Wind ‘compensated for shortfall’ in other generation last winter, says NGESO

Last winter, wind generation output compensated for any shortfall in other forms of generation on many of the days when demand/supply margins were tight, according to NGESO.
In a summary of the 2021/22 winter and consultation about the upcoming winter the system operator said times when margins are tight do not necessarily occur on the days with the highest demand, but on the days with the biggest shortfall of generation. NGESO said the main drivers of lower margins came from nuclear and CCGT plant being less available than had been notified at the time of the Winter Outlook Report in the autumn of 2021.
Nuclear generation availability was lower than forecast through most of the winter with a high breakdown rate (ie unexpected outages) for nuclear of 20%.
Gas generation output was lower than in the previous winter. The open cycle gas turbine (OCGT) breakdown rate was forecast at 5% but in the end was significantly higher than expected, at 11%. Coal, combined cycle gas turbines (CCGTs) and biomass plant had a slight increase in expected breakdown rate compared to the previous winter. There are a number of different reasons for the lower than anticipated availability of generators and no common theme, said NGESO. Wind generation output was high throughout most of the winter.
Coal provided the same proportion of generation as the previous winter, with overall levels remaining low.
As regards the network, there were constraints in the England-Scotland border because of delays in connecting a major windfarm. Additional outages and delays were required for bird nest removal, which meant restrictions ran beyond autumn and into the winter months.
The system operator noted that high gas prices drove up the cost of network outages combinations, as the price of replacement energy generated in another area to replace energy that could not be transmitted “rose to extraordinary levels”.