WOODCOTE VALLEY ROAD, PURLEY, CROYDON Mantle

Transcription

WOODCOTE VALLEY ROAD, PURLEY, CROYDON
10% RENEWABLE ENERGY REPORT
for
Mantle Developments UK Ltd
December 2011
Project no. 587
Woodc ot e Va l l e y Roa d, Pur l e y, Cr oydon
10% R enew able Ener gy R eport
WOODCOTE VALLEY ROAD, PURLEY, CROYDON
10% RENEWABLE ENERGY REPORT
Mantle Developments UK Ltd
DATE
REVISION
DATE
PREPARED BY
REVIEWED BY
COMMENTS
0
14/12/2011
Max Campbell
Mark Heptonstall
For Comment
1
20/12/2011
Max Campbell
Mark Heptonstall
PV modules moved to flat roof
2
21/12/2011
Max Campbell
Mark Heptonstall
PV modules mounted flat
The current report provides a brief overview of the wide range of opportunities for renewable energy
and is not intended as detailed design advice. As such data and information should only be treated
as INDICATIVE at this stage of the process. Further investigation can be undertaken when more
accurate and detailed information is required on specific measures.
No part of this document may be reproduced or transmitted in any form or by any means, in whole or
in part, without the written permission of C80 Solutions.
Whilst C80 Solutions has endeavoured to ensure that all information contained within this document
is correct, it cannot be held responsible for any inaccuracies within or problems arising out of the
use of this document.
C80 Solutions
Suite 2
Enterprise House
249 Low Lane
Horsforth
Leeds
LS18 5NY
1
E: mail@c80solutions.co.uk
W: www.c80solutions.co.uk
Contents
Page
1.0 Introduction ......................................................................................................... 4
1.1 About C80 Solutions ......................................................................................................... 4
1.2 Introduction to Development ............................................................................................. 4
1.3 Planning Policy ................................................................................................................. 5
1.4 Methodology..................................................................................................................... 6
2.0 Total Predicted Annual Energy Demand of the Development......................... 7
3.0 Baseline Carbon Emissions of the Development............................................. 9
4.0 Overview of Renewable Technologies ............................................................ 10
4.1 Wind Turbines ................................................................................................................ 10
4.2 Solar Photovoltaics (PV) ................................................................................................. 14
4.3 Solar Thermal ................................................................................................................. 17
4.4 ASHP (Air Source Heat Pump) ....................................................................................... 20
4.5 GSHP (Ground Source Heat Pump)................................................................................ 22
4.6 Biomass Boiler ............................................................................................................... 25
5.0 Feasibility Study of Renewable Technologies ............................................... 28
6.0 System Size to Provide 10% CO2 Reduction.................................................. 31
2
Tables
Table
Description
Page
1
Part L compliant construction specifications
7
2
Baseline Predicated Annual Energy Demand
8
3
Baseline Associated Carbon Emissions of the Development
9
4
Feasibility Study of Renewable Technologies
29
5
SAP Results and Amount of PV per Plot
31
6
Carbon Emissions of the Development with 6.5kWp Solar PV
33
7
Percentage Reduction in Carbon Emissions from 6.5 kWp Solar PV
33
Figures
Figure
Description
Page
1
Proposed Site Plan
5
2
Sectional diagrams of horizontal axis and vertical axis wind turbines
10
3
Example of a mast mounted wind turbine
11
4
Example of a roof mounted wind turbine
11
5
A solar PV Module
14
6
Solar PV array
14
7
Reduction in solar PV panel efficiency with angle and orientation
15
8
Solar irradiation map of the UK
15
9
Simple solar thermal installation diagram
17
10
Flat plate collectors
17
11
Evacuated tube collectors
17
12
ASHP
20
13
ASHP diagram
20
14
A ground source heat pump
22
15
Slinkies (coiled pipes) in a trench
22
16
Biomass boiler
25
17
Wood pellets
25
18
33
20
Proposed South West Elevation showing possible location of 14 PV panels
Proposed Roof Plan showing possible location of 12 PV panels mounted at
30 degrees on flat roof
Estimation of Solar PV System Performance
21
25 Year Feed-in Tariff Financial Calculation
36
19
34
35
3
1.0 Introduction
1.1 About C80 Solutions
C80 Solutions are independent Sustainability and Energy Consultants providing carbon
reduction solutions to help the UK achieve its carbon emission reduction target of 80% by
2050 - as set out in the Government's Climate Change Act 2008.
Our range of affordable but comprehensive solutions for the residential market are broken
down into two sectors; i) Compliance and ii) Consultancy.
Compliance:
Our Residential Compliance services include; Code for Sustainable Homes Assessments,
SAP Calculations, On Construction Energy Performance Certificates, Water Efficiency
Calculations and Air Tightness Testing.
Consultancy:
Our experience and exposure to residential compliance combined with previous
employment and IEMA accredited training means we have built up a vast amount of
experience and knowledge which enables us to provide our clients with invaluable advice.
Our Residential Consultancy services include; Renewable Energy Feasibility Studies,
Energy Statements, Code for Sustainable Homes ENE7 Reports, Part L Compliance
Reports and Feed-in Tariff reports.
1.2 Introduction to Development
C80 Solutions have been instructed by Mantle Developments to prepare a renewable
energy report for the proposed residential development on Woodcote Valley Road, Purley,
Croydon. The report will demonstrate how the predicted CO2 emissions from the
development will be reduced by at least 10% through the use of on-site renewable energy
technology.
The site is located in south London in the London Borough of Croydon. The site’s existing
use class is residential and it has some mature trees located on the site boundaries.
The proposed scheme is for 11 new build flats in a single 3 storey block built to achieve
code for sustainable homes level 4. The site also contains associated parking, cycle
storage and amenity space for the residents. The proposed site plan for the development
can be seen below in figure 1.
