In yesterday’s blog I discussed how much people enjoy proving everyone else wrong. Given various popular conspiracy theories I wondered whether contrarians believed they were latter-day Don Quixotes? However, when it comes to debunking domestic renewable energy there is one area where it was deserved. Wind Turbines on a house are a pants idea. An exception to prove the rule?
Does anyone recall walking into B&Q throughout 2009 in High Wycombe and seeing that Windsave domestic wind turbine? Have you read about David Cameron’s eco-bling-wind-turbine on his house? Now this isn’t to say I always been so dubious. I fell for the advertising and thought it would be a good idea to bolt a couple of these bad-boys to my house. Of course I never did. Much like all of these technologies I actually took the time to read about them. You don’t have to scratch the surface very far to find out that small wind turbines on homes don’t work.
Regardless, it remains one of the most common questions I get asked during the summer show season. “What about a wind turbine on my house?” they say. The idea certainly has taken root in the public imagination, maybe more so that the far more practical and proven solar panels. This remains true after the domestic wind turbine was proven to be a thorough waste of time. I believe Paul Mobbs in his book “Energy After Oil” (Matador Publishing 2005) was one of the first places I became conscious of the problem. He calculated the optimum size and spacing for wind turbines to operate at the highest efficiency. Do you know what he found? Much as Goldilocks found there is such a thing as too small and too large, there is an optimum mid-size for a wind-turbine. This is far larger than the size of ones you find on houses and smaller than the ones on wind-farms.
The reason why it is smaller than the ones actually built is that “larger is better” is the mantra of financial return on investment. The bigger turbines simply are more profitable. However it is a good idea to make far more use of available space with far more mid-sized turbines. The one planned at Highworth School is one such example and there is one up the hill at Flackwell Heath. The power drop off is rapid as the turbine blade width decreases. Technically the power is proportional to the square of the turbine blade radius. Simply making half the size doesn’t mean you get half the power. You actually get one-quarter the power. If they get too small they are out of the Goldilocks zone and will yield very little useful energy in comparison to the needs of your home.
The other problem is WHERE to put them. The power you can generate decreases with wind speed (obviously) but the drop off is also rapid. Technically power is proportional to the cube of the wind speed. The manufacturers point to the average wind speed in the UK as proof of how good their products are. In reality you will only ever get that wind speed in open countryside, some distance from trees, and above a certain height. If you are in a suburb of High Wycombe the surrounding houses and trees make the air turbulent. It doesn’t blow straight, it gusts in random directions. Not only will your domestic, roof-mounted, wind turbine generate very little usable energy it might also shake your house apart. And don’t get me started about the potential noise and nuisance to your neighbours.
Now if you live in open space somewhere outside of High Wycombe on a hill then it will be a different story. Even then a small wind turbine should be mast mounted. In the future it is likely that all schools will have one or more small turbines operating from playing fields. All villages in outlying areas are likely to have them as well. Around Wycombe we can expect the larger commercial wind-farms to grow up along the M40 corridor. These are the sort of scales wind power will operate at.
So, Don Quixote was right, well sort of. When it comes to wind power – turbine size matters. If you want to enter the wonderful world of home power generation then Photovoltaics remain the safest bet. If you don’t have the roof space for panels then the next generation of combined heat power (CHP) system may be for you. House mounted “domestic” wind turbines are a terrible advert for wind power and gives every contrarian an excuse to suggest ALL wind power is bad. Of course this is also nonsense. Bigger wind turbines are what will keep the lights on increasingly in future. Wind is predictable and dependable. It may not blow all the time, everywhere, but this is no more of a “problem” than the operational down-times of coal or nuclear power stations.
Wind power is a technology for your community, not your home. From there it scales up and up and up.