Hydrogen electricity storage system is a system that stores large amounts of electricity (up to 100 million kW) for long periods of time (up to 100 hours), and is composed of solid oxide fuel cells, solid oxide electrolysis cells, hydrogen storage tanks, high-temperature heat storage devices, and control devices.

Electricity network companies deploy the hydrogen power storage system at the sites of decommissioned fossil fuel-fired power plants where the high-capacity trunks of the electricity network are located.The hydrogen power storage system located in each location will be installed so that their total output capacity exceeds the maximum power demand within the power network area by approximately 5%.

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"Hydrogen power storage system that utilizes renewable energy"

https://www.global.toshiba/content/dam/toshiba/migration/corp/techReviewAssets/tech/review/2013/07/68_07pdf/f04.pdf