Written by Colin Cameron Friday, 23 September 2011 14:03
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The tail-end of Hurricane Katia brought plenty of rain and wind to Britain last week – so much, in fact, that wind-produced electricity was more than the grid could cope with.
National Grid, which manages the electricity transmission network, asked 13 windfarms to stop producing electricity for periods between September 10 to 14.
Locally, the An Suidhe windfarm, on the hills between Loch Fyne and Loch Awe, was asked to reduce generation.
A spokesman for National Grid said: “National Grid balances supply with demand on a minute by minute basis, and can ask power generators to come on and off the network to keep it balanced, making sure we all continue to receive secure energy supplies.
“In this case, some windfarms were asked to reduce their generation as supply was outstripping demand and our priority is always to operate the network as safely as possible.
“If there is too much generation, we sometimes use what’s called the balancing mechanism (BM) to accept offers for power stations to stop producing (and vice versa, we can use the BM to accept a bid to generate more power).
“We do this to make sure the supply/demand balance stays in balance, or else it could affect things like system frequency and voltage.”
The balancing mechanism is used to compensate generation companies for potential loss of production, and in last week’s storms, the total compensation paid was was £2.6m.
The National Grid spokesman added: “As we move into winter – and particularly after the clock change in October – electricity demand tends to increase. So while we can’t definitely say we won’t have to reduce generation over the winter, it is less likely given people use more electricity.
“This situation tends to arise when it is warm and there is relatively low demand, but the wind is still blowing.”
According to the British Wind Energy Association, wind turbines start operating at wind speeds of 4 to 5 metres per second (around 10 miles an hour) and reach maximum power output at around 15 metres/second (around 33 miles per hour). At very high wind speeds, i.e. gale force winds, (25 metres/second, (5-plus miles/hour) wind turbines shut down.