Hydropower can be a valuable resource in maintaining bulk power system reliability, according to a new report from the Department of Energy’s (DOE) HydroWIRES initiative.
HydroWIRES was launched in April 2019 by the DOE’s Water Power Technologies Office to understand and improve the contributions of hydropower and pumped storage hydropower (PSH) to reliability, resilience, and integration in the electric system.
The study analyzed the role of hydropower over a range of extreme events using a combination of historical data and simulation-based analysis.
The study looked at two main categories of events: the sudden loss of large generation assets and changes in net load due to extreme weather such as heat waves and cold snaps.
The scenarios used to evaluate hydropower’s role during extreme events were applied only to the Western Interconnection where hydropower constitutes between 20 and 25 percent of generation capacity.
The study found that hydropower could be critical in stabilizing the Western Interconnection after a sudden loss of generation. Historical data and simulation showed that hydropower is a major resource for inertial and governor response during extreme events. Specifically, the study found that hydropower facilities contribute between 30 and 60 percent of governor response to help stabilize system frequency after an outage.
Hydropower facilities also have significant reactive power capability that can help maintain voltage stability during extreme events, the study found. And while coal and nuclear plants can also provide reactive power, hydropower, like gas-fired plants, do not always operate at full power, enabling them to provide more reactive power support when needed. The study showed that hydropower is a major source of reactive power under all seasonal, loading, and water availability conditions.
The study also found that hydropower’s storage capability and dispatch flexibility are critical to ensuring system reliability during extreme weather events. Simulations of periods of extreme weather when wind and solar generation were significantly depressed, even though the impact on system load was not extreme, showed that hydropower resources were able to fill in energy and capacity gaps.
At least 40 percent of the nation’s hydropower resources are pumped storage and peaking or reservoir hydropower plants that can store water to produce electricity at times of greatest need. At least 18 percent of hydropower resources are run-of-river plants.
During a multi-day cold wave scenario, hydropower resources’ long-term storage capability was key in ameliorating the situation, the study found. In both historical and simulated scenarios, hydropower can contribute “significantly to grid reliability and resilience during extreme events,” the study found.
“The analyses in this study suggest that as the magnitude and frequency of extreme and stressful grid conditions increase, hydropower will continue to play a vital role in power system reliability and resilience,” the report’s authors concluded, adding, however, that “more work needs to be done to fully assess the role of hydropower under all potential combinations of future grid states and extreme events.”