Duration Portfolio Energy Storage aligns layered peak demand with right-sized batteries, enabling peak shaving, gas peaker replacement, and solar-plus-storage synergy while improving grid flexibility, reliability, and T&D deferral through two- to four-hour battery durations.
Key Points
An approach that layers battery durations to match peaks, cut costs, replace peakers, and boost grid reliability.
✅ Layers 2- to 4-hour batteries by peak duration
✅ Enables solar-plus-storage and peak shaving
✅ Cuts T&D upgrades, emissions, and fuel costs
The debate over energy storage replacing gas-fired peakers has raged for years, but a new approach that shifts the terms of the argument could lead to an acceleration of storage deployments.
Rather than looking at peak demand as a single mountainous peak, some analysts now advocate a layered approach that allows energy storage to better match peak needs and complement ongoing efforts to improve solar and wind power across the grid.
"You don’t have to have batteries that run to infinity."
Some developers of solar-plus-storage projects, bolstered by cheap batteries, say they can already compete head-to-head with gas-fired peakers. "I can beat a gas peaker anywhere in the country today with a solar-plus-storage power plant," Tom Buttgenbach, president and CEO of developer 8minutenergy Renewables, recently told S&P Global.
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Others disagree. Storage is not disruptive for generation, but will be disruptive for transmission and distribution, Kris Zadlo, executive vice president and chief development officer at Invenergy, told the audience at a Bloomberg New Energy Finance conference last spring. Invenergy, like many renewable power developers, develops generation, energy storage and transmission projects.
But there is another path that avoids the pitfalls of positions on either end of the all-or-none approach. "Do the analysis of the need itself," Ray Hohenstein, market applications director at Fluence, told Utility Dive. If the need is only two hours in duration, it may be best served by a two-hour battery. "You don’t have to have batteries that run to infinity."
Storage vs. fossil fuel peakers
Energy storage has several benefits over traditional fossil fuel peaking plants, Hohenstein said. It is instantaneous, it has no emissions and requires no fuel, and has limited infrastructure needs. It can also help the grid absorb higher levels of renewable generation by soaking up excess output, such as solar power at noon, and many planned storage additions will be paired with solar in the next few years. But the one thing energy storage cannot do, he said, is provide limitless energy.
So, instead of looking at replacing an individual peaker, Hohenstein advocated a "duration portfolio" approach that uses energy storage to shave peak load.
If the need is for 150 MW of resources that will never need to run for more than two hours at a time, then a battery is "quite cheap," significantly less than a four or eight-hour battery, said Hohenstein. "If you fill up your peak by duration layer, it could be more cost effective."
NREL research driver
Fluence’s approach is informed by research by Paul Denholm and Robert Margolis at the National Renewable Energy Laboratory (NREL), released last spring.
The NREL researchers looked at the California market where they said 11 GW of fossil fuel capacity is expected to be retired by 2029 because of new once-through-cooling requirements that are taking effect. A lot of that capacity is peaking capacity and, according to NREL’s analysis, a large fraction could be replaced with four-hour energy storage, assuming continued storage cost reductions and growth in solar installations.
The key in NREL’s research was the level of solar power penetration. There is a "synergistic" relationship between solar penetration and storage deployment, the researchers wrote, and other studies suggest wind and solar could meet 80% of U.S. demand as these trends continue.
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