Martin's "Teapots"

Hello,

I've had my mother-in-law draw my attention to a TV news report which referred to the REF study. It is rather difficult to get the message across to the layperson that 'capacity factor' is not a sensible measure of the effectiveness of wind turbine's performance. In this context, neither do TV journalists seem able to interprete these figures meaningfully.

To recap, capacity factor is calculated by dividing actual output by the output that would be generated by a turbine operating continuously (365 x 24 hours) at its rated capacity. Any validity it has is as a crude relative measure of performance for comparison between turbines. As an absolute measure of performance it really doesn't add much value. In practice most turbines globally operate economically at capacity factors between 20 and 30%, and in this respect the Scottish performance is actually very good, as might be expected for one of the best wind environments in Europe.

There is plenty of non renewable electricity generating plant that operates at capacity factors lower than 20%, e.g. open cycle gas plants which are used for reacting to rapid fluctuations in electricity demand can operate economically at very low capacity factors. Dinorweg (?) operates at a very low capacity factor, as do some of the other hydro plants. I suspect that this year's capacity factors for our very numerous ailing nuclear plants are going to end up towards the bottom of the range.

Unfortunately none of this helps with trying to get the mother-in-law back onside.

regards