent one from Real Goods for $25 per
week. Please see the attached module for an exercise with the solar pathfinder. This is a fantastic exercise
for students to do, so I encourage the rental!
A solar pathfinder is a dome-shaped glass that you orient to solar south (it has a compass and directions to
correct for declination).
Estimating the Solar Resource
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Author: Presenter
In the base of the solar pathfinder is a “worksheet” that allows you to estimate hours of sun each day. These
are designed for specific regions (based on latitude). The pseudo vertical lines represent hours in each day
(in half-hour increments). The “12” indicates solar noon, the time when the sun is highest in the sky, which
might not necessarily correspond with 12:00 PM. Along the center vertical line are the months. Winter
solstice is the top pseudo horizontal line and summer solstice is the lowest pseudo horizontal line. You can
see from this that December has fewer hours of sunlight than June.
Along each pseudo horizontal line at numbers ranging from 1 to 9. Each of these numbers is a percentage.
The sum of the numbers along a single pseudo horizontal month line is 100.
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Author: Presenter
In this image of the pathfinder, you can see three objects in the sky that would shade a solar array placed in
this location. The first obstruction is a building to the East. The second is a conifer tree to the west. The last
is a deciduous tree to the southwest. Clouds don’t count!
By outlining these three obstructions, we can find out how much energy we would sacrifice by siting a solar
system in this location.
S
W
E
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Author: Presenter
If we look at the influence of the building on solar energy, we see that its impact differs throughout the
year. To find how much shading we get, we must add the shaded numbers for each month as follows:
June (lowest line): 1+1+2+2+3 = 9%
July (next up): 1+1+2+3+3 = 10%
May: 1+1+2+3+3 = 10%
August: 1+1+2+2+3 = 9%
April: 1+2+2+3 = 8%
September: 1+2+2 = 5%
October: 1 %
To figure out how much energy we lose each year due to shading from this building, we need solar energy
information for each month. We calculated this for Morrisville from the weather station; however, not
everyone has weather station data available to them. Luckily, that information is available on the Web for
many cities at: http://www.nrel.gov/gis/solar.html.
June (lowest line): 1+1+2+2+3 = 9%
July (next up): 1+1+2+3+3 = 10%
May: 1+1+2+3+3 = 10%
August: 1+1+2+2+3 = 9%
April: 1+2+2+3 = 8%
September: 1+2+2 = 5%
October: 1%
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Author: Presenter
If we take the average incoming solar energy for each day and multiply it by the percentage lost due to
shade, we can determine daily energy. We can multiply that by the number of days in each month to get
monthly incoming energy. If we sum this column, we can calculate the total annual incoming solar energy
for this particular PV array.
If we take the adjusted total annual energy divided by the measured total annual energy, we can determine
what percentage of annual solar energy we are losing due to shade. For example, our measured annual
incoming solar energy at the MSC campus is 1267.2 kWh/m2/day. Since we know our adjusted annual
energy is 1188.2 kWh/m2/day, we lose approximately 6.2% of our annual solar energy due to shading.
Month
January
February
March
April
May
June
July
August
September
October
November
December
kWh/m2/day
1.5
2.4
3.4
4.4
5.3
5.6
5.4
4.9
3.8
2.4
1.4
1.1
Percentage
Lost
0
0
0
8%
10%
9%
10%
9%
5%
1%
0
0
Daily
Energy
1.5
2.4
3.4
4.048
4.77
5.096
4.86
4.459
3.61
2.376
1.4
1.1
Total annual energy
3/30/2009
Is this a good spot to site an array? What can be done to reduce our losses? What if it was a tree shading
the array? Class discussion.
Monthly
Energy
46.5
67.2
105.4
121.44
147.87
152.88
150.66
138.229
108.3
73.656
42
34.1
1188.24
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Author: Presenter
Following is a very brief overview of some of the solar energy systems available. We will cover solar
photovoltaics, solar hot water, solar thermal electricity, and passive solar heating.
Solar energy systems
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Author: Presenter
Solar photovoltaics (PV) systems convert solar energy into electrical energy. As light photons strike the
surface of the PV module, excited electrons are directed through conductors to a load, and back to the PV
module. PV systems can be interconnected with our national electrical grid. With this, a net metering
agreement can be set up with the electrical company. Net metering allows you to use the grid as a storage
facility. When your PV panels are generating more electricity than you need, the utility company accepts the
electricity onto the grid. If your PV panels are not generating electricity but you have an electrical demand,
the utility company provides you power from the grid.
Photovoltaics
3/30/2009
For more on the photovoltaic effect, please watch “The Science of the Solar Cell” and use the accompanying
quiz provided. For a more general overview of PV, please watch “The Power of the Sun” and use the
accompanying quiz provided.
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Author: Presenter
One technology available for solar thermal electricity uses parabolic mirrors and a heat exchange fluid.
Incoming sunlight strikes a curved mirrored surface. The sun rays are redirected and concentrated to a
single point. A pipe carrying a high temperature fluid is heated. This warms the fluid inside of the pipe,
which is carried to a heat exchanger. The heat exchanger combines the hot solar fluid with a cool water. The
water is heated to steam, which turns a turbine (connected to a generator). The generator creates electricity.
Once the solar fluid is cooled, it returns to be warmed again by the parabolic mirrors.
A great video of a system is here: http://www.youtube.com/watch?v=3OLjooHY1VA
Solar Thermal Electricity
Parabolic mirrors
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Author: Presenter
Here is an overview of an active solar thermal system for domestic hot water. Solar energy is absorbed by
the solar collector (flat plate or evacuated tubes) which heats a solar fluid (usually water and propylene
glycol). The hot solar fluid enters a heat exchanger in a hot water storage tank. This storage tank mixes in
cold water from the well or city supply, which gets warmed by the solar fluid. In the tank, a thermocline is
formed, with hot water rising to the top (lower density) and cold water sinking to the bottom (higher
density). Hot water for the house is drawn from the top portion of the tank.
Solar Hot Water
Images courtesy of John Siegenthaler
Domestic solar hot water system
• Flat plate collector (low temp)
• Evacuated tubes (higher temp)
• Solar hot water tank with heat exchanger
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Author: Presenter
Homes can be designed to take full advantage of solar energy. This particular home shown here has many
of the classic features of a passive solar home design. Large windows facing south collect winter sun (think
of a greenhouse). Notice the eaves over the windows. These allow sun in when it is low in the sky (solar
noon in winter), but provide shade for the windows when the sun is high in the sky (solar noon in summer).
Solar energy coming in the windows heats a large thermal mass, usually concrete, stone or slate. This
collects warmth and slowly radiates it back through the night as the house cools. Small windows to the
north reduce the losses of energy that most homes experience. Since cold winds often come from the north,
planting conifer trees on that side of the house reduce cold winds striking the house.
Passive Solar Heating
Passive solar homes greatly reduce heating bills in the winter because so much energy is collected on sunny
days. In fact, if it is sunny outside in the winter, the house will be warm down to -5° F without supplemental
heat. Now that’s solar power!
Thermal mass
Conifers to the north
Large windows facing south
3/30/2009
Small windows to north
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Summary
• New York has an adequate solar resource for
solar PV, solar hot water, and passive solar homes
• Solar power can be easily converted to solar
energy (and we can account for shading)
• Incoming solar energy is affected by many factors
such as latitude, cloud cover, and time of year
• Many systems can take advantage of solar energy
3/30/2009
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Contact Information
Phil Hofmeyer, Ph.D.
Assistant Professor
Ph: 315-684-6515
Email: hofmeypv@morrisville.edu
Web: http://people.morrisville.edu/~hofmeypv/
Ben Ballard, Ph.D.
Director, RETC
Assistant Professor
Ph: 315-684-6780
Email: ballarbd@morrisville.edu
Web: http://people.morrisville.edu/~ballarbd/
Solar Pathfinder Module
Renewable Energy Training Center
Morrisville State College
Overview: This module is designed to provide students with hands-on experience using one of
the most common solar energy evaluation tools on the market, the Solar Pathfinder. The
Renewable Energy Training Center does not endorse the use of the Solar Pathfinder; however,
this module is specific to this particular tool. While purchasing a Solar Pathfinder may be
beneficial in the long-run, it may be difficult to come up with the money. Solar Pathfinders can
be rented from various places such as Real Goods ($25/week, www.realgoods.com).
By the completion of this module, students will be able to:
1. Identify shading concerns with siting a solar energy collector
2. Measure solar energy lost throughout the year by shading structures
3. Differentiate between magnetic south and solar south (and correct for declination)
Materials Required:
1. 4-5 posts with flagging
2. 1 solar pathfinder for each group of students (max 5 students per group)
3. Data sheet for recording information (1 per group)
Module duration: 2 hours (can be broken into several class periods if necessary)
How to use a solar pathfinder (see the example provided in the PowerPoint presentation for a
visual demonstration and for the mathematics):
1. Select the appropriate sun path worksheet for your latitude.
2. Put the worksheet into the pathfinder, aligning the leveling triangle into the appropriate
slot.
3. Pull the brass tab beside the compass out. This will allow the surface of the pathfinder
to pivot left to right. Adjust the pathfinder worksheet and set your magnetic declination.
I hold the leveling triangle and rotate it left or right as needed. If you do not know your
declination, go to http://www.ngdc.noaa.gov/geomagmodels/Declination.jsp and type
in your zip code. If you live in NY, you will rotate the pathfinder worksheet to the right.
For example, in Morrisville, our declination is roughly 12.5° West of North. I need to
move the worksheet to the right until the white dot aligns with -12.5°.
4. If you have a handheld pathfinder, try your best to level the pathfinder by centering the
bubble. If you don’t have steady hands, you can use a small bean bag or a pole to help.
5. Align the pathfinder compass so that the red arrow points north (you should now be
looking south). Are you looking at magnetic south or solar south at this point? You have
corrected for magnetic declination, so you are aligned with solar south.
6. Now put the dome glass over the pathfinder worksheet. The single brass post should
align with the south side of the pathfinder.
7. Standing to the north, look over the leveled pathfinder. You should see a reflection of
the obstacles around you. You can see the sun, clouds, trees, buildings, etc.
8. To determine how much shading you will receive, outline the obstacles with the white
crayon. The pseudo vertical lines represent hours in each day (in half-hour increments).
The “12” indicates solar noon, the time when the sun is highest in the sky, which might
not necessarily correspond with 12:00 PM. Along the center vertical line are the months.
Page 1
Winter solstice is the top pseudo horizontal line and summer solstice is the lowest
pseudo horizontal line. You can see from this that December has fewer hours of sunlight
than June. Along each pseudo horizontal line at numbers ranging from 1 to 9. Each of
these numbers is a percentage. The sum of the numbers along a single pseudo
horizontal month line is 100.
9. Subtract the percentage lost to shade for each month. Multiply this percentage by the
average monthly solar energy received for your location (can be found at:
http://www.nrel.gov/gis/solar.html). Sum this for all months to determine the total
amount of solar energy you will receive over the year with shading. This is your
“adjusted solar energy” value.
10. To determine the annual percentage of energy lost due to shading, take the adjusted
solar energy divided by the unadjusted annual solar energy. This will give you the
percentage of solar energy available that you will capture.
For the classroom module, you have a lot of options. Below is one module that has worked well
in the past. Please see the attached Excel workbook for an example worksheet and data for NYS
solar energy.
Step 1: Identify a site to locate a fictional solar array (roughly 30’ x 15’) oriented to solar south.
Ideally this site would have a small obstruction at several of the corners (such as a building or
trees) that will appear on the solar pathfinder. Once located, place a flagged post at each corner
of the array and label each corner by direction (e.g. NW, SE, etc.). Stake a center location as
well.
Step 2: Before going out to the field, give the students a quick primer on how to use the solar
pathfinder. Use the proper sun path worksheet for your latitude.
Step 3. Give each group 5 copies of the sun path worksheet (photocopies are fine). They will use
1 worksheet for each corner post and one at the center post.
Step 4. Have the groups rotate through all five stations, outlining the shading structures at each.
Each sun path worksheet should be marked (e.g. NW, SE, center, etc.) so that the students are
able to remember the obstructions for each corner. Once each group has completed this, you
can head inside.
Step 5. Use the attached Excel worksheet so that each group can determine the shading losses
at each corner. If you average the shading at each corner, you can get the mean condition of
shading for this array.
Step 6. Have the students calculate yearly energy and yearly percentage of energy lost due to
shading.
Page 2
Questions:
1. How does the “mean” condition compare to the center station in terms of shading?
Should they be the same? Why or why not?
2. How could you modify the shape of the array to reduce shading?
3. How could you modify the environment to reduce shading?
4. Is it better to modify the environment or move the array? Why?
5. What is magnetic declination? How can we correct for it?
6. How does shading impact the cost of solar energy?
Page 3
Layout of a fictional solar array
Correction for declination in central New York. The white dot is aligned with -12° indicating that
this pathfinder is correcting for 12 degrees west of north.
Page 4
To correct for declination, move the small brass pin from closed position (left image) to the
open position (right image). Now you can use the triangle bubble level to move the solar
worksheet from left to right.
Page 5
Images from all four corners and the center of an array show how shadows from one object
impact the solar array in different times of the year.
Page 6
Name ______________________________
“Power of the Sun” quiz
1. The solar energy that strikes the Earth’s surface for one hour is enough to provide all of the
electricity needs of the Earth for ___________________.
2. Isaac Newton hypothesized that light was made up of particles that traveled in _____________.
3. Christian Huygens hypothesized that light spreads by _________________.
4. Thomas Young’s experiments gave evidence that the ____________ theory seemed correct.
5. Albert Einstein provided evidence that light is made up of packets of energy called __________.
6. Who was right, Newton or Huygens? _______________
7. The first “solar battery” was invented by which company? ___________________
8. Silicon was used by Bell scientists because it is _____________ and because it acts as a
_________________.
9. Solid silicon does not work electronically unless _________________ are introduced.
10. The two most commonly used impurities for silicon semiconductors are __________________
and ___________________.
11. A P-N junction attracts “holes” to the ___________ side and electrons to the ___________ side.
12. Power photo cells were first demonstrated in what application? __________________________
13. NASA wanted solar cells for what application? _____________________________
14. Sputnik died after a few weeks. Why? ____________________________________
15. Nearly every cell phone call passes through ___________________ equipment.
16. The first major industrial solar electric users were in the _______________ industry.
17. Japan has gone to solar power so quickly because it has few _____________ resources.
18. Solar power is driven globally what which two countries? ______________ and ____________.
19. The world’s largest solar PV installation is in which country? ___________________.
20. Powerlight’s integrated solar panels provide what three benefits to industries?
______________, ____________________, and _______________________.
21. The main reason that solar electricity is not widely used in the U.S. is __________________.
22. As solar PV costs are decreasing, prices of energy from fossil fuels are ___________________.
23. The world’s largest publicly owned solar array is in which U.S. city? _______________________.
24. In many parts of the developing world, solar PV is ideal for power production. Why is this?
_____________________________________________________________________________.
25. Describe one method for transporting solar-cooled vaccines in rural parts of Africa. _________
_____________________________________________________________________________.
Name ______________________________
“Power of the Sun” quiz
1. The solar energy that strikes the Earth’s surface for one hour is enough to provide all of the
electricity needs of the Earth for __[1 year]_________________.
2. Isaac Newton hypothesized that light was made up of particles that traveled in _
[straight lines]_____.
3. Christian Huygens hypothesized that light spreads by ___[waves]______________.
4. Thomas Young’s experiments gave evidence that the _[wave]_________ theory seemed correct.
5. Albert Einstein provided evidence that light is made up of packets of energy called
____[photons]______.
6. Who was right, Newton or Huygens? ____[Both]___________
7. The first “solar battery” was invented by which company? ___[Bell] ________________
8. Silicon was used by Bell scientists because it is _[abundant]____________ and because it acts as
a _[semiconductor]________________.
9. Solid silicon does not work electronically unless ___[impurities]______________ are introduced.
10. The two most commonly used elements for silicon semiconductor impurities are
__[boron]________________ and _____[phosphorous]______________.
11. A P-N junction attracts holes to the __[P]______ side and electrons to the _____[N]______ side.
12. Power photo cells were first used in what application? _______[Radios]___________________
13. NASA wanted solar cells for what application? ___[space exploration]____________________
14. Sputnik died after a few weeks. Why? ______[dead batteries]____________________________
15. Nearly every cell phone call passes through __[solar powered]_________________ equipment.
16. The first major industrial solar electric users were in the ___[oil]____________ industry.
17. Japan has gone to solar power so quickly because it has few _[fossil fuel]__________ resources.
18. Solar power is driven globally what which two countries? __[Germany]____ and ___[Japan]___.
19. The world’s largest solar PV installation is in which country? _[Germany]__________________.
20. Powerlight integrated solar panels provide what three benefits to industries?
__[electricity]_________, ____[cooling]_____________, and _____[heating]______________.
21. The main problem that has stopped solar electricity in the U.S. is ____[cost]______________.
22. As solar PV costs come down, prices of energy from fossil fuels are ___[increasing]___________.
23. The world’s largest publicly owned solar array is in which U.S. city? __[San Francisco]_________.
24. In many parts of the developing world, solar PV is ideal for power production. Why is this?
___Many reasons…_____________________________________________________________.
25. Describe one method for transporting solar-cooled vaccines in rural parts of Africa. _________
__[camels – pretty neat!]________________________________________________________.
Name __________________________
Silicon Solar Cells
1. Rank the following colors from highest energy to lowest energy:
Green, orange, red, blue, yellow, violet
2. Electrons have a
a
charge.
charge, neutrons have a
charge, and protons have
3. In Bohr’s model, the electron closest to the neutron has the fastest revolution time and the lowest
energy state.
a. True
b. False
4. Where does energy go as an electron falls from high energy orbits to lower energy orbits?
.
5. Which wavelength of visible light will jump a Hydrogen electron to its highest energy state?
a. orange
b. violet
c. light blue
6. The outermost shell electrons are known as
7. The most abundant element in photovoltaic modules is:
a. Phosphorous b. Boron
c. Silicon
d. dark blue
electrons.
d. Hydrogen
8. Electrons move toward positive fields and “holes” move toward negative fields.
a. True
b. False
9. Doping is the process of introducing impurities into the silicon grid. Which two are used?
a. Hydrogen
b. Boron
c. Light
d. Phosphorous
10. Solar cells “use up” electrons over time. Therefore, their lifespan is limited to 20-25 years.
a. True
b. False
Name __________________________
Silicon Solar Cells
1. Rank the following colors from highest energy to lowest energy:
Green, orange, red, blue, yellow, violet
Violet, blue, green, yellow, orange, red
2. Electrons have a
[negative]
and protons have a [positive]
charge, neutrons have a
charge.
[neutral]
charge,
3. In Bohr’s model, the electron closest to the neutron has the fastest revolution time and the lowest
energy state.
a. True
b. False
4. Where does energy go as an electron falls from high energy orbits to lower energy orbits? [It is
emitted as light]
.
5. Which wavelength of visible light will jump a Hydrogen electron to its highest energy state?
a. orange
b. violet
c. light blue
6. The outermost shell electrons are known as [valence]
7. The most abundant element in photovoltaic modules is:
a. Phosphorous b. Boron
c. Silicon
d. dark blue
electrons.
d. Hydrogen
8. Electrons move toward positive fields and “holes” move toward negative fields.
a. True
b. False
9. Doping is the process of introducing impurities into the silicon grid. Which two are used?
a. Hydrogen
b. Boron
c. Light
d. Phosphorous
10. Solar cells “use up” electrons over time. Therefore, their lifespan is limited to 20-25 years.
a. True
b. False
Summary of Comments on Slide 1
Page: 1
Number: 1
Author: Presenter
This lecture is designed to provide teachers and students with an overview of the hydro resource and micro
hydroelectric systems. Please see the attached module for measuring the hydro resource.
1
The Hydro Resource and Micro Hydroelectricity Systems
The
T
he S
Solar
olar R
Resource
esource
Overview
•
•
•
•
Review of the Hydrologic Cycle
System components
Measuring head and flow
Generating power from water (examples)
6/22/2009
2
Page: 3
Number: 1
Author: Presenter
Add to, or subtract from this list as needed. In general, students may learn this is earth science, but it is
important to remind them of the hydro cycle for several reasons. First, it is nice to have intentional
redundancies among classes to reinforce how much their education in one area relates to other areas.
Second, this is important to give them the foundation of what it means to have a renewable resource
powered by the sun. Additionally, we all struggle with terminology. Sprinkling in terminology where we can
reminds us of its importance.
1
Hydrologic Cycle
• Key terminology
» Insolation
» Evaporation
» Transpiration
» Evapotranspiration
» Sublimation
» Condensation
» Precipitation
» Infiltration
6/22/2009
» Sub-surface flow
» Ground water
discharge
» Overland (surficial)
flow
» Freshwater storage
» Oceanic storage
3
Page: 4
Number: 1
Author: Presenter
I generally do not do a powerpoint for this. I like to engage the class to see how much terminology they
know and if they understand the processes. As the hydro cycle is indeed a cycle (with many loopholes and
pathways), it is difficult to pick a starting point. I generally start with the sun and incoming insolation. This
provides the energy to keep these processes going. The sun leads to evaporation of freshwater and oceanic
water storage. Cooling temperatures in the upper atmosphere lead to condensation of water molecules.
Further condensation leads to precipitation, which strikes the ground (or plants in the process of
interception). Depending upon the surface, precipitation is either absorbed into the ground (infiltration) or
collects into overland flow (surficial flow) or freshwater storage. Once water enters the ground, subsurface
flow fills soil air spaces (can discuss water tension, cohesive forces, soil water pressure, etc.). Ground water is
often picked up through plant roots during the process of photosynthesis, where it is transpired back into
the atmosphere. Together with evaporation, this process is known as evapotranspiration. Groundwater
entering freshwater or oceanic storage enters through the process of groundwater discharge.
1
Hydrologic Cycle
Insolation
condensation
sublimation
Precipitation
Transpiration
Surficial
flow
Freshwater
storage
Oceanic storage
Infiltration
Subsurface flow
6/22/2009
Evaporation
Groundwater
discharge
4
Page: 5
Number: 1
Author: Presenter
This is important to stress and I often have a class discussion here.
We are always concerned about what happens to the water resource before it gets to us and what happens
once it leaves our sight. In this way, large hydro systems are often renewable (the process is cyclic and
continuous), but not necessarily sustainable (can have deleterious effects on water flora, fauna, and human
health). Micro hydro systems tend to be more sustainable than large hydro systems, as we will soon see!
1
Hydro Power
• For most hydro systems, we are interested in
only certain processes in this cycle
» Oceanic storage (wave, tidal, ocean current)
» Freshwater storage (wave, pumped storage, dams)
» Overland flow (streams and rivers)
• Though our systems use these processes, we
must keep in mind that it is a cycle
» Water is replenished in our systems due to
incoming solar energy
6/22/2009
5
Page: 6
Number: 1
Author: Presenter
These are data from the MSC weather station. Feel free to use any data you have available to you for your
location. NOAA publishes a great deal of information, as does the Weather Channel (.com). For many of us
in NY, rainfall is fairly well distributed throughout the year, though we do see more during the summer and
fall months. This is counterintuitive to many people. It is important to show the importance of real data, not
just what people “feel” is a wetter time of the year. Polling the class is a good way to see what they think
and what they know.
1
Measuring the hydro resource
In central New York, when do we get most of our
precipitation?
MSC mean rainfall (2003-2008)
Inches of Rainfall
5
28 inches per year
4
3
2
1
0
6/22/2009
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
6
Page: 7
Number: 1
Author: Presenter
This is where people often begin thinking about the “wet” season. Though rainfall peaks during the summer,
stream discharge peaks during the spring. These data came from the USGS site referenced. Find a stream
near you and generate a similar figure from their data (which is easily imported into Excel). I made a
histogram displaying the mean condition of stream discharge (long-term data set). Over that, I made a
scatter and line plot of a year chosen arbitrarily. This particular graph shows a flood condition in the spring
and a drought in the late summer and early fall. Why is this important? Well, it is important because if you
are monitoring a stream to consider a hydro system, we need to know how much water can be diverted.
This shows the importance of measuring throughout the year, and over successive years to get the most
accurate information.
1
Measuring the hydro resource
Mean
2006
1000
500
Ju
ly
Au
gu
Se
st
pt
em
be
r
O
ct
ob
er
No
ve
m
be
De
r
ce
m
be
r
ay
Ju
ne
M
Ap
ril
0
Ja
nu
a
Fa ry
br
ua
ry
M
ar
ch
Cubic Feet per Second
Chenango River Discharge
1500
http://waterdata.usgs.gov/nwis/
6/22/2009
7
Page: 8
Number: 1
Author: Presenter
Now that you have a good idea of the resource, we will discuss micro hydro systems briefly. Here is a
diagram of a very simple direct current (DC) hydro system. Micro-hydroelectric system components are
quite similar to that of large hydro systems, only smaller. The system begins with a water intake (generally a
screened box in an existing stream pool) that diverts a small proportion of the stream flow into a pipe or
sluiceway (known as the penstock). The penstock brings water to a series of jets, which spin the hydro
turbine runner. Water leaving the turbine returns to the stream through a tailrace. The turbine is connected
to a generator, which uses electromagnetic induction to generate electron flow, which generates electricity.
This electricity can be sent through conductors to any electrical end use (e.g. lights, refrigeration, and
