DOE program aims at low cost, long duration storage to meet grid needs when renewable penetration rises above 50%.
As renewable penetration grows, the need for energy storage grows as well. However, existing storage technologies may not be able to meet that need.
A Department of Energy (DOE) grant program aims to address that problem by trading efficiency for low cost.
Existing storage technologies fall short in terms of duration. Lithium-ion batteries, which have captured about 90% of the energy storage market, can economically run for about four hours. Pumped hydro storage, which accounts for the most energy storage today in terms of capacity, can generate power by releasing water from storage reservoirs for up to 20 hours under certain conditions.
But as renewable energy penetration reaches and surpasses 50%, the need for even longer durations will grow.
The need for longer durations is particularly applicable to areas where solar power dominates the resource mix.
In a future where 70% of power is generated by solar panels, it is easy to imagine a scenario where a couple of cloudy days in a row could create a gap in meeting customer demand, Michael Jacobs, senior energy analyst at the Union of Concerned Scientists, told Utility Dive.
Filling that gap is the aim of a program at the DOE that is providing funding for technologies that can extend energy storage durations to up to 100 hours.
Last month, the DOE's Advanced Research Projects Agency-Energy (ARPA-E) awarded just over $28 million to 10 projects that aim to push the limits of energy storage duration. ARPA-E's Duration Addition to electricitY Storage (DAYS) program aims to push the duration of energy storage systems out to 100 hours.
One hundred hours, just a little more than four days, is an exponential leap from current durations but the role of ARPA-E is to focus on early stage technologies that are not yet commercial or quite ready for the private sector.
"Wind and solar will clearly be the cheapest forms of electric energy in the future," Paul Albertus, the director of the DAYS program, told Utility Dive. So, "it is pretty clear that over the next 10 years or so" the need for longer duration energy storage is going to grow, he said.
Some pumped hydro storage could get to the 100-hour mark, but the cases are limited and most max out at around 20 hours, Joseph Manser, a fellow at ARPA-E who helped set up the DAYS program, told Utility Dive. Lithium-ion batteries could be arrayed to discharge for 100 hours, but that would be very expensive.
What the DAYS program is looking for is not tweaking existing technology or even a technological breakthrough but for technologies that "trade off costs in unique ways," Manser said.
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