Metrics for evaluating the impacts of intermittent renewable generation on utility load-balancing

This study has developed metrics to evaluate the impact of intermittent renewable generation on the electric load demand that must be balanced by dispatchable generation resources, allowing examination of the general impacts of accommodating high renewable penetration levels. The metrics focus on the sizing, utilization and coordination of load balancing resources to meet the load demand in time. Insights gained from increasing the renewable penetration level in California as an example indicated the following. The balancing generator fleet displayed low capacity factors at high penetration levels. At penetration levels above 45% with no uninterruptable base load, surplus generation occurred and increased exponentially. The occurrence of daily maximum and minimum load points became increasingly unpredictable, rendering fixed time-of-use electricity pricing inappropriate. Capacities of peaker and base load generator type increased and decreased respectively. Net load variability decreased on the 24-h timescale and increased on all shorter timescales, implying changes in the temporal dispatch of balancing generators. The use of energy management strategies such as energy storage was found to be necessary in order to accommodate high renewable penetration levels with minimal impact. The simple metrics allowed identification of key areas to be addressed in order to accommodate high renewable penetrations.