toasters). Often times, there is a battery bank to store electricity until it is required. Unlike solar systems,
micro hydro systems are highly site-specific.
1
6/22/2009
8
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Number: 1
Author: Presenter
The system intake functions to pool water to provide a continuous supply of water to the penstock. Intakes
can be located in a natural pool or in a man-made holding tank. Because the intake functions to filter debris
from enter the system, the intake is generally the area of highest maintenance in a functioning hydro
system. As such, it should be accessible and sturdy. There are a variety of intake options available. This
image shows the use of a pre-existing water holding structure that was converted to a micro hydro intake.
1
System components: Intake
• Water enters penstock
through the intake
• Remove debris
• High maintenance
• Accessible
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Author: Presenter
PVC pipe is a commonly used penstock material. In fact, most hydro system use PVC at some point in the
penstock (may include the hydro turbine manifold). PVC is easily found in most hardware stores, so system
components are easy to order. Schedule 40 PVC can only be used for low pressure systems because it
cannot withstand high psi conditions near the turbine. PVC also has the advantage of very low resistance
losses in straight sections. However, because it is rigid, it requires sharp bends, often exceeding 22.5°, where
water turbulence in the penstock reduces pressure at the turbine (potential energy is lost through
conversion to kinetic energy, which reduces power output at the turbine).
1
System components: Penstock
• PVC
» Cheap, light, and rigid
» Low pressure systems
» Easily available at
hardware stores
» Low losses (in straight
sections)
» Freezing issues
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Number: 1
Author: Presenter
Polyethylene tube is more commonly used than PVC because it comes in 40’ lengths or as flexible 100’+ coil
lengths. Polyethylene is easily found up to 1” diameter, however, many micro hydro systems require 2” to 3”
penstock material. These are more difficult to find and tube fittings (couplers, ball valves, Ts, drain valves,
etc.) are expensive. The penstock is often the most expensive part of a micro hydro system because of this.
Polyethylene is somewhat freeze-resistant because of its flexibility. HDPE (high-density polyethylene) can
withstand over 100 psi, so this material is useful in high-head systems. Because you often do not need to
make abrupt angles with polyethylene, friction losses due to turbulence are minimized, often resulting in
lower total system losses as compared to PVC (even though PVC has a lower friction coefficienct than PE).
1
System components: Penstock
• Polyethylene tube
» Flexible
» Longer lengths
» Lower losses in sweeping bends
» Freeze resistant
» Expensive components
» Difficult to purchase
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Author: Presenter
This particular model is the ES&D stream engine. A comparable turbine is the Harris hydro wheel. Both
models are designed for high head, low flow streams and are capable of producing over 1.5 kW of
continuous power (up to 13,000 kWh per year of electricity). This is quite impressive, as the average home
uses about 8,400 to 12,000 kWh per year. Both turbines employ a Pelton style runner (water strikes the
runner along its circumference). Both also have options to regulate the voltage depending upon
transmission distance and invertoer/battery bank needs.
1
System components: Turbine
• High head, low flow
•
•
•
•
6/22/2009
1, 2, and 4 nozzle designs
12, 24, 48, VDC options
120 VAC options
Pelton wheel with bronze
runner
12
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Number: 1
Author: Presenter
Micro hydro systems generally have smaller battery banks than equivalent wind and solar systems. Wind
and solar are both highly intermittent resources, meaning that battery banks must be large enough to
withstand several days of no wind or sun without being depleted. Conversely, micro hydro systems have
continuous power production, so the battery bank is always being replenished.
1
Batteries for hydro systems are very similar to those used in other renewable energy systems. They should
be lead-acid batteries with deep cycle capability. This allows the battery to be depleted and recharged many
times before battery failure. They can be wet cell or sealed gel batteries. The wet cell require more
maintenance, but they often last longer and are less expensive. Batteries can be wired in series to increase
voltage or in parallel to increase capacity. Generaly, several series strings are linked in parallel to get the
proper voltage and capacity needed.
System components: Batteries
•
•
•
•
Lead-acid
Deep cycle
Generally 2 to 6V
Wet cell or sealed (gel)
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Author: Presenter
Charge controllers, or specifically diversion controllers in micro hydro systems, monitor battery bank
voltage. Hydro turbine must always be connected to an electrical load. Without a load attached, the runner
would spin too quickly and burn out the bearings. When the battery bank is low, the diversion controller
sends electrons to the batteries. When the battery bank is fully charged, excess electrons are sent to a
diversion load where they are “dumped” as quickly as possible.
1
Charge controllers can easily be set with jumpers to a range of DC voltages. It is important to note that
input voltage from the turbine must match the battery bank voltage. So, if your turbine is set to transmit 24
VDC, the battery bank must be wired to 24 VDC as well.
System components: Charge controller
• Monitors battery bank voltage
• When the battery bank is “full”,
electrons are diverted to a
diversion load (a.k.a. dump
load)
• Can be jumped from 12,24,
and 48 VDC depending upon
input and battery bank (they
must match!)
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Author: Presenter
A diversion load is installed to protect the battery bank from over charging (“boiling” off hydrogen gas and
reducing lifespan). Diversion loads are often resistance heating elements which very quickly dump electrons.
These can be as simple as an air heating element with a fan or something more useful throughout the year
such as a heating element in an electric hot water tank. This turns an excess of electrons to a useful energy
load.
1
System components: Diversion Load
• Waste electrons as quickly as possible
• Resistance heating elements
• Protect the battery bank
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Author: Presenter
Most of our houses use alternating current (AC), not direct current (DC). If we generate and store DC, we
need a way to convert it to something we can use in our households. An inverter converts DC to AC by
increasing the voltage with a transformer (from 24VDC to 120/240 VAC), modifying the current signal from
constant polarity (DC) to an alternating polarity sine wave (AC), and by adjusting the frequency to match
our standard 60 hertz (60 AC sine waves per second).
1
The inverter is the brains of the operation, often integrating a charge controller to monitor battery bank
voltage if one is present. Most inverters can produce a sine wave indistinguishable from the “grid”
electricity.
System components: Inverter
• Converts direct current (DC) to alternating
current (AC)
• Can match the utility signal (voltage, shape
and frequency)
6/22/2009
16
Generating power
Now that you understand the system
components, how does one actually generate
power with a micro hydro system?
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Number: 1
Author: Presenter
If you look at the hydro power formula, two of the values will be constants (water density and acceleration
of gravity) and turbine efficiency is given by the manufacturer (generally between 80 and 93% for water
turbines). This means we only really need two numbers from our stream to estimate power output: the flow
and the head.
1
Measuring the hydroelectric resource
• Power generation from water is dependent on
five variables:
» P=gQH
» Power in watts (P)
» Turbine efficiency (eta, )
» Water density (rho, ; usually 1000 kg/m3)
» Acceleration of gravity (g, 9.81 m/s2)
» Quantity of water flow (Q, in m3/s)
» Vertical distance (head, H, in meters)
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Author: Presenter
It is often easier to work with students in gallons per minute and have them convert to the metric system.
We often have a difficult time working with cubic meters instead of gallons. This is a simple conversion
factor.
1
Measuring a stream – flow
Flow rate (Q)
• Quantity of water passing a given point over a
given amount of time
» Cubic meters per second
» Gallons per minute
» 1 GPM = 0.000063 m3/s
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Author: Presenter
There are many ways to measure flow, depending upon how large the stream is. For the smallest streams,
simply find a location where the water is constricted and time how long it takes to fill a 5-gallon bucket. For
example, if it takes 20 seconds to fill a 5-gallon bucket, you have a flow of 15 gallons per minute. Another
option is to build a temporary weir wall and measure its volume. If you time how long it take to fill to a
certain point, you can again estimate flow rates.
1
Please see the attached module for measuring flow in a stream for additional ideas.
Measuring flow
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Author: Presenter
The relationship between head and pressure is very important for a hydro system. For every 2.31 feet of
elevation difference between the intake and the penstock, there is an increase of 1 pound of pressure per
square inch (psi) at the turbine. Another way to say this is that each foot of head provides 0.433 psi.
Monitoring pressure in the penstock is very important. If you have 100 feet of elevation between the
penstock and the turbine, you should expect approximately 43.3 psi at the turbine. If you are only reading
15 psi, you know that there is a problem (intake plugged, hole in the penstock, not enough flow, etc.).
1
Measuring the hydro resource - head
Head (H)
• Head is the vertical distance of the hydro
system (from intake to turbine)
• Relationship of head
and pressure
2.31 feet
1 psi
6/22/2009
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Author: Presenter
Assessing head can be fairly straightforward (using a clinometer) or more complex (for example, using a
total station or other surveying equipment). What you are trying to design when measuring head is a
stream profile diagram.
1
Measuring head
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A stream profile diagram indicates several things. On a stream profile diagram you should have total
elevation gain from the turbine to the intake, contours of the stream, horizontal distances between
important contour points, actual penstock distances between points, and total length of the penstock tube
system. This will allow you to better determine how much penstock material you need, where rough spots
will occur during installation, and how much friction you will build in the pipe system.
1
It is also important for the stream disturbance to know areas that are at greatest risk. Particularly steep
sections of a stream are most sensitive to disturbances.
Stream profile diagram
1,110 feet of penstock
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Number: 1
Author: Presenter
If we measured a small stream and determined that it has approximately 20 GPM and 140 feet of head, we
can convert those numbers to metric to get into the standard formula. We also want to know what pressure
we should expect at the turbine with this system so that we can buy the penstock materials that will be able
to withstand the pressure.
1
Hydro power - example
• Small stream:
» 20 GPM flow, 140 feet of head, 85% turbine
efficiency
§ 1 psi ·
¹
©
•
Pressure: 140 ft¨ 2.31 ft ¸
•
Flow:
§ 0.000063 m 3 /s ·
¸¸
20 GPM ¨¨
1 GPM
¹
©
•
Head:
§ 0.305 m ·
140 ft ¨
¸
© 1 ft ¹
6/22/2009
60.6 psi
0.00126 m 3 /s
42.7 m
24
Page: 25
Number: 1
Author: Presenter
Here is just one example of the hydro power formula. The variables are quite easy to plug into the formula
(nothing is squared like the wind power formula). You’ll notice that I used the values we converted to
metric, as Watts is an SI unit of measurement. The continuous power output is 448.6 watts. While power
production is important, we are more concerned with energy production.
1
To convert power to energy, we must multiply by time. To convert watts to watt-hours, we must multiply by
the number of hours it is “on.” In this case, the turbine is producing power 24 hours per day (unlike wind
and sun). So, I multiply 448.6 Watts by 24 hours and I get 10766.4 watt-hours. We buy our electricity not in
watt-hours, but in kilowatt-hours (kWh). Because there are 1,000 watt-hours in one kWh, I must divide by
1,000 to get my kWh produced each day. This gives me 10.77 kWh per day produced by this stream. If I
want yearly energy production, I multiply my daily energy by the number of days in a year (365.25,
accounting for leap years). This gives me 3,932 kWh per year. Not bad! My relatively energy efficient house
uses about 340 kWh per month, or 4,080 kWh per year. The national average ranges from 700 to 1,000 kWh
per month.
Hydro power: example
• P= g Q H
» Power = 0.85*1000 kg/m3*9.81 m/s2*0.00126 m3/s *
42.7 m
» Power = 448.6 watts
• Yearly energy in kWh?
» 448.6 W *24 hrs/day * 365.25 days/yr = 3,932 kWh/yr
• My house uses about 4,000 kWh/yr
6/22/2009
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Number: 1
Author: Presenter
If you look at the hydro power formula, you will notice that head and flow are equally weighted. It is often
easier to describe this with numbers than symbols for students, however. In this example, I simply switch the
values for head and flow. Where previously we calculated power output as a function of 20 GPM and 140
feet of head to get 448.6 watts, this example uses 140 GPM and 20 feet of head. Interestingly, we get the
same power output. This is exceedingly important! Just because someone has a lot of water does not mean
you get more power output. You need both head and flow to generate power (or a lot of one and a little of
the other).
1
Hydro power: what if?
• If we go from 20 GPM flow and 140 ft of head
to 140 GPM and 20 ft of head?
• What power (watts) should I expect?
• P= g Q H
» Power = 0.85*1000 kg/m3*9.81 m/s2*0.00882 m3/s *
6.1 m
» Power = 448.6 watts
6/22/2009
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Number: 1
Author: Presenter
A reiteration for emphasis. Calculating penstock losses are a bit beyond the scope of this module, but
please feel free to contact me at hofmeypv@morrisville.edu if you would like more information on
calculating penstock losses. It is a great exercise if you have the right class and enjoy a small bit of math.
1
Hydro power
• Head and flow have equal importance in
determining power (and energy) in a hydro
system
» What we have just calculated does not take
penstock losses into account
» This will reduce power output
6/22/2009
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Page: 28
Number: 1
Author: Presenter
This part is not necessary for the module, but it does have a useful discussion point. What I would like to do
now is compare a micro hydro system with a residential wind turbine. We’ll start off by reminding ourselves
about how much energy a small stream can produce in a year.
1
Hydro power: a comparison
• 20 GPM and 140 ft of Head
• Yearly energy in kWh?
» 448.6 W *24 hrs/day * 365.25 days/yr = 3,932 kWh/yr
• My house uses about 4,000 kWh/yr
6/22/2009
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Number: 1
Author: Presenter
I have gone onto the NYS Wind Resource Explorer and zoomed into the area surrounding Morrisville State
College. Most of Morrisville is in a class 1+ wind site, though there a few areas with class 2 and class 3
winds. We’ll select the best case scenario and say that we have a class 3 wind site (bright orange) to install a
residential wind turbine.
1
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Author: Presenter
The question I need to ask myself is this. How large of a turbine do I need to generate a comparable
amount of electricity? I will work backward. I know that to be comparable, I need to generate 3,932 kWh per
year. This means I need approximately 10.8 kWh per day (3,932 ÷ 365 days). This means I need and average
power production of approximately 0.45 kW (or 450 Watts; 10.8 kWh/day ÷ 24 hours/day). I know that a
wind turbine is about 30% efficient in terms of how often they are spinning in this area. So, I can now plug
my values into the wind power formula:
P=0.5* A V3, Where P is power in watts, eta is turbine efficiency, rho is air density (1.2 kg/m3), A is
windswept area (m2), and V is wind speed (m/s). Since windswept area equals pi*r2, I can substitute this into
the wind power formula. By crunching the numbers, I get a rotor radius of 1.5 meters, which is a rotor
diameter of 3 meters. With roughly 3.3 feet per meter, we must have a 10 foot rotor diameter. This is
drastically larger than a hydro turbine that easily sites on a student’s desk (and more expensive)!
1
…to wind!
•
•
•
•
•
Class 3 site (7 m/s average; 15 mph)
Turbine at 30% efficiency
P=0.5* A V3
450 W = 0.5*0.3*1.2 kg/m3*(3.14*r2)*(7 m/s)3
r = 1.5 meters, diameter = 3 meters
This means to get an equivalent amount of
energy, I need a 10’ wind turbine rotor!
6/22/2009
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Number: 1
Author: Presenter
Micro hydro systems have a lot of benefits: Relatively inexpensive systems to install and maintain, constant
power production when sized appropriately and freezing issues are addressed, minimal impacts on stream
organisms, and very high turbine efficiency. However, there are some important hurdles. Because micro
hydro systems are still associated with large hydro systems, many people do not consider them sustainable.
As such, they cannot be net metered like wind and solar. No incentives are available for micro hydro
systems. Additionally, kits are very difficult to make beforehand because it is highly site-dependent (unlike
solar systems, for example). Additionally, relatively few potential users have adequate knowledge of their
site (head and flow, distance to end usage, permitting processes necessary, etc.).
1
So, what bother with micro hydro?
•
•
•
•
(Relatively) inexpensive
Constant power production (not intermittent)
Minimal impacts
Turbines have high efficiency (80% to 90+%)
Challenges
• Not considered “renewable and sustainable”
• Permitting process may be required
• Highly selective sites
• Currently cannot be net metered
• Little knowledge of our resource
6/22/2009
31
Contact Information
Assistant Professor
Ph: 315-684-6515
Ben Ballard, Ph.D.
Director, RETC
Assistant Professor
Ph: 315-684-6780
Micro Hydroelectricity Module
Overview: This module is designed to provide students with hands-on experience measuring
and mapping the micro hydro resource. This module will give students the tools and experience
necessary to measure vertical elevation gain (head), slope, and water flow. With this
information, a student can create a stream profile diagram, estimate pressure at the turbine,
and estimate power output from the turbine.
1. Build a simple clinometer
2. Measure vertical angles, horizontal distance, calculate vertical distance, measure stream
volume and velocity, and estimate stream flow.
3. Develop a stream profile diagram.
Materials Required (1 for each group):
1. 1 plastic protractor
2. 1’ length of string
3. 1 small weight (e.g. ½” nut)
4. Clear tape
5. 100’ measuring tape
6. 12’ measuring tape
7. Flagging
8. Pencil and paper
9. 5 gallon bucket
10. Stopwatch
11. Tennis ball
12. Waders (optional)
Module duration: 3 hours (can be broken into several class periods if necessary)
This module requires the use of a stream. The reality is that without a stream, it is very difficult
to discuss micro hydro resources and systems. The stream may be very small (5 GPM) or it can
be a large trout stream. Identify an appropriate stream near the classroom, if possible. We will
assume that a system could be installed, but likely will not be installed. Before starting the
module, identify a suitable site for the fictional turbine and intake to be located.
Build a simple clinometer
A clinometer is a tool that measures the angle of elevation using right triangle trigonometry.
1. Tape the length of string to the center of the protractor base (the flat portion of the
protractor).
2. Tie the nut on the other end of the string.
3. When held parallel to the ground, the nut should extend through the 90° mark on the
protractor (the rounded portion of the protractor should be facing the ground).
Page 1
4. You can optionally tape a straw to the top of the protractor if you would like a sighting
line.
To use the clinometer, you will need two people; one to hold the clinometer and one to read the
angles on the protractor.
1. Have the students begin at the turbine location (downstream of the intake location).
2. The student sighting the clinometer should look uphill and sight on an object less than
100’ away at the approximate height of his/her eye level (another student walking uphill
makes for a great sighting target).
3. The second student should record the angle in which the string crosses the protractor.
4. Subtract the measured angle from 90° to get the actual angle of the slope.
5. With the 100’ tape, measure the distance between the turbine location and the sighted
object. Be sure to hold the tape as tight as possible between the two points to get an
accurate measurement.
6. If you have the distance and the angle, you can use some simple trigonometry to get
vertical distance. The sin of the measured angle (90° - protractor angle) multiplied by
the distance measured between the two points will give you the vertical elevation gain
(see figure 1 below).
Figure 1. Calculating vertical distance from an angle and distance measurement.
Page 2
7. Continue this in successive steps until you reach the location for the intake. Be sure to
make stops anywhere there is a large change in slope (whether it gets significantly
flatter or steeper). This will help you make a more informative stream profile diagram.
8. By the time students are finished, they should have a table that looks something like
figure 2 below.
Figure 2. Example table with the stream sections measured, protractor angles observed and
actual angles, measured distances and calculated distances. Note that if you have the measured
distance between two points and the calculated vertical angle, you have the hypotenuse and
opposite side of a right triangle. You can then use Pythagorean’s theorem to calculate the
horizontal distance (a2+b2=c2). Measured distance is the penstock length between points.
Building a stream profile diagram
1. If you have vertical distance and horizontal distance between each point, you have all of
the information needed to build a stream profile diagram (by hand or in Excel).
2. To create a profile diagram in Excel, create three additional columns: stream section,
cumulative vertical distance, and cumulative horizontal distance and enter in the data.
3. Label the stream sections sequentially from 1 to …. The cumulative columns will simply
be adding the horizontal distance and vertical distance for each stream section (see
figure 3).
4. Once you have cumulative data, you can start graphing. Highlight the cumulative height
and cumulative horizontal columns. Create a scatter plot figure. Set the x-axis as
cumulative horizontal and the y-axis as cumulative height. Set the axis scales
appropriately. Label your axes.
5. At each point, indicate the cumulative pressure obtained in the elevation gain (recall
that each foot of head increases pressure by 0.43 psi). This can be calculated by hand or
in Excel by subtracting the intake height from the previous point and multiplying by
0.43. Continue for each successive point (remember, pressure is cumulative).
6. Add pertinent information for the system (such as cumulative run distance or penstock
length, intake location, turbine location, etc.) (Figure 5).
Page 3
Figure 3. Adding cumulative columns and stream section columns. Note that several columns
have been hidden in this example (e.g. protractor readings and actual angles).
Figure 4. Scatter plot of horizontal and vertical distance of each stream section.
Figure 5. Completed stream profile diagram
Page 4
Measuring stream flow
This section will describe measuring stream flow on a moderately sized stream. For smaller
streams (high head systems), measuring the amount of time required to fill a 5 gallon bucket or
50 gallon drum will suffice. Larger streams require alternative methods. Described below is a
frequently used method that involves estimating the volume of a section of stream and
estimating stream velocity over that volume of water.
1. Find an accessible site along the stream that does not have irregular features (pools,
sharp drops, back eddies).
2. Set up two points, an upstream reference point and a downstream reference point,
preferably 5 to 20 feet apart.
3. From these two points, run a 100’ tape across the stream (perpendicular to flow) (Figure
6).
Figure 6. 100’ tapes stretched across the surface of the water, with depth measurement
locations identified.
4. At regular intervals (e.g. 1’ intervals), measure the depth to the stream bed along both
100’ tapes.
5. Each section of the stream will have a length (distance between 100’ tapes), a width
(the interval distance), and a height (distance between the water level and the
streambed). This will allow you to calculate volume for each section (LxWxH) and derive
an average volume for the stream.
6. If you have a flow meter, simply measure stream velocity at 60% of the depth at each
measured interval (Figure 7). Once you have measurements at each interval, you can
average them for a stream velocity average.
7. If you do not have a velocity meter, try the float test! Find a bright colored, floating
object (apple, orange, grapefruit, tennis ball, etc.) and throw it above the upstream
tape. Record the time necessary for the object to float from the upstream tape to the
downstream tape. Repeat five times and find the average time.
Page 5
Figure 7. Measuring stream velocity for a moderately sized stream with a velocity meter.
8. Though it is tempting to say this is the flow rate, it is not. Because the streambed is not
perfectly flat, there will be more turbulence at the bottom of the stream than at the
water surface (Figure 8). This means we must account for this turbulence by multiplying
the recorded float time by a constant. For our purposes, multiplying by 0.8 is sufficient
(though this should change depending upon the actual streambed components).
Figure 8. Turbulence at the streambed can reduce water velocity considerably relative to the
smooth water at the stream surface. To get an average stream velocity, either measure at 60%
of the depth of the stream with a velocity meter or, if using the float method, multiply the time
necessary to travel from the upstream tape to the downstream tape by 80%.
9. Once you have the volume of the stream calculated and the time necessary to travel,
you can determine volume per unit time (which is flow). For example, if you find that
your volume measurements average out to be 10’ L x 8’ W x 1.7 ‘ H, your measured
volume is 136 ft3. If it took 6 seconds for your apple to float down the 10 feet between
tapes, your adjusted time is 4.8 seconds (6 x 0.8). This means that your flow rate
estimate on this stream is 28.3 ft3/s (136 ÷ 4.8).
You are now ready to put your flow value into the hydro power formula!
Page 6
Example worksheet:
Group 2
Group members: Tara, John, Steve, and Michelle
Distance from upstream line to downstream line
12 feet
Distance across upstream line
5.2 feet
Distance across downstream line
4.9 feet
Number of sectors on upstream line
4
Number of sectors on downstream line
4
Sector spacing
1 feet
Upstream
Sector
Downstream
Depth
Sector Depth
Average
Sector
Depth
Average
Sector
Volume
1
1.5
1
2.3
1
1.725
1
20.7
2
2.2
2
3.4
2
3.74
2
44.88
3
3.1
3
1.9
3
2.945
3
35.34
4
1.1
4
2.3
4
1.265
4
15.18
Average stream volume
29.025
cubic feet
Recorded Float Times
Float
Time (s)
1
6.5
2
7.5
3
7
4
7
5
6
* note: 1 ft3/s = 448.8 GPM;
Average float time
Flow Rate:
6.8 seconds
4.3 cubic feet per second
0.121 cubic meters per second
1915.8 gallons per minute
1 ft3/s = 0.0283 m3/s
Page 7
Estimating Hydro Power
If we assume that the flow and head measured were for a small stream, we can measure
expected power output. We do not want to take all of the water from the stream, let’s assume
that we will divert only 10% of the water. Since we measured 1916 GPM, we can safely divert
approximately 192 GPM into the penstock (0.012 m3/s). We measured a head of 67.7 feet (20.5
m). Since this is a high head, low flow system, we can use a Pelton-style runner with 89%
efficiency. What is our expected power output and our expected yearly energy from this
stream?
P=ηρgQH
In this case, our values are:
η = 0.89 (turbine efficiency)
ρ = 1000 kg/m3 (water density)
g = 9.81 m/s2 (acceleration of gravity)
Q = 0.012 m3/s (estimated flow rate)
H = 20.5 m (estimated head)
If we plug these values into the formula, we get:
P = 0.89*1000*9.81*0.012*20.5 = 2147.8 Watts
Since we know there are 1000 Watts in 1 kilowatt, we have 2.1 kW expected form this system.
Recall that energy is power * time, so to get yearly energy:
24 ℎ𝑜𝑜𝑜𝑜𝑜𝑜𝑜𝑜 365 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑
2.1478 𝑘𝑘𝑘𝑘 �
��
� = 18,814 𝑘𝑘𝑘𝑘ℎ/𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦
𝑑𝑑𝑑𝑑𝑑𝑑
𝑦𝑦𝑦𝑦𝑦𝑦𝑦𝑦
A typical home uses between 8,400 and 12,000 kWh per year, so this small stream could easily
power 1-2 homes (or 4-5 energy efficient homes).
Page 8
Summary of Comments on Biofuel Resources
Overview
Biofuel Resources:
Overview
6/18/2009
1
Overview

