On a blustery day, wind turbines will be turning and generating lots of lovely clean power. Last summer the Met Office issued a yellow weather warning for wind in Scotland. A few bridges were shut and ferries cancelled, but that was the day wind turbines produced 100% of Scotland’s power needs.
But when extreme weather and very strong winds hit, turbines sometimes need to be shut off. All modern wind turbines are are set to stop turning automatically if there’s too much energy in the wind. Some will shut down if the average speed of the wind is over a certain level for a period of time, while others will stop after a super strong gust (something like 100mph).
It’s pretty rare that we’ll see strong enough winds in the UK to stop the turbines - and certainly not to stop all of them. High winds affecting 40% or more of the UK’s turbines would occur in around one hour every ten years (pdf).
The reason turbines shut down like this is for safety - if the wind is too fast it can put major stress on the blades and mechanisms inside the turbine causing lots of friction and long term damage. It’s much safer to have the turbines stop and then start again when wind is a bit slower and safer.
It’s pretty straightforward to predict, too, so the National Grid know when there will be lots of wind power produced, and when they will have to switch off. That means they can easily plan for the variation.
The other reason turbines may stop turning on windy days is when there’s too much renewable energy being fed into the National Grid. The grid was originally built around a few centralised power stations, rather than lots of small generators feeding in. When it’s too windy and turbines are producing lots of clean power, the grid people ask some wind turbines to switch off to stop the grid from getting overloaded. This isn’t a problem with wind turbines, they’re just doing their job, the real a problem lies with the grid which needs to be upgraded to support a new smarter energy system.
If you’re wondering what happens when it’s not windy - we’ve also written about that!
Banner image: Nigel Goodman, creative commons.