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Forum Index : Windmills : Constant speed?

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petanque don
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Joined: 02/08/2006
Location: Australia
Posts: 212

Posted: 03:00am 23 Feb 2007

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In a perfect world would a windmill be set up at run at a constant speed?

Could pulse width modulation be a method to vary the load to achieve this?

Basic PWM information is at

http://www.cpemma.co.uk/pwm.html

Gill

Senior Member

Joined: 11/11/2006
Location: Australia
Posts: 669

Posted: 11:13am 23 Feb 2007

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I see the whole point of a wind generator as being to convert the winds energy into electrical energy. The faster the wind blows the more energy it can impart into our system. The windmill uses propellor blades which are in essence a screw (inclined plane). The faster the wind blows, the faster the blades must move. Idealy, Variable pitch blades would allow us to extract the winds energy most effiently as indeed the large commercial windfarms do. Having a constant speed can not extract more of the winds energy and therefor is definately not desirable.

Could it be that you are seeking not max power from your mill but a specific type of output? Say a fixed voltage and/or a fixed frequency?
A fixed speed may seem the solution though the control and ineffiencies would be a major challenge. For my part, a fixed voltage of 240v ac @ 50Hz is best achieved with an inverter off a battery bank in spite some losses.

was working fine... til the smoke got out.
Cheers Gill _Cairns, FNQ

KiwiJohn
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Joined: 01/12/2005
Location: New Zealand
Posts: 691

Posted: 04:07am 24 Feb 2007

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I believe your idea of using PWM to vary the load and hence vary the speed of a wind generator has some merit.

As far as I can see the advantage would come during light wind conditions when the system could reduce the load on a turbine that would otherwise stall.

petanque don
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Joined: 02/08/2006
Location: Australia
Posts: 212

Posted: 03:06am 27 Feb 2007

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My thoughts were that when there is a modest breeze that having no load on the windmill may help to get the windmill moving initially and being able to harvest a few watts in marginal conditions could be an improvement on having no output from the wind mill.

This would have to be balanced against having the bearings turning for a longer period and increased wear of the bearings.

Logic would suggest that there would be no advantage to being able to reduce the load under very windy conditions when the windmill would be producing full output or possibly even furling.

KiwiJohn
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Joined: 01/12/2005
Location: New Zealand
Posts: 691

Posted: 05:16am 27 Feb 2007

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That makes sense to me!

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