U.S. Energy sources
Biomass defined
Plants and solar energy storage
Bioenergy defined
Biomass energy sources/supply
Dedicated bioenergy crops: food vs. fuel
Biomass conversion processes/pathways
(general)
6/18/2009
2
Page: 3
Number: 1
Author: Presenter
Subject: Presentation Notes
Date: 6/18/2009 8:54:15 AM
I usually give a quick, general introduction on energy use, dependence on fossil fuels, energy security, etc. The main
points here are: most of our current energy use is fossil fuel-based, and renewable energy represents a small
percentage of the total (6%). It is interesting to note that biomass represents almost half of the renewable energy
sources. Most people think of wind and solar, but those are currently pretty small contributions. Biomass has a
significant role to play in our energy future…
1
U.S. Energy Sources
…a fossil-fuel dependent country (>85%)!
Source: (2005) http://www1.eere.energy.gov/biomass/pdfs/final_billionton_vision_report2.pdf
Page: 4
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:15 AM
Q: What is biomass? Is it renewable? Why/why not?
Q: What is the primary source of energy for biomass (and most renewable energy resources)? SUN!
Q: How is energy from the sun captured by plants? Photosynthesis!
1
Biomass

Living matter (dead or alive); any organic
matter which is available on a renewable or
recurring basis
A tiny, but critically important % of earth’s
matter
For humans, an enormous energy supply
Continually replenished by the SUN
› Through the process of: PHOTOSYNTHESIS
6/18/2009
4
Page: 5
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:15 AM
Basic plant biology stuff: Plants use sunlight, carbon dioxide and water to make sugars (e.g., glucose: C6H12O6), the
building block/energy source for plant “parts”!
1
Review of Photosynthesis
Conversion of light energy
into chemical energy by
living organisms
CO2
6 CO2 + 6 H2O
H2O
C6H12O6 + 6 O2
6/18/2009
5
What are sugars used for in plants?

Primary cell walls
› Microfibrils (500,000 cellulose chains, cellulose
molecules are >6,000 sugars long)

Secondary cell walls
› Much thicker than primary walls
› Cellulose microfibrils, hemicellulose, and lignins

Starch
› Food storage in seeds (endosperm)
6/18/2009
6
Page: 7
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:18 AM
Sugars and the energy stored in them are used to make plant compounds, most of which are used for plant support
structures (cell walls, as indicated on the previous slide). From a chemical standpoint plants are organic (composed
mostly of C, H, and O). The processes we use to access the energy stored in plants rearrange the C, H, and O into more
convenient, “energy dense” forms. One of the first steps to make plant material more energy dense is to remove the
water (~75% for many green plants)…more on processing later.
1
Figure 12.2 (from Brady and Weil 2002): “Typical composition of representative green-plant materials. The major types
of organic compounds are indicated at left and the elemental composition at right. The “ash” is considered to include
all the constituent elements other that carbon, oxygen, and hydrogen (nitrogen, sulfur, calcium, etc.).”
Typical composition of plant matter
Reference: Brady, N. C., and R. R. Weil. 2002. The Nature and Properties of Soils (13th Edition). Upper Saddle River,
NJ: Prentice-Hall, Inc.
dry
matter
25%
water
75%
Oxygen
42%
cellulose
45%
polyphenols
2%
fats & waxes
2%
sugars &
starch
5%
lignin
20%
protein
8%
Carbon
42%
hemicellulose
18%
Types of plant compounds
Hydrogen
8%
Ash
8%
Elemental composition of biomass
(Figures adapted from: Brady and Weil, 2002)
7
Page: 8
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:18 AM
Image and following text from Wikipedia (although we are generally hesitant to use Wikipedia as a reference, the
following is pretty good):
Cellulose is an organic compound with the formula (C6H10O5)n, a polysaccharide consisting of a linear chain of
several hundred to over ten thousand (1Ȕ4) linked D-glucose units.[1][2]. Cellulose is the structural component of the
primary cell wall of green plants, many forms of algae and the oomycetes. Some species of bacteria secrete it to form
biofilms. Cellulose is the most common organic compound on Earth. About 33 percent of all plant matter is cellulose
(the cellulose content of cotton is 90 percent and that of wood is 50 percent).[3]
1
Plant Biomass

Lignin (sometimes "lignen") is a complex chemical compound most commonly derived from wood and an integral part
of the cell walls of plants.[1] The term was introduced in 1819 by de Candolle and is derived from the Latin word
lignum,[2] meaning wood. It is the most abundant organic polymer on Earth after cellulose, employing 30% of nonfossil organic carbon[3] and constituting from a quarter to a third of the dry mass of wood. The compound has several
unusual properties as a biopolymer, not least its heterogeneity in lacking a defined primary structure.
Plants store solar
esis
energy through photosynthesis
as “sugars” such as cellulose and lignin.
› Cellulose is a polysaccharide (chain) of 6-carbon
sugars (e.g., glucose: see image above).
› Lignin is the substance, or “glue,” that holds cell
walls together.

