Performance analysis and improvement of a small locally produced wind turbine for developing countries

Nienke Hosman (2012)

A 1.8 [m] hugh Piggott design wind turbine has been tested in the Open Jet facility (OJF) at the TU Delft. Then the model has been adjusted with a new simplified rotor design: No cord or pitch (twist) variance along the blades. This new design has been benchmarked with the original design.

COMMENT by Hugh Piggott.  (I am not sure why there is no ‘comment’ button on this LDocument page, so I am using my editing rights to add this remark and pointing to a new forum topic so that others can reply.)  I need to point out that there is a flaw in the way Nienke approaches the question of predicting energy production at a site with mean windspeed 4 m/s.  In the real world (which is not a wind tunnel) the wind is often almost stopped and often stronger than average.  If you can find out the distribution of windspeeds (expressed in hours per month at each speed) and multiply the hours by the power in each case, then you can arrive at a realistic prediction of the kWh of energy produced in a month.  You will find that the average power is always higher than the power at the average wind.  This is because the average of the cubes of a distribution of numbers is always more than the cube of the average of those numbers.  It’s called the ‘Energy pattern factor’ and in a typical European windspeed distribution with Weibull k value of 2 then you will see about 1.9 times more energy in the wind than it would have if it were blowing constantly all the time at the mean windspeed.

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