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Why wind farms will have to shut down for 38 days per year … when it gets too windy

Wind farms may have to shut down when it gets too windy because the National Grid cannot cope with a surge in power, a study has found.

This could lead to the sites being shut down for 38 days a year – at present they are switched off for 25.

Britain is expected to increase wind power capacity seven-fold by 2020 to 26.8 gigawatts (GW), which would put additional strain on the network and could lead to overload at times of weak demand and high wind speeds.

The rapid rise in renewable energy from wind and solar plants is set to bring significant problems for the network as it tries to incorporate an output which is intermittent and more difficult to predict than that from thermal plants.

‘It will become increasingly necessary to restrict the output from wind generation onto the system to ensure sufficient thermal capacity is synchronised,’ said the network operator the 2020 transmission system report published yesterday.

Based on historic data, wind turbines will have to be switched off for 38 days every year when wind power production exceeds 35 per cent of installed wind capacity and demand falls below half the levels seen at peak time, National Grid said.

In Germany, where more than 25GW of wind capacity is already in place, high wind speeds coinciding with low power demand, for example overnight during summer time, have caused negative wholesale power prices as producers are forced to sell renewable energy to the grid.

One of the keys to solving this in Britain will be developing storage facilities which can act as ‘sink’ for wind and solar power.

‘National Grid believes that suitable funding streams should be introduced to support innovative storage technologies to bring them to a point where they are made viable,’ the report added.