4
Figure 1: Proposed Site Plan
1.3 Planning Policy
Policy EP16 of the Croydon Unitary Development Plan states:
“The Council will encourage all developments to incorporate renewable energy, but will
require proposals for non-residential developments exceeding 1,000 square metres
gross floorspace, and new residential developments comprising 10 or more
units,
whether
new
build
or conversion, to incorporate renewable energy
production equipment to off-set at least 10% of predicted carbon emissions, except
where:
a) the technology would be inappropriate;
b) it would have an adverse visual or amenity impact that would clearly outweigh the
benefits of the technology; and
c) renewable energy cannot be incorporated to achieve the full 10%.
Where the 10% requirement cannot be achieved on major developments, a planning
obligation will be sought to secure savings through the implementation of other local
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renewable energy schemes.”
The reason for this condition is in the interests of sustainability and to minimize the impact
of the development on the effects of climate change.
1.4 Methodology
The methodology that has been applied in this report is as follows:
1. Prepare baseline SAP 2009 Calculations for the 11 dwellings based on the Part L
2010 compliant construction specification designed for the development. These
baseline calculations will not contain any form of renewable technology.
2. From the Part L compliant Baseline SAP calculations, the predicted energy demand
for the development in kWh/year can be established. Standard carbon emission
factors from SAP 2009 will be applied to this figure to ascertain the predicted CO2
emissions in kgCO2/year for the whole site before any renewable technology is
incorporated.
3. Multiplying the site wide predicted CO2 emissions figure by 10% will provide the
CO2 reduction target required from renewable technology. This target will be above
and beyond what is required to comply with Part L of Building Regulations since the
Baseline SAP calculations will already be complaint with Part L.
4. Carry out a renewable energy feasibility study to ascertain which LZC technologies
would be suitable for the development. A particular technology will be chosen by the
developer after presenting the suitable options.
5. The last stage is to establish the sizing of suitable renewable technologies to meet
the 10% CO2 emission reduction target. As the new build properties must achieve
code for sustainable homes level 4, a dwelling emission rate of 25% less than Part
L 2010 is a mandatory requirement. In this regard, an amount of renewable
technology will be entered into the Baseline SAP calculations until the 25%
emissions target has been achieved. A check will then be carried out to ensure that
this amount of technology provides the 10% CO2 reduction needed to satisfy EP16.
6
2.0 Total Predicted Annual Energy Demand of the Development
Baseline SAP 2009 calculations were prepared based on the construction specification
shown in table 1 below.
Aspect
Fabric U-values
2
W/m K
Roof
0.13
Walls external
0.26
Ground Floor
0.15
Windows
1.70
Doors
1.80
Party Walls
0.00
Thermal Bridging
Ventilation
New Build
Airtightness
m3/(hr.m2)
Mechanical
Ventilation
Boiler
Heating
Controls
Water Heating
Renewables / LZC
Low energy
lighting
Table 1: Part L compliant construction specifications
0.04 (ECDs)
5
Mechanical Ventilation with
Heat Recovery
90% Efficiency Gas
condensing boiler, boiler
interlock. Load
Compensator
Time and temperature zone
control
110L cylinder
None
100%
Based on using the specification outlined in table 1 above, this would create a total
predicted energy demand for the development of 54,578 kWh/year. The breakdown of
this predicted energy demand can be seen in table 2 below. The figures quoted have been
derived from the Design Stage SAP 2009 Calculations for the development.
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Predicted Annual Energy Requirements:
Space
Heating
Water
Heating
Lighting,
Pumps, Fans
Total Predicted
Energy
Requirement
(kWh/yr)
Plot
No.
Units
Gas
Gas
Electric
Plot 1
Plot 2
Plot 3
Plot 4
Plot 5
Plot 6
Plot 7
Plot 8
Plot 9
Plot 10
Plot 11
1
1
1
1
1
1
1
1
1
1
1
kWh/yr
kWh/yr
kWh/yr
kWh/yr
kWh/yr
kWh/yr
kWh/yr
kWh/yr
kWh/yr
kWh/yr
kWh/yr
2,339
2,402
2,167
1,369
1,714
1,499
1,600
862
1,826
2,416
2,050
2,573
2,594
2,514
2,286
2,562
2,483
2,530
2,539
2,398
2,457
2,521
673
720
630
504
655
601
630
641
574
593
659
5,585
5,716
5,310
4,158
4,931
4,583
4,760
4,042
4,797
5,466
5,230
20,243
27,455
6,880
54,579
Site Total
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Table 2: Baseline Predicated Annual Energy Demand
8
3.0 Baseline Carbon Emissions of the Development
Total Energy Demand (kWh/yr)
Associated Total CO2 (kgCO2/yr)
Space Heating
20,243
4,008
Water Heating
27,455
5,436
Fixed Electrical
6,880
3,556
Site Total
54,579
13,000
Table 3: Baseline Associated Carbon Emissions of the Development
Carbon Factors Used (from SAP 2009)
Gas = 0.198 kg CO2/kWh
Electric = 0.517 kg CO2/kWh
In order to satisfy EP16, the development needs to reduce predicted site wide CO2
emissions by 10% from on-site renewable energy sources. Therefore, since the
development’s predicted CO2 emissions is 13,000 kgCO2/yr, this would equate to a
reduction of 1,300 kgCO2/yr. In other words, providing the total site emissions comes to
equal to or less than 11,700 kgCO2/yr (13,000 – 1,300) when renewable technology is
added to the SAP calculations, this would prove that the 10% reduction target has been
met and policy EP16 has been complied with.
