For high VRE-share power systems, firm peaking technologies (FPTs) are critical to assuring load is covered when VRE output is not physically or economically available. This project focused on understanding determinants of FPT needs in near-100% VRE systems and their operating performance requirements. The crucial problem is covering load when the profiles for both wind and solar are so low that no amount of VRE investment will cover load. The related problem is that VRE investment seeking to cover load in low-VRE hours creates surpluses of output that must be spilled in high-VRE hours. This analysis uses the static version of EPRI’s U.S. Regional Economy, Greenhouse Gas, and Energy Model (US-REGEN) to simulate near-100% share VRE systems, defined as systems built to the point that VRE cannot beat a $1,000/MWh delivery threshold. Regions are analyzed independently (no trade) to capture the implications of the widely varying local VRE resource endowments represented in REGEN’s 16 state-level regions. In the simulations, the hourly load-VRE gaps in each region define the FPT service needs.
A base FPT Scenario shows the need for FPT capacity in all regions, the frequency of dispatch, the need for hours of continuous operation, capacity factors, and ramping needs. A BEES Scenario shows how batteries can cover the gaps between VRE and loads, the degree that BEES costs are offset by reductions in low-productivity VRE investments, and what drives the limits to BEES effectiveness. An H2+BEES Scenario examines the value of seasonal storage in extending the benefits of BEES.
The results highlight the challenge of high VRE attainment, the need for substantial FPT investment to provide backup, the value of battery storage, and the potential for mixes of battery and seasonal storage to fully cover backup needs.