When burned, these sugars break down and
release energy, giving off CO2, heat, and
steam…
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Page: 9
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:19 AM
The conversion of biomass to electricity, heat, steam, and (liquid) fuels, etc. is discussed later in more detail.
1
Bioenergy
Bioenergy,
or biomass energy, is
renewable energy from biological
sources
Biomass
energy can be converted into
electricity, heat, steam, and (liquid)
fuels
6/18/2009
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Page: 10
Number: 1
Author: Presenter
Image source: http://eo.ucar.edu/kids/green/images/carboncycle.jpg
Date: 6/18/2009 8:54:19 AM
Conceptually (ideally), the carbon dioxide produced by biomass when it is burned will be sequestered by plants
growing to replace the fuel. In other words, it is a cycle with zero net impact. It’s not always zero, but when compared
to fossil fuels, it’s a significant improvement (for carbon, as well as for pollutants like NOx and SOx)
1
Biomass: Carbon-neutral Energy?
The Carbon Cycle
http://eo.ucar.edu/kids/green/images/carboncycle.jpg
10
Page: 11
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:19 AM
There is an enormous amount of energy stored in land biomass (25,000 EJ total storage; EJ = Exajoules or 1018) and a
LOT of land biomass produced annually (400,000 Mt/yr; that’s 400,000 million tons per year!), which represents a huge
quantity of stored biomass energy (3000 EJ/yr). This is impressive when compared to the total amount of energy we
humans consume (the other small bars on the figure). Note: the US consumes about 103 EJ of primary energy
annually (you may have heard the often referenced statistics that the US population represents about 5% of the world
population but consumes about ¼ of the energy…).
1
Figure data reference: Boyle, Godfrey. 2004. Renewable Energy (2nd edition). Oxford University Press, 450 pages
(ISBN:0-19-926178-4)
Bioenergy Supply: Global Energy Comparisons
Annual Energy Storage or Use
(EJ/yr)
3500
3000
3000
25,000 EJ total storage in land biomass
400,000 Mt/yr land biomass produced
2500
2000
1500
1000
500
451
56
16
Biomass
Energy
Consumed
Food Energy
Consumed
0
Energy Storage Total Primary
by Land
Energy
Biomass
Consumption
(compiled data from Boyle 2004)
6/18/2009
11
Page: 12
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:19 AM
What are some of the biomass energy sources that we have available to us? This is a list of some of the most
common… can you think of others?
One of the key points of this slide: Other than the last item in the list, these are some type of “waste” or secondary
product derived from another process (co-products?). This is a good thing. It means we have energy resources
(previously underutilized) that are available to us, if we choose to utilize them.
1
Discussion point: Are they really wastes if we find value in them? These could be classified as wastes, but if they
become an energy supply, is it fair to call them wastes? Co-products is one term that has been proposed for them. This
argument may be harder to make for municipal solid waste (MSW)…it is still garbage! Some MSW facilities operate
“energy recovery” systems—OCRRA in Onondaga County is one local example.
Biomass Fuel Sources

biomass processing residues (e.g., from pulp and
paper operations)
agricultural and forestry wastes
urban wood wastes
municipal solid wastes
landfill gas
wastewater treatment gas
animal wastes
terrestrial & aquatic crops grown solely for energy
purposes: dedicated bioenergy crops
6/18/2009
12
Page: 13
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:22 AM
Renewable energy sources represent 6% of the total energy consumed in the US in 2005. 50% of those renewable is
biomass. Of that biomass 87% is wood!
Q: What do you think the sources of biomass are? What type of biomass contributes the most to that 50%?
1
Solar
1%
87% of the
biomass is wood
or wood
processing
residues
U.S.. Energy Consumption:
Renewables (6% of total)
by Source (yr. 2005)
Wind
3%
Hydro
41%
Biomass
50%
Geothermal
5%
U.S. Energy Consumption by Energy Source, 2001-2005 (Source: US Energy Information Administration www.eia.doe.gov, Accessed: 3/2008)
13
National Biomass Supply

Assessment of whether
land resources in the
U.S. could sustainably
produce over 1 billion
tons of biomass
annually =
Enough biomass to
replace ~30% of the
country’s petroleum
consumption
14
Page: 15
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:25 AM
The report concludes that the resource potential exists for more than 1 billion tons of biomass annually; however,
there are a number of challenges that must be overcome to realize that potential (see next slide).
The report found that there is over 1.36 billion tons from forest and agricultural land that is not currently being utilized:
368 M tons from forests
998 M tons from ag. land
1
15
Page: 16
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:25 AM
1 Billion tons of annual biomass is possible, but to meet that mark, these challenges have to be overcome…the last
item is probably the biggest one. $4/gallon gasoline is a good motivator, as we saw in 2008!
1
National Biomass Supply Challenges

Meeting targets for yield
increases
Improving production and
harvesting/transportation
efficiency
Connecting the potential
supply with end users
Changing attitudes of
producers
and consumers
6/18/2009
16
Page: 17
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:25 AM
The food vs. fuel issue has good potential for classroom discussion…
I suspect teachers (and students) with an agricultural background will have some understanding/familiarity with this
issue. Corn is an easy example to start this discussion, since it has been prominent in the media (and everyone is
familiar with corn).
1
Food vs. Fuel
A debate over scarce resources
A
farmer has a choice; grow corn to be used
as ethanol or as a food (human or cattle or…)
› Corn can serve as a biofuel (ethanol from the
fermentation of sugars)
› As a result, land is taken out of food production
which increases the price of corn on the food
market
› What should this farmer do?
6/18/2009
17
Page: 18
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:26 AM
The issue does not go away, even if we focus on a dedicated energy crop (like willow) that does not have a direct use
as food/feed. The land that is BEST suited for growing willow is the same land that is being used for agricultural crops!
Granted willow will survive on poorer sites, but it will grow bigger, better, faster, and cheaper on higher quality sites!
Also remember that low quality sites are often poorly drained sites…sites where access with large equipment is difficult
(you still need to be able to get on the site in the spring for site preparation and planting and late winter for
harvesting).
1
Food vs. Fuel
A debate over scarce resources
But,
what about a crop like willow?
› Ethanol production, combustion (heat)
gasification (heat+electricity)
› Willow grows best on which types of land?
› On which types of land do crops grow best?
› The food vs. fuel debate does not end with corn
or soybeans, but can be an issue for any
dedicated bioenergy crop
6/18/2009
18
Page: 19
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:35 AM
They are all energy sources, even the “rocks” (see photo descriptions below). Guess that energy source! Is it biomass or
not?
Photos:
TopLeft: Cedar logs (by P. Hofmeyer)
TopRight: Dairy manure lagoon (by B. Ballard)
BotLeft: Municipal solid waste (Source: National Renewable Energy Laboratory, Photographic Information Exchange;
http://www.eia.doe.gov/cneaf/solar.renewables/page/mswaste/msw.html)
BotRight: Raw oil shale crushed for retorting; Uinta Basin, Utah. Source: Source: Argonne National Laboratory (http://
ostseis.anl.gov/guide/photos/index.cfm)
1
Bioenergy,
gy or not?
Yes!
Yes!
Yes!
No!
19
Page: 20
Number: 1
Author: Presenter
Q: What is energy density?
Q: What is volumetric energy density?
Date: 6/18/2009 8:54:35 AM
This concept can be demonstrated/explored further in the woodgas camp stove experiment(s)
1
Abundant, renewable vs.
Energy Dense?

Biomass is a great renewable energy source.
However, it is typically not a good
(unprocessed) fuel, because it often contains
more than 70% air/void space.
This results in a low volumetric energy density
makes it difficult to collect, ship, store and use.
20
Page: 21
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:35 AM
Table from various sources, primarily Appendix A of “Thermal Data for Natural and Synthetic Fuels” (Gaur and Reed,
Dekker, 1998) as reported on: http://www.woodgas.com/densification.htm (Last accessed: 6/14/2009)
Notes paraphrased from http://www.woodgas.com/densification.htm :
Volume energy density, (kJ/liter, MJ/m3 , Btu/ft3) is an important factor for biomass (biofuel). Most biofuels are
relatively light. Therefore, volume has important implications for collecting, shipping, storing and using biomass. The
table above illustrates the dramatic difference between high density and low density biomass fuels. The dense biomass
fuels are 3 to 4 times heavier than wood chips, though not as dense as coal or diesel.
1
Biomass Energy Density
FUEL
Bulk Density
(kg/liter)
Mass Energy Density
(MJ/kg)
Volume Energy Density
(MJ/liter)
0.19
20
3.8
0.54
20.5
11.1
0.68
20
13.6
Peanut shell pellets (3/8”)
0.65
19.8
12.9
Corn
0.76
19.1
14.5
Softwood chips
(“Denver dry”, 7% MCWB)
Coconut shell
(broken to ¼” pieces)
Sawdust pellets (¼”)
(Home Depot)
Soybeans
0.77
21 (?)
16.2
1.1 (?)
32.5
35.7
Biodiesel
0.92
41.2
37.9
Diesel
0.88
45.7
40.2
Coal
(bituminous)
(Source: Gaur and Reed, Dekker, 1998)
21
Page: 22
Number: 1
Author: Presenter
Date: 6/18/2009 8:54:35 AM
To continue the discussion of what bioenergy resources are available, we also need to consider how we can access/
utilize that energy source. We have many energy needs, as indicated in the slide. There are many conversion pathways
that we could take to meet those various needs. See additional notes below… This slide (or the next) is a convenient
jumping off points for the “wood gasification” activity/experiments.
Following notes from: http://www.woodgas.com/conversion_paths.htm (last Accessed on 6/14/09; some edits):
1
This chart traces the various routes available for biomass conversion to fuels, chemicals, or heat. Sunlight plus carbon
dioxide, water, and nutrients makes the biomass originally. Biomass can occur naturally or be raised for food or forest
products. Much of the available biomass is a by product of these activities. If the biomass is relatively dry (wood,
municipal solid waste, etc.) it is a candidate for the thermal conversion processes, pyrolysis, gasification or combustion;
if very wet it is more suited to the biological processes digestion or fermentation. Processes are available for
converting biomass to fill all our human needs.
Paths of Biomass Energy Conversion
SUNLIGHT
Carbon Dioxide
Water
Land (nutrients)
PRODUCT FARMING (existing)
ENERGY FARMING (potential)
Agriculture Ɣ Silviculture Ɣ Industry
Aquaculture Ɣ Silviculture Ɣ Agriculture
Farm & Forest
Products
Municipal
Wastes
BIOMASS FOR ENERGY
Residues
maceration
drying & densification
BIO-CONVERSION PROCESSES (Wet)
Extraction
Digestion
Fermentation
& Distillation
THERMAL CONVERSION PROCESSES (Dry)
Gasification
air
Chemicals
Methane
Ethanol
Low-BTU gas
Pyrolysis
Liquefaction
Combustion
Oil Ɣ gas Ɣ
charcoal
Oil Ɣ gas
Heat
systems
oxygen
Med-BTU gas Ɣ methanol Ɣ ammonia
Needs:
CHEMICALS
GASEOUS FUELS
(adapted from: Solar Energy Research Institute, 1988)
LIQUID FUELS
SOLID FUELS
ELECTRICITY
HEAT
22
Contact Information
Ben Ballard, Ph.D.
Director, RETC
Assistant Professor
Ph: 315-684-6780
Assistant Professor
Ph: 315-684-6515
Summary of Comments on Gasification
Wood Gasification
1
Overview – Wood Gasification

Renewable fuel resources: Wood/biomass
Utilization of wood resources: sustainability
Conversion methods/processes/technologies
What is gasification? Pyrolysis? Combustion?
Gasification applications: past, present, future
Intro: The woodgas camp stove
Optional topics/concepts: themodynamics,
efficiency, energy density
2
Page: 3
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:38 AM
I usually give a quick, general introduction on energy use, dependence on fossil fuels, energy security, etc. The main
points here are: most of our current energy use is fossil fuel-based, and renewable energy represents a small
percentage of the total (6%). It is interesting to note that biomass represents almost half of the renewable energy
sources. Most people think of wind and solar, but those are currently pretty small contributions. Biomass has a
significant role to play in our energy future…
NOTE: It may be useful to utilize the “Biofuel Resources: Overview” presentation before/in conjunction with this
presentation.
1
U.S. Energy Sources
…a fossil-fuel dependent country (>85%)!
Page: 4
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:42 AM
Pose the question to the class: Why use wood as a fuel?
Discuss/explore their level of understanding of natural resources/renewable resources.
presentation.
1
Aside: the photo is Viburnum lentago (nannyberry) – a very old shrub (>75 yrs.). We probably don’t want to start using
nannyberry as a biofuel, since it grows quite slowly (and the wood has a very aromatic—some say foul—odor)! (Photo
by B. Ballard)
Why use wood as a fuel?
4
Page: 5
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:47 AM
Q: What is are the characteristics of a renewable energy source?
Discuss/explore their level of understanding of renewable resources/energy.
Q: Are all renewable energy sources sustainable? (leads into next slide, but you can see if/what they know and then
proceed)
1
Define: Renewable Energy
Renewable Energy:
› Energy flows which are replenished at the
same rate that they are used
› Sources that are continuously replenished
by natural processes
Q:
Are all renewable energy sources
sustainable?
Page: 6
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:47 AM
These are relatively self-explanatory. However, “social injustices” may not be obvious. You can use an example such as:
the displacement of millions of Chinese people who by the building of the Three Gorges Dam—large-scale hydro may
be renewable, but the environmental and (negative) social impacts are tremendous! There are positive social benefits
too, of course, but from the perspective of the people that lost their homes...
Discussion Q: Is wood a sustainable resource? Why or why not? Renewable? Pollution, environmental problems?
Health hazards? Other?
1
Definition based on: Boyle, Godfrey. 2004. Renewable Energy (2nd edition). Oxford University Press, 450 pages
(ISBN:0-19-926178-4)
Sustainable Energy Defined
An
energy source that:
› Isn’t significantly depleted by continued
use (i.e., renewable resource),
› Doesn’t cause significant pollution or
other environmental problems, and
› Doesn’t perpetuate significant health
hazards or social injustices
(Boyle 2004)
Page: 7
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:47 AM
Q: What is biomass? Is it renewable? Why/why not?
Q: What is the primary source of energy for biomass (and most renewable energy resources)? SUN!
Q: How is energy from the sun captured by plants? Photosynthesis!
presentation.
1
The Fuel Resource: Biomass

Living matter (dead or alive); any organic
matter which is available on a renewable or
recurring basis
A tiny, but critically important % of earth’s
matter.
For humans, an enormous energy supply.
Continually replenished by: the SUN
Through the process of:
PHOTOSYNTHESIS
Page: 8
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:48 AM
To continue the discussion of what bioenergy resources are available, we also need to consider how we can access/
utilize that energy source. We have many energy needs, as indicated in the slide. There are many conversion pathways
that we could take to meet those various needs. See additional notes below… This slide is a convenient jumping off
points for the “wood gasification” activity/experiments. Our focus will be on the circled thermo(-chemical) processes…
which could potentially address all of the needs listed on the bottom of the slide, depending on the application of
gasification/pyrolysis processes we choose.
1
Following notes from: http://www.woodgas.com/conversion_paths.htm (last Accessed on 6/14/09; some edits):
Paths of Biomass Energy Conversion
This chart traces the various routes available for biomass conversion to fuels, chemicals, or heat. Sunlight plus carbon
dioxide, water, and nutrients makes the biomass originally. Biomass can occur naturally or be raised for food or forest
products. Much of the available biomass is a by product of these activities. If the biomass is relatively dry (wood,
municipal solid waste, etc.) it is a candidate for the thermal conversion processes, pyrolysis, gasification or combustion;
if very wet it is more suited to the biological processes digestion or fermentation. Processes are available for
converting biomass to fill all our human needs.
SUNLIGHT
Carbon Dioxide
Water
Land (nutrients)
PRODUCT FARMING (existing)
ENERGY FARMING (potential)
Agriculture Ɣ Silviculture Ɣ Industry
Aquaculture Ɣ Silviculture Ɣ Agriculture
Farm & Forest
Products
Municipal
Wastes
BIOMASS FOR ENERGY
Residues
maceration
drying & densification
BIO-CONVERSION PROCESSES (Wet)
Extraction
Digestion
Fermentation
& Distillation
THERMAL CONVERSION PROCESSES (Dry)
Gasification
air
Chemicals
Methane
Ethanol
Low-BTU gas
Pyrolysis
Liquefaction
Combustion
Oil Ɣ gas Ɣ
charcoal
Oil Ɣ gas
Heat
systems
oxygen
Med-BTU gas Ɣ methanol Ɣ ammonia
Needs:
CHEMICALS
GASEOUS FUELS
(adapted from: Solar Energy Research Institute, 1988)
LIQUID FUELS
SOLID FUELS
ELECTRICITY
HEAT
8
Page: 9
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:48 AM
There are many potential sources of low-grade wood, especially in NY and much if the northeast. AND: It’s renewable!
It’s local! It’s abundant (but caution to keep it sustainable).
Wood chips can be used directly, as depicted in this photo taken at the Lyonsdale Biomass (NY) combined heat and
power (CHP) plant.
1
Photo by: B. Ballard
Fuel Sources: Low-grade wood
9
Page: 10
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:49 AM
Example of a dedicated woody biomass crop: willow plantation (towards the end of the first growing season of
planting).
We can grow woody crops specifically for energy. Willow has many desirable characteristics that make it a good
candidate for a bioenergy crop (e.g., see: http://www.esf.edu/pubprog/brochure/willow/willow.htm OR http://
www.esf.edu/willow/).
1
Photo by: B. Ballard
Dedicated Bioenergy Crops
10
Page: 11
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:50 AM
Chips from wood residues or dedicated bioenergy crops can be densified at collection/processing facilities (second
photo shows the pellet presses). You could discuss why pelletization is desirable (handling/transport/storage,
consistency of the fuel, moisture, energy density, etc.). These photos were taken at the New England Wood Pellets
facility in Schuyler, NY.
You could also discuss the jobs associated with fuel procurement, processing, shipping, etc. You could also discuss the
jobs associated with the design, manufacturing, installation, and servicing of combustion devices (stoves, boilers, etc.).
Local jobs are important! Local energy supplies help ensure energy security (e.g., reduce dependence on foreign oil).
1
Photos by: B. Ballard
Feedstock for gasifiers: wood pellets
Page: 12
Number: 1
Author: Presenter
More detailed notes on the next slide…
1
What is gasification?