9
4.0 Overview of Renewable Technologies
4.1 Wind Turbines
General Description
Wind turbines convert the kinetic energy from the wind into mechanical energy which is
then used to drive a generator that converts this energy into electricity. When the wind
blows the large aerodynamic blades are forced round, driving a turbine which generates
the electricity. The stronger the wind, the faster the blades turn and the more electricity is
produced.
In the UK we have approximately 40% of Europe’s total wind energy resource, but this
resource is still largely untapped with only 2.5% (July 2010) of the UK’s electricity
production coming from wind energy.
Wind turbines can be either horizontal axis or vertical axis turbines. Horizontal axis
turbines are the more familiar windmill type where the blades rotate in a vertical plane
about a horizontal axis and the turbine is dynamically rotated on its tower to face the wind.
Most domestic scale wind turbines are horizontal axis devices.
Vertical axis turbines do not need orientation into the wind, although some of the earlier
versions required a power source to start rotating due to their high torque. More recent
models have helical blades that have low torque and do not require external power to start
the blade rotating. Vertical axis turbines are more suited to small scale applications due to
their low environmental impact and no noise.
Figure 2: Sectional diagrams of horizontal axis and vertical axis wind turbines
10
There are two types of domestic sized wind turbine:
Mast mounted: these are free standing and are erected in a suitably exposed position.
They are often around 2kW to 6kW in size. The masts are usually located close to the
building that will be using the generated electricity.
Figure 3: Example of a mast mounted wind turbine
Roof mounted: these are smaller than mast mounted systems and can be installed on the
roof of a home where there is a suitable wind resource. Often these are around 1kW to
2kW in size. Building mounted turbines are relatively new editions to the renewable
energy market and some concerns have been expressed about the performance of these
types of systems given the lower wind speeds and increased turbulence in built up areas.
One study has shown that in some urban environments micro-wind turbines may never
payback their embodied carbon emissions.
Figure 4: Example of a roof mounted wind turbine
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Wind turbines can be a grid connected system (connected to the national grid) or an off
grid system. Both require an inverter to convert the generated direct current (DC)
electricity into alternating current (AC) mains electricity. Off grid systems also require a
battery to store any unused or excess generated electricity. With a grid connected system
any electricity that is not used at the time of generation is exported and sold to the grid.
Please see section 8.6 on Feed-in Tariffs.
Suitability – Environment & Building
Generally speaking the ideal site is a smooth top hill with a flat, clear exposure, free from
excessive turbulence and obstructions such as large trees, houses or other buildings.
The electricity generated at any one time by a wind turbine is highly dependent on the
speed and direction of the wind. The wind speed itself is dependent on a number of
factors, such as location within the UK, height of the turbine above ground level and
nearby obstructions.
It is recommended to undertake a professional assessment of the local wind speed for a
full year at the exact location before proceeding. In practice, this may be difficult,
expensive and time consuming to undertake. Therefore it is recommended that if you are
considering a domestic building mounted installation, then you only consider a wind
turbine under the following circumstances:


The local annual average wind speed is 6 m/s or more.
There are no significant nearby obstacles such as buildings, trees or hills that are
likely to reduce the wind speed or increase turbulence.
Building mounted wind turbines require caution due to the loads that are imposed on the
building’s structure and the transmission of vibration into the structure.
Energy Generated
Wind turbines are rated by their power output in kW at a given wind speed. A viable 2.5
kW wind turbine installation should generate around 4000 kWh pa, which is equivalent to
an average household’s electricity consumption. However, it does not follow that a 2.5kW
installation can supply a house with all its electricity because the peak power demand in
many houses exceeds 10kW and there can be prolonged periods of calm when the wind
speed is below average.
Carbon Savings
A viable 2.5 kW wind turbine installation should offset around 2,000kg of CO2.
Cost Savings
If all the electricity generated is consumed in the household the money saved @
11.5p/kWh is £460.
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Capital Costs
Mast mounted wind turbines are often around 2kW to 6kW and cost around £3000 per kW
installed. Roof mounted wind turbines are often around 1kW to 2kW in size and cost
around £1800 per kW installed.
Typical Payback
Generally, investment in a wind turbine should be recouped where there is a minimum
average wind speed of 5 m/s. A well-sited, 2.5 kW wind turbine could provide payback
within a period of about 15 years.
Lifespan
Turbines can have a lifespan of up to 20 years. For battery storage systems, typical
battery life is around 6-10 years, depending on the type, so batteries may have to be
replaced at some point in the system's life.
Maintenance
Turbines require service checks every few years to ensure they work efficiently.
Maintenance of small-scale turbines is generally limited to visual assessments and an
annual oil check, which in most cases can be incorporated into a site’s annual
maintenance schedule and does not require the turbine installer to be present.
Noise
Turbines make more noise in higher wind speeds, but because the background noise also
increases, they are barely audible.
Planning
Planning issues such as visual impact, noise and conservation issues have to be
considered. System installation normally requires planning permission from the local
authority, although it is hoped that, in future, small building-mounted turbines may be
granted ‘permitted development’ status.
Land Use
Roof mounted systems have no additional land use. Mast mounted systems will require
adequate land for construction and maintenance purposes.
Financial Incentives – FIT or RHI
Since wind turbines generate electricity they are viable for feed-in tariffs providing the
products and installer used are MCS certified. A dwelling with a 2.5kWp installation will
generate around £1,068 revenue a year. The tariffs for wind turbines are fixed for 20
years.
13
4.2 Solar Photovoltaics (PV)
General Description
The energy in sunlight is converted into electricity by photovoltaic (PV) cells, which are
semiconductor devices. Each PV cell is made from one or two layers of semiconducting
material, usually silicon. When light shines on the cell it creates an electric field across the
layers. The stronger the sunshine, the more electricity is produced.
