Electricity

Getty Images

Anyone in the UK might remember the sunny, breezy days parts of the UK enjoyed in late May. As a result, on one of those days, the wholesale price for electricity - usually £50 per megawatt hour - turned negative for nine hours.

What's going on? Professor Michael Grubb, chair of the government panel on technical experts, told BBC Radio 4's Today Programme that on that sunny, breezy days when the prices turned negative - May 26 - the renewable energy providers wanted to sell as much power as possible.

Renewable energy has a fixed price so "they bid against each other until the prices went negative. So they paid out to the system but they got their guaranteed payments".

The UK has gone a full week without using electricity generated from coal, the system operator has reported.

That's the first time since coal was first used for making electricity in the 19th century.

"As more and more renewables come on to our energy system, coal-free runs like this are going to be a regular occurrence," said National Grid Electricity System Operator (ESO) director Fintan Slye.

"We believe that by 2025 we will be able to fully operate Great Britain's electricity system with zero carbon," he said.

Last year renewable power sources accounted for 27.5% of UK electricity generation.