In the 135 years since the Holborn Viaduct station opened in 1882, coal generation has been a necessary part of the energy mix in the UK. While there have been coal-free periods previously, the longest continuous period prior to Friday was in May 2016, when coal wasn’t required for 19 hours. This happened again on Thursday 20th April, leading the National Grid to accurately predict that the following day would be entirely coal-free.
During that 24 hour period, renewable generators – including wind, solar and hydro sources – supplied almost a fifth (18.1%) of the UK’s electricity, with less than half (47.4%) produced by gas generators, with the remainder coming from both nuclear and European interconnectors. The ability to keep the UK’s system balanced without its traditional mainstay baseload technology for an entire day is being heralded as a milestone, demonstrating the UK’s progress in its transition to a low carbon energy system.
A coal-free future
The Government committed the UK to a coal-free future last year, vowing to close all coal plants by 2025. However, the fuel has already been in decline for some time: in 2016, it made up just 9% of the UK’s energy generation, down from 23% in 2015, as a number of plants closed under the Large Combustion Plant Directive or became less economic to run because of the price of carbon tax, and a lower price of gas making CCGTs more competitive in the market. The reduced role of the remaining eight coal plants in the UK’s energy mix is predominantly driven by the fact that coal is increasingly uneconomic to run, leading to some concerns that the plants will close before the 2025 deadline. Watching how many coal plants bid into future T-4 capacity market auctions will be interesting, as the penalties for withdrawing from these contracts are expected to rise.
Whilst Friday’s achievement demonstrated that the UK is increasingly able to meet demand with low carbon sources, coal still remains an important part of the energy mix during peak periods, particularly in the winter. Its decline is a further signal that the UK requires investment in new, more efficient gas plant to avoid any capacity crunches in the mid-2020s as the new fleet of nuclear plants are being built. To date, the capacity market has failed to incentivise any significant new investment to replace our older and less efficient plant and instead has encouraged investment small diesel and gas standby plants, which have a lower efficiency and higher emissions that many of the first generation combined cycle plants that are currently moth-balled.
Coal plants are a major source of frequency support for the Grid, with the ability to rapidly increase or decrease load in response to Grid frequency. Whilst next generation power plants will be under more pressure to be frequency responsive, the future will also see more electricity consumers taking on these balancing duties.
The uncertainty surrounding new investment in cleaner and more efficient conventional plant may be some way to being resolved, but the increasing ability of renewable and low carbon sources to help meet demand is a positive sign that the UK is moving in the right direction towards meeting its carbon targets.