A process that converts carbon-based
materials (e.g., wood/biomass) into
combustible gases (principally CO + H2) by
reacting the solid fuel at high temperatures
with a controlled (limited) amount of oxygen
12
Date: 6/18/2009 9:25:50 AM
Page: 13
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:50 AM
Background information for Instructor: (Excerpt from: http://gekgasifier.com/forums/showthread.php?t=9 (last
accessed 6/17/09))
Gasification is best thought of as a process of staged combustion. It is a series of thermal events put together in a
controlled manner, so as to produce an output gas with combustion potential.
1
The 4 processes of gasification.
Gasification is made up for 4 discrete thermal processes: Drying, Pyrolysis, Combustion and Reduction. All 4 of these
processes are naturally present in the flame you see burning off a match, or on a piece of firewood. Gasification is
merely the technology to pull apart and isolate these separate processes, so that we might interrupt the "fire" and pipe
the resulting fuel gas elsewhere so as to make fire in a place other than directly on top of the wood.
Two of these processes tend to confuse all newcomers to gasification. Once you understand these two processes, all
the others pieces fall in place quickly. These two non-obvious processes are Pyrolysis and Reduction. Here's the quick
cheat sheet.
Pyrolysis:
Pyrolysis is the application of heat to raw biomass, in an absence of air, so as to break it down into charcoal and
various tar gasses and liquids.
Biomass begins to "fast decompose“ once its temperature rises above around 240C. The biomass breaks down into a
combination of solids, liquids and gasses. The solids that remain we commonly call "charcoal". The gasses and liquids
that are released we collectively call "tars".
The gasses and liquids produced during lower temp pyrolysis are simply fragments of the original biomass that break
off with heat. These fragments are the more complicated C, H and O molecules in the biomass that we collectively
refer to as volatiles. As the name suggests, volatiles are "reactive". Or more accurately, they are less strongly bonded in
the biomass than the fixed carbon, which is the direct C to C bonds.
Thus in review, pyrolysis is the application of heat to biomass in the absence of air/oxygen. The volatiles in the biomass
are "evaporated" off as tars, and the fixed carbon-to-carbon chains are what remains--otherwise known as charcoal.
Reduction:
Reduction is the process stripping of oxygen atoms off completely combusted hydrocarbon (HC) molecules, so as to
return the molecules to forms that can burn again. Reduction is the direct reverse process of combustion. Combustion
is the combination of an HC molecule with oxygen to release heat. Reduction is the removal of oxygen from an HC
molecule by adding heat. Combustion and Reduction are equal and opposite reactions. In fact, in most burning
environments, they are both operating simultaneously, in some form of dynamic equilibrium, with repeated movement
back and forth between the two states.
(Source: Jim Mason - http://gekgasifier.com/forums/album.php?albumid=2&pictureid=3 )
13
Reduction in a gasifier is accomplished by passing carbon dioxide (CO2) or water vapor (H2O) across a bed of red hot
char (C). The hot char is highly reactive with oxygen, and thus strips the oxygen off the gasses, and redistributes it to as
many single bond sites as possible. The oxygen is more attracted to the bond site on the C than to itself, thus no free
oxygen can survive in its usual diatomic O2 form. All available oxygen will bond to available C sites as individual O,
until all the oxygen is gone. When all the available oxygen is redistributed as single atoms, reduction stops.
Through this process, CO2 is reduced to CO. And H2O is reduced to H2 and CO. Combustion products become fuel
gasses again. And those fuel gasses can then be piped off elsewhere to do desired work elsewhere.
Comments from page 13 continued on next page
Here are two graphics which summarize the situation. The first shows the chemical transformations that happen in
Reduction. And the second shows the input and outputs for each of the 4 main processes of gasification.
(if these do not show up, you can find them in the album here: http://gekgasifier.com/forums/album.php?albumid=2 )
Last edited by jimmason; 03-22-2009 at 03:30 AM.
13
Page: 14
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:50 AM
Most student can relate to combustion/burning of a gas such as propane or natural gas (methane). Combustion of
biomass is more complex, since it involves several processes occurring simultaneously (evaporation, pyrolysis,
combustion, reduction—see the match example on subsequent slides). I suggest starting with something less
complicated than biomass combustion…e.g., propane (C3H8) gas combustion.
Ask the students:
Q: What do we need for combustion to occur?
[A: fuel + oxygen (+ ignition source)]
Q: Remember? combustion=oxidation (“adding oxygen”)
1
What is combustion?
Q: In this photo, what is burning?
[Likely response: gas; it’s actually propane gas (C3H8)]
Q: What happens to propane (C3H8) when it is combusted?
A: When we combust a gas like propane, we add oxygen and release energy (heat and light; it is an exothermic
reaction) plus carbon dioxide and water vapor (if combustion is complete; i.e., there is enough oxygen provided). If
combustion is incomplete (not enough O), the reaction will also yield CO + H.
Note: If the source of oxygen is air, then nitrogen (N2) will also be produced (though it does not impact the reaction).
Fuel + Oxygen Æ HEAT + Water + Carbon dioxide
C3H8 + 5O2
Æ HEAT + 4H2O + 3CO2
Limit O2 Æ HEAT + H2O + CO2 + (CO + H2)
(both combustible )
14
Page: 15
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:51 AM
(Excerpt from: http://gekgasifier.com/forums/showthread.php?t=9 (last accessed 6/17/09))
Reduction:
Reduction is the process stripping of oxygen atoms off completely combusted hydrocarbon (HC) molecules, so as to
return the molecules to forms that can burn again. Reduction is the direct reverse process of combustion. Combustion
is the combination of an HC molecule with oxygen to release heat. Reduction is the removal of oxygen from an HC
molecule by adding heat. Combustion and Reduction are equal and opposite reactions. In fact, in most burning
environments, they are both operating simultaneously, in some form of dynamic equilibrium, with repeated movement
back and forth between the two states.
1
Reduction in a gasifier is accomplished by passing carbon dioxide (CO2) or water vapor (H2O) across a bed of red hot
char (C). The hot char is highly reactive with oxygen, and thus strips the oxygen off the gasses, and redistributes it to as
many single bond sites as possible. The oxygen is more attracted to the bond site on the C than to itself, thus no free
oxygen can survive in its usual diatomic O2 form. All available oxygen will bond to available C sites as individual O,
until all the oxygen is gone. When all the available oxygen is redistributed as single atoms, reduction stops.
Through this process, CO2 is reduced to CO. And H2O is reduced to H2 and CO. Combustion products become fuel
gasses again. And those fuel gasses can then be piped off elsewhere to do desired work elsewhere.
.
.
.
Last edited by jimmason; 03-22-2009 at 03:30 AM.
15
Page: 16
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:51 AM
As mentioned on a previous slide, combustion of biomass is fairly complex...but you can explore this at the level you
feel is most appropriate for your students.
Q: In this photo, what is burning?
[Likely response: Wood]
1
Q: What part of the wood…what else is burning?
[Possible answers: gases, oils, tars]
What is combustion?
16
Page: 17
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:51 AM
What else is burning?
Closest to the matchwood, pyrolysis (pyro=fire, lysys=split or decompose) uses the heat from combustion to release
oil vapors from the wood to form char. In the presence of oxygen (and heat) the char (Carbon) is then converted to CO
and H. Both combustible gases! Also, oil vapors, tars, other hydrocarbons are either combusted or released as smoke.
Note: smoke is an indicator that combustion is not complete—smoke = inefficient combustion process!
1
What is combustion?
Flaming combustion
CO2 + H2O
(via heat from flame above)
(via heat from flame above)
(Solar Energy Research Institute, 1988)
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Author: Presenter
Date: 6/18/2009 9:25:53 AM
Biomass can be gasified pyrolytically (i.e., without oxygen) by heating to >400 C, yielding also 25% charcoal and LOTS
of condensible tars). These tars are not desirable if we are interested in utilizing the gases produced. Therefore, most
gasification systems utilizes a limited/metered amount of oxygen to yield a higher quality, lower tar product (also
called producer gas).
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Gasification is a thermo-chemical process, where
flammab gases.
heatt converts solid biomass into flammable
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Date: 6/18/2009 9:25:54 AM
“Four processes” adapted from: http://woodgas.nl/GB/woodgasification.html (last accessed 6/12/09)
Excerpt from: http://www.distributeddesign.net/tiki-index.php?page=Gasification
Gasification in a Nut Shell
The gist of the process is as follows. Heat from combustion is applied to biomass fuel. The heat performs three
different functions depending on its intensity. Firstly, in the coolest part of the system, the fuel dries out. Then as the
fuel heats up further, a process called pyrolysis takes place. In pyrolysis gases are driven out of the biomass leaving
behind predominantly carbon in the form of char. The hottest process, know as Reduction takes place when the
cocktail of really hot gasses from pyrolysis swirl round the super hot char and the two inter-react with one another in
full blown gasification to create “Woodgas” which with any luck can then be put to work.
Gasification is a very efficient method for extracting energy from carbon rich organic materials and there are many
technologies for achieving it; but here we will only discuss gasifiers that use combustion to provide the heat they need
and ‘breath’ air to provide the oxygen for that combustion.
The process of gasification is a thermo chemical process, which uses heat to convert carbonaceous materials into
gaseous components. The gas is referred to by several different terms including “Producer gas”, “Syn-gas” and
“Woodgas”. Woodgas is the name I will try to stick to because Woodgas excludes fuel sources derived from fossil or
liquid fuels and the point here is that we want to make use of “waste” biomass.
When “woody” fuels are heated to temperatures of approximately 600-1000°C, the solids undergo thermal
decomposition, and become gas-phase products and these typically include carbon monoxide, hydrogen, methane,
carbon dioxide, and steam. Along with these gases solid char (charcoal) and tars are also formed. The remaining
products of these processes are ashes.
The chemistry of gasifaction is complicated and there are several separate processes involved and though they are all
distinct phases they will tend to overlap and intermingle depending on scores of factors but that’s what makes it so
interesting.
1
Gasification consists of four processes:
1. Drying - by using heat (supplied by burning some
of the wood), water evaporates from the wood.
2.
Pyrolisis - above 270°C (heat supplied by
burning some of the wood) the wood structure
breaks apart chemically. Long molecules are
made smaller. Charcoal/char and tar-oil gases
are created.
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Date: 6/18/2009 9:25:54 AM
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3.
Combustion (oxidation) – (with a limited/controlled
supply of air, this process is also referred to as
“flaming pyrolysis” in a gasifier)
› part of the carbon (char) is oxidized (burned) to
form carbon dioxide (CO2), and
› Hydrogen (H) is oxidized to form water (H2O).
› A lot of HEAT is released (temperatures up to
1400°C !). This heat is necessary for the next
step…
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Author: Presenter
Date: 6/18/2009 9:25:54 AM
Summary of the chemical reactions (also from http://woodgas.nl/GB/woodgasification.html)
Oxidation, produces energy:
C + O2
CO2
1
H2 + 0.5 O2
4.
Reduction - In the reduction area several key
conversions take place, and these require
significant HEAT
›
›
›
H2O
Reduction, takes away energy:
C + CO2
2CO
C + H2O
CO + H2
CO2 + H2
C + 2H2
CO + 3H2
Carbon (char) reacts with CO2 and converts it to
carbon monoxide (CO).
Carbon also reacts with H2O, “stealing” an oxygen
atom producing carbon monoxide and hydrogen
gases.
Some of the char (C) also binds with H to create
methane, and some CO reacts with H to form
methane + water.
21
CO + H2O
CH4
CH4 + H2O
Page: 22
Number: 1
Author: Presenter
Date: 6/18/2009 9:25:55 AM
Note to those building this woodgas camp stove (directions provided in another part of this module): A larger tin can
may be used, though the close-fitting 15-oz. size works well, because it limits the air intake from above (between the
two cans). This can be an important consideration, because if the burner air ports are located above the outside tin can
“sleeve”, then the entire combustion/pyrolysis process proceeds too rapidly due to increased draft (more air less
pyrolysis/woodgas produced, more “complete” combustion). This can result in temperatures hot enough to melt the
bottom of the aluminum can!
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The following discussion is more of a FYI than something that you would use with your HS students…also, these are my
(Ben’s) current interpretations/understanding of the gasifier. While working on my PhD, my major professor would
often remind me: “you are an expert if you know 10% more than your audience does”. So, depending upon my (your)
audience…
Gasification Reaction Zones
What is an “inverted downdraft gasifier”? To answer this question it is helpful to look at two basic types of gasifier
designs: updraft and downdraft.
Updraft gasifiers are lit from the bottom of the fuel stack, fuel is added from the top, and air is drawn up through vents
at the bottom for (partial) combustion of the fuel. Hot gases and tars from partial combustion (pyrolysis) rise up
through the fuel stack. Updraft gasifiers typically produce large amounts of tar, since the gases cool as they rise
through the fuel and tars condense/are not destroyed.
Downdraft gasifiers are also lit from the bottom of the fuel stack, and air (from inlets/ports) and hot gases and tars
(from pyrolysis) are pulled/sucked down through the combustion/flaming pyrolysis zone—this “cracks” the tars formed
from pyrolysis of the wood/fuel.
The batch-loaded camp stove looks similar to an updraft gasifier, except the fuel is lit from the top, which does not
allow the gases and tars from pyrolysis to be cooled. Instead, the heat from flaming pyrolysis rises, reducing the
amount of tars produced (and any combustible gases and tars are immediately combusted at the burner at the top of
the stove). Therefore, the camp stove functions more like a downdraft gasifier with regard to where the hot gases and
tars travel through the system relative to the flaming pyrolysis zone and the unburned fuel. Hence the name, “inverted
downdraft gasifier”.
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Date: 6/18/2009 9:25:55 AM
Excerpt (with minor edits) from: http://www.woodgas.com/gasification.htm (last accessed 6/15/09)
Biomass can be gasified pyrolytically by heating to >400 C, yielding also 25% charcoal and LOTS of condensibles: tars).
Or it can be gasified with air to make "producer gas" (typically CO 22%; H2 18%; CH4 3%, CO2 6% and N2 51%). OR it
can be gasified with oxygen to make synthesis gas (typically 40% CO, 40% H2, 3% CH4 and 17% CO2, dry basis) which
can be used to make methanol, ammonia and diesel fuel with known commercial catalytic processes (e.g., FischerTropsch).
1
What is woodgas?
Typically woodgas consists of:
22% carbon monoxide (CO)
18% hydrogen (H2)
3% methane (CH4)
6% carbon dioxide (CO2)
51% nitrogen (N2)
.
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Author: Presenter
Date: 6/18/2009 9:25:55 AM
During World War II over a million gasifiers were in use (primarily by the civilian sector, while the military used the
petrol). For a more comprehensive history of woodgas, refer to:
1
Gasification Applications

Gasification is not a newly discovered
process…
It was used in the past for heating, lighting,
and vehicle fuel.
During World War II over a million gasifiers
were in use!
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Number: 1
Author: Presenter
Date: 6/18/2009 9:25:56 AM
Source: National Academy of Sciences, 1983 "Producer Gas: Another Fuel for Motor Transport“
(This document is available free from books.google.com)
For more history information/references, see: http://www.woodgas.com/history.htm
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Wood Gasification: Mobile Apps.

