UK generation margins seen at 6.7% this winter, with tight periods in December

Forecast UK electricity generation margins this winter are broadly in line with recent winters, with some tight periods most likely to occur in the first half of December, National Grid Electricity System Operator said in an early Winter Outlook report July 28.

The system operator has published early-view power and gas winter outlooks due to the unprecedented risks posed by Russian gas flow disruptions. Complete reports will be published in the autumn.

"Our current Base Case margin is 4.0 GW [de-rated] / 6.7% with an associated loss of load expectation (LOLE) of 0.1 hours," National Grid ESO said.

This was within the Reliability Standard for LOLE of three hours, it said.

The calculation assumed an average cold spell peak demand of 59.5 GW.

It also assumed that on the tightest days power prices would be higher in Great Britain than in Europe, leading to interconnector flows into GB.

"We assume that interconnectors are able to provide 5.7 GW net imports at times when GB needs it," it said.

There was uncertainty on French nuclear availability that could lead to more export flows from Great Britain to France when system margins were not tight, it added.

The ESO's base case also assumed non-availability this winter of mothballed CCGTs at Baglan Bay, Severn Power and Sutton Bridge.

Not in the base case, however, were the roughly 2 GW of coal plant National Grid ESO had contracted or expected to contract for this winter, it said. This would be additional.

"Operationally, we expect some tight periods that are most likely to occur in the first half of December. We may need to use our operational tools, such as issuing electricity margin notices (EMNs), to manage these periods," it said.

Meanwhile the system operator's early-view gas winter outlook has proposed three base demand scenarios: for a mild winter (369 million cu m/d demand), a "Beast from the East" winter, representative of an extreme cold snap (418 million cu m/d): and a sustained cold winter like 2010/11, which saw the highest-ever daily gas demand (468 million cu m/d).

Assumptions National Grid proposes to apply to the scenarios include sustained maximum CCGT gas plant demand for gas and sustained gas interconnector exports to Europe.

A more developed gas winter outlook report is scheduled for Sept. 5.