ESO gives early warning of tight supply margins over winter

National Grid Electricity System Operator (ESO) has warned of tight supply margins over the coming winter, partly due the shutdown of the Dungeness B and Hunterston B nuclear power stations.

The ESO gave the warning in an early version of its annual winter outlook released to help the energy industry and markets prepare for the season.

The ESO forecast a de-rated supply margin of 4.3GW – or 7.3 per cent – in its base case compared to 4.8GW – or 8.3 per cent – in its outlook for last winter.

The body predicted that underlying demand across both transmission and distribution networks would peak at 59.5 GW during an average cold spell.

In contrast to its previous winter outlook, when it forecast a reduction of 3 to 4 per cent, the ESO did not assume any suppression in demand due to the ongoing coronavirus pandemic.

The ESO said it expects 110.6GW of nameplate generation and interconnector capacity to be available to meet the winter demand peak, which was de-rated to 63.8GW.

The numbers are based on the assumption that neither the Dungeness B nor Hunterston B nuclear power stations will be available for the full winter.

EDF announced in July that it would immediately begin decommissioning Dungeness B after finding new faults at the plant. Hunterston B received regulatory clearance in April to begin a final six-month period of generation after being taken offline in 2018 due to the discovery of cracks in the graphite core. EDF had previously said the power station would cease generating by January 2022.

The figures also assume that the Baglan Bay, Severn Power and Sutton Bridge combined-cycle gas turbine plants will remain unavailable in line with publicly stated positions.

The Severn Power and Sutton Bridge plants were both mothballed last summer after the owner of all three – Calon Energy – went into administration. They were returned to the company’s directors in May but remain in a dormant state. The subsidiary operating the Baglan Bay power station was placed into receivership in March.

They additionally assume that the 1.4GW North Sea Link interconnector to Norway will come online in October.

The ESO said there is still some uncertainty over the availability of supply and that the de-rated supply margin could range from 3.1 GW – or 5.3 per cent – at the low end to 5.4GW – or 9 per cent – at the high end. The bottom of this range would represent “a level of tightness that has not been seen in the electricity market since before the Capacity Market delivery years started in 2017/18.”

Nevertheless, the ESO assured: “We may see some tight margins again this winter, but we’re confident there’ll be enough electricity to keep Britain’s lights on.”