Long-duration energy storage for reliable renewable electricity: The realistic possibilities

ABSTRACT

Several American 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. Long-duration storage technologies (that is, those that provide from 10 to hundreds of hours of storage) have much cheaper energy storage capital costs than lithium-ion batteries. Long-duration storage plays unique roles, such as seasonal and multi-year storage, that increase the affordability of electricity from variable renewable energy. We compare realistic options for seasonal energy storage, including underground hydrogen, pumped hydro, pumped thermal, and compressed air systems. To make 100 percent renewable electricity reliable and more affordable, such long-duration storage technologies can be employed.

KEYWORDS:

• Long-duration energy storage
• pumped hydro
• hydrogen energy storage
• compressed air energy storage
• pumped thermal storage

Acknowledgments

The authors thank Tyler H. Ruggles and Katherine Z. Rinaldi for reviewing this piece. This work was supported by a fellowship from SoCalGas in support of Low Carbon Energy Science and Policy and a gift from Gates Ventures LLC to the Carnegie Institution for Science.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1. See: https://www.nytimes.com/2021/02/17/climate/texas-blackouts-disinformation.html

2. See https://www.nytimes.com/2021/07/14/climate/renewable-energy-batteries.html

3. See https://www.greentechmedia.com/articles/read/how-to-build-a-green-hydrogen-economy-for-the-u.s-west

4. See https://www.greentechmedia.com/articles/read/utah-aims-to-shatter-records-with-1000-mw-energy-storage-plant

5. Current compressed air energy storage facilities rely on natural gas to pre-heat expanding air, and so are not carbon-free. Future designs that are carbon-free are not yet in operation, and the energy density of compressed air is much lower than the energy density of compressed hydrogen, affecting scalability of the technology.

6. See https://www.wsj.com/articles/startup-claims-breakthrough-in-long-duration-batteries-11626946330

7. See https://www.energy-storage.news/long-duration-pumped-heat-energy-storage-startup-malta-raises-us50-million-in-series-b-round/

8. See https://www.greentechmedia.com/articles/read/energy-vault-lands-110m-from-softbanks-vision-fund-for-gravity-energy-stora

9. See https://pubs.rsc.org/en/content/articlelanding/2021/ee/d1ee01835c

Additional information

Notes on contributors

Jacqueline A. Dowling

Jacqueline A. Dowling (Jackie) is a doctoral candidate in chemistry at the California Institute of Technology with a minor in environmental science and engineering. Her Ph.D. research focuses on energy storage from both a systems and technical perspective. She works with macro-scale models to understand the roles of energy storage in low-carbon electricity systems. In lab, she develops catalysts to improve electrolytic hydrogen production. Her advisor is Caltech chemistry professor Nathan S. Lewis, and they collaborate closely with Ken Caldeira at Carnegie Science.

Nathan S. Lewis

Nathan S. Lewis is the George L. Argyros Professor of Chemistry at the California Institute of Technology. Lewis is best known for developing artificial photosynthesis technology that enables sustainable production of hydrogen fuel using sunlight, water, and carbon dioxide. Lewis is also interested in weather-based, data-driven modeling of deeply decarbonized electricity and energy systems based on variable renewable energy and technologies for long-term grid storage.