Buffering intermittent renewable power with hydroelectric generation: A case study in California

Hydroelectric generation has the ability to buffer intermittent renewable generation. The objective of this paper is to explore the changing roles of hydropower and pumped storage dispatch in response to increasing renewable penetrations. A novel aggregate model of hydro resources in the state of California is used in conjunction with the Holistic Grid Resource Integration and Deployment model (HiGRID), a modeling tool that resolves hourly grid resource dispatch and management, to observe the impacts of increasing renewable penetration. The effects on the grid are explored by incrementally increasing the installed wind and solar capacity to meet the electric demand for California while re-dispatching hydro energy and capacity resources to balance the electrical power system. Increasing renewable generation results in increased periods of over generation, reducing the practical achievable renewable penetration. By adjusting the dispatch of hydropower to complement renewable generation a significant increase in the achievable renewable penetration can be implemented (8.0% for solar only, 2.2% for wind only and 2.8% for 50/50 mixture of wind and solar). Additionally, dispatching hydro to support renewables serves to increase the system-wide capacity factor, delay the onset of curtailment, and reduce the total curtailment at corresponding renewable penetrations.