Author Topic: Perminent Magnet Alternators Windturbine  (Read 2017 times)

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Perminent Magnet Alternators Windturbine
« on: June 04, 2014, 09:02:55 PM »
I have seen several manufactures stating 500-1800watts wind turbines using 4ft diameter blades on PMA wind turbines.  Is there any truth to the numbers?


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Re: Perminent Magnet Alternators Windturbine
« Reply #1 on: June 05, 2014, 02:06:06 AM »
There were small turbines fitted to some aircraft to power auxiliaries that achieved similar figures but you are looking at wind speeds of 200mph and upwards.

In reality you are being taken for a ride by silly adverts from crazy manufacturers, I guessed this was the origin of the aluminium blades question.

The power in the wind rises as the cube of wind speed so if you take an unrealistically high wind speed you might see these figures. Even so trying to make a small PMA handle 500W for more than a few seconds is a challenge. When you look at the specification for some of these PMA's you will see that they multiply open circuit volts by short circuit current and claim this to be power ( total nonsense).

As a source of power you are looking at winds normally met on real sites, there is no point in including the output from gales that may happen twice a year, it contributes nothing.

A really good wind site with average winds in the 12mph region will have useful winds often enough up to about 30mph, beyond that the contribution will be small. You can expect possibly 200W plus from a good 4ft machine but even then it will come as a compromise to its low wind performance unless it has mppt.

I suspect that Hugh Piggott's 4ft machine is one of the best and he realistically claims about 150W. Even so on most days on a normal wind site the average power will be in the 10's of watts.

Even thinking about going off grid with an 8ft axial machine will mean very Spartan living unless it is an incredibly windy site or you back it up with a lot of solar.

What matters with wind is the average power generated on a typical day, it will be an order of magnitude below the machine's nominal rating even if realistic. Claims of 800W for a 4ft machines are well beyond the Betz limit for any wind speed you are likely to see.