Wind Farm Efficiency ....

How efficient is a wind farm ?  I'm not entirely sure I know how that's measured and costed.  There appear to be that many variables and subjective views on the subject.  I came across the following two quotes from a 'pro windfarm' site ...

"Wind turbines operate when the windspeed is within certain limits. There has to be enough wind for the blades to turn – typically 3-4m/s (or 7-9mph, 6-8 knots). When the windspeeds get to 25m/s (56mph, 49 knots), turbines typically shut down to protect the structure from excessive loads"

"As windspeeds increase, so the energy generated by the turbine does as well. At some point where windspeeds are around 15m/s (34mph, 29 knots), the maximum (or rated) capacity of the turbine is reached. A limit has to be set to define the sizes of the various components – gearbox, generator, cables, rotor blades)."

That equates to a about a F3 -F7 range.  Key point for me is that peak capacity of the windfarm is around the 15m/s mark ( top end of a F4 ). 

The Solway Firth has 100 3MW turbines planned for Luce Bay.  The Strategic Environment Assessment from the Scottish Government quotes that the average wind speed for the Solway Firth is unlikely to exceed 8.5 m/s.  Without being too exact about the arithmetic, that is rougly half of the speed required to read peak efficiency. 

Another source, reputedly using data from NASA from the previous ten years worked out an average of 9.5 m/s.  I'm not going to get hung up over the difference, nor suggest that the "efficiency" will be as simple as outlined above, but perhaps serves to illustrate the amount of spin / misinformation / call it what you want ... that is out there. 

It's almost an argument for siting the windfarm further offshore.  But then that would cost more money and decrease the profit.  Or am I just cynical ?  Where would the optimim location be ?  Who knows ?  As I've looked into this subject, I can't help feel that we're being 'guided' by industry bodies that perhaps have a slightly coloured 'green' agenda ...

Windfarms are here to stay - there's no question about that.  There's too much politics, government money, face at stake now.  Finding a balance between location and impact is going to be difficult to achieve.  The development in the Firth of Forth seems okay, but the Solway proposal feels too near the coast ....