
Considering hydropower accounts for 29% of renewable generating power in the United States, it may be worth questioning why so few studies have examined hydro hybrids, or hydropower plants that use utility-scale batteries.
To get a better idea of the potential benefits or profitability of hydro hybrids, Idaho National Laboratory (INL) researchers recently did just that in a new report, thanks to funding from the Department of Energy’s Water Power Technologies Office.
“Batteries offer all kinds of benefits like reduced cost of maintenance, increased production, and investment and production tax benefits,” said Hill Balliet, a power systems engineer at INL and contributor to the paper.
Additionally, hydro hybrids have advantages over wind and solar power, the report said. Solar and wind power operators can’t choose how much the sun shines or how much the wind blows, but hydropower plant operators (especially ones with access to reservoirs) can control their outflow.
“With solar and wind, you’re tied to the forecast, which isn’t always predictable,” said Venkat Durvasulu, a power systems engineer at INL. “With hydropower, it’s possible to calculate a few days out roughly how much water will be coming downstream, and hydropower owners can get a good idea of how much power they can generate.”
This predictability means that utility-scale batteries attached to hydropower systems can make better use of the plant’s interconnection headroom, the report said, which in turn could increase the profitability and grid benefit of hydro hybrids. Additionally, hydro hybrids have the ability to restart the grid after a blackout event.
Operating a hydropower plant comes with additional costs related to environmental protection, recreational activities, local wildlife, and more. Some of this lost revenue could be offset through the use of utility-scale batteries, the report suggests.
Additionally, a “major barrier” to hydro hybrid research is the fact that existing models don’t account for avoided costs like reduced maintenance, wear and tear, power grid stability, voltage regulation, production tax credits, carbon credits, and more, the report said. As part of the study, researchers developed Hydro + Storage Sizing, an online tool that gives users an estimate of how profitable different battery sizes might be, taking avoided costs into account.
“There are other untapped values and opportunities too,” Balliet said, “more jobs, improved load-carrying capacity, lower operational and environmental costs, better water management, and greater profits.”
Today, hydropower provides about 6.2% of total U.S. utility-scale electricity generation and 28.7% of total U.S. utility-scale renewable electricity generation. Meanwhile, pumped storage hydropower is the largest contributor to U.S. energy storage, representing 96% of utility-scale energy storage capacity as of 2022.
Earlier this year, INL announced it was seeking a hydropower utility to collaborate on a case study, funded by WPTO, to understand how small hydro plants operating at 10 MW or less can be upgraded to provide emergency power to critical loads during outages.
This effort builds on the successes of previous field demonstrations, INL said. In 2021, INL partnered with Idaho Falls Power, a municipally owned utility, to demonstrate how its five hydropower plants could be configured and modified to improve frequency response and maintain stability with larger loads during black start when paired with an ultracapacitor.
Ultracapacitors, which store and quickly discharge large amounts of energy, provide oscillation damping and fast frequency response to the generating plants. To isolate the city’s plants and test them in various configurations, two 4-MW load banks were brought in. A load bank is a unit filled with resistive heater elements that draws current and dissipates it in the form of heat. Researchers use load banks to test how an electric generation source will react when disconnected from its normal load.
This 2021 demonstration proved that small hydropower plants combined with integrated energy storage technologies could be responsive enough to replace natural gas during a black start in some cases.
INL also collaborated in 2023 with Fall River Rural Electric Cooperative to show how retrofitted and upgraded plant components and systems (hydro governor controls and protection circuits) could allow the co-op’s hydropower plants to run independently from the grid to provide emergency power to critical loads.