Since individual cells only generate a small amount of electricity, they are usually grouped
in rectangular modules that comprise transparent cover, a metal mounting frame and a
back plate, thus forming a weatherproof enclosure. Modules are often then grouped into
arrays. PV cells can also be moulded into solar slates or solar tiles for integration into
roofs.
Figure 5: A solar PV Module
Figure 6: Solar PV array
PV installations are not described in terms of their area but are rated according to their
peak power output (kWpeak or kWp). The module areas currently required per kWp
output for the different technologies are:


monocrystalline = 7 m2
polycrystalline = 10 m2
The building roof should have good access to solar radiation and be free from shadowing
as this has a detrimental effect on the generation ability of the PV panels. Due to the way
in which they are electrically connected, even if one small area of a panel is
overshadowed, the efficiency of the panel - and even the PV array - will be significantly
reduced, meaning that the output is much lower than predicted. It is essential, therefore,
that PV products are mounted away from trees, other roof obstacles and shadows cast by
surrounding buildings. Rural and suburban sites are likely to have access to more sunlight
for longer periods of the day than inner urban locations where other buildings and trees
can cast shadows.
14
Ideally, PV panels should be sited on south-facing roofs pitched at 30° to 45° from
horizontal to maximize solar gain throughout the year. For flat roofs, angled mounting
frame kits are available but care should be taken to ensure one row doesn’t overshadow
the row behind. Shallow angle mounting reduces energy capture and increases the risk of
dirt accumulation.
Figure 7: Reduction in solar PV panel efficiency with angle and orientation
Energy Generated
In most parts of the UK, PV installations will generate around 800 kWh annually per kWp
of installed capacity. The highest UK solar irradiation is in south-west England and South
Wales; it is lowest in north-east Scotland (see map below). A typical domestic 3 kWp
installation should generate an annual yield of around 2400 kWh – which is the equivalent
of a small household’s annual electrical consumption.
Figure 8: Solar irradiation map of the UK
15
Carbon Savings
A typical domestic 3 kWp installation will offset approximately 1248 kg per annum of power
station CO2 emissions.
Cost Savings
A typical domestic 3 kWp installation will save a maximum of £276 a year, providing all the
electricity generated is consumed in the home. This is based on an electricity price of
11.5p/kWh.
Capital Costs
Approximately £6000 per kWp installed.
Typical Payback
Around 10 to 15 years for an optimized system that’s eligible for the feed-in tariffs.
Lifespan
Manufacturers often give a 25 or 30 year guarantee. Output does degrade slightly over
time (rate dependent upon technology).
Maintenance
Since there are no moving parts the maintenance for PV systems is negligible. The panels
may require periodic cleaning, although when at tilt angle, run-off from rain is usually
sufficient.
Noise
Usually the only system noise is from the inverter cooling fans, which, if audible at all,
should be no louder than computer cooling fans. The inverter converts the generated DC
electricity into mains AC electricity.
Planning
Solar PV generally comes under the scope of ‘permitted development’ so planning
permission is not required – although it is wise to check with the local planning
department. Planning permission will usually be needed in conservation areas and
national parks, and on listed/heritage buildings.
Land Use
The solar PV panels would be fitted to the roof structure therefore they would not require
any further land use or special provision of land.
Since PV panels generate electricity they are viable for feed-in tariffs providing the
products and installer used are MCS certified. A new build dwelling with a 3kWp
installation will generate around £866 revenue a year. The tariffs for PV are fixed for 25
years so PV panels will provide the owner with a return on their initial investment.
16
4.3 Solar Thermal
General Description
Solar collectors (panels) absorb solar radiation and convert it to heat which is transferred
to a hot water cylinder by circulating fluid through a series of pipes to pre-heat the water in
the cylinder. This pre-heated water is then further heated to useable temperature by an
auxiliary system (boiler or electric immersion heater).
Figure 9: Simple solar thermal installation diagram
There are two standard types of collector: flat plate and evacuated tube.
Flat plate collectors are simple but effective devices, comprising a dark plate within an
insulated box with a glass or durable plastic cover. The plate is usually coated with a
‘selective’ coating to ensure that it has high absorption but low emissivity (heat loss by reradiation).
Figure 10: Flat plate collectors
Figure 11: Evacuated tube collectors
Evacuated tube collectors are more sophisticated, with a series of metal strip collectors
inside glass vacuum tubes. Their efficiencies are usually higher and they are more
effective in cold weather because of their low heat losses, but they do tend to be more
expensive than flat plate collectors, and succumb more easily to vandalism.
17
Both collector types can capture heat whether the sky is overcast or clear. Depending on
UK location, 900–1100 kWh of solar energy falls on each m2 of unshaded UK roof surface
annually. The annual energy captured by the two types is:


Flat plates: 380–450 kWh per m2 of collector.
Evacuated tubes: 500–550 kWh per m2 of collector.
A typical solar domestic system features 4 m2 of flat plate or 3 m2 of evacuated tube,
providing 50% to 65% of the energy required annually for water heating. Panels vary in
size but are usually around 2 to 3m2 depending on manufacturer and collector type.
Most domestic solar systems are known as indirect systems. The pipes connecting the
collector to the hot water cylinder connect to a heat exchange coil inside the cylinder. The
coil supplied by the solar system can either be in a dedicated solar cylinder that feeds preheated water to an existing domestic hot water cylinder served by a boiler, or it can be the
lower coil in a purpose built twin-coil cylinder where the upper coil is connected to the
boiler to provide the ‘top-up’ when needed.
As with PV panels, the collectors must be free from overshadowing.
As with solar PV, the optimum orientation for mounting solar thermal collectors is due
south with a 30° to 40° pitch. For individual systems, storage space must be available to
house hot water tanks within dwellings.
Energy Generated
A typical domestic-sized installation has an annual yield of 1600–2000 kWh.
