Using Wind Turbines in Urban Built-up Areas
Wind turbines generally don’t work well in built up areas, where they may be placed downwind from houses, tall hedgerows or trees.
An area might still be very windy, but this wind is made up of eddies and gusts with a lot of turbulence. Eddies come from various directions and the turbine cannot respond quickly enough to differing wind directions.
However, turbulence has an even more marked effect. A wind turbine doesn’t really work by wind pushing the blade around – most of the energy happens close to the blade tip which works on the basis of lift coming from areas of high and low pressure, similar to the wing of an aircraft. We all know what happens to the wing of an airplane when it hits turbulence. The same thing happens to the blade of a wind turbine, and the output of the turbine is decimated by this effect.
For this reason, a wind turbine must be as high as you can get it, and as far away from obstacles in the direction of prevailing winds. There are very few instances where a turbine can work effectively in a built up area, so unless you happen to be on the western edge of a housing estate, or have a site which is wide open to wind from anywhere between SW and NW, a turbine won’t work for you.
To assess the effects of obstacles, you should obtain a wind rose from the met office for your area, and estimate the percentage of wind you will lose due to obstacles located at different compass points from the turbine base.
David Cameron notoriously put a turbine on the roof of his house, and many people believed that this is a simple solution to our energy needs. It isn’t – rooftop turbines are the snake-oil of the domestic wind energy market. There are interesting efforts to make vertical axis machines that will work, but none of them are convincing as yet…
Category: Wind Turbines 3 comments »
May 26th, 2009 at 2:44 pm
Guys
What do you think of the Swift rooftop wind turbine from Renewable Devices in Scotland ??? Is this a snake ?
Ray
June 27th, 2009 at 8:59 pm
Hi Raymond, A lot of well-meaning people are trying to develop a wind energy system which would work in cities, but studies of the results have all been disappointing. I personally think the long-term solution for urban dwellers is going to be solar photovoltaic, but only when the price of panels falls to the promised Holy Grail of US$1 per watt. Many manufacturers are working towards that target in the next year or two.
Because of turbulance, wind will only work in areas with an open aspect. There are many such sites that have not been harnessed, and I think that should be the priority. But you can’t help people living in urban areas wanting a turbine…
July 4th, 2009 at 8:50 am
There are many well-meaning people trying to make a turbine suitable for urban dwellers – after all, they make up the majority of our population. However, I don’t think you can get away from the fact that the energy in the wind, and the turbulance makes this a non-starter in most cases.
I think in a few years time solar PV will come down in price sufficiently for this to make more sense. Personally, if I was an urban dweller, I would wait for that…. Q