Microgeneration – Urban Wind Turbines

If, like me, you’ve considered making electricity by installing green technology on your house, then you may be considering a wind turbine to go on the roof.

I’d like to dissuade you if I can.

What? Why on earth would you do that, I hear you say (or something like it!)

Wind energy is great in the right place; it is potentially available 24hrs a day, unlike solar energy. So what’s the problem? Read on my friend…..

Putting a wind turbine on the roof of your house is like buying a Solar panel and then leaving it indoors by a window. You’ll get something from it but it will never achieve anywhere near its full potential. Even with the Feed-in-Tariffs available it would take a ridiculous amount of time to pay for itself, or even off-set the carbon produced in its manufacture, delivery and installation.

I’ve done a lot of research into this because I wanted to install a turbine at our house in Portugal. (We already have solar water heating)

A turbine needs to be in clear air, at least 10m or 30ft above the nearest obstruction in order for it to operate at best efficiency. This is because the blades of the turbine need smooth flow across them, to turn them quickly. The house, or any other nearby obstructions, creates disturbances in the air flow, reducing the output of the turbine dramatically. So, if you can site the turbine away from the house, on a free standing mast, and 10m above the nearest obstructions (upwind and downwind), then you have a potential location for a turbine.

The other factor of course is the wind resource itself. The average energy available in the wind increases in proportion to the average wind speed cubed. So if you have a Site A, with double the average wind speed of site B, then Site A has eight times the potential out put of Site B, using the same turbine.

If you are still tempted, you can install an anemometer (wind measuring instrument), on a mast at the same height as your prospective turbines hub and record the average wind speed for a year. Check out the manufacturers predicted output graphs for your proposed turbine, against your wind data.

If you are in an urban environment, you will probably find that you saved yourself a lot of money!

Of course, if money is no problem and you have a good site, then the turbine will start paying back to the environment as soon as it’s running.

If you are off the grid, it’s a different story…..

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