Is Long-duration Energy Storage an Electric Industry Game-changer?
by Bob Shively, Enerdynamics President and Lead Facilitator
The availability of storage is fundamentally changing operation of the electric grid. As it becomes more prevalent, it will also fundamentally change electric markets as traders and utilities can arbitrage prices across periods of time much as is done in today’s natural gas markets. But today’s rapidly growing installations of lithium-ion batteries provide storage that is mostly useful only across short time periods of up to six hours. And most existing pumped hydro storage is usually designed for storage across daily cycles of six to 24 hours. No long-term storage of up to 100 hours, let alone seasonal storage of many months, is currently available to replicate the benefits of natural gas storage. So for now, electric systems with growing renewables must rely on natural gas generation to back the longer-term variability of renewable output. But researchers and start-up companies are working feverishly to develop the next big breakthrough in electricity storage.
A review of the potential value of long-duration energy storage (LDES) to electric grids was recently published in Nature Energy. A summary of the article by its authors summarized its conclusions:
- LDES can potentially deliver significant value in decarbonization strategies with the potential to lower the cost of electricity in carbon-free grids by as much as 15-40%.
- LDES cost targets of $50/kWh for energy capacity, if achieved, will be sufficient to drive initial deployment.
- LDES is likely to be a partial substitute for clean firm generation capacity but displacing all firm power capacity will require dramatic cost reductions.
- Electrification of other energy uses such as building heating and transport will make it more difficult for LDES to replace firm generation capacity, especially in Northern latitudes with high winter heating needs.
- Energy capacity cost and discharge efficiency are the most important drives of LDES value in carbon-free grids.
- LDES duration of well above 100 hours (but less than 650 hours) is necessary for delivering the largest energy cost reductions and to substitute for firm energy.
Compressed air energy storage in Ontario, Canada
Photo credit: Hydrostor
Energy Vault crane mechanical storage in Lugano, Switzerland
Photo credit: Energy Vault
So what technologies might provide LDES in the future? Potential technologies are reviewed in a piece by David Roberts of Canary Media. They include:
- Forms of electrochemical storage with different characteristics than lithium-ion batteries including flow batteries and liquid metal batteries.
- Chemical fuel storage such as hydrogen, hydrogen-derived ammonia, and synthetic methane.
- Mechanical storage, which includes pumped hydro, compressed-air energy storage, and kinetic energy in masses such as lifting blocks with a crane and propelling heavy train cars uphill.
- Thermal energy storage including molten salts, ceramic fire bricks, and pumped thermal storage using reciprocating heat pumps.
Roberts concludes that all these technologies are far from being a certain thing, although he believes that hydrogen may have the best prospects for large-scale deployment over the midterm to long term. He also sees potential in some of the thermal storage technologies. The fact that no long-duration energy storage is a sure thing also leads Roberts to believe that society very much needs to develop clean firm energy sources such as new nuclear technologies, fossil fuels with carbon capture and storage, bioenergy, geothermal, and green hydrogen used in combustion or combined-cycle turbines.
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