A second GB Capacity Market Notice (CMN) of Summer 2022 was issued on the 11th August at 13:34, as National Grid’s forecast of surplus capacity over the evening peak fell below the required 500MW 4 hours ahead of delivery.
In addition to their de-rated margin forecasts, National Grid publish their forecast loss of load probability at midday on the day before delivery, before subsequently updating at 8, 4, 2 and 1 hours before delivery. The above chart shows these forecasts for the evening peak on the 11th August. Loss of load probability (LoLP) gives an indication of the scarcity of available generation capacity for each settlement period, and would sit at 0% on a comfortable, well-supplied day. As delivery time approached on the 11th, availability improved, LoLP dropped significantly and the CMN was cancelled.
Despite the eventual cancellation, CMNs in summer months are vanishingly rare, and are typically used to manage winter peak demand. In the record-breaking heat this summer, demand for cooling has been strong and some generators across the UK and the Continent have struggled in the high temperatures (e.g. challenges for cooling for French nuclear plants, barging coal to southern German coal plants and low hydro). These factors, when combined with low wind (around 2GW on 11th August), are likely to have caused the tight margins leading to the CMN.