Malcolm Scott asks for a reply to his letter (October 13) about wind energy.
Wind turbines are simply prayer flags for the “big society”. This is why.
We are not told the truth about the contribution.
Developers give the energy potential of a wind farm as “installed capacity” – 9.2Mw for Reeves Hill. Actual output is another matter.
The first consideration is “load factor” – the average electricity generated over a year as a percentage of “installed capacity”.
The Reeves Hill developer uses an unrealistic load factor of 30 per cent which is nevertheless embedded in the “facts” given to the Herefordshire Council planning committee.
Wern Ddu in Denbighshire, a comparable wind farm, achieved a load factor of 19.4 per cent in 2010.
Note that the word “average” can mislead. Wind is highly variable and unpredictable; we do not know how variable on Reeves Hill because the developer will not release the data.
In line with Government policy, the planning committee was informed that it is not for them to consider commercial viability or productivity of the project. All they were allowed to know was the “equivalent number of homes”
supplied. But this fantasy figure is bumped up 50 per cent by an unrealistic load factor and divided by national household energy requirement. If households were technically able to rely on wimore than 50 per cent of the time.
The variable strength of the wind does not correspond to the pattern of demand on the National Grid as was well-publicised in the cold, still spell around last Christmas.
Grid supplies have to be tailored to demand because mains frequency must be kept at 50Hz and excess cannot be tolerated. The obligation to accept all renewable generation means that other supplies must be adjusted. To iron out the consequences of wind variability, there has to be back-up “spinning reserve” matching 90 per cent of the output of wind for when the wind does not blow. The reserve must be readily available and most generators are slow to adjust. Even conventional gas is not flexible enough and so, as the percentage of wind in our energy mix increases, suitable, but less efficient and more expensive, conventional fossil fuel generators (such as “open cycle”
gas plants) will have to be built.
We are not told the truth about costs.
The grid cannot cope with too much wind either. Take-up is guaranteed for all renewable generation, and so, wind energy producers are paid over the odds to shut their turbines down.
Expensive shut downs (one wind farm was paid £1.2 million to stop producing for 8.5 hours this September) are bound to increase with the proportion of wind in our energy mix.
Our Government is loading the dice even more in favour of developers with the forthcoming “presumption in favour of development”.
DR CHRISTINE HUGH-JONES,
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