Transmission system demand during the most recent bank holiday weekend did not drop to the extreme low levels expected over the Bank Holiday weekend, National Grid ESO (NGESO) said in its weekly update on system operation – although it did touch a new record low of 15.1 GW. The slightly higher than expected demand was partly because distribution-connected wind, which reduces demand on the transmission system, started to generate later than expected and after the early morning demand minimum.
Demand was at its lowest at 6AM on Sunday 10 May, when it was at 15,355MW. However that included a demand boost of 238MW, which NGESO contracted via its new Optional Downward Flexibility Management (ODFM) product.
The system operator said it had signed up 3o providers for the new ODFM product and said it wanted more volume. Interested parties can sign up for a webinar at 2pm on 21 May to find out more about the service.
The system operator has also signed so-called ‘SuperSEL’ (stable export limits) contracts with large plant – including Sizewell B, which reduced its output by 660MW over the period. In SuperSEL NGESO called for plant that had useful system characteristics – such as providing inertia – to make offers to operate at lower power production than normal. This is the first time NGESO has signed such a contract for Sizewell and that option remains in place until June. NGESO has already called on Grain and Drax to operate under SuperSEL conditions.
To maintain demand at a level that would keep beneficial plants in operation, NGESO also turned down 979MW of wind power and increased exports across the interconnector so it could bring on 1.8GW of CCGT and biomass plant.
NGESO said the cost of the two new measures (SuperSEL and ODFM) would be recovered via balancing ‘use of system’ charges, which means they will be socialised across customers. The alternative would be to include the cost in so-called ‘cash-out’. This is the cost of measures taken at the second of dispatch by the system operator, which is paid by market participants who are ‘out of balance’ (delivering or buying more or less than promised) in a way that is unhelpful to the system. If the cash-out route was used it would put such participants at risk of unforeseen and substantial costs. But cash-out prices work both ways and using that route would provide a financial boost for market participants who are ‘out of balance’ in a way that helps the system - a regular market strategy for some companies, who argue that NGESO could make more use of cash-out to provide a market for last-minute balancing.
The system operator expects more low-demand period during the upcoming bank holiday when it expects lows of 15.2GW (on Sunday 24 May) and 15.4GW (on Monday 25 May). But it currently anticipates that demand will be still lower the following weekend, potentially falling as low as 14.6GW on Sunday 31 May. The predictions, which are weather-dependent and also depend on patterns of activity as the lockdown is eased, will be refined closer to the time.