Battery storage systems seen shifting toward more abundant elements than lithium

Cost and limits on the availability of key materials currently used in battery manufacture have set a floor on lithium-ion battery costs and may constrain future deployment, inspiring a shift toward chemistries that use more earth-abundant elements, according to a Massachusetts Institute of Technology study.

"Fossil fuel power plant operators have traditionally responded to demand for electricity—in any given moment—by adjusting the supply of electricity flowing into the grid," Robert Armstrong, MIT Energy Initiative director and chair of the "Future of Energy Storage" study, said in a statement.

"But variable renewable energy resources such as wind and solar depend on daily and seasonal variations as well as weather fluctuations; they aren't always available to be dispatched to follow electricity demand," Armstrong said, adding that the study has found energy storage can help VRE-dominated electricity systems balance electricity supply and demand while maintaining reliability in a cost-effective manner, and that in turn can support the electrification of many end-use activities beyond the electricity sector.

Lithium-ion batteries will continue to be a leading technology for electric vehicles and short-duration storage, but their storage capacity costs are unlikely to fall low enough to enable widespread adoption for long-duration, or greater than 12-hour, electricity system applications, the study said.

Cost, lifetime, and manufacturing scale requirements for long-duration energy storage favor exploring "novel electrochemical technologies," like redox-flow and metal-air batteries that use inexpensive charge-storage materials and battery designs that are better suited for long-duration applications, and while several configurations have shown promise, "knowledge gaps" in important scientific, engineering, and manufacturing challenges suggest there is high value for government support in these areas, the researchers said.

One potential near-term thermal energy storage approach is based on reducing the cost of converting heat to electric power, which is the main component of overall thermal energy system cost, by reusing steam turbines at existing power plants and adding thermal storage and new steam generators in place of existing fossil-fuel boilers, according to the study.

"This retrofit can be done today using commercially available technologies, and it may be attractive to plant owners and local communities as a way to use assets that would otherwise be abandoned as electricity systems decarbonize," the study said.

Wholesale power price changes

Time-of-use pricing in which power prices increase with scarcity and decrease with abundance will become increasingly important as zero fuel cost renewable energy becomes more widespread, the researchers said.

"The distribution of hourly wholesale prices or marginal value of energy will change in deeply decarbonized bulk power systems, with many more hours of zero or very low prices and more hours of high prices compared to today's wholesale markets," the study said.

This is because variable renewable energy-dominant bulk power systems with storage will have relatively high fixed (capital) costs and relatively low marginal operating costs compared to today's power systems, which largely rely on thermal generators, the study said.

Growing reliance on variable renewable energy generation, with zero marginal cost, "greatly increases the percentage of hours when prices, represented by marginal system costs in our modeling, are under $5/MWh," the researchers said, adding that the effect increases as the carbon constraint becomes more stringent, in other words when allowable emissions are ratcheted down.

Relatively high capital costs coupled with many more hours when power prices are very low will create financing challenges for both renewable energy generation and storage, particularly since regulators will likely continue to cap extremely high prices that could otherwise support cost recovery, according to the study.

As a result, future wholesale electricity price patterns and the goal of decarbonizing other sectors through electrification with decarbonized electricity also "reinforces the benefit of adopting retail pricing and retail load management options" that reward electricity consumers for shifting electricity uses away from times when high wholesale prices indicate scarcity to times when low wholesale prices signal abundance, the study found.

The Alfred P. Sloan Foundation and the Heising-Simons Foundation provided core funding for MITEI's Future of Energy Storage study, with MITEI Members Equinor and Shell providing additional support.