The UK has seen a huge growth in wind farm installations, with the cumulative offshore and onshore wind installed capacity in the UK in 2016 recorded at 12.1GW, according to Wind Europe’s Wind in Power: 2016 statistics report.
However, because of a lack of energy storage, the UK electricity grid is unable to handle the large amounts of intermittent electricity created by renewable sources like wind farms during times of low energy demand. Too much or too little power can throw off the balance of the grid and create problems suppling energy to customers.
As we move towards the summer months, which typically sees a much less energy used across the country, the National Grid is having to find a way to stop electricity created from wind farms overloading the grid.
The National Grid Summer Outlook 2017 report predicts some of the lowest demand for electricity so far. This is down to the fact that people use less power for heating and other indoor appliances during the warmer summer months – particularly overnight and on weekend afternoons.
The report said that for the last few years both peak and minimum levels of demand on the transmission systems has continued to fall. Actual summer minimum demand for summer 2016 fell to 16.8GW, or 17.8GW when corrected for weather.
The National Grid said it expects this trend to continue this year, with summer minimum demand 500MW lower than the 2016 weather corrected outturn. The peak transmission system demand forecast for high summer is 35.7GW, while the summer minimum is 17.3GW. The minimum available generation is expected to be 38GW in the week commencing 31 July.
Pay to prevent
As the minimum demands on the transmission system fall, the report said that National Grid anticipates that there “may be times this summer when there is more generation on the system than is needed”. The solution suggested is to “curtail flexible generation” like gas units and large wind farms.
The report added that it may also be necessary to instruct “inflexible generators”, including nuclear power plants and some hydro and wind farms to “reduce their output during these periods of low demand”.
This will be done as part of the National Grid’s Demand Turn Up (DTU) Service, which pays large energy users and generators to either increase demand or reduce generation when there is too much energy on the system.
Phil Sheppard, director of gas and electricity operations, said that to make sure the National Grid is prepared in February 2017 it completed a “successful tender” for the DTU Service - procuring 138.6MW of fixed DTU provision.
“We dispatched this service for the first time in summer 2016 to help us manage periods when demand was low and generation output was high,” said Sheppard. He added that it is “just one of the tools and services we can use to balance the system during the summer”.
This kind of flexibility means we’re using power in a "smarter way", Maf Smith, RenewableUK’s deputy chief executive told PE, allowing us to fine-tune when and where we generate electricity.
He added that wind power allows us to adjust output in "a matter of seconds", unlike old-fashioned power plants which take longer to ramp up and down. "National Grid’s Summer Outlook report shows that wind brings greater stability and resilience to our electricity system, as well as displacing the demand for fossil fuels," Smith said.
Six renewable energy companies were successful in bidding for the DTU procurement this February, with the bidders paid an availability fee of roughly £1.50/MWh for 2MW of capacity.
Simec Lochaber Hydropower secured contracts for 30MW; SSE secured contracts for 29.4MW; wind power company Engie won 15MW; biomass waste energy supplier MVV Environment Ridham won 20MW; demand response company Restore won 25MW; clean technology company Alkane energy won 19.2MW.