In 2018 National Grid commissioned LCP Delta to develop an approach to calculating the incremental EFCs (equivalent firm capacities) for wind and solar plants, with a view towards setting deratings for their participation in future capacity auctions.
Our Unserved Energy Model (UEM) is a capacity assessment tool used by National Grid and BEIS for security of supply analysis. It stochastically simulates outages, demand and renewable generation across many thousands of simulations to provide a view on the likelihood, duration and severity of system security events.
This project involved the development and implementation of a methodology within the UEM to calculate the contribution to system security provided by an incremental amount of different intermittent technologies. Separate EFCs are calculated for onshore wind, offshore wind and solar, and the data behind the calculation accounts for the geographic distribution of these plant.
The EFC for an incremental amount of capacity is typically lower than the average EFC of the fleet, as the contribution to system security diminishes as the penetration of an intermittent technology increases. For example, the twentieth GW of offshore wind has a lower contribution than the first GW, due to system security events on a system with 20GW of offshore wind being heavily driven by periods where there are low levels of wind.
The results of this modelling were used to produce the “EMR Delivery Body Consultation – De-Rating Factor Methodology for Renewables’ Participation in the CM” final report by National Grid in January 2019.