Have you ever passed a wind turbine on a blustery day and wondered why it's not turning?

It's not broken. It's stopped because the national grid, the network which transports electric power around the country, can't take any more.

And we're not just missing out on all that green energy, the grid has to pay wind turbine owners to turn them off, costing the taxpayer £1bn pounds a year.

So with ever increasing demand, how will it keep up?

Science Correspondent Martin Stew tells Lucy Watson what you need to know.