Building integrated wind turbines (BiWTs) are suddenly appearing on architectural projects everywhere. Unfortunately, they are just ‘green’ ornamentation, spinning more for show then producing a viable amount of renewable energy. I’m reminded of the Saturday Night Live set from the 1990’s with the large industrial fans spinning in the background. So far the data and life cycle analysis for the wind turbines that fit on/in buildings doesn’t justify their installation today – the case is very different for utility scale wind turbines (those larger then 50m diameter). This paper explores the technical, economic, and energy potential issues of Building integrated Wind Turbines.
The basic physics of wind around buildings and in an urban environment, along with the size limitations for these turbines are the downfall for productive energy generation:
• There is too much turbulence around buildings which significantly reduces the efficiency and power output of the turbines.
• Wind power is equal to the square of the area of a turbine. A larger swept area is much exponentially better then a smaller rotor – but you can’t mount an utility scale 60m diameter turbine in a city.
• Then there are the engineering issues of vibration, ice, noise and more…
Kate Galbraith in the September 3, 2008 edition of the NY Times covered this trend and got a great quote from Jay Leno: “People seem fascinated by the turbines,” Mr. Leno said. “You go, ‘Look! It’s spinning!’ ”
The spinning rotors may look good (and there are a new generation of exceptionally well industrial designed products available), but they just don’t perform. Electricity from rooftop turbines may cost $1.50 a kilowatt hour or more – compared to large wind electricity that can be less then $.10/kwh.?
The definitive word on BiWTs is the Davis Langdon article from 2006: Wind and the Global Warming Imperative that concludes:
At present, it does not seem technically feasible or economically worthwhile to mount wind turbine on large commercial buildings as a means of providing significant renewable energy.
Case closed or is it? We still have to address a client’s interest in with a constructive discussion that leads to a better result.
Case studies
There are several case studies of installed turbines that are worth examining. London is the center of research and building integrated wind turbine installations. One of the better known projects is the Southwark project by Brian Dunlop Associates and Gas Dynamics. In an article by Dan Hill – a senior consultant at Arup and founder of the city of sound blog, quotes Mr. Dunlop:
“There’s plenty of data for photovoltaic performance in urban locations but very little regarding urban wind power. From a planning point of view, we want to put to bed fears over noise and vibration, and so far the results have proved positive.”
Dunlop does add, though, that there is an enormous amount of data to be analysed. “The equipment used collects information every second using sophisticated software created by Gas Dynamics,” he says. “At the moment South Bank University is analysing data gathered from the first three months.”
On the challenges of predicting wind speed and direction (key to commercial wind generation), Dan continues:
Arup’s engineers are also modelling the way wind moves through open urban spaces, which sounds impossibly complex. Arup’s Rupert Blackstone:
“Modelling urban wind movement is a real challenge. It’s almost impossible to be predictive because every environment has local characteristics that affect air flow. The surface roughness — meaning the variation in height of a neighbourhood’s buildings — has a huge influence on the wind resource available. There’s really no point in extrapolating from meteorological data — you have to be location-specific in your analysis.”
The primary value of urban wind turbines is aesthetic. The spinning rotors can animate an urban space and function as public art, like Ned Kahn’s sculptures that make visible the natural processes that surround us. To return to Dan’s essay:
Wind turbines, as with other renewable energy sources, are only likely to increase in number throughout urban space, and personally I’m all for them. I’ve never quite understood arguments against their introduction – a few messy bird-kills here and there aside – and have personally almost always found them aesthetically appealing. I recall Justin Good’s piece for Design Observer, when he almost systematically ‘proved’, in that way philosophy doctorates do, that “wind farms are objectively beautiful.”
However, the article was predicated on the most likely current siting for wind farms – rural environments – and so hinged on the suggestion that people found wind farms unappealing as they resembled modernist sculptures, and so “don’t want the ideology of high modernism disrupting the very different order of the natural world.”
In urban environments, smaller vertical axis wind turbines can look like modernist sculptures and all the better for it, perhaps more universally at ease in this setting. With some of the newer wind turbines on the market, they’re not a million miles away from the Alexander Calder or Barbara Hepworth sculptures that we see at the Fundaçion Joan Miro or pinned to the side of John Lewis in Oxford Street.
Are we integrating wind into buildings or just sticking turbines onto as an afterthoughts? Retrofitting existing structures will never create optimal conditions for power generation. Here are several projects that attempt to integrate turbines aerodynamically and aesthetically into their overall design.
SOM’s Pearl River Tower is such an example but this only works where there is a single wind direction and clear air to both the windward and leeward sides. Bahrain World Trade Center is rumored to spin the turbines with electric motors. Don’t even get me started by David Fisher’s farce of interlayering ‘turbines’ between floors of his rotating tower.
Economics
The overall economics on renewables vary depending on government subsides. For us in the architecture biz- most energy generation tech costs more $$ then clients want to spend. Even the old standby diesel gen set costs $10s for any significant output. compared to gas turbines or fuel cells, diesel is cheap, but low efficiency and has nasty emissions. Biogas/biomass fuels require more complicated plants and emission controls – but low cost fuel offsets this. Fuel cells and nasa quality PVs are the most expensive tech per sf to install. Cogen ups the efficiency of internal combustion/fuel cells to being the most competitive tech when costs justify a solid amount of power & heat.
Wind turbines are cheap and old school tech that is becoming refined, but don’t produce much zap at a small scale. Solar thermal is the most efficient/$$$ of all renewable energy systems. So the first thing to add to ANY building are solar hot water panels/storage tanks.
