There is still the potential for as much as 3.5 terawatts (TW) of 10-hour energy pumped storage hydropower (PSH) in the United States, according to a new report from the National Renewable Energy Laboratory (NREL).
Pumped storage hydropower is “a mature and proven method of energy storage with competitive round-trip efficiency and long life spans” that will make it “crucial to bridge gaps in electricity production as variable wind and solar production continue to comprise an ever-larger portion of the United States’ energy portfolio,” according to the report, Closed-Loop Pumped Storage Hydropower Resource Assessment for the United States.
NREL said it would soon publish a second technical report that would combine the data from the first report with additional resources to “examine how hydropower’s low-cost, flexible energy could support tomorrow’s grid.” Both studies are funded by the Department of Energy’s (DOE) Water Power Technologies Office.
A DOE report last winter found hydropower can be a valuable resource in maintaining bulk power system reliability.
Pumped storage hydropower comprises 23 gigawatts (GW) of the nation’s 24 GW of energy storage capacity, nonetheless, no new large pumped storage hydropower station has been built in the United States since the 1990s, the report noted, adding that “attempts to quantify technical potential capacity from PSH project applications to the Federal Energy Regulatory Commission (FERC) suffer from inconsistent site and cost evaluation methodologies and likely are not representative of all PSH opportunities.”
The NREL study seeks to better under understand the technical potential for pumped storage hydropower development by developing a national-scale resource assessment for closed-loop pumped storage hydropower. The report identifies 14,846 potential sites that could technically support pumped storage hydropower. It also details how much a plant might cost and how much energy it could produce.
Excluding undevelopable lands such as national parks and critical habitat for endangered species, the report found that even with using a conservative minimum head height (the difference in elevation between the two reservoirs), technical potential for pumped storage hydropower sites can be found “broadly across the western United States, the Appalachian Mountains, and the Ozark Mountains, as well as in Alaska, Hawaii, and Puerto Rico.”
To create the maps in the study the NREL researchers fixed parameters like dam height and storage duration. They selected a 10-hour energy storage duration because, they said, it tends to be more cost competitive with 4-hour battery energy storage technologies. The researchers also used their geospatial algorithm to search the country for all possible sites. Users can sort and filter those sites by head height, energy capacity, and cost. NREL plans to update the map to give users more control.
“We want to build an interactive map where you can check boxes on and off to choose between 12-hour or 8-hour storage, 40-meter or 60-meter dam height. Whatever people want,” Stuart Cohen, an NREL model engineer and a co-author on both reports, said in a statement.
The study’s results demonstrate a wide cost distribution and suggest that the most cost-competitive sites could be found where the existing topography supports very high head heights, the report’s authors said. And while these results are promising for the future of PSH in the United States, continued expansion of this work will improve PSH resource characterization, and additional grid modeling will help illuminate its potential future in the U.S. energy portfolio,” they said.