Wind Energy - the Basics

THE BASICS

We all know that it's possible to get energy from the wind. You may have seen the wind turbines on Anglesey and elsewhere which are connected to the National Grid. They're amazing feats of engineering. There are smaller turbines for domestic use, too, but before thinking about buying one you need to be aware of what they can and can't do.

A typical household needs a reliable electricity supply, a cooker, hot water, a washing machine, light and warmth.

A wind turbine next to your house coupled to a small generator will, when there is adequate wind, supply electricity - enough for some lights, a TV, a radio, and a computer, though probably not all at once.

A wind generator won't power your electric cooker, washing machine or electric fire. It won't be very happy with your kettle or food mixer, either.

You'll need some rechargeable batteries (about ten car batteries-worth) to keep things going on tranquil days, and to "smooth out" the intermittent nature of the supply so that you get a steady voltage. You'll also need an inverter to convert it to 250 Volts A.C. so that your electrical gadgets will work.

If it's calm for more than a few hours your batteries will go flat and everything will stop, unless you switch off most of your electrical stuff or put your mains supply back on.

It's possible to do lots of calculations showing what wind power can do. But before you get blinded by figures you need to remember that when the wind stops, your generator stops. You have to rely on the batteries and hope for windier weather.

It's not easy to get data on the MEASURED output of wind turbines. No-one seems to write about it. I guess once the turbine is sold, the company loses interest ... and how many private individuals are going to log the data and publish it?

Most turbine manufacturers don't publish data, either ...

Lots of boffins will tell you how much energy you'll get if you know the windspeed and the size of the turbine and how high up it is, and a lot of other technical stuff.

Most people aren't interested in all that. They're not scientists. They're ordinary people, concerned about the environment and wondering if they should spend their hard-earned cash on a wind turbine. Will it be worthwhile, or just an expensive ornament?


SOME BASIC SUMS

Let's think about energy.

A light bulb is 100 watts. That's a measure of how much energy it uses.

A low energy light bulb uses about 20 watts. They don't get so hot; that's how they're designed. They're good for background lighting but I find them difficult to read by.

A telly or computer is about 200 watts; a mains radio is less because there's no screen - probably 50 watts.

A kettle is about 1000 watts. A washing machine with heater OFF is about 1000 watts; with heater probably 3000 watts . An electric cooker is around 3000 watts with the oven and a couple of rings switched on.

Now ... a 2 metre diameter wind turbine will probably supply about 500 watts in a strong breeze (about 25mph), and a lot less in a moderate breeze. If the windspeed halves, you get one eighth of the power - about 60 watts.

You can do the sums. Why not watch the weather forecasts for a few days, and look at the windspeeds?

If you're happy with that (it's enough to have a stand-alone power supply for lighting, etc, independent of the grid), read on .....



Nigel Deacon / Habitat21 website

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