Vehicle modifications included:
› 1) a gas generator, 2) a gas reservoir, and 3)
carburetor modifications and additional plumbing
to convey, filter, and meter the gas into the engine
(Source: National Academy of Sciences, 1983 )
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Number: 1
Author: Presenter
Date: 6/18/2009 9:25:58 AM
Source: National Academy of Sciences, 1983 "Producer Gas: Another Fuel for Motor Transport“
(This document is available free from books.google.com)
For more history information/references, see: http://www.woodgas.com/history.htm
1
(Source: National Academy of Sciences, 1983 )
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Author: Presenter
Date: 6/18/2009 9:25:58 AM
Book is available online at: http://www.gengas.nu/byggbes/index.shtml (there are other sites also…)
Construction of a Simplified Wood Gas Generator for Fueling Internal Combustion Engines in a Petroleum emergency.
2nd Edition by BEF PRESS by: H. LaFontaine, Biomass Energy Foundation, lnc. Miami, Florida and F. P. Zimmerman, Oak
Ridge National laboratory, Energy Division FEMA lnteragency Agreement Number: EMW-84-E-1737 Work Unit: 3521 D
for: Federal Emergency Management Agency Washington, D.C. 20472 "This report has been reviewed in the Federal
Emergency Management Agency and approved for publication. Approval does not signify that the contents necessarily
reflect the views and policies of the Federal Emergency Management Agency." Date Published: March 1989 APPROVED
FOR PUBLIC RELEASE: DISTRIBUTION UNLIMITED Prepared by: Oak Ridge National laboratory Oak Ridge, Tennessee
37831-6285 for the U.S. Department of Energy.
GASIFICATION
1
Construction of a Simplified Wood Gas Generator for Fueling Internal Combustion
Engines in a Petroleum Emergency (book produced by the Federal Emergency
Management Agency, 2nd ed. 1989)
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Author: Presenter
Date: 6/18/2009 9:25:59 AM
Some more recent mobile applications. To avoid any potential copyright infringement on the photos from these sites,
we are just providing the URL so you can find your way to them:
http://woodgas.nl/GB/woodgasification.html
“Around Sweden with Wood in The Tank” Vovlo conversion: http://www.vedbil.se/indexe.shtml
Less refined, but interesting Chevy truck conversion: http://www.whatiamupto.com/gasification/woodgastruck.html
Other nice photos of Finnish gasifiers: http://www.ekoautoilijat.fi/tekstit/kalustoesittely.htm
1

Some interesting, more recent conversions…
http://www.whatiamupto.com/gasification/woodgastruck.html
some very nice looking…lots of stainless steel:
1968 DeLeuxe equipped Volvo 142
http://www.vedbil.se/indexe.shtml
http://www.whatiamupto.com/gasification/woodgastruck.html
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Author: Presenter
This slide sets up the need for more efficient wood stoves…
Date: 6/18/2009 9:26:00 AM
Half of humanity cooks over wood fires (the poorer half), a lot of wood is used…
Q: Why is this problematic? [A: last bullet]
1
Other Woodgas Applications

Half of humanity cooks over wood fires
Nearly half the world's wood supply is used as
fuel.
PROBLEMS: Wood fires cook slowly, the smoke
causes glaucoma and lung diseases, fires can
burn children, fires burn too much fuel,
requiring that wood be gathered from greater
and greater distances.
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Author: Presenter
Date: 6/18/2009 9:26:00 AM
This paper is the basis for the woodgas camp stove activity that accompanies this module.
1
Small Stationary Applications

A Wood-gas Stove For Developing Countries
(Reed and Larson, 1996)
› 300g (0.7 lbs.) of sticks or chips
burn for 30-45 minutes at high
efficiency with low emissions
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Author: Presenter
Date: 6/18/2009 9:26:04 AM
For those wishing to experiment at a scale larger than a woodgas camp stove, there is an “open source” engineering
project developed and maintained by ALL Power Labs in Berkeley, CA: The Gasification Experimenter's Kit (GEK) which
can be found at: http://www.gekgasifier.com/
They sell kits (completely assembled, or in various stages of fabrication). They also provide free plans online.
1
Gasification Experimenter’s Kit (GEK)

Experimentation at a larger
scale than a woodgas
camp stove…
Stationary or mobile
applications
“Open source” engineering
project developed and
maintained by ALL Power
Labs in Berkeley, CA
http://www.gekgasifier.com/
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Author: Presenter
Date: 6/18/2009 9:26:06 AM
This may be more detail than you want to include in your class, but I put it here for your consideration/reference.
The main point here is that these large-scale systems are technically possible, but they require a lot of biomass to run
them, and they are expensive to build (large capital investment).
Excerpt from: http://www.woodgas.com/small_gasifiers.htm
Gasifiers are usually rated in kW (or Horsepower) of output, either kWth or kWel and vary from . If you have a large
quantity of biomass (ie MSW) you might like a 100 ton/day unit which would yield about 20 MWthermal or about 4
MWelectric at 20% efficiency. Could cost you $10 Million (at $2000/kW capacity). These large gasifiers can be fixed bed
(updraft or downdraft), fluidized bed,...
1
Large-scale Gasification Applications

Large gasifiers can be
fixed bed (updraft or
downdraft) or fluidized
bed gasifiers.
Large quantity of
biomass (e.g., MSW): a
100 ton/day unit would
yield about 20 MWthermal
or about 4 Mwel (at
20% efficiency of
thermal to electric)
BUT, expensive: $10M
($2000/kW capacity)
http://www.woodgas.com/small_gasifiers.htm
32
Biomass Gasification

Conversion efficiencies vary depending on the
size and sophistication of the system used
› Some applications are 80-90% (e.g., wood
gasification boilers)

Large-scale gasification plants have not proven
financial viability (yet)
BUT, the potential exists for production of:
› Electricity from biomass-fed gas turbines
› Liquid fuels (methanol, Fischer Tropsch diesel) as
petroleum substitutes
› Hydrogen or other fuel for fuel cells
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Author: Presenter
Date: 6/18/2009 9:26:07 AM
This could be used as the Summary slide. You could discuss each of these points in more detail and explore some
other concepts.
Demonstrate efficiency through an example:
Q: What usually happens when you start a fire? What is one of the common outputs from a fire?
[A: smoke]
1
Q: What is smoke?
A: An intermediate combustion product such as tars and oils (think tiny droplets)—so smoke is an indication of
incomplete combustion and inefficiency. (Smoke is also a significant pollutant.)
Why is gasification important?
Q: Why are liquid/gaseous fuels more versatile?
A: Easily transported/stored (usually), often more energy dense (more energy in a given volume of fuels: could use
wood vs. wood pellets vs. charcoal—this could be done with a simple experiment with woodgas camp stoves)
Benefits include:
Gasification technologies are typically more
efficient than traditional combustion
technologies. No SMOKE!
Gaseous fuel can be produced from a solid
fuel, resulting in a potentially more versatile
fuel
Small- to large-scale applications
Mobile or stationary applications
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Author: Presenter
Date: 6/18/2009 9:26:09 AM
We have compiled a list of potential demonstration and experiments for use with the woodgas stove—most of these
are presented with the basic idea/concepts/questions. They could be readily tailored/expanded upon for your
particular students/course.
1
Woodgas Camp Stove “Lab”

Build and test a woodgas stove
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Author: Presenter
Date: 6/18/2009 9:26:11 AM
These are provided for instructors that would like to expand/tailor the gasification module for a particular class (e.g.,
physics, chemistry…thermodynamics). The slides on energy density are important—worth looking at if you choose to
have the students do that experiment with different fuels in the woodgas stove.
1
Other concepts to
incorporate/consider
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Author: Presenter
Q: What is energy density?
Q: What is volumetric energy density?
Date: 6/18/2009 9:26:11 AM
This concept can be demonstrated/explored further in the woodgas camp stove experiment(s)
1
Abundant, renewable vs.
Energy Dense?

Biomass is a great renewable energy source.
However, it is typically not a good
(unprocessed) fuel, because it often contains
more than 70% air/void space.
This results in a low volumetric energy density
makes it difficult to collect, ship, store and use.
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Author: Presenter
Date: 6/18/2009 9:26:11 AM
Table from various sources, primarily Appendix A of “Thermal Data for Natural and Synthetic Fuels” (Gaur and Reed,
Dekker, 1998) as found at: http://www.woodgas.com/densification.htm (Last accessed: 6/14/2009)
Notes paraphrased from http://www.woodgas.com/densification.htm :
Volume energy density, (kJ/liter, MJ/m3 , Btu/ft3) is an important factor for biomass (biofuel). Most biofuels are
relatively light. Therefore, volume has important implications for collecting, shipping, storing and using biomass. The
table above illustrates the dramatic difference between high density and low density biomass fuels. The dense biomass
fuels are 3 to 4 times heavier than wood chips, though not as dense as coal or diesel.
1
Biomass Energy Density
FUEL
Bulk Density
(kg/liter)
Mass Energy Density
(MJ/kg)
Volume Energy Density
(MJ/liter)
0.19
20
3.8
0.54
20.5
11.1
0.68
20
13.6
Peanut shell pellets (3/8”)
0.65
19.8
12.9
Corn
0.76
19.1
14.5
Softwood chips
(“Denver dry”, 7% MCWB)
Coconut shell
(broken to ¼” pieces)
Sawdust pellets (¼”)
(Home Depot)
Soybeans
0.77
21 (?)
16.2
1.1 (?)
32.5
35.7
Biodiesel
0.92
41.2
37.9
Diesel
0.88
45.7
40.2
Coal
(bituminous)
(Source: Gaur and Reed, Dekker, 1998)
38
Laws of Thermodynamics
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Number: 1
Author: Presenter
Date: 6/18/2009 9:26:19 AM
This is really a trick question. When we say “Turn off the lights when you leave the room. We need to conserve
electricity!”, we are actually not using the word “conserve” the same way as in the 1st law. When we are talking about
conserving electricity in the quote above, we usually mean “wise use” of electricity.
1
1st Law of Thermodynamics

In any transformation of energy from one form
to another, the total quantity of energy remains
unchanged (energy is always conserved)

Why then do we say: “Turn off the lights when
you leave the room. We need to conserve
electricity!”?
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Number: 1
Author: Presenter
Date: 6/18/2009 9:26:19 AM
Q: Why? A: We always lose some energy as heat in the energy conversion process.
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2nd Law & Conversion Efficiency

There is a limit to the efficiency of any heat
engine.
Useful energy output < energy input
Why?
EFFICIENCY =
(useful output)/(required input) × 100%
Page: 42
Number: 1
Author: Presenter
Date: 6/18/2009 9:26:19 AM
Note: This type of figure is called a Sankey diagram – a flow diagram where the width of the arrows is proportional to
the (energy) flow quantity.
The purpose of including this Sankey diagram is to demonstrate the inefficiency (“lost energy”) of our energy systems:
about 58% is “lost” (i.e., 59.3 EJ/103 EJ x 100% = 58%)
1
You can then relate this back to the 1st and 2nd laws of thermodynamics, among other things!
Contact Information
Ben Ballard, Ph.D.
Director, RETC
Assistant Professor
Ph: 315-684-6780
Assistant Professor
Ph: 315-684-6515
Woodgas Module
Overview: This module is designed to provide students with hands-on experience with biomass
gasification using the “woodgas camp stove”.
1. Build a simple gasifier (woodgas camp stove)
2. Demonstrate the safe use of hand tools
3. Describe the basic process of wood gasification
4. Explain one or more ways that wood gasification is more efficient than “traditional”
combustion of wood
Concepts/processes: gasification/pyrolysis, ventilation (air/oxygen) and combustion, energy
density, efficiency (relate to smoke)
Module duration: 2-3 hours with both the PowerPoint presentations and a camp stove activity
(can be broken into multiple class periods if necessary)
PowerPoint presentations: annotated slides are provided.
Wood gas camp stoves:
Materials and supplies required for each student (pair of students; most tools can be shared
between 1-2 pairs/groups):
1. 12-oz aluminum soda/beverage can
2. 14.5 to 16-oz “tin” can (e.g., a soup can, large enough to nest a soda can in; other sizes
will work and can be experimented with)
3. 4” Scratch awl (or comparable tool—can be fabricated from 1” dowel and a deck
screw—screw into dowel, then cut head and sharpen)
4. 7/16" x 5" Center Punch (or comparable tool—can be fabricated by sharpening the end
of a metal bolt)
5. Hammer
6. 3/16" dowel (cut to ~6" length, sharpened with a pencil sharpener)
7. Swing-a-way hand-operated can opener (can be shared between 1-2 groups/pairs)
8. 12” Ruler (optional)
9. Sharpie marker (dark color)
10. Fuel: wood pellets, nut shells, dry branches (broken into small pieces), charcoal, coal,
etc.
11. Fire starter gel (enough to coat 6-8 wood pellets (or other biomass fuel))
12. Bottle (e.g., prescription bottle) to mix gel and fuel in (optional)
13. Lighter (instructors will probably want to wield the lighter…)
14. Gloves and safety glasses (for working with metal and hot stoves/pans)
15. Data sheet for recording information (1 per group)
16. Options for “something to cook” or heat up: pot/can of water (tea or cocoa, soup),
marshmallows (with toothpicks to cook with), etc.
17. Gallon metal can with a piece of welded wire mesh (suggested, to shelter the stoves and
provide something to place a cooking pot on)
Page 1
Woodgas Module
Instructions: Although the Woodgas Camp Stoves “visual instruction guide” is fairly selfexplanatory, the following instructions can be used in conjunction with the included visual
guide. Be sure to read the caution statement and other notes at the bottom of the visual
instruction guide.
1. Assemble the necessary materials and tools as outlined above.
2. Start by turning the aluminum soda can upside down. Mark vent hole locations using a
permanent marker. A total of 12 to 15 vent holes generally works quite well. Be sure to
be careful using the awl (they are sharp!). Use a hammer to tap the awl.
3. Using a permanent marker and a ruler mark a reference line approximately 1 inch from
the top of the aluminum can for the burner air inlet ports. Different arrangements
(number and spacing) of inlet ports can be used. 10 air inlet ports seem to work quite
well. The red and blue scale printed along the edge of the first page of the “visual
instruction guide” can be used for a 10 port arrangement.
4. Using the awl, carefully punch the air inlet holes. This is best done by hand (without the
use of a hammer, since the sides of the aluminum can will tear easily). You can expand
the air inlet holes using a sharpened wood pencil or a dowel. A diameter of 3/16” (0.5
cm) works quite well.
5. The final step with the aluminum can is the removal of the top. After all your hard work
punching holes, be sure to take your time using the can opener to remove the top. Once
you've removed the top, set the aluminum can aside.
6. Now take the “tin” can and remove any paper label (if still attached). Then mark out five
vent hole locations. One should be in the bottom (center) of the can. The other four
holes can be placed around the perimeter of the base of the can. Using a hammer and a
center punch, carefully make the vent holes.
7. Next, assemble the stove: nest the aluminum soda can snugly inside the soup can. The
aluminum soda can should rest on the bottom of the tin can. If necessary, use the awl to
bend the sharp edges of your air vent holes in the tin can so they do not puncture the
aluminum can or prevent the aluminum can from being properly seated on the bottom
of the tin can.
8. Select a fuel source, preferably a renewable biomass fuel! Measure out the quantity
(mass or volume) that you plan to use. The stove’s maximum capacity is about ½ inch
below the burner air inlet ports.
9. Load the fuel into the aluminum can.
10. Select a smokeless, non-explosive starter gel (or lamp oil).
11. Coat or soak 6 to 8 pellets in the starter gel/oil and then load them on the top of the
fuel in the aluminum soda can.
12. Before igniting the fuel in the soda can, be sure you are in a well ventilated area,
preferably outdoors (or a chemistry lab with a ventilated hood), far enough away from
flammable or explosive materials (general fire safety rules apply). If doing this
experiment/demonstration outdoors, it is useful to place the camp stove inside a gallon
can (see step#14 photo). A layer of small gravel can be placed in the bottom of the
gallon can to ensure ventilation at the bottom of the camp stove. The fuel in the wood
gas camp stove should be ignited from the top of the fuel in the aluminum soda can.
Page 2
Woodgas Module
13. After a couple of minutes, the wood gas camp stove should begin to produce gas, and
flames should appear at the burner air inlet ports. As the gas production proceeds, the
color and quality of the flame will change.
14. If you used a gallon can to shelter your camp stove, a section of welded wire mesh can
be placed over the top of it to hold a small pot, and you can boil some water for a hot
beverage or soup!
15. Eventually the camp stove will stop producing gas, and it will shift over to a charcoal
burn.
16. The charcoal burning provides excellent heat for toasting marshmallows!
Other experiments: There are many options available for expanding the wood gas camp stove
demonstration. Here are some suggested experiments (and questions) that can be conducted
using the wood gas camp stove (in increasing complexity):
“Experiment” 1 (Demonstration, as outlined above): Build and run the stove on wood pellets. It
is a dramatic and fascinating demonstration for most people, especially kids: the solid fuel at the
bottom of the can is separated from the combustion of the woodgas at the top of the can.
Experiment 2: Compare traditional combustion (e.g., a “campfire”: small quantity of sticks in a
ventilated gallon can, light from the bottom, etc.) to gasification. Suggested questions:
Hypothesize which will burn longer using the same mass of wood? Why? Which will produce the
most smoke? Why? What is smoke made up of? Which do you think is most efficient at
converting an equal mass of wood to usable heat? Why? How could you test that (scientifically)?
[Possible approach: The time it takes to boil an equal volume of water (in identical containers),
and the length of time that the boiling is sustained—is a pretty well established approach, but
they may think of other approaches that would work.]
Experiment 3: Try several ventilation and/or burner designs (e.g., modify air inlet: size, shape,
number, locations/height). Example questions: What designs did you try (sketch, describe)? Why
did you select those designs? How did they work in comparison to the “standard” 10-inlet
burner design? What criteria did you use for comparison (e.g., length of gas burn, time needed
to boil water, duration of water boiling, color or type of flame output, robustness to breezes—
does one design work better in windy conditions?) and what were the outcomes?
Experiment 4: Built two identical stoves; select two different fuels: describe the fuels in terms of
their physical density, shape, size, moisture content, etc.; hypothesize what their relative energy
densities are (e.g., which will burn longer/boil water longer if you use the same volume of the
two fuels; alternatively, the same mass of the fuels). There are countless fuel combinations that
could be evaluated: wood pellets vs. nut shells, wood pellets vs. charcoal briquette, wood
pellets vs. anthracite (coal), rabbit droppings vs. commercial wood pellets, rabbit droppings vs.
pelletized rabbit feed! [Suggest/require that a standard/fair method for comparing the energy
output be used—e.g., the boiling water approach from the previous experiments].
Page 3
Woodgas Camp Stoves
R E N E WA B L E E N E R G Y T R A I N I N G C E N T E R
M O R R I S V I L L E S T AT E C O L L E G E
Carefully punch 12 to
15 vent/draft holes.
*You can use these bars to mark 10 evenly-spaced holes around the perimeter of the soda can.
Tools & supplies for making
a woodgas camp stove
Scale Bar = 1”
1
2
3
Punch and expand holes.
4
5
10 holes:
3/16” diam.
(0.5 cm), evenly
spaced*
Alternate burner designs:
Cut slits or punch holes.
Remove top.
Mark a reference line
about 1 inch from top
for burner air inlets.
6
Punch air vent holes in the tin can.
7
Assemble stove: nest cans by
seating soda can snugly in/on
bottom. The stove is now
complete!
These woodgas stoves are batch loaded, easy to build, fun to use, and nearly smokeless when properly fired. Our design is an adaptation of the "batch-loaded, inverted
down-draft gasifier" described by Ray Garlington (http://www.garlington.biz/Ray/WoodGasStove/) and based on Reed and Larson’s 1996 paper “A wood-gas stove for
developing countries”. For more “woodgas” information, see: http://www.woodgas.com/ . Note: any references to or images of commercial products or brands does not
constitute endorsement of any particular product or brand by the RETC; they are simply for illustration purposes.
Using the Woodgas Camp Stove
9
8
Load the fuel into the
soda can (maximum
level up to burner air
inlet ports).
10
Select a fuel: wood
pellets, chips, twigs,
nut shells, corn, etc.
11
Ignition source/lighter – light the top
of the fuel in soda can.
14
13
Starter gel/lamp oil
(smokeless, non-explosive)
Steps 12-17: Placing the
stove in a gallon can
with sand or gravel in
the bottom serves as a
windbreak and safety
measure (vent holes
optional). Wire mesh can
support a pot or pan to
cook, boil water, etc.
Test it out. Boil some water,
and enjoy a hot beverage!
Woodgas production & combustion
(shortly after ignition)
16
Charcoal burn
(after woodgas combustion ends**)
17
Make good use of the hot charcoal embers…toast some marshmallows!
15
Renewable Energy Training Center, Morrisville State College
12
Soak 6-8 pellets in starter
gel/oil and load them on top
of the fuel in the soda can.
CAUTION: Although these camp stoves generally burn cleanly and efficiently, if they are not fired properly, they can produce carbon monoxide (CO) gas and some smoke (tars). Carbon monoxide
is a significantly toxic gas, but it is difficult to detect because it is colorless, odorless, tasteless, and non-irritating. Therefore, stoves should only be used outdoors with adequate ventilation.
**After woodgas flames go out, there is typically a small amount of smoke (and potentially CO) produced for 30-60 seconds while the stove transitions to charcoal burning. New cans may also
produce unpleasant fumes during the first firing. These stoves are not toys! Adult supervision required. Never leave any fire unattended.
Gasification Reaction Zones in the
Woodgas Camp Stove
“Inverted Downdraft Gasifier”
Aluminum
Soda can
(12-oz.)
Woodgas
Combustion
Zone
Burner
air inlet ports
“Tin” Can
(15-oz.)
Rising
Pyrolysis Gas
“Woodgas”
Downward-burning
Flaming Pyrolysis
Zone
Ungasified
Fuel/Drying
Zone
Air in
Air in
Air in
Renewable Energy Training Center, Morrisville State College
Charcoal
“Reduction”
Zone
Summary of Comments on Fuel Cells – an
Introduction
Page: 1
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:07 AM
This presentation is designed to provide HS teachers with introductory teaching materials on fuel cells. We do not
cover all types of fuel cells (except a general overview). We make use of a simple “reverse electrolysis” experiment to
demonstrate the basic principle of the “fuel cells effect”.
1
Fuel Cells –
An Introduction
R E NEWABLE E NE RGY
T RAINING C ENTER
Overview

Batteries vs. Fuel Cells:
› storage vs. conversion devices

General overview of fuel cell types
Introduction to Dr. Schmidt’s fuel cell/”gas
battery” experiment (lab activity)
Relationship of the “gas battery” fuel cell effect
to PEM fuel cells
Challenges of fuel cells
Page: 3
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:08 AM
An electrolyte (a.k.a. and ionic solution) is any substance containing free ions that behaves as an electrically conductive
medium.
1
Batteries

A battery (or electrochemical cell):
› Two electrodes made of dissimilar metals, are
immersed in a conducting liquid electrolyte.

