Power for 127 Hours: The Economics of Long-Duration Energy Storage

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Power for 127 Hours: The Economics of Long-Duration Energy Storage

The United States cannot run on 80% renewable electricity without reliable long-term energy storage. New research compares the costs of 14 different types of energy storage.

Hunter, Chad A., et al. “Techno-economic analysis of long-duration energy storage and flexible power generation technologies to support high-variable renewable energy grids.” Joule 5.8 (2021): 2077-2101. DOI: https://doi.org/10.1016/j.joule.2021.06.018 

By 2050, over 80% of America’s electricity could be supplied by renewable wind and solar energy. However, wind and solar cannot provide electricity around the clock. A technology called energy storage can store renewable electricity during the day and discharge it when needed, for instance, during a late-night dishwasher run. Most energy storage technologies can perform continuously for four to six hours. But to support 80% renewables, energy storage must last longer: between 12 and 120 hours.  

Electricity providers are under pressure. By law, they must forecast their energy offerings 20 to 30 years in advance. Providers want to choose an energy storage technology that supplies America’s future power needs for the lowest cost. However, it’s difficult to find accurate cost estimates for long-duration storage technologies because most are commercially unproven.  

Researchers at the National Renewable Energy Laboratory (NREL) in Colorado sought to fill this data gap. The NREL team, led by Dr. Chad Hunter, compared the monetary costs and revenues of fourteen different energy storage technologies that can operate for 12 hours or more. They published their results in the journal Joule. The researchers modelled costs and revenues through 2050 as if each technology were located in a fictitious Western U.S. power grid comprised of 85% renewable energy. They excluded any technology “not congruent with a low-carbon future.”  

The researchers ranked the 2050 net cost results for two duration categories: 12 hours and 120 hours. The lowest-cost 12-hour technology is the lithium-ion battery – an unsurprising result, as lithium-ion batteries are commercially proven. Today, these batteries only last about four hours, but the authors are optimistic that the duration of lithium-ion batteries can reach 12 hours by 2050. In the 120-hour category, the lowest-cost technology is storage of hydrogen, a cleaner fuel than gas or coal, in underground salt caverns. Unfortunately, few caverns offer the right dimensions and conditions for hydrogen storage, thus, there are only two active storage caverns in the United States. 

Significantly, the study points to a natural gas plant outfitted with carbon capture as the next most cost- effective option. Carbon capture technology traps and liquefies harmful air pollutants at the mouth of the smokestack. This finding is especially timely. 2021 has seen a flurry of legislation in Congress to fund carbon capture technology for America’s preexisting natural gas plants. Should this legislation pass, carbon capture technology could vault to the top of the contenders. 

For the first time, electricity providers have an apples-to-apples comparison of fourteen technologies that are low in carbon emissions and high in reliability. Armed with this information, they can quickly determine the technology that is lowest-cost, longest-duration, and carbon-free. The next generation deserves a constant supply of energy, affordable power bills, and a livable climate. Electricity providers can use Dr. Hunter’s work to ensure these outcomes decades before they happen. 

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