Carbon Savings
A typical installation will reduce CO2 emissions by 400–1000 kg per annum, depending on
the fuel/energy displaced and conversion efficiency.
Cost Savings
Cost savings depend on the system type and orientation, the fuel/energy displaced and
the energy conversion efficiency of the existing hot water supply. A typical 4m2 domestic
installation that generates 1600 kWh of heat energy a year with an existing 90% efficient
gas boiler will save approximately £57 per year based on gas price of 3.2p/kWh.
Capital Costs
£2000–£4000 installed on a new build property. Installing solar thermal systems on an
existing dwelling can cost up to 30% more than for new build due to the additional
infrastructure required to support the system being added to existing hot water systems. A
flat-plate collector, including a twin-coil unvented cylinder costs in the region of £ 930 per
m2 collector installed. An evacuated tube collector, including a twin-coil unvented cylinder
costs in the region of £ 945 per m2 collector installed.
18
Typical Payback
8 to 20 years generally quoted: depends on fuel displaced, conversion efficiency, and
fossil fuel/energy price escalation.
Lifespan
30 years.
Maintenance
Solar water heating systems generally come with a 5-10 year warranty and require little
maintenance. A yearly check by the householder and a more detailed check by a
professional installer every 3-5 years should be sufficient
Noise
Solar collectors are considered to be silent in operation. Usually the only system noise is
from the small circulation pump which should be no louder than a modern central heating
pump.
Planning
Solar thermal generally comes under the scope of ‘permitted development’ so planning
permission is not required – although it is wise to check with the local planning
department. Planning permission will usually be needed in conservation areas and
national parks, and on listed/heritage buildings.
Land Use
The solar PV panels would be fitted to the roof structure therefore they would not require
any further land use or special provision of land.
Since solar panels generate renewable heat they will be viable for the renewable heat
incentives when they begin in June 2011.
19
4.4 ASHP (Air Source Heat Pump)
General Description
Air source heat pumps (ASHPs) use the same principles as ground source heat pumps
(GSHPs). The heat pump takes low-grade energy from the surrounding air by means of a
fan pulling the outside air over a heat exchanger (evaporator); this energy is then
upgraded and the higher temperature refrigerant is released by means of another heat
exchanger. In ASHPs this heat exchange can be to the air inside the dwelling or the heat
exchange can be to water.
Therefore there are two main types of air source heat pump system:

An air-to-air system produces warm air which is distributed to the different rooms
by ducts and supply grills. These systems are unlikely to provide hot water as well.

An air-to-water system distributes heat via a wet central heating system. Heat
pumps work much more efficiently at a lower temperature than a standard boiler
system would. So they are more suitable for underfloor heating systems or larger
oversized radiators, which give out heat at lower temperatures over longer periods
of time.
Figure 12: ASHP
Figure 13: ASHP diagram
Unlike GSHPs, where the temperature of the ground is relatively stable throughout the
year, in an air source heat pump the source air temperature range can be highly variable.
Air source heat pumps operate at their most efficient when the source temperature is as
high as possible, but in the UK the mean air temperature for winter is lower than the mean
ground temperature. All of these factors have an impact on seasonal efficiency for ASHPs,
which is lower compared to GSHPs.
ASHPs are not particularly suited to cold winters, where coils may need to be defrosted or
an alternative source of heating used in particularly severe conditions.
20
They are best suited to new build applications as they are most efficient when supplying
low temperature distribution systems such as under-floor heating or oversized radiators.
Energy Generated
The efficiency of air source heat pumps is determined by their Coefficient of Performance
(COP), which is the ratio of the units of heat out to units of electricity in. To maximise the
efficiency of a heat pump it is important to have a low heating distribution temperature, and
in these circumstances typical CoPs are about 2.5, which equates to an efficiency of 250%
compared to a typical condensing gas boiler with a 90% efficiency.
Capital Costs
Costs for installing a typical ASHP system suitable for a detached home range from about
£6,000 to £10,000 including installation. Running costs will vary depending on a number of
factors including the size of the dwelling and how well insulated it is.
Typical Payback
ASHPs can have a pay-back of between 8 and 15 years, however this depends on a
number of such as; the CoP of the heat pump, the heat distribution system, fuel costs, the
type of fuel that they displace, if the system is providing hot water as well as space
heating, temperature settings etc.
Lifespan
Air source heat pumps have a life expectancy between 20-25 years.
Maintenance
System maintenance is minimal.
Noise
Air source heat pumps emit noise from the fan and compressor which can cause a
nuisance. They should not be sited in close proximity to bedrooms or neighbouring
properties.
Planning
ASHPs are one of the few microgeneration systems that fall outside any permitted
development rights and as such planning permission will be required. However, once
ongoing legal technicalities have been resolved, it is expected that air source heat pumps
will be permitted developments.
Since air source heat pumps generate renewable heat they will be viable for the renewable
heat incentives when they begin in June 2011.
21
4.5 GSHP (Ground Source Heat Pump)
General Description
A few metres underground remains at a constant temperature of about 10 to 15 degrees in
the UK. It is possible to transfer this latent heat to a dwelling by installing a ground source
heat pump. The heat pump draws heat from the ground via a ground collector (slinky) or a
ground probe (bore hole) depending on the available area on site.
Figure 14: A ground source heat pump
Figure 15: Slinkies (coiled pipes) in a trench
Heat pumps work in much the same way as a fridge in reverse. In a fridge the heat is
transported from inside to outside, whereas a heat pump takes heat stored below the
ground and transports it via the heating system to the house interior. In order to upgrade
the low temperature heat from the ground into a higher, more useful temperature the
system contains a compressor which increases the pressure and therefore the
temperature of the systems refrigerant.
Heat pumps operate most efficiently when the temperature difference between the heat
source and the heat demand is smallest. They are therefore most suited to work with
underfloor heating which run at between 35 and 40 degrees as opposed to radiators which
typically operate at about 60 degrees.