When you construct an electrochemical cell,
you create a voltage between two electrodes.
Current flows from the positive to negative
ive
t.
electrode until chemical changes stop it.
Page: 4
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:08 AM
Copper-zinc cell: Insert sheets of copper and zinc into beaker of dilute sulphuric acid (or even a lemon.)
Voltage of about 1 volt appears between the two electrodes. (Copper is positive.)
Chemical energy is stored in a battery, until it is connected to an external load (e.g., a light bulb).
1
Chemical Energy Storage

A battery is a store of chemical energy that can be
converted into electrical energy.
As electrode chemical reactions proceed,
chemical energy is converted into electrical
potential energy.
Chemical energy is exhausted
when reaction can proceed no further
› (e.g. when a Zn electrode is dissolved
in a sulfuric acid Cu and Zn cell.)
Page: 5
Number: 1
Author: Presenter
DC – direct current
Date: 6/18/2009 11:33:08 AM
Fuel cells are like electrochemical cells (batteries), but energy is stored in a gaseous form, not as electrodes of
dissimilar metals. Fuels are stored in separate containers and brought together in a reaction chamber (unlike a sealed
electrochemical cell containing electrodes and electrolyte). The fuel cell is not a storage device, but rather a conversion
device…
1
Fuel Cells (vs. Batteries)

Fuel cells are devices that convert fuel (such as
hydrogen, methane, propane, etc.) directly into
DC electricity.
The process is an electro-chemical reaction
similar to a battery.
Unlike a battery, fuel cells do not store the energy
with chemicals internally.
Instead, they use a continuous supply of fuel
(chemical) from an external storage tank.
Page: 6
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:09 AM
The beauty of a fuel cell (e.g., a PEM fuel cell) is that the input into the cell is oxygen, hydrogen (and electrons) and the
end product is water!
Image from: http://en.wikipedia.org/wiki/File:Pem.fuelcell2.gif (accessed 6/18/09)
1
Fuel Cells
O2 + 4e- + 4H+ j 2H2O
Image: http://en.wikipedia.org/wiki/File:Pem.fuelcell2.gif
18-Jun-09
6
What is a Fuel Cell?

Fuel cells are usually classified by the type of
electrolyte they use.

Most fuel cells are powered by hydrogen, which
can be fed to the fuel cell system directly or
can be generated within the fuel cell system by
reforming hydrogen-rich fuels such as
methanol, ethanol, and hydrocarbon fuels.
18-Jun-09
7
Page: 8
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:09 AM
This slide illustrates a Proton Exchange Membrane fuel cells or Polymer Electrolyte Membrane (PEM) fuel cell, which
uses a hydrogen fuel source (the conducting ion) and a Pt catalyst
Image from: http://en.wikipedia.org/wiki/File:Fc_diagram_pem.gif (last accessed: 6/18/09)
The following description is an adaption from Dr. Azmin’s introductory lecture on fuel cells (http://
material.eng.usm.my/stafhome/mariatti/EBP412/Lect1.FuelCellGeneral.PPT ;last accessed 6/17/09; Dr. Azmin’s personal
website can be found at: http://aazmin.com/).
1
The anode: conducts the electrons that are freed from the hydrogen molecules so that they can be used in an external
circuit. It has channels etched into it that disperse the hydrogen gas equally over the surface of the catalyst.
Chemistry of a Fuel Cell

The cathode: the positive side of the fuel cell, has channels etched into it that distribute the oxygen to the surface of
the catalyst. It also conducts the electrons back from the external circuit to the catalyst, where they can recombine with
the hydrogen ions and oxygen to form water.
The electrolyte: ion exchange membrane. The membrane blocks electrons. This specially treated material, looks similar
to ordinary kitchen plastic wrap.
Anode side:
2H2 Æ 4H+ + 4e-

Cathode side:
O2 + 4H+ + 4e- Æ 2H2O

Net reaction:
2H2 + O2 Æ 2H2O
The catalyst: is a special material that facilitates the reaction of oxygen and hydrogen. It is usually made of platinum
powder very thinly coated onto carbon paper or cloth. We will demonstrate the important role that the Pt catalyst
plays in the laboratory activity included in this module (using Dr. Schmidt’s experiment).
http://en.wikipedia.org/wiki/File:Fc_diagram_pem.gif
18-Jun-09
8
Page: 9
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:09 AM
*System efficiency depends on fuel type, fuel processing method, and manufacturer’s design
Notice that PEM fuel cells have several advantages: they are commercially available, have (relatively) lower cost, can
operate at much lower temperatures, and have stationary, portable and vehicle applications.
Aside: Ballard Power (no relation) is a company leading the PEM fuel cells industry.
1
Characteristics and applications of common types of fuel cells
Fuel Cell Type:
Proton Exchange Phosphoric Acid Molten Carbonate Solid Oxide Fuel
Membrane (PEM) Fuel Cell (PAFC) Fuel Cell (MCFC)
Cell (SOFC)
Operating
Temperature:
80°C
(200°F)
200°C
(400°F)
650°C
(1200°F)
600-1000°C
(1100-1800°F)
Expected Early
Market :
Available
1992
Reintroduction
(2007)
Pre-commercial
Available
(small systems)
20-45%
35-40%
40-60%
30-70%
0.1 – 250 kW
200-400 kW
250 kW – 3 MW
1 kW – 1 MW
Cost (est.) Cost
Target:
$1,500-4,000/kW
$25-50/kW
$6,000/kW
$1,800/kW
? $400/kW
? $400-$800 /kW
(2010)
Applications:
Stationary/
Stationary/CHP
Vehicles/Portable
Stationary/CHP
Marine
Stationary/CHP/
Portable
System Electric
Efficiency Ranges
(HHV)*:
Size Range:
Slide adapted from: Klein, 2006, University of Wisconsin-Madison
http://ecow.engr.wisc.edu/cgi-bin/get/me/370/klein/lecture/fuelcelllecture.pdf (last accessed 6/12/09)
(Adapted from: Klein, 2006, University of Wisconsin-Madison)
Page: 10
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:10 AM
We looked at many different options for an instructive and affordable fuel cell kit or experiment. Most commercially
available educational kits for fuel cells are expensive (hundreds of $), and they are not necessarily instructive (i.e., you
can’t actually see what is happening). The activity that we selected to share with you is a relatively inexpensive one. It’s
not one that we developed ourselves, but we have permission from the author to share it with you (and you can use it
for your classes). The most expensive parts are the platinum electrodes (~$15 per foot). We found some platinum
coated nickel wire that should do the trick. It’s still not cheap, but you could get set up for an entire class for less than
the cost of a single fuel cell model car kit.
1
Fuel Cell Fundamentals –
A Simple Experiment
R E NEWABLE E NE RGY
T RAINING C ENTER
Page: 11
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:15 AM
For detailed descriptions and instructions, please refer to the manual provided in you binder.
Link to the experiment manual: http://www.geocities.com/fuelcellkit/pdf/FC1101e.pdf
1
Simple Fuel Cell Experiment

“Discovering the principle of the fuel cell at
home or in school”, by Dr. Martin Schmidt
From: Dr. Martin Schmidt [mailto:fuelcellkit@yahoo.co.uk]
Sent: Wednesday, June 17, 2009 4:14 PM
To: Ballard, Benjamin
Subject: AW: request: fuel cell manual for educational use
Dear Professor Ballard,
I am very touched by your message. I gladly support your initiative to teach physical and chemical principles that lead
to an understanding of fuel cells. Feel free to reproduce data and copies in whatever form that support your
educational goals in New York State. It would be kind to mention my name and website.
Professor Schoenbein who published this experiment and its correct interpretation for the first time in 1839 was
German (like me) who settled down in Switzerland (like me). About 150 years later I re-invented this experiment (and
later re-discovered it) which is why I feel emotionally somehow attached to it. I feel privileged like Newton who stated,
referring to Galilei, that he could see further because he stood on the shoulders of giants. It taught me that it can be
good to go back to the roots to understand better.
With kind regards
Martin
Dr. Martin Schmidt
Physicist
fuelcellkit@yahoo.co.uk
See how to build your own fuel cell:
http://www.geocities.com/fuelcellkit/
--- Ballard, Benjamin <ballarbd@MORRISVILLE.EDU> schrieb am Mi, 17.6.2009:
Von: Ballard, Benjamin <ballarbd@MORRISVILLE.EDU>
Betreff: request: fuel cell manual for educational use
An: fuelcellkit@yahoo.co.uk
Datum: Mittwoch, 17. Juni 2009, 4:34
Dear Dr. Martin Schmidt,
http://www.geocities.com/fuelcellkit/pdf/FC1101e.pdf
We are working with a network of high school educators here in New York State on renewable energy and related
topics. We are providing these teachers with educational modules that include simple experiments and
demonstrations that they can incorporate into their classroom. We discovered your website and “gas battery”
experiment. We too were discouraged by the high cost of fuel cell kits. Your experiment is a much more economical
approach and provides an opportunity for students to actually see what is happening. Would it be acceptable to
reproduce and share your manual for this purpose? We would like to provide printed copies to them, as well as access
to the electronic file (if you prefer, we can direct them to your website for access to the electronic file).
Thank you for your time and consideration. Sincerely, Ben Ballard…
Supplies & Materials

Small glass with water and ½ to 1 tsp. table salt
Digital voltmeter
One 6 volt battery (4.5 or 6 volt battery works well)
Wire leads with alligator clips (4)
2 platinum wires as electrodes (most expensive part:
$15+ per foot!)
Optional:
› Rubber bands (to secure wires on the glass)
› Paper clips/pencil leads (alternate electrodes; control
experiments)
› Alternative energy source to “charge” the fuel cell
Definitions

Ions - charged particles that occur under the
influence of the polar water molecules.
› metals and hydrogen form positive ions (a
anions),
› non-metals form negative ions (ccations).

Example: when dissolved in water NaCl
(common salt) forms:
› Na+ (anion) and
› Cl- (cation)
Understanding electrolysis
To
carry out electrolysis it is necessary
to introduce two similar electrodes into
a solution (e.g., the salt water solution).
Page: 15
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:16 AM
Slide content and notes developed (with permission for reproduction of content) from: FUELCELLKIT (Dr. M. Schmidt),
which can be found at: http://www.geocities.com/fuelcellkit/ (last accessed: 6/18/09)
Notes:
Chemistry!
1
you may want to come back to this again later (or not!).
“AN OX”: Anode -- Oxidation
“RED CAT”: Reduction – Cathode
“LEO the lion says GER”: Lose Electron is Oxidation and Gain Electron is Reduction
Electrolysis reactions
Excerpt from FUELCELLKIT (Schmidt, 2000):
Cl- migrates to the positive electrode (anode), is discharged (give up an electron) and forms gas molecules (Cl2), which
rise to the surface as small bubbles.
Na+ migrates to the negative electrode (cathode) and is discharged there (takes up an electron). Sodium, a highly
reactive metal, is unstable in water and is immediately converted in a secondary reaction to sodium hydroxide (NaOH).
For this to happen, an OH- ion must be torn from the water (H2O), leaving an H+. The H+ ions join to form hydrogen
molecules (H2), which rise at the cathode as small bubbles.
The reaction products of the electrolysis of common salt solution are hence chlorine gas (Cl2) and hydrogen gas (H2).
Anode (+)
“RED CAT”
(Schmidt, 2000)
Cathode (-)
“AN OX”:
“LEO the lion says ‘GER’”
(FUELCELLKIT/M. Schmidt, 2000)
Initial setup – verify no voltage
Understanding electrolysis
To
carry out electrolysis it is necessary
to introduce two similar electrodes into
a solution (e.g., the salt water solution).
The
electrodes are connected to the
terminals of a source of direct current
(e.g. a battery).
Page: 18
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:16 AM
What happens when you apply the battery to the electrodes?
Can you smell the chlorine gas? The hydrogen gas has no odor, but you should clearly see the bubbles!
1
Electrolysis
Page: 19
Number: 1
Author: Presenter
It is also called a “gas battery” or “reverse electrolysis”
Date: 6/18/2009 11:33:16 AM
1
From electrolysis to the gas battery

If you remove the external voltage (battery)
from the electrolysis experiment, the rising gas
bubbles stop but many of them are left sticking
to the electrodes.
An electric voltage will still be measured on
such a cell even after the external voltage is
removed.
The fact that gas-covered electrodes can
supply electricity is the fuel cell effect.
Page: 20
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:16 AM
FUELCELLKIT/M. Schmidt, 2000: “But why does our gas battery work? We do not have different electrode materials and
hence no voltage should appear! This objection would be perfectly correct, were there not to be gas bubbles on the
electrodes as a result of the electrolysis. In our example of a salt solution, we in effect have a chlorine and a hydrogen
electrode, i.e. different electrodes. here we see a further important point: the chemistry takes place not in the electrode
but exclusively at its surface.”
1
Observe: The “fuel cell effect”
The platinum (Pt) acts as a catalyst (unlike zinc coated paper clips…try them to see). Pt is used as a catalyst in many fuel
cell applications (e.g., Proton Exchange Membrane Fuel Cells).
Refer to the “manual” for a complete description of the fuel cell effect, galvanic elements, etc.
Page: 21
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:16 AM
Solar cells? Wind turbine(s)? You may need to do some series (and parallel) circuits to get the voltage or amperage you
require.
1
Control Experiment/Others

Try paper clips as electrodes
Try pencil leads as electrodes

Do these function like the Platinum?

Other power supplies? Are there renewable
energy supplies that make sense? Can you
build one from the supplies in your kit?
Page: 22
Number: 1
Author: Presenter
Date: 6/18/2009 11:33:16 AM
Now that you have completed the experiment(s), can you identify the role that Pt plays in this PEM fuel cell?
This slide illustrates a Proton Exchange Membrane fuel cells or Polymer Electrolyte Membrane (PEM) fuel cell, which
uses a hydrogen fuel source (the conducting ion) and a Pt catalyst (on each electrode).
Image from: http://en.wikipedia.org/wiki/File:Fc_diagram_pem.gif (last accessed: 6/18/09)
1

Anode side:
2H2 Æ 4H+ + 4e-

Cathode side:
O2 + 4H+ + 4e- Æ 2H2O

Net reaction:
2H2 + O2 Æ 2H2O
http://en.wikipedia.org/wiki/File:Fc_diagram_pem.gif
Making the connection…
Platinum catalyst
18-Jun-09
22
Other resources for teaching:

There are many online resources for additional
fuel cell educational materials, research, etc.

