Urban wind, urban legend?

Urban wind,
urban legend?
Mark.Runacres@vub.ac.be
1
Overview
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Introduc)on Small and medium-­‐sized wind turbines Urban wind energy: case study Brussels Summary and conclusions
2
Introduc,on
3
Urban wind energy - introduction
• Wind has the poten)al to provide 50% of European electricity • Wind energy has low power per land area: 1-­‐3 W/m2 ‣ can be higher for offshore, but 6 W/m2 is unusual ‣ German solar farms reach 5 W/m2 • Ci)es have high power use per land area: 20-­‐50 W/m2
(150 m2 for Mumbai) • Urban wind energy will not provide a large frac)on of the energy needs of any major city. This will always require large-­‐scale genera)on
4
Urban wind energy - introduction
• There is no such thing as centralised genera)on of renewable energy • A en)rely non-­‐fossil, non-­‐nuclear electricity produc)on of electricity means living around power plants
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Urban wind energy - introduction
• Bringing power produc)on closer can create awareness and goodwill • There is a lot of unused space in ci)es: rooUops • If there is wind, this space may be used • Secondary benefits only count if the energy produc)on is economically viable in the first place
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Urban wind energy - introduction
Ques)on of this contribu)on: • Can wind energy produce local electricity in an urban area ‣ in a economically viable manner ‣ safely ‣ with limited impact on surroundings ? • Feasibility depends on viability and impact
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Some defini,ons
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Small and medium-sized wind turbines
• Small wind turbines (IEC 61400-­‐2 defini)on) ‣ “a system of 200 m2 rotor swept area or less that converts kine)c energy in the wind into electrical energy” ‣ d ≲ 16 m ‣ Prated ≲ 50 kW • Medium-­‐sized wind turbines ‣ working defini)on: 50 -­‐300 kW ‣ 16 m ≲ d ≲ 35 m
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Power and energy
• In good condi)ons ‣ A 1000 kW turbine will produce around 3 500 000 kWh/yr ‣ A 100 kW turbine will produce around
350 000 kWh/yr ‣ A 5 kW turbine will produce around 13 000 kWh/yr • The average Belgian household consumes 3500 kWh/yr of electricity
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Feasibility of a SMWT project
• Economic viability: measured with a metric such as ‣
‣
‣
‣
levelised cost of energy (LCOE) payback period internal rate of return (IRR) secondary benefits (e.g. of greening of company image) have tangible monetary value • Impact: safety, shadow flicker, noise, vibra)ons, biodiversity
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Viability of small and medium wind turbines 12
Small and medium wind turbines
• Challenge of small and medium wind turbines: ‣ immature market ‣ low-­‐cost → low budget for resource assessment and si)ng + limited )me for measurements ‣ generally complex environment
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Rule 1: Know the market
• 14
VUB database of small wind turbines
• Turbines < 100 kW • 762 turbines and coun)ng ‣ Most extensive survey to date ‣ HAWT ‣ VAWT ‣ Other concepts
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VUB database of small wind turbines
• Typical entry: main characteris)cs of turbine
+ comments: measured P-­‐curve, cut-­‐in or start, ...
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Rule 2: know the wind resource
• Es)mate the available wind resource
with the aim of predic)ng the energy produc)on for an appropriate wind turbine • This is in prac)ce not always easy to do cheaply and reliably
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building!level.!The!rules!of!thumb!for!the!installation!of!wind!turbines!in!an!urban!environment!
(D2.4)!provide!a!clear!way!to!tackle!this!problem.!These!rules!however!first!required!validation!
through!CFD!simulations,!which!we!performed!for!individual!buildings!(D2.1)!and!building!blocks!
(D2.3).!One!of!the!more!striking!rules!was!the!requirement!to!place!wind!turbines!at!least!50!%!
higher!than!building!height!(Wegley!et!al,!Siting!handbook!for!small!wind!energy!conversion!systems,!
1982).!This!is!prohibitively!high!for!many!of!Brussels'!most!suitable!locations!(as!shown!in!the!study!
by!Runacres!et!al,!BIM!E11O359!final!report,!2014),!such!as!The!Hotel!(94!m!tall)!or!the!SISP!building!
Peterbos!in!Anderlecht!(ca.!66!m).!The!CFD!study!we!performed!in!this!period!was!aimed!to!
investigate!the!range!of!validity!of!the!50!%!requirement.!
Rule 3: proper micrositing
• Op)mal loca)on and height of the turbine ‣ 3-­‐D model of the site or building ‣ Combined with computa)onal fluid dynamics
For!a!standard!reference!case!(Mertens,!PhD!thesis,!TU!Delft,!2006),!our!CFD!models!agree!well!and!
confirm!the!abovementioned!rules!of!thumb.!The!reference!case!however!has!a!low!heightOtoOwidth,!
(‘virtual wind tunnel’)
unlike!the!buildings!we!envisage!in!the!BCR,!as!we!show!below.!
Figure!2!(left)!shows!the!recirculation!zone!above!and!beyond!The!Hotel.!The!maximum!height!of!the!
wake!is!about!30!%!above!the!building,!but!this!is!well!beyond!the!building!itself.!The!freeOstream!
