Alternative green electricity storage options being considered in the USA

Source: What's next in long-term energy storage, Vox.

Lithium-ion batteries are not the only way to store renewable electricity. The US Department of Energy’s Advanced Research Projects Agency (ARPA-E) is funding research by 10 organisations to create long-term energy storage systems that cost US$0.05 per kilowatt hour or less.

It is called the DAYS (Duration Addition to electricitY Storage) Program. The DAYS Projects fall into two categories: 1. Systems that provide daily cycling in addition to longer duration, less frequent cycling 2. Systems that do not provide daily cycling, but can take over when daily cycling resources are either filled or depleted.

A list of DAYS Projects is provided here but please refer to the links below for more information.
- 1. Sulphur Flow Batteries.
- 2. Innovative electrolyzer/fuel cell combination using hydrogen peroxide for storage instead of hydrogen.
- 3. Zinc-bromine flow batteries.
- 4. Thermovoltaics. Using PV panels to make electricity to heat carbon blocks.
- 5. Electricity to magnesium manganese oxide.
- 6. Pressurising water underground.
- 7. Liquid Air Energy Storage.
- 8 to 10. Three other electricity to heat programs aim to raise the efficiency of storing electricity as heat then using it to heat a gas to drive turbines. (DAYS Project Descriptions, ARPA-E).

Further reading:
- Department of Energy announces new projects to extend grid energy storage. APRA-E, September 18, 2018.
- APRA-E: Duration Addition to electricitY Storage (DAYS): Project Descriptions (pdf)
- Energy Storage 2020: It’s not just about lithium-ion batteries any more. CleanTechnica, January 5, 2020.
- U.S. research teams aim for long-duration storage at $0.05/kWh. PV Magazine International. December 30, 2019.