Tuesday February 5, 2013

I'll get back to our experiences with windows in a few weeks following up on last week's column.

In the mean time, with the Vermont legislature debating whether to institute a three-year moratorium on what detractors refer to as "industrial wind power," and debate raging in the nearby towns of Windham and Grafton about a potential wind farm, I figured I should weigh in.

As readers of this column know, I am a strong proponent of renewable energy, including wind power. But I'm also not shy about pointing out situations in which wind power doesn't make sense. This week I'm going to focus on those misguided or less attractive wind power applications. Next week I'll cover where we should be heading with wind power and discuss projects like the one proposed for Windham and Grafton.

Don't put wind turbines on buildings Wind turbines almost never make sense on buildings - even tall buildings. When I started researching "building-integrated wind" a few years ago for my newsletter, Environmental Building News (EBN), I thought I was going to write an article that painted a positive picture of putting wind turbines on top of buildings. After all, tall buildings can get the turbines up high where it's windier, and like rooftop photovoltaic (PV) systems, the power is generated right where it will be used.

But the more I dug into it, the more clear it became to me that building-integrated simply does not make sense.

First, wind turbines installed on buildings have to be small so that they won't affect the building's structure, so the power-generation potential is limited.

Second, wind turbines generate significant noise and vibration. That can be okay when the turbines are a quarter-mile away, but on a building it can be a real problem - particularly with a steel-framed commercial building that transmits noise and vibration throughout the structure.

Third, dealing with turbine installations on buildings increases costs significantly. Special attachments are required, and loads may have to be distributed downward through the building.

Fourth, even if the economics work out it's hard to believe that insurance companies would embrace the installation of wind turbines on buildings. I suspect that insurers would raise insurance rates significantly, due to the increased liability - or perceived liability - of blades flying off wind turbines or rooftop towers collapsing and damaging roofs. Insurance rates wouldn't have to rise very far for those costs to exceed the value of the generated electricity.

Finally, it turns out that all that wind swirling by tall buildings is highly turbulent. Wind turbines don't like turbulence; they do much better with like laminar wind flow. Some types of wind turbines apparently do better with turbulence than others, but most don't perform well in such conditions.

When I was researching my EBN article, I spent weeks trying to track down performance data on building-integrated wind turbines, but could find almost none. I knew that that data was being collected by manufacturers (up to a dozen manufacturers were producing wind turbines specifically designed for installations on buildings), and the fact that they didn't want to share it made me suspicious that it was far worse than those manufacturers were claiming.

With a lot of anecdotal evidence of extremely bad performance of building-integrated wind turbines, I got more and more discouraged about the practicality of putting turbines on buildings, and I ended up titling my May, 2009 EBN article "The Folly of Building-Integrated Wind." Wind turbines don't belong on buildings.

After my article came out, I finally tracked down some performance data from the Boston Museum of Science, which installed building-integrated wind turbines from five different manufacturers. As I suspected, the performance was terrible - far lower than manufacturer claims.

With ground-mounted wind turbines, smaller is not better Even when we stick with ground-mounted wind turbines, the performance and economics of small machines (a few tens of kilowatts (kW) of rated output and less) is usually very poor. With wind turbines there is a huge economy of scale. Homescale wind power rarely makes good economic sense - except in locations where there is strong, steady wind.

I'm disappointed by this. I would really like to think that I could install a cost-effective wind turbine at my home, but I can't. A good site for wind power - where there is a strong 15- mph wind much of the time - wouldn't be a place you'd want to live. And with small wind turbines you can't put them too far from the place where the power will be used or fed into the utility grid. So even if your property rises up to a ridge, putting a small wind turbine there may not be feasible in terms of getting the power down to your house or feeding it into the power grid.

Studies I've examined where actual performance of small, ground-mounted wind turbines has been collected, the measured output has been significantly below the predicted output. Plus, the maintenance requirements are significant. Compared with the alternative - arrays of PV modules that just sit there with no moving parts - it's just a whole lot more difficult to justify small wind. The economics usually don't work.

Next week, we'll look at where wind power can make sense: much larger wind turbines that can be aggregated into wind farms.

Alex Wilson is the founder of BuildingGreen, Inc. and the Resilient Design Institute (www.resilientdesign.org), both based in Brattleboro. Send comments or suggestions for future columns to alex@buildinggreen.com.