British wind farms are now solving the same problems they create for the grid operator — and lowering consumer bills in the process.

With fewer and fewer fossil generators left in the U.K. generation mix, and more and more renewables, the network is under strain. But more than 100 large wind farms are now providing grid services to balance out the variable nature of renewables.

A new "power-available" signal gives National Grid ESO visibility into all participating wind farms, allowing the grid operator to see how much they can contribute to providing grid stability. This was the final piece of the puzzle required to enable wind farms to participate in those flexibility markets.

All this is part of National Grid ESO's plans to be able to support a fossil-fuel-free network by 2025. The latest solution comes just in time. The grid operator has been forced to curtail wind power in huge volumes this summer due to a lack of fossil-fuel generators to provide essential flexibility. The cost of balancing the grid over the summer has more than doubled this year to an anticipated £826 million ($1.03 billion). 

Barnaby Wharton, director of future electricity systems at RenewableUK, said the industry had to agree on a standardized means of delivering the signal. Once that was done, all that was left was the installation of the necessary systems at the grid control room to actually be able to read it.

That’s easier said than done, as many of the developers and asset owners had been developing their own solutions for accessing the flexibility markets. In 2012, a proposal was made to change the grid code to include the development of a power-available signal. That proposal was settled in 2015. Since then, the working group, including the major wind asset owners, trade group RenewableUK, National Grid ESO and regulator Ofgem, has steered the effort to develop the live data feed itself.

When that work began, all new wind projects were also ordered to ensure their hardware was future-proofed for participation from 2016 onward. That meant a pipeline of available capacity has been building while the regulatory and market changes were underway. With several gigawatts of offshore wind coming on during that period, the available capacity is substantial.

Now, all the pieces of the puzzle have aligned with firm frequency response market contracting on a day-ahead basis. The lower limit for participation has also been dropped from 10 megawatts to 1 megawatt. 

Surfing the renewables wave

Jean Hamman, operational energy manager of National Grid ESO, told GTM the grid operator is better equipped than ever to deal with the surge in renewables on the grid.

“From a system-operator point of view, it feels a little bit like surfing, and we're just staying ahead of this wave that's just getting stronger and stronger and everything is renewable,” he said in an interview.

Keeping the grid stable requires positive reserve, voltage control and frequency control. Wind was historically excluded from those markets because it was too expensive, Hamman explained. That’s because the primary method via which wind farms could participate was to curtail output, and curtailing wind meant compensating plants for lost generation certificates.

But “as the amount of renewable generation increased so fast and the fuel cost is zero, we now often have conditions where over half the generation comes from renewables,” he said. “During these times, there’s less capacity for fossil-fuel plants on the system to provide response. [The power-available signal] enables wind to take up this shortfall — as it does for energy — and secure the system while also driving down the overall cost.”

The power-available signal gives the control room full visibility into wind farms’ potential to help by feeding in the live data from post-2016 wind farms. Before it was put in place, "we did not know how much positive reserve there was on a wind farm once we reduced the output,” he said. If a wind farm is reduced in output by 20 megawatts but wind speeds have doubled at that site since then, there is much more than 20 megawatts on hand for flexibility services.

With the signal in place, however, “the grid can optimize wind farms to provide all those services: voltage and frequency response, and positive reserve," Hamman said. "We've opened up half the generation capacity in the country to all the markets that they can now play in,” adding up to much more flexibility at much lower costs.

It also means the country needs to keep fewer fossil-fuel plants sitting idle waiting to provide reserve power, which also cuts costs for ratepayers. 

The addition of solar farms’ signals will boost the availability of capacity further, as will the addition of new wind farms.

More opportunities down the renewables road

It’s taken eight years to reach this stage as a unified standard was developed and new flexibility markets were created. The power-available signal, and the services it unlocks, arrived just in time to help the U.K. manage the challenging grid conditions created by the decrease in demand during coronavirus lockdowns, public holidays and some windy but sunny weather conditions.

The opportunities don’t end here. As more gas shifts off the U.K. grid, providing sufficient inertia becomes the next challenge, according to RenewableUK's Wharton.

“We need to move more quickly to a situation where those services can be provided by either artificial or virtual responses, through batteries, or by existing assets and new assets such as the wind we have on the system. The power-available signal is really exciting because it's part of that journey toward enabling wind to provide more of those services that would traditionally have been provided by thermal generation.”

For generators, operating in a market that is in the very earliest stages of its post-subsidy life, the opportunity to access some additional revenue doesn’t hurt either.