Based on an article by JoAnna Wendel, Pacific Northwest National Laboratory (PNNL).
A modelling study led by the US Department of Energy’s Pacific Northwest National Laboratory (PNNL) indicates that pairing battery energy storage systems with hydropower plants could significantly reduce turbine wear, extend asset life, and create new revenue opportunities for dam operators. The approach may also offer environmental benefits by improving downstream flow conditions.
As currently operated, the electric grid stores very little energy. Electricity generated from hydropower, fossil fuels, and other sources is typically consumed immediately. However, as battery energy storage systems become more cost-effective and capable, researchers are increasingly examining how storage can be integrated with existing generation assets to improve grid performance.
PNNL researchers have found that adding batteries to hydropower facilities allows operators to decouple water flow from real-time electricity demand. This flexibility can reduce mechanical stress on turbines while enabling hydropower plants to participate more actively in evolving energy markets.
“Hydropower has traditionally acted as the battery of the grid, with water stored in reservoirs ready to spin turbines when needed,” said Vishvas Chalishazar, a senior power systems research engineer at PNNL. “But now our grid ‘battery’ has the opportunity to have batteries of its own.”
Reducing mechanical wear through operational flexibility
The research team modelled the operation of an existing hydropower plant hypothetically paired with a 60 MW, two-hour battery energy storage system. Results showed that the combined system could increase annual revenue by approximately US$6 million, while significantly reducing turbine start-stop cycles—a major contributor to mechanical wear.
“With battery energy storage systems costing in the tens of millions, dam operators would recoup their investment in less than a decade,” Chalishazar said.
Hydropower turbines are designed to start and stop quickly, but repeated cycling accelerates fatigue in mechanical components and increases maintenance costs. When power generation is not required, operators often use synchronous condensing to keep turbines spinning without producing electricity, maintaining grid synchronisation and enabling rapid response to demand.
However, synchronous condensing is not always feasible. High tailwater levels can prevent safe air injection, forcing operators to shut down turbines entirely. Restarting turbines takes time, during which opportunities for grid support and revenue generation may be lost.
Case study: Bagnell Dam, Missouri
To quantify the potential economic benefits of adding batteries to hydropower, PNNL partnered with Ameren, owner and operator of Bagnell Dam on the Osage River in Missouri. The 240MW facility comprises eight turbines and generates more than 500 GWh annually.
Using historical operational data, researchers simulated dam performance with the addition of a 60 MW, two-hour battery system. In periods when grid demand did not require hydropower generation, turbines could continue operating and charge the battery instead of shutting down. Once the battery reached full charge, turbines could be placed into condensing mode, avoiding a full stop.
The model showed that turbine start-stop cycles could be reduced to fewer than five per unit per year, compared with approximately 201 cycles annually without battery integration. With each cycle costing around US$500 in maintenance and lost production, this equates to savings of roughly US$100,000 per year.
New market participation and grid services of adding batteries to hydropower
Beyond maintenance savings, battery integration enables hydropower plants to respond to rapid fluctuations in electricity demand without imposing additional stress on turbines. This capability is increasingly valuable as grids accommodate higher penetrations of variable renewable energy and growing loads from sources such as data centres.
“Adding a battery enables these large, heavy machines to respond at a timescale that they weren’t built to respond at,” Chalishazar said.
By allowing instantaneous dispatch from storage, the battery-supported hydropower plant in the study was able to participate in more dynamic energy markets, contributing to the estimated US$6 million annual revenue increase.
Environmental and future considerations
The researchers also note potential environmental benefits. Frequent turbine shutdowns and restarts can create turbulent flow conditions downstream, complicating fish passage. Continuous turbine operation produces smoother flow regimes that may reduce ecological impacts.
PNNL is now extending its analysis through partnerships with Grant Public Utility District and Energy Northwest in Washington State. The team will examine a range of facility types, including reservoir-based and run-of-the-river hydropower plants, as well as a small single-turbine facility between Packwood Lake and the Cowlitz River.
In each case, the focus will be on how battery integration affects operational flexibility, revenue potential, and grid resilience.