GSHPs are well-suited to new build applications as their efficiency is improved when
supplying low temperature distribution systems such as under-floor heating.
Heat pumps have a typical operating temperature limit of 55°C and are not generally
suitable for operation with traditional wet radiator systems.
Either a horizontal or vertical ground collector is required; the choice will depend on land
area available, local ground conditions and excavation costs.
Energy Generated
The efficiency of ground source heat pumps is determined by their Coefficient of
Performance (COP) of the pump, which is the ratio of the units of heat out to units of
electricity in. Ground source heat pumps should have a CoP of 3 or more, in order to gain
22
good carbon savings. That means that for every unit of electricity put into the system, 3
units of heat are produced. In other words the GSHP has an efficiency of 300% compared
to a condensing gas boiler with 90% efficiency.
Capital Costs
The cost of a professionally installed GSHP ranges from about £1,200 to £1,700 per kW of
peak heat output. This includes the cost of the distribution system. Vertical borehole
systems would be at the higher end of this scale, due to greater installation costs. A typical
8kW system would therefore vary between £9,600 and £13,600. Installing a heat pump to
replace a gas-fired heating system is less economically favourable than one replacing
electrical or oil heating systems.
Typical Payback
GSHPs can have a pay-back of between 8 and 15 years; actual figures will depend to a
great extent on the type of ground collector, ground conditions, the type of fuel that they
displace and economies of scale for the installation.
Lifespan
GSHP technology is low in maintenance as systems have very few moving parts. Systems
can have an operating life of over 40 years.
Maintenance
System maintenance is minimal. The piping infrastructure, like utility piping infrastructures,
rarely requires maintenance. Only the pump may require maintenance work and it is easily
accessible.
Noise
Heat pumps can emit constant noise due to the operation of the compressor. Although
this is generally low level noise, locating heat pump units in close proximity to bedrooms
should be avoided.
Planning
It is unlikely that planning permission will be required for the installation of a ground source
heat pump, since the pipes are buried below ground and the only visible part of the system
is the pump itself. However, it is wise to check with the local planning authority if the site is
located in a Conservation Area.
Land Use
If a large enough land area is available, horizontal ground collectors are buried at a depth
of approximately 1.2m and spaced 0.75m apart. The land area required is dependent on
both the capacity of the heat pump and heat conductance of the soil type in which the
pipes are buried. As a space saving alternative to horizontal collectors, slinkies - consisting
of coiled pipes buried in a trench can be used.
If land space is limited the ground collectors can be installed vertically in a borehole, drilled
up to 100m deep in the ground. Multiple boreholes are commonly used in large
installations where very high levels of heat extraction are required.
23
Since ground source heat pumps generate renewable heat they will be viable for the
renewable heat incentives when they begin in June 2011.
24
4.6 Biomass Boiler
General Description
The term biomass refers to organic matter such as timber and crops grown specifically to
be burnt to generate heat and power. Biomass can be sustainable and generally carbon
neutral because the carbon released in the combustion process is offset by the carbon
trapped in the organic matter during its growth.
Biomass technologies have developed greatly over recent years and modern wood-fuel
boilers are highly efficient, clean and smokeless. There are two main types of wood fuel
which can be used in biomass boilers – wood pellets and wood chips, however smaller
systems for domestic buildings may also use logs.
The wood chip or wood pellets are fed automatically into the boiler from the fuel store
using an auger screw system. The fuel then burns in the combustion chamber, where a
regulated flow of oxygen ensures a clean and efficient combustion process. The resulting
hot gases then heat water in a heat exchanger which feeds the hot water storage tank and
then ultimately the heating circuit - such as radiators.
Biomass boilers are as controllable as modern gas condensing systems; heating controls
allow the user to adjust all elements for the central heating and domestic hot water.
Figure 16: Biomass boiler
Figure 17: Wood pellets
There are several factors that will influence the type of boiler suitable for a particular
project.
Space – If there is limited space on site then storage of wood fuel could be a restriction.
Wood chips will occupy up three times more room than wood pellets for the same weight
of wood. Biomass boilers also tend to be larger than conventional fossil fuel boilers, so
there will need to be a large enough space to house the unit.
25
Size of the building – Typically the larger the building is, the greater requirement for
space heating and therefore the larger the boiler needs to be. Larger systems will
consume more fuel and therefore tend to be automated systems with minimal manual
intervention. Biomass boilers with automatic auger feed mechanisms and fuel stores are
generally too large for domestic installations. However, domestic systems allow the user to
fill a hopper attached to the boiler.
Access – For most systems a fuel delivery vehicle will need to access the site. Fuel can
be delivered in a variety ways, however for bulk chips and pellet orders direct access to
the fuel store is critical. For small domestic deliveries it is important to have a dry place to
stack logs or store bags of pellets. Projects in urban areas will need to be mindful of the
number of fuel deliveries (large vehicle movements) necessary throughout the year as this
may have planning implications.
Fuel supply – Generally if space and access are not a problem larger projects would
consider wood chip; however if space is at a premium or the area is sensitive to a greater
number of fuel deliveries then pellets are the preferred option.
Energy Generated
One tonne of wood pellets has an energy content of 5,000kWh and costs in the region of
£160 which equates to 3.2p/kWh. One tonne of wood chips has an energy content of
around 3,000kWh and costs about £50, which equates to 1.6p/kWh. A tonne of logs has
an energy content of 4,200kWh and costs £60, which equates to 1.4p/kWh.
Carbon Savings
The carbon savings from a biomass boiler depends on what type of fuel is being displaced.
