There has been much academic debate on the ability of wind to provide a reliable electricity supply. The model presented here calculates the hourly power delivery of 25GW of wind turbines distributed across Britain's grid, and assesses power delivery volatility and the implications for individual generators on the system. Met Office hourly wind speed data are used to determine power output and are calibrated using Ofgem's published wind output records. There are two main results. First, the model suggests that power swings of 70% within 12 h are to be expected in winter, and will require individual generators to go on or off line frequently, thereby reducing the utilisation and reliability of large centralised plants. These reductions will lead to increases in the cost of electricity and reductions in potential carbon savings. Secondly, it is shown that electricity demand in Britain can reach its annual peak with a simultaneous demise of wind power in Britain and neighbouring countries to very low levels. This significantly undermines the case for connecting the UK transmission grid to neighbouring grids. Recommendations are made for improving ‘cost of wind' calculations. The authors are grateful for the sponsorship provided by The Renewable Energy Foundation.
A model of a large and distributed installation of wind generators has been produced for the UK and used to analyse the power output characteristics for each January in the last 12 years. It suggests that
1) Although the aggregate output of a distributed wind carpet in the United Kingdom is smoother than the output of individual wind farms and regions, the power delivered by such an aggregate wind fleet is highly volatile. For example, if 25GW of wind turbines had been installed, with full access to the grid, in January 2005 the residual demand on the supporting plant would have varied over the month between 5.5 and 56GW.
2) Wind output in Britain can be very low at the moment of maximum annual UK demand (e.g. 2 February 2006); these are times of cold weather and little wind. Simultaneously, the wind output in neighbouring countries can also be very low and this suggests that intercontinental transmission grids to neighbouring countries will be difficult to justify.
3) The volatile power swings will require fossil fuel plants to undergo more frequent loading cycles, thus reducing their reliability and utilisation.
4) Reduced reliability will require more thermal capacity to be built to compensate, whilst achieving the same level of system reliability. Cost of wind calculations would be more accurate if they included this factor.
5) Reduced utilisation will encourage generators to install lower cost and lower-efficiency plants rather than high-efficiency base load plants. These have higher CO2 emissions than high efficiency plants. Carbon saving calculations would be more accurate if they included this factor.
6) Power swings from wind will need to be compensated for by power swings from gas-powered plants which in turn will induce comparable power swings on the gas network as plant ramps up and down. This will have a cost implication for the gas network. Calculations of cost of wind would be more accurate if they included this factor.