Getting to zero fossil fuel electricity
Back in 2016, Britain had its first ever zero-coal hour. Then, 8 years later, the last coal-fired power station shut forever. However, we are still heavily reliant on fossil fuels. Gas has been burnt to provide electricity every hour of every day since the 1980s. Phasing out gas is the next step on the road to clean power, and a major milestone may be just around the corner. Since 2019, NESO has been preparing the electricity system to be capable of running with zero fossil fuels when there is sufficient renewable output for short periods by 2025.
Running with zero fossil fuels has been a multi-year project because it is technically much more difficult than phasing out a single fuel (coal). The grid relies on inertia, a service that absorbs fluctuations in supply and demand, like shock absorbers. Inertia is essential for keeping the lights on, but is only produced by conventional power stations – coal and gas, plus nuclear, biomass and hydro. The grid must also balance output from variable renewables using dispatchable power – options that are available instantly to meet demand. This means gas and other sources will remain essential for managing peaks in demand and shortfalls in wind and solar power for years to come.
Since 2020, NESO has introduced new tools to keep the grid stable without fossil fuels for short periods of time, such as the Dynamic Containment service for rapid frequency control, better voltage management, and systems to restart the network using clean power. It also trialled new ways for homes and businesses to offer flexibility, tested market changes to encourage low-carbon solutions, and ran the Demand Flexibility Service to reward shifting electricity use.
To date, the grid has never operated with less than 6 GW of conventional generation, and gas alone has never fallen below 0.74 GW. Turning off all gas plants, even briefly, will be moving the power system into new territory, and so must be handled carefully. The minimum fossil fuel generation fell steadily through the 2010s. In 2010 it had never gone below 12.5 GW, but by 2018 it was reaching below 2.5 GW. After that, progress stymied, as we started hitting the current limits of operability.
The minimum hourly share of Britain’s electricity generation from fossil fuels each quarter since 2010, and how much lower this could have been if all curtailed wind energy could have been used.
Around this time, curtailment of wind power picked up sharply, as the grid could no longer handle peak output. Wind farms have to be shut off, and generators elsewhere in the country (usually gas) turned on to replace their output. If that curtailed electricity could instead have been used, Britain could have theoretically reached zero need for fossil fuels back in 2019, and renewables plus nuclear could have supplied all the country’s demand for over 250 hours last year.
Britain is not alone in moving away from fossil fuels. Worldwide, seven countries have so far managed to run their electricity systems with no fossil fuels for at least a month, including Sweden, Tajikistan, and Costa Rica. Some large countries have managed to get below 10% fossil, including France (due to high nuclear share) and Brazil (extensive hydropower). Britain’s best so far is 22%, ahead of 30% in Germany, 50% in the US, Japan and South Korea, and 56% in China.
Getting to even short periods of zero-carbon electricity will require more than just new technology. It will mean upgrading the grid to handle higher peaks in renewables, expanding storage, and making full use of flexibility from homes, businesses, and industry. It will also take faster connections for clean energy projects and investment in backup solutions that don’t rely on fossil fuels.
The lowest monthly-average share of fossil fuels in national electricity mixes. Data from Ember
