Scottish wind farms received a record $7.2 million to shut down this month after hurricane-force gusts produced more electricity than could be consumed.
Unusually strong summer winds blowing as high as 115 miles an hour swept the Scottish Highlands on Aug. 7, prompting National Grid Plc to ask energy generators to curtail production, according to the London-based company's commercial-operations manager Claire Spedding. The weather resulted in the U.K. grid operator awarding a record 7.3 million pounds in total payments across a range of technologies.
"It was a perfect storm: very windy, very sunny, but not actually that warm," Spedding said in a phone interview. The Aug. 7 winds blew on a Sunday afternoon when power consumption on the national grid also hit a record low, she said.
Rapid growth in renewables has caused power congestion on particularly windy or sunny days across the world. National Grid sometimes pays operators to switch off in order to balance its network. The company also pays generators to raise output to fill gaps when demand surges. The winds on Aug. 7, which prompted a weather warning from the Met Office, also disrupted train services because of fallen trees.
It's not just wind farms that receive payments to occasionally to switch off. National Grid paid other fuel types such as hydro, nuclear and oil 8.75 million pounds in the first three months of the year, compared to 10.08 million pounds for wind, it said. The company can also curb trading with other countries through interconnectors.
The morning of Sunday Aug. 7 saw power demand fall to record lows amid seasonally cool temperatures during a month when many people are on vacation.
"When you get temperatures above 25-ish degrees (Celsius) you start to see the impact of people using air conditioning," Spedding said. "We haven't really got to those kind of temperatures."
Wind farms have received more than 255 million pounds to idle since payments began in 2010, according to National Grid. Spedding said the payments cost less than building an over-sized grid that can handle power surges on unusually windy days.
"Although that one day will have cost consumers a lot of money for constraints it's a relatively infrequent occurrence," she said. "It's still a better outcome for households to spend that amount of money on one day restricting the power that's being generated rather than building a network that's sized to cope with that amount of power."
National Grid is also building a new 1-billion pound link with Scottish Power Ltd., known as "the Western Bootstrap" that will improve the flow of energy from Scotland to England when it comes online in summer 2017, she said.
The problem isn't unique to the U.K. grid operators. China and Germany are also struggling to absorb the influx of renewable power, forcing turbines to stand idle and focusing attention on the efficiency of investments. Even with double the installed wind capacity, China is producing less electricity from turbines than the U.S.
Wind farm opponents, such as the Renewable Energy Foundation, say payments are evidence that the U.K. should stop installing turbines. But Spedding said the issue isn't unique to wind.
"The payments that we make aren't specific to any kind of generator," she said. "We constrain generation types right across the network. Any arguments against any particular type of generator would apply to all of them."