SIR, - Mr Carlile questions the accuracy of figures quoted concerning the potential electricity output from the Blackmains wind farm proposal (December 29).
I would like to respond to his specific concerns with the following clarifications:
1) Based on wind farm output figures for the past three years, Mr Carlile writes that the 30% load factor claimed for the Blackmains project is unachievable. While this will vary from year to year and from site to site, longer term trends provide a more accurate estimate of likely average annual output over a wind farm’s 25 year lifetime. According to statistics from the UK Department of Energy and Climate Change, between 1998 and 2009, the average load factor for all wind farms in Scotland was 29.2%. The technology used in operational wind farms is also older and generally less efficient than would be installed at this or other wind farms in the future. The Blackmains site has a good wind resource so an estimated average load factor of 30% over 25 years is realistic.
2) Mr Carlile is concerned that, given the variability of electrical output from wind farms, the claim that output at Blackmains equates to supplying 10,000 households with electricity is misleading. Using officially approved figures from DECC, we have quoted this number to provide a meaningful illustration of 55 gigawatt hours of electricity based on average household electricity consumption. Although a modern wind turbine cannot always operate at maximum output, it will be generating electricity for 70-85% of the time. So while it is true that other sources of energy are required to provide baseload, the level needed is not nearly as great as Mr. Carlile implies. At the same time, we accept that onshore wind is one of a range of sources making up the energy mix required to meet current and future energy needs and have never claimed otherwise.
3) Mr Carlile argues that the estimated load factor of a wind farm takes no account of electricity consumed by each turbine during the wind farm’s operation. In fact, all energy sources consume electricity in the process of generating electricity. However, burning fossil fuels is far more energy intensive (and environmentally damaging) than the small amount of electricity required to operate a wind turbine. Whereas a wind turbine will typically generate 30 times more electricity during its lifetime as is used during its manufacture, a coal-fired power station will only ever deliver a third of the total energy used in construction and fuel supply.
We appreciate the constructive discussions we have had with the local community so far and will provide more information concerning our investigations of the Blackmains site over the coming months.
In the meantime, we are pleased to answer any specific questions about the proposal. Please visit www.blackmainswindfarm.com for more details.