The annual home equivalent for each project has been calculated based on an annual energy yield estimate for the project and an average annual domestic energy consumption figure.
Estimated energy yield
The annual wind resource available at each site has been derived from the long term average wind speed recorded in the UK Wind Speed Database (NOABL: http://www.bwea.com/noabl/index.html), extrapolated to the proposed hub height of the turbines. The derived wind speed is then fed into a Rayleigh probability distribution to estimate the frequency at which each wind speed will occur yearly. The wind speed distribution is then combined with the published power curve for a target wind turbine to give a yearly gross energy yield. The gross yield figure is then factored to account for losses, including: wake losses (calculated using a computer model), availability losses (3%), electrical losses (3%) and control losses (3%).
Annual domestic energy demand
The average annual domestic energy demand in the UK has been assumed as 4,700kWh per home per annum. This figure has been derived from the Department of Energy and Climate Change’s published data for the period 2005 – 2009 http://www.decc.gov.uk/en/content/cms/statistics/energy_stats/regional/electricity/electricity.aspx. The highest recorded annual average during this period was 4,670kWh per home in 2007.
Calculation
Energy yield (kWh) ÷ domestic energy use ( kWh/household)