ESO creates downward flexibility service to manage low summer demand

National Grid Electricity System Operator (ESO) has announced a new downward flexibility service to help it cope with unusually low electricity demand over the summer due to the coronavirus pandemic.

Providers will be paid to either lower generation or raise demand. The ESO said it expects to require up to 3GW of flexibility at a time and call on the service as often as one in every three days between May and August.

The ESO has set itself the target of making the power grid ready for zero-carbon operation by 2025. One of the main issues it will need to address is how to maintain the stability of the power grid during periods in which asynchronous renewables provide the bulk of generation, leaving it susceptible to abrupt changes in frequency.

This issue was first expected to emerge over the summer season when demand is lowest and solar output is high. In November, the ESO launched the pathfinder for a new stability service incorporating inertia – the resistance electricity system to changes in frequency.

Inertia is provided by synchronous generators that use rotating masses spinning in harmony with the frequency of the power grid. In the past this has meant the turbines of coal and gas power stations, although the ESO seeking to procure inertia from purpose-built assets such as synchronous compensators as part of its second stability tender.

However, the problem of low inertia is expected to materialise faster than previously anticipated due the large drop in electricity demand resulting from the coronavirus lockdown. In a recent update, the ESO said it may have to curtail renewable output and reverse interconnector flows in order to make room gas generation and maintain a sufficient level of inertia.

It also floated the possibility of resurrecting its demand turn-up service in some form, as it now appears to have done. The service ran for three years between 2016 and 2018 but was discontinued due to low participation.

Its successor will be open to units of at least 1MW in capacity. Providers must be able to sustain the service for at least three hours and will not be able to provide any other balancing or ancillary service at the same time. They will be paid for utilisation but not availability.

The service is scheduled to go live on 7 May. The ESO said it plans to issue the final terms by the end of this week.