If you had $10k to spend on small scale generation, a diesel gen-set is still the cheapest till you look at the fuel costs and the emissions. Wind/PVs shine with the free fuel. PVs have the lowest maintenance costs, just requiring an occasional washdown. As to output, it depends on your location. If cost was no object then PV or a cogenerating fuel cell is the route to go.
If you care about emissions, wind/PVs are the cleanest, then fuel cells, then gas turbines, and in the far, far distance are the other fossil fuels, with coal/nuclear being the far worst by several orders of magnitude of environmental impact. There are some noxious chemical and emissions associated with the manufacturing of silicon wafers and carbon fiber for wind turbines and PVs, but all manufacturing processes have embedded energy and emissions.
The main disadvantage of small wind is the LCA where they just don’t generate enough zap to justify the embedded energy.
Engineering challenges
The structures of buildings are engineered to provide for occupancy safety and comfort. A wind turbine adds significant complexity (and cost) when attempts are made to integrate them with occupied structures.
First off, the vibrations of the rotors and generating gear need to be isolated from occupied spaces. There is mature vibration isolating technologies and methods that can be used, so this isn’t a prohibitive issue, but one of cost to solve.
Ice shedding is a major issue for wind turbines in areas with cold winters. This is an unacceptable safety risk for turbines in urban areas or adjacent to structures. While de-icing technology is being developed, they reduce the efficiency of the turbine.
Ducted turbines can have increased efficiency for wind blowing from optimum angles. Placing turbines in the centered within a structure, such as those proposed by SOM for the Pearl River Tower, force the architects to shift the building cores to one side or another. This reduces floor efficiency and may introduce code issues that need resolving.
Emissions
I was using emissions as shorthand for the broad lifecycle impact. Yes, the actual generation of energy via nuclear reactors has minimal releases of toxic/damaging emissions. I think you can agree that used nuclear fuels are extremely toxic and dangerous. If they are not ‘encapsulated’ they become mobile, i.e. an emission. Plus uranium mining is a destructive process. Like most hardrock mining uranium extration produces many emissions included intentional/unintentional releases of radiation, heavy metals, and acids that have poisoned many regions (including the Colorado River watershed).
The materials used in fuel cells and solar panels are more benign – though not impact free. It has recently become known that nitrogen trifloride, used in the fabrication of semiconductors, is one of the most potent GHGs out there and not regulated by Kyoto. There are no energy generation technologies that are 100% benign – 100% of the time, except photosynthesis.
We are not likely about to see the emergence of Building integrated Nuclear Reactors as was fantasized about in the 50s. Since cold fusion was a hoax, I doubt that we will have building integrated fusion either in the near future. Building destructive fusion/fission is available if you are a nuclear state, but not to average citizens.
Avian Deaths and Turbines
It is a fallacy that wind turbines kill lots of birds. Exponentially more birds die from crashing into windows and buildings, being fried by power lines, eaten by cats, run over by cars, or from anthropogenic toxins then will ever be hit by a turbine – even poorly located windmills in major migration routes. The US Forest Service published a thorough study on bird deaths that states:
500 million to possibly over 1 billion birds are killed annually in the United States due to anthropogenic sources including collisions with human-made structures such as vehicles, buildings and windows, power lines, communication towers, and wind turbines; electrocutions; oil spills and other contaminants; pesticides; cat predation; and commercial fishing by-catch….
38 dead birds found while monitoring nocturnal migrants at a small sample of turbines. McCrary et al. (1983, 1984) estimated that 69 million birds pass through the Coachella Valley annually during migration; 32 million in the spring and 37 million in the fall. The 38 avian fatalities were comprised of 25 species, including 15 passerines, seven waterfowl, two shorebirds, and one raptor. Considering the high number of passerines migrating through the area relative to the number of passerine fatalities, the authors concluded ‘that this level of mortality was biologically insignificant’. (McCrary et al. 1986)
This is the statistics from one of the oldest wind farms in the country that utilizes turbines close to the ground and other obsolete design feature. If we get rid of the electric grid, we can save 100 million+ birds/year! (Okay, they don’t distinguish between high-tension and local distribution lines).
Conclusions
The symbolism of integrating wind turbines into buildings is their greatest architectural value. Cities and buildings introduce to much turbulence into the air stream to make wind turbines practical. Then there is the increased complexity of the structure and need to isolate the building occupants from vibration. For true sustainable onsite energy generation, other technologies provide significantly more power, more consistently, at lower costs.
©2008 Barry Lehrman
References:
Dan Hill, City of Sound www.cityofsound.com/blog/2007/11/reading-a-recen.html accessed October 1st 2008
Kate Galbraith, ‘Assessing the Value of Small Wind Turbines’; The NY Times, September 3, 2008 www.nytimes.com/2008/09/04/business/04wind.html
www.theengineer.co.uk/Articles/303005/High+powered.htm
www.theengineer.co.uk/Articles/299825/Silent+revolution.htm
Erickson et al. A Summary and Comparison of Bird Mortality from Anthropogenic Causes with an Emphasis on Collisions USDA Forest Service Gen. Tech. Rep. PSW-GTR-191. 2005 1029
1986
USDA Forest Service Gen. Tech. Rep. PSW-GTR-191. 2005
Justin Good; What is Beauty? Or, On the Aesthetics of Wind Farms; www.designobserver.com/archives/entry.html?id=14344
Davis Langdon; ‘Wind and the Global Warming Imperative’ ; Building Services Journal; 06/06 www.davislangdon.com/upload/StaticFiles/EME%20Publications/BuildingServicesJournal/WindTurbines_BSJ_June06.pdf
© 2007 Barry Lehrman
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