In the Government’s 2009 Standard Assessment Procedure (SAP) grid electricity has a
carbon emission factor of 0.52 kgCO2/kWh, mains gas has a carbon factor of 0.2
kgCO2/kWh and biomass has a carbon factor of 0.03 kgCO2/kWh. Therefore where the
alternative is electric heating, biomass displaces 0.49 kg of CO2 per kWh of delivered heat
and where the alternative is mains gas heating, biomass displaces 0.17 kg of CO2 per
kWh of delivered heat. So for a standard dwelling heated by a gas boiler that uses around
18,000 kWh per year, a biomass boiler would save 3060 kg CO2. This saving would be
significantly more if electricity was being displaced.
Cost Savings
The cost savings from a biomass boiler depends on what type of fuel is being displaced,
the efficiency of the boiler and the type of biomass fuel used. If the biomass boiler was
90% efficient and it ran on wood pellets the energy running costs would be silighty more
than a 90% efficient gas boiler since the average mains gas price is 3p/kWh and wood
pellets retail at around 3.2p/kWh. Cost savings are more likely when replacing electric
heating since the average price for electricity is 11.46p/kWh (according to SAP 2009).
Capital Costs
As a general guide for domestic installations the price per installed kW (including flue, fuel
storage, fuel feed, commissioning and design, exc VAT) is around £450 - £600. So a
15kW pellet boiler would cost approximately £9,000.
Wood chip boilers cost
26
approximately £250 - £450 per kW installed. Log boilers tend to be cheaper than both
wood chip and wood pellet boilers; for example a 20kW system suitable for a 3 or 4 bed
property would cost in the region of £150 - £200 per kW installed (£3,000 to £4,000).
Typical Payback
Depends on fuel displaced and type of system. Payback periods will be reduced when the
renewable heat incentives begin in June 2011.
Lifespan
25 years.
Maintenance
Automated feeding and de-ashing systems mean that maintenance requirements are
minimised. In addition, the majority of boilers have a built-in modem, which automatically
contacts the site engineer if a performance problem is detected. Smaller boilers normally
require an annual visit while much larger boilers may need a quarterly visit. Most UK
installers offer ongoing maintenance contracts.
Noise
Some people find the fan noise of certain wood pellet stoves intrusive.
Planning
Biomass boilers generally fall under permitted development rights (i.e. planning permission
is not required) unless the flue exceeds 1m above the roof height or if it is installed on the
principal elevation which is visible from a road on buildings in Conservation Areas and
World Heritage Sites. Not all biomass equipment is approved for operation in smokeless
zones.
Land Use
A dry, covered fuel store is required with adequate space – wood is bulky, and often bulk
discounts depend on logs or pellets being delivered in sizeable quantities, e.g. tonne
loads.
Since biomass boilers generate renewable heat they will be viable for the renewable heat
incentives when they begin in June 2011.
27
5.0 Feasibility Study of Renewable Technologies
This section will assess the technical viability of the following renewable energy
technologies for the site in order to rule out unfeasible options:
-
Mast mounted wind turbines
Roof mounted wind turbines
Solar PV (Photovoltaic) Panels
Solar Thermal Panels
GSHP (Ground Source Heat Pump)
Biomass
Micro Combined heat and power (CHP)
The following observations have been made with regard to the technical feasibility of
integrating renewable energy technologies into this development.
Renewable Technology
Feasible
Mast Mounted Wind
Turbine
No
Roof Mounted Wind
Turbine
No
Reasons
Currently the BWEA suggests a large wind turbine to be viable
where wind speed is 7m/s or above. According to the NOABL
database the average wind speeds for the site postcode (CR8
3AG) are 4.6 m/s at 10m, 5.4 m/s at 25m and 6 m/s at 45m
height. Therefore the wind speeds are not sufficient for a Wind
turbine to be viable.
The surrounding area isn't free from obstructions such as
buildings and trees that could cause uneven and turbulent wind
patterns.
Depending on the exact location of existing and proposed trees
there may be sufficient open land for a mast mounted wind
turbine to be installed.
Surrounding properties aren't far enough away to be unaffected
by turbine noise, reflected light and shadow flicker.
Currently the BWEA suggests a small scale wind turbine to be
viable where wind speed is 6m/s or above. According to the
NOABL wind map the average wind speeds for the site
postcode (CR8 3AG) are 4.6 m/s at 10m, 5.4 m/s at 25m and 6
m/s at 45m height. Therefore the wind speeds are not sufficient
to be viable since the average wind speed isn't greater than 6
m/s at hub height.
The surrounding area isn't free from obstructions such as
buildings and trees that could cause uneven and turbulent wind
patterns.
Roof mounted wind turbines are not yet a proven
technology and a number of technical problems have been
identified by manufacturers which are being investigated to
rectify these issues.
28
Solar PV (Photovoltaic)
Panels/Tiles
Yes
Solar Thermal Collectors
Yes
ASHP (Air Source Heat
Pump)
No
GSHP (Ground Source
Heat Pump)
No
Biomass Boiler
No
Micro CHP
No
The proposed dwelling has both South East and South West
facing areas of roof
The roofs should be free from overshadowing for most of the
day from other buildings, structures or trees.
There is sufficient unshaded roof area.
The proposed dwelling has both South East and South West
facing areas of roof
The roofs should be free from overshadowing for most of the
day from other buildings, structures or trees.
There is sufficient unshaded roof area.
There will be a year round hot water demand.
All the proposed housetypes have space for a hot water
cylinder close to the solar panels.
Solar thermal collectors would be compatible with the planned
heating system.
There is space inside the dwelling for a hot water cylinder.
An external ASHP can’t be located away from the bedrooms to
avoid potential noise issues.
The proposed dwellings do have a sufficient area of land where
horizontal piping could be installed.
The proposed dwellings do have a sufficient area of land where
vertical piping could be installed, however it is unknown
whether the ground is free from obstacles such as sewers,
tunnels etc.