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Small and medium wind turbines: resource
assessment + siting
• Feasibility ‣ Turbine choice ‣ Resource assessment ‣ Turbine si)ng ‣ Technical feasibility and impact • Use measurements and numerical simula)ons ‣ Resource assessment: measurements ‣ Micro-­‐si)ng: numerical simula)ons
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The poten,al for wind energy in Brussels
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!
Windspire!
Wind potential in Brussels: global wind
l!the!necessary!data!have!been!assembled!and!formatted;!the!calculated!power!time!series!
conditions
ataset!with!an!accompanying!note!(deliverable!D1.1)!has!been!sent!to!ULBOATM!(project!11)!
1/08/2013.!
• Wind maps based on terrain informa)on and meteo data
Figure!1:!Roughness!map!(left)!and!wind!speed!at!10!m!above!mean!building!height!(right)!for!the!Brussels!
Region.!
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Wind measurements: site selection
• Result ‣ 4 sites were selected: » Hilton » ULB Campus Solbosch » Elia » Port of Brussels
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Wind measurements: results
• The Hotel: ‣ building height 94 m ‣ close to porte de Namur ‣ Over 1 yr of measurements ‣ Average wind speed:
5.8 m/s ‣ This is comparable to the wind at the Belgian coast (at normal hub height)
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Wat would a wind turbine on The Hotel
produce?
• The Hotel: ‣ Yearly produc)on » Sonkyo Windspot : 14200 kWh/yr » Ennera: 8170 kWh/yr ‣ Dynamic payback )me » KMO: Sonkyo Windspot & Ennera : 7 jr (10-­‐12 yr without support) ‣ IRR: » Sonkyo Windspot: 17.2 % » Ennera: 15.1 %
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Wind measurements: results
• Other high-­‐rises (Manhatan-­‐tower): comparable results • Lower buildings (40 m): condi)ons much less favourable • Unclear: poten)al for medium-­‐sized turbines in semi-­‐
open terrain • 12 m above ground (typical hub height < 15 m): ‣ mean wind speed 3.7 m/s ‣ comparable to Schoondijke (Zeeland)
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Impact of rooNop-­‐mounted wind turbines
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Building-mounted small wind turbines
• Turbine should not affect structural health of building • Impact on occupants and surrounding should be negligible • Impact on air traffic should be negligible • Impact on biodiversity should be negligible
Portland, Oregon (2009)
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Results: characterisation of vibrations
• This is not in the public domain, so we needed to measure, no data available, so this is really necessary to prepare a rooUop moun)ng • We measure on the ground (three turbines of our own turbines on different loca)ons) • The vibra)on data of these turbines are then combined with wind measurements on rooUops
and with building models (subcontractor Greisch, Liège)
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Results: characterisation of vibrations
−20
• Vibra)on spectrum only weakly dependent on wind speed. 1−3 m/s
3−5 m/s
5−7 m/s
7−9 m/s
−40
−60
Acceleration PSD (m/s )
2 2
−80
• Some increased damping at higher wind speeds (aero damping, fore-­‐aU in par)cular). −100
−120
−140
−160
−180
−200
−220
0
2
4
6
8
Frequency (Hz)
10
12
14
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Results: characterisation of vibrations
• What about different turbines? Dominant modes are from the mast, which has roughly standard dimensions and usually similar s)ffness (steel) so dominant frequencies vary litle over different types of HAWT. • So vibra)ons are quite generic (independent of wind speed and turbine type)
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Results: structural impact of vibrations
• Structural impact negligible if wind turbine is mounted on the suppor)ng structure of the building • Local reinforcements may be necessary when turbine mounted away from suppor)ng column • Damping methods will mainly address possible acous)c issues, rather than structural (vibra)ons above ~ 50 Hz).
Dallas, Texas (2011)
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Shadow flicker
• Guideline – d = 2 )mes height – max 30 h/yr – max 30 min/day • The Hotel – Shadow moves fast enough
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Impact of rooftop-mounted wind turbines
• Structural effect of vibra)ons:
very limited • Visual impact
• Noise: ‣ direct: inaudible ‣ through vibra)ons: inves)ga)on ongoing • Biodiversity: very litle impact • No risk for air traffic
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Pilot projects
• We are preparing full feasibility reports to prepare building permit requests in Brussels • We plan to finish end 2015
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Wind situation in Brussels
• Wind condi)ons on high-­‐rises comparable to condi)ons at the Belgian coast ‣ Payback )mes < 10 yr ‣ IRR > 15 % ‣ This is very good for distributed genera)on • BUT: only true for good wind turbines, in a good loca)on, properly installed • Semi-­‐open terrain not measured • Impact very limited. Detailed feasibility study always required
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Economic impact — long term
• In the long term, and providing the problem of rooUop crowding can be managed, there is the poten)al for roughly 50 sites for rooUop-­‐mounted wind turbines in Brussels, resul)ng in a power produc)on of the order of 1.5 GWh/yr
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Summary
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There is a poten)al for wind energy in the BCR Projects can be economically viable with low impact Brussels has the technological assets required Now is the )me for pilot projects
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Thank you
Mark.Runacres@vub.ac.be
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