ESO gives early view of winter supply margins

National Grid Electricity System Operator (ESO) has given an early view of expected electricity supply margins over the coming winter ahead of its usual Winter Outlook released each Autumn.

The ESO has forecast a de-rated margin 4GW – or 6.7% – representing a slight increase on the 3.9GW – or 6.6% – margin predicted for last winter. However, this forecast assumes there is no disruption gas supplies and Great Britain is able attract 5.7GW of interconnector imports from the rest of Europe during tight periods.

Average cold spell demand was assumed to peak at 59.5GW, including 1.2GW of operational reserve, with the de-rated capacity available to meet this demand exceeding the peak by 4GW.

The ESO said this base case assumes normal market conditions, meaning “there is no disruption to fuel supplies for thermal power stations and that electricity interconnectors between Great Britain and Europe continue to operate in response to market signals, including scarcity prices, as they have done in previous winters.”

In line with their Capacity Market obligations, the ESO said interconnectors are assumed to provide 5.7GW of net imports when needed. It noted that it expects 2.7GW of additional interconnector capacity to be available when compared to last winter, with the new ElecLink and North Sea Link interconnectors to France and Norway respectively both in full operation and the IFA interconnector to France returning to full capacity following a fire in November last year.

“There is uncertainty on the availability of the French nuclear fleet for winter,” the ESO. “This could lead to more export flows from Great Britain to France when our system margins are not tight.”

With regards to gas supplies, the ESO said: “There are risks and uncertainties this winter as a direct result of possible shortfalls in Europe’s gas supply. As noted elsewhere, while Britain is not reliant on Russian gas to the extent that the rest of Europe is, it is clear that the cessation of flows of gas into Europe could have knock-on impacts, including very high prices.

“As a prudent system operator, we are working closely with BEIS, Ofgem and National Grid Gas Transmission to assess the potential scenarios that may arise, and taking steps to ensure we are well prepared to maintain safe and secure operation of the electricity system.”

The ESO said this includes working with the Department for Business, Energy and Industrial Strategy (BEIS) to delay the closure five generation coal units, which would collectively provide around 2GW of de-rated capacity. It said four of these five units has so far confirmed their availability but these are not included in its forecast supply margin for the winter as they will not be available in the market.

Among other things, the ESO said it also working with transmission owners to minimise the impact of network outages, for example, by aligning planned outages in a way that minimises constraints.

The supply margin additionally assumes that the Baglan Bay, Severn Power and Sutton Bridge combined-cycle gas turbine plants all remain unavailable in line with public announcements.

The ESO forecasts for daily margins suggested supplies are likely to be tights in later November and early December.