It is possible to have a low-grade heat distribution system e.g.
underfloor heating, oversized radiators.
A basic ground study to check if the site is suitable for ground
source heat pumps has not been conducted.
There is not sufficient space inside all the proposed dwellings
for the heat pump.
There is an established fuel supply chain for the area.
There isn’t sufficient space for a delivery vehicle. (vehicular
access to fuel storage, turning circle etc)
There isn't sufficient space inside the proposed dwellings for a
wood-fuel boiler and associated auxiliary equipment.
There isn't sufficient space for fuel storage to allow a
reasonable number of deliveries.
Micro CHP is gas-fired and therefore is not generally classed as
a renewable energy technology
Micro CHP is ideal for high-density residential developments as
there is a sufficient year round heat and electrical demand. The
relatively low-density of the site makes it unsuitable for the
application of micro CHP.
Table 4: Feasibility Study of Renewable Technologies
29
Based on the feasibility study in table 4 above, the following technologies have been
identified as being feasible for the proposed development.


Solar PV (Photovoltaic) Panels/tiles
Solar Thermal Panels
Following discussions with the developer of the site it was concluded that their preferred
technology from the above list of feasible technologies was Solar PV panels. Therefore
this technology will be taken forward for sizing and calculation of the contribution to CO2
reduction.
30
6.0 System Size to Provide 10% CO2 Reduction
The developer is proposing to install solar photovoltaic panels to the roof of the new block
of flats. Due to the restricted amount of suitable roof area on the plots, because of the
dormer windows and balconies, it is suggested that a high efficiency 250w solar pv panel
is utilized on this development.
Solar PV was added to the sap calculations in increments of 0.25kWp until a 25%
improvement in the Dwelling Emission Rate (DER) over the Target Emission Rate (TER)
was achieved – to achieve the mandatory requirement in ENE1 for code for sustainable
homes level 4. The results of this process can be found in table 5 below.
In essence a total of 6.5 kWp (26 No. 250w panels) will need to be installed on the project
to ensure that the mandatory 25% improvement of DER over TER needed for code level 4
properties is achieved. It is proposed to split the PV array into 3.5kWp (14 No. 250w
panels) on the South-West facing roof of the development and 3kWp (12 No. 250w panels)
on the flat roof of the development.
A check was then carried out to establish what percentage of site wide CO2 is reduced
from the 6.5kWp array of solar pv. According to the SAP software, the 6.5 kWp of pv
generates 5,105 kWh/year which provides a CO2 reduction of 2,639 kgCO2/year (based
on a carbon factor of Electric = 0.517 kg CO2/kWh) Since the site wide CO2 emissions
before renewables are added is 13,000 kgCO2/year, this represents a 20.3% reduction
which is more than sufficient to satisfy EP16.
Plot
1
2
3
4
5
6
7
8
9
10
11
TER
DER
%
Improvement
Code Level
(ENE1)
12.87
12.91
13.6
14.93
11.97
12.71
12.17
10.68
14.72
15.12
13.51
18.36
17.7
18.28
19.88
16.05
15.72
15.25
14.56
19.33
19.77
18.43
29.9
27.06
25.6
24.9
25.42
19.15
20.2
26.65
23.85
23.52
26.7
4
4
4
3
4
3
3
4
3
3
4
PV (kWp) Prorata
based on floor area
(SW Roof 45°)
PV (kWp) Prorata
based on floor
area (Flat Roof)
0.36
0.38
0.33
0.24
0.34
0.30
0.33
0.32
0.28
0.30
0.33
3.50
0.31
0.32
0.28
0.20
0.30
0.26
0.28
0.27
0.24
0.26
0.28
3.00
Table 5: SAP Results and Amount of PV per Plot
As can be seen from the above not all of the dwellings achieve code level 4 based on the
% improvement of DER over TER and the floor area prorata share of kWp of solar pv.
However as stated in the code for sustainable homes 2010 technical guide under category
ENE1 Dwelling Emission Rate:
31
“Where a building contains multiple dwellings, it is acceptable to asses this issue based on
the average energy performance of all the dwellings within the building.”
In this case the SAP calculations show the following TER and DER for the site as a whole:
This means the overall percentage improvement of DER over TER is as follows:
100 – (( Average DER) x 100) = 100 – (( 13.12 ) x 100) = 25.02%
Average TER
17.50
The above calculation shows that the minimum percentage improvement of 25% to
achieve code level 4 has been satisfied and therefore all dwellings on the site now reach
this level.
32
Table 6 below shows the CO2 emissions of the development following the introduction of
6.5kWp of solar PV.
Total Energy Demand (kWh/yr)
Space Heating (gas)
20,243
4,008
Water Heating (gas)
27,455
5,436
Fixed Electrical
6,880
3,556
Solar PV
-5,105 (generated)
-2,639 (reduced)
Site Total
49,473
10,361
Table 6: Carbon Emissions of the Development with 6.5kWp Solar PV
Baseline (no PV) (2)
13,000
With PV
10,361
Reduction in CO2 (1)
2,639
% Reduction (1) / (2) x 100
20.3%
Table 7: Percentage Reduction in Carbon Emissions from 6.5 kWp Solar PV
Table 7 above shows the percentage reduction in CO2 emissions contributed by the solar
PV panels. Therefore the installation of 6.5kWp of solar pv will achieve significantly
greater than the 10% CO2 reduction required to satisfy EP16.
Figure 18: Proposed South West Elevation showing possible location of 14 No. 250w PV panels
33
Figure 19: Proposed Roof Plan showing possible location of 12 No. 250w PV panels mounted
horizontal on the flat roof
34
35
36
37
38

WOODCOTE VALLEY ROAD, PURLEY, CROYDON Mantle

Transcription

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