One website that we recommend looking at for
resources for teachers and students is:
http://www.fuelcells.org/ced/education.html
Acknowledgements

We thank Dr. Martin Schmidt for graciously
sharing his instructional materials for the fuel
cell experiment.
Fuel Cells
Overview: This module is designed to provide students with hands‐on experience with a simple experiment that demonstrates the basic chemical/physical principles of a fuel cell. By the completion of this module, students will be able to: 1. Build a simple gas battery 2. Use a voltmeter 3. Describe the basic process of electrolysis and reverse electrolysis 4. Explain the main difference between batteries and fuel cells 5. Explain the role of platinum catalyst in a fuel cell (?) Concepts/processes: electrolysis, reverse electrolysis, fuel cell effect, catalysts Module duration: 2 hours with both the PowerPoint presentation and lab activity/experiment (can be broken into multiple class periods if necessary) PowerPoint presentation: Annotated slides are provided. These could be used in conjunction with the lab activity (during the same class, or in a prior class session). The PowerPoint presentation includes an overview of the experiment and makes the connection between the simple lab experiment and Proton Exchange Membrane (PEM) fuel cells, which typically use a platinum catalyst similar to that demonstrated in the lab experiment below. Fuel Cell Laboratory Activity: The Fuel Cells module has been developed primarily around a simple, relatively inexpensive experiment (as fuel cells kits/experiments go): “Discovering the principle of the fuel cell at home or in school” written by Dr. Martin Schmidt. Dr. Schmidt graciously agreed to allow us to utilize his “manual” and share it with you for educational use, which we have included in your module packet. Dr. Schmidt’s contact information and website address are provided below. Materials and Supplies  Small glass with water and ½ to 1 tsp. table salt  Digital voltmeter  One 6 volt battery (4.5 or 6 volt battery works well)  Wire leads with alligator clips (4)  2 platinum wires as electrodes (most expensive part: $15+ per foot!)  Optional: › Rubber bands (to secure wires on the glass) › Paper clips/pencil leads (alternate electrodes; control experiments) › Alternative energy source to “charge” the fuel cell Dr. Martin Schmidt Physicist fuelcellkit@yahoo.co.uk See how to build your own fuel cell: http://www.geocities.com/fuelcellkit/ (the activity we have included in this module) Page 1
Discovering the principle of the fuel cell at home or in school
Introduction
Fuel cells convert chemical to electrical energy. Engines and turbines with generator can also do this but
there is a lot more interest in fuel cells. It is reported that the latter have a much higher efficiency than
internal combustion engines and that the future of energy supply is unthinkable without them. In cars,
houses and wherever energy is required, they will be found in future in the same places and numbers as
car engines and single-storey heating are found today.
If this is true I think everyone should be better informed about this matter.
About the author
Dr. Martin Schmidt is a physicist and was head of marketing and sales with a company
that develops, manufactures and sells fuel cells. Of course he was often asked how
fuel cells actually work. He likes to answer such questions with an experiment, but it
irritated him that commercially available kits are expensive and uninstructive.
While studying historical reports he had the idea of reproducing the experiments of fuel cell pioneers
with very simple apparatus in order to make the principle of the fuel cell comprehensible. It was really
simple but nevertheless most instructive, and he considered that everybody who is interested in fuel
cells should be in a position to reproduce this experiment and understand it. In this way the idea arose
to create a website on the subject and to offer on it the only components that are are not readiy
available, the two platinum electrodes.
Objective
In the following the principle of the fuel cell will be explained in a simply way that will be understood by
everyone. We shall focus only on the basic electrochemical phenomena and not on today's technical
applications, about which one can read on numerous websites. The instructions are written for all
interested persons, even for those having little prior knowledge of the subject. Even if it may appear
somewhat long-winded to the specialist: please read everything first before experimenting!
A key objective is naturally to build oneself a fuel cell, originally referred to as a "gas battery". For
this purpose, two platinum wires are needed which act as electrodes. All other ingredients will be found in
the kitchen cupboard, tool-box or supermarket. This fuel cell is too weak to drive a lamp or motor. All
effects will only be seen on a voltmeter: they appear as quite a high voltage of about 1.4 V, i.e. they are
easily detectable. The small power output is a result of the low surface area of our platinum electrodes. If
you have larger quantities of platinum lying about at home, you can reproduce the small gas battery
described here on a larger scale. It will certainly work but will be extremely expensive. In this case, we
would rather advise you to buy a kit containing a higher power fuel cell which, however, will be quite
uninstructive since one cannot see how it works. Teachers who want to deal with the fuel cell in physics
or chemistry classes will want to have both: a small gas battery for eperimentation by the pupils and a
professional fuel cell that can do more work than just operate a voltmeter.
In the tracks of the researchers
In the second half of the 18th century and during the entire 19th century, scientists were fascinated by the
phenomena and possibilities of electricity. Quite early on already, researchers saw and described effects
which were to become the foundations of fuel cell development. Among the pioneers were:
http://www.geocities.com/fuelcellkit
1
© FUELCELLKIT 2000. Unauthorised reproduction prohibited.
MSC RETC - Reproduced with permission 6/18/2009
Ed.1101e
Alessandro Volta, Pavia
1745-1827
Johann Wilhelm Ritter, Jena
1776-1810
Christian Friedrich Schoenbein,
Basel
1799-1868
William Robert Grove, Oxford
1811-1896
Volta was the first to place the observations of the electrical phenomena on a scientific footing. Ritter
continued to develop the understanding of electricity up to his early death in numerous experiments and
today is considered to be the founder of electrochemistry. Schoenbein and Grove, who became friends
through their exchange of experiences, systematically researched what we nowadays refer to as fuel
cells. At that time they were still called gas batteries. This term is highly instructive and describes the
fundamental principle much better than the abstract designation fuel cell.
The experiments which Schoenbein conducted in the summer of 1838 in his institute at the University of
Basle can be easily understood and reproduced. The effects are strong and clearly visible, and various
sources report that Ritter had seen them too. However, at that time the most sensitive measuring
instruments were freshly prepared frogs' legs, one's own tongue or one's finger. Ritter reported in
February 1801 on experiments in which he exposed himself to frequent, intense electrical shocks.
Afterwards he felt ill, had to stay in bed for several days and even after 10 days did not feel well again. No
wonder that he no longer overloaded his "measuring instrument". Today we have a much easier time. We
no longer have to collect fresh frogs at dawn for our experiments or risk our own health, but can buy
inexpensive, highly sensitive digital multimeters in the hobby section of a supermarket.
In the following we shall approach the subject in simple steps.
Step 1: Understanding electrolysis
Fundamentals
Electrolysis, known at that time as "splitting of water", was especially fascinating to the researchers. An
electrolyte is a substance in which ions are present, in our case a solution in water. This can be an acid,
alkali or salt solution. Ions are charged particles that occur under the influence of the polar water
molecules, a process known as dissociation. Metals and hydrogen form positive ions, non-metals form
negative ions. The following table shows examples.
Substance in solution
H2SO4
NaOH
NaCl
Name
sulphuric acid
caustic soda
common salt
Positive ions (cations)
+
+
H ,H
+
Na
+
Na
Negative ions (anions)
2SO4
OH
Cl
To carry out electrolysis it is necessary to introduce two similar electrodes into the solution. They are
connected to the poles of a source of direct current (DC, e.g. a battery). The positively charged ions
2
Ed.1101e
(cations) migrate to the minus pole, also known as the cathode. The negatively charged ions (anions)
move to the plus pole (anode). On the electrodes the ions are discharged and are then present as neutral
particles (atoms or molecules). In this form they react with the chemical environment: they precipitate on
the electrode, escape upward as a gas or are involved in secondary reactions. This will be illustrated by
an example.
An important example
In the following a solution of common salt is always assumed, it being most easily prepared and
+
harmless. Common salt (NaCl), dissolved in water, dissociates to sodium ions and chloride ions (Na and
Cl ). Cl migrates to the positive electrode (anode), is discharged (give up an electron) and forms gas
molecules (Cl2), which rise to the surface as small bubbles. One can smell the chlorine gas (as in a
+
swimming pool with chlorinated water). Na , on the other hand, migrates to the negative electrode
(cathode) and is discharged there (takes up an electron). Sodium, a highly reactive metal, is unstable in
water and is immediately converted in a secondary reaction to sodium hydroxide (NaOH). For this to
+
+
happen, an OH ion must be torn from the water (H2O), leaving an H . The H ions join to form hydrogen
molecules, which rise at the cathode as small bubbles. The reaction products of the electrolysis of
common salt solution are hence chlorine gas (Cl2) and hydrogen gas (H2).
Step 2: From electrolysis to the gas battery
When one removes the external voltage source from our electrolysis experiment, the effervescence of the
rising gas bubbles stops but many of them are left sticking to the electrodes. J. W. Ritter is accredited
with the observation that an electric voltage could be measured on such a cell after the external voltage
had been detached. The fact that gas-covered electrodes can supply electricity is nothing other than the
fuel cell effect. One can also call it a gas battery or reverse electrolysis, or a special kind of galvanic
element.
Schoenbein carried out such experiments in 1838 in a systematic manner, interpreted them correctly and
published his results for the first time in January 1839 in the Philosophical Magazine. The elements that
produced electricity in his experiments were the electrode pairs hydrogen/chlorine and hydrogen/oxygen.
Hence we are actually following in the footsteps of the fuel cell pioneers! Let us look at the situation more
closely.
Step 3: Understanding galvanic elements
In the simplest case a galvanic element consists of the arrangement
ANODE - ELECTROLYTE - CATHODE.
Such elements allow chemical energy to be converted into electrical energy.
The best-known case is when anode and cathode are of different metals, e.g. copper (Cu) and zinc (Zn).
2+
The base metal, in this case Zn, corrodes: positively charged Zn ions go into solution, leaving electrons
2+
at the Zn electrode (which becomes a minus pole). When Zn ions precipitate on the Cu electrode, they
need 2 electrons for discharging. Hence there occurs a deficiency of electrons on the Cu electrode (which
becomes a plus pole). Such an electrical inbalance must be corrected. The electrons would prefer to
migrate in a direct path from the minus pole through the electrolyte to the plus pole, but an electrolyte
conducts only ions and not electrons, i.e. is an insulator for the latter. These must therefore make the
detour around an external circuit (and perform work for us) before the charges can be equalized.
The spontaneous (exothermic) corrosion reaction of the zinc thus provides us with electrical energy. All
the batteries we use in portable electrical or electronic appliances work basically according to this
principle.
Step 4: The gas battery as a galvanic element
But why does our gas battery work? We do not have different electrode materials and hence no voltage
should appear! This objection would be perfectly correct, were there not to be gas bubbles on the
electrodes as a result of the electrolysis. In our example of a salt solution, we in effect have a chlorine
and a hydrogen electrode, i.e. different electrodes. here we see a further important point: the chemistry
takes place not in the electrode but exclusively at its surface.
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Step 5: The gas battery as reverse electrolysis
On the gas-covered electrodes and in the electrolyte solution, the reverse reaction to electrolysis takes
place. As a result of the electrolysis, hydrogen and chlorine gas are present. These recombine to form
hydrochloric acid (HCl), a synthesis. Here, however, we must observe an important restriction: this
reaction can only take place when platinum electrodes are used. Without the catalytic effect of the
platinum surface, this reaction cannot proceed spontaneously (exothermally) at room temperature. The
scientific term here is heterogeneous catalysis.
Instructions for experimentation
Apparatus
·
·
·
·
·
one small glass with water and a knife-tip of common salt
one high impedance voltmeter with ranges of 0-2 VDC and 0-20 VDC (an inexpensive digital
multimeter from the hobby section of a supermarket will suffice; an old needle instrument will also do,
but the effects will be seen less clearly)
one 4.5 volt battery
experimental cables, preferably with small crocodile clips (the resourceful experimenter can do
without these cables but they are easier to work with)
2 platinum wires as electrodes
Experimental procedure: electrolysis and gas battery
·
·
A knife-tip of common salt is dissolved in water in a small vessel (glass or plastic). The solution is
turbid at first but will become clear after a while (better for observing what happens at the electrodes).
The two platinum wires (electrodes) are fixed at the edge of the glass (preferably by means of the
crocodiles clips on the cables). The platinum electrodes should not be too far from each other (a few
millimetres is ideal), but should not touch.
·
The platinum electrodes are connected to the
voltmeter (polarity is unimportant). The very first
time one will measure no voltage, even in the
most sensitive VDC range (except for small
effects from stray electromagnetic fields). On
repetition of the experiment, however, the
electrodes may be no longer identical
(adsorbed traces of gas from the previous
experiment) and one can already see very
small effects.
·
The voltmeter is switched to the 0-20 VDC range and the battery connected to the platinum
electrodes (plus to plus, minus to minus pole). One observes vigourous gas evolution at the
electrodes (the chlorine gas can be smelt when close enough). The gas mixture is in principle
explosive but the small quantities make the experiment harmless. The voltage of the battery is
measured on the voltmeter (between 4 and 5 V).
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·
The battery is disconnected, preferably without shaking the glass so that as many gas bubbles as
possible remain adhered to the electrodes. Now we have no more electrolysis but the voltmeter still
shows a voltage of about 1.4 V which slowly sinks (switch voltmeter to a more sensitive range as
needed). Our cell now functions as a gas battery or fuel cell! It is true that it cannot drive anything
other than a voltmeter, but the effect is clearly observable (for higher power, e.g. to drive a lamp or
motor, one needs larger vessels and greater electrode areas).
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·
By reconnecting the battery for a short time (after switching the voltmeter to a suitable range), one
can recharge the gas battery as often as desired and repeat the experiment.
Experimental procedure: modification
·
Acids and alkalis may also be used as the electrolyte (e.g. sulphuric acid, hydrochloric acid or caustic
soda) but this is dangerous because of the caustic nature of the substances. Don't do it! The effects
are not stronger than with the simple "common salt fuel cell". Instead try out some unusual
electrolytes like orange juice or vinegar. These organic acids are admittedly rather weakly dissociated
electrolytes but one still sees a clear, if rather weaker, effect.
Experimental procedure: control experiment
·
It was stated above that the catalytic effect of the platinum is a prerequisite that the fuel cell can
function at all. This can be proven by using electrodes having no catalytic effect. These could be
straightened paper-clips in the simplest case, but leads from refillable pencils are ideal because they
do not enter into any reactions whatsoever with the electrolyte or the reaction products. Repeat the
experiment with such electrodes (caution, they are fragile). One then sees evolution of gas at the
electrodes as before, but after disconnecting the battery the voltage is only very small. It is still a
galvanic element but not a gas battery or fuel cell. The changes to be seen in the short-time, very low
voltage are changes in the chemical environment of the electrodes: at the minus pole, as already
explained, a little caustic soda (NaOH) is formed and hence slightly changed local conditions arise.
This effect also occurs, by the way, at the platinum electrodes but it is masked by the much stronger
fuel cell reaction.
Theory
Introduction
Actually one could discover and explain the whole of electrochemistry through these simple experiments,
but we shall not go that far. A few fundamentals of basic electrochemical processes will nevertheless be
mentioned.
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Electrolysis
Anodic reactions
Electron release (oxidation)
Formation of chlorine (gas) molecule
Overall reaction
Cl -> Cl + 1 e
2 Cl -> Cl2
2 Cl -> 2 e + Cl2
Cathodic reactions
Electron acceptance (reduction)
Secondary reaction: formation of caustic soda
Formation of hydrogen (gas) molecule
Overall reaction
Na + 1 e -> Na
Na + H2O -> NaOH + H
2 H -> H2
+
2 Na + 2 e -> 2 NaOH + H2
-
-
+
-
Fuel cell reaction
This is practically the reverse reaction to electrolysis, the synthesis of hydrochloric acid. In the following,
0
+
the overall reaction, partial reactions and standard potentials E of the redox pairs H2/H and Cl2/Cl are
given.
Overall reaction
Electron acceptance (reduction)
Electron release (oxidation)
H2 + Cl2 -> 2 HCl
Cl2 + 2 e -> 2 Cl
+
H2 – 2 e -> 2 H
0
-
E (Cl2/Cl ) = 1.36 Volts
0
+
E (H2/H ) = 0 Volt (by definition)
The standard potentials are defined for normal conditions (normal pressure, room temperature, activities
= 1). However, one usually works under other conditions in a free experiment, particularly with
concentrations not corresponding to an activity of 1 (i.e. in an approximately 1 molar solution). This leads
in practice to somewhat different electrochemical potentials or voltages between the electrodes.
+
2If one were to conduct the experiment with the redox pairs H2/H and O2/O , the classic synthesis of
water from its elements, one would obtain a voltage of 1.23 V.
On close observation, one sees initially after disconnecting the battery a higher voltage than can be
explained by theory. It is about 2 V but very quickly drops to the expected value of 1.4 V. The probable
explanation is that the cell has a certain electrical capacity, as with a capacitor, that is able to store a part
of the electrical charge from the battery for a short time. It thus has nothing to do with the fuel cell effect.
The end result of all chemical reactions
By the way: you may have found it disturbing that we started from a common salt solution but ended up
with hydrochloric acid, i.e. complete reversibility is not obtained. This is, however, not the end of all the
reactions in our cell: since caustic soda was formed during the electrolysis, the following neutralization
reaction will occur after the fuel cell reaction (HCl synthesis):
NaOH + HCl -> NaCl + H2O
The end result is finally common salt and water, the starting products. In practice, the equation will not be
balanced exactly since during electrolysis bubbles of chlorine and hydrogen will be lost, and the
remaining gas is not reconverted fully during the fuel cell reaction. But in theory a closed system is
possible in which the sum of the starting products equals that of the end products.
Ecological aspects
Note 1
Our experiment is simple and instructive, but does not make ecological sense at all. A battery, in which
chemical energy is converted to electrical energy, is used to charge our gas battery and at the end we
obtain electrical energy again. But if we imagine obtaining the electrical energy to charge the gas battery
from wind power or a photovoltaic system, then sensible applications of the gas battery alias fuel cell can
be devised. We should then be dealing with a fuel cell that converts hydrogen. There exist many ideas, in
some cases experimental projects, on the subjects of hydrogen generation and storage, and naturally on
fuel cells.
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Note 2
There are different types of fuel cells that are distinguished by the type of electrolyte material and hence
the operating temperature. Not all require as a fuel pure hydrogen, which is extremely demanding with
respect to generation, transport and storage. The higher the operating temperature, the less critical is the
question of the fuel. High temperature fuel cells can be operated with natural gas or biogas without much
trouble. The higher the temperature, the less dependent one is on the participation of (usually very
expensive) catalysts in the basic chemical reaction. On the other hand, high operating temperatures
place very high demands upon the materials used, which is why only highly specialized companies can
offer feasible concepts and systems. Pioneer work in this field has been done especially by SiemensWestinghouse (USA) and Sulzer Hexis (Switzerland). In the (probably long) transition time to a hydrogen
economy, this type of fuel cell in particular is considered to be of great importance.
Note 3
Electrical energy is frequently generated by large power stations fuelled by fossil fuels. In this process, a
large part of the fuel energy appears as unused waste heat. This is unsatisfactory because the waste
heat also represents the consumption of primary energy and hence the generation of CO2. If one
complements this situation with stationary, decentralized systems that generate a part of the electrical
energy in the household itself, the waste heat can be utilized in a sensible manner. If one does not use
the waste heat (e.g. for the production of hot water), then the ecological advantage of a decentralized
system disappears. For this reason, some European countries prohibit the use of decentralized system in
residences merely for electricity generation. Stationary fuel cell systems that can be operated with natural
gas or heating oil have great advantages for this application: high efficiency, silent operation and low
maintenance and emissions.
In media such as the Internet one can find an increasing number of references to this subject.
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Contact Information
Ben Ballard, Ph.D.
Director, RETC
Assistant Professor
Ph: 315-684-6780
Assistant Professor
Ph: 315-684-6515