STANFORD, CA - Several U.S. states mandate zero-carbon electricity systems based primarily on renewable technologies such as wind and solar power. Reliable and affordable electricity systems based on these variable resources may depend on the ability to store large quantities of low-cost energy over long timescales. Multi-decadal datasets reveal the role and value of long-duration (10 hours or greater) energy storage, and inform policy and technology investment decisions.
The inclusion of long-duration storage lowers costs of renewable electricity systems over a range of modeled technologies, according to a study (August, 2020) by Zeller-Resnick fellow Jacqueline Dowling and Nathan S. Lewis of the California Institute of Technology in Pasadena, California, co-authored by Tyler Ruggles, Mengyao Yuan, Fan Tong and Ken Caldeira of the department of global ecology at the Carnegie Institution for Science, and Steven J. Davis of the University of California, Irvine, in Irvine, California. These system benefits remain robust across multiple decades of historical wind and solar weather data, for different electricity systems (solar only, wind only, wind and solar), with and without battery storage, in the U.S. and three of its regional power grids.
A 10% reduction in long-duration storage costs would reduce electricity system costs twice as much as would a 10% reduction in battery costs. As a complement to long-duration storage, Li-ion battery storage may be used for less than 10 hours, such as overnight. Costs of charging and discharging, rather than costs of storage facilities, dominate long-duration storage costs. One long-duration energy storage example, power-to-gas-to-power technology with renewable hydrogen gas, would benefit greatly from continued innovations in fuel cells, electrolyzers, and other conversion devices.
Long-duration storage would offer multiple cost advantages for electricity systems that depend on wind and/or solar generation technologies. Long-duration storage avoids overbuilding generation, reduces reliance on short-term battery storage, and provides an expanded suite of low-cost options to deploy systems with a range of generation asset mixes. Indeed, long-duration storage would facilitate an affordable transition to meet wind and solar mandates beyond 80%, and open a path to 100% carbon-free electricity.