Seasonal storage of hydrogen to balance renewable generation will be cost-competitive in 2050, says DNV GL, a Norway-based consulting firm that advises the energy and shipping industries.

The firm modeled nonstop production of hydrogen every summer, using electrolysis units powered by market electricity. The hydrogen would be compressed and stored underground in salt caverns or depleted gas fields, and the following winter would be converted nonstop to electricity, using fuel cells. Daily balancing would be achieved using batteries and pumped hydro. To the extent the entire grid ran on renewables in the summer, the hydrogen would be “green,” or renewably produced.

A project along these lines is under development in Utah, and would use underground salt caverns to store hydrogen. The hydrogen would be renewably produced by 2045, to help Los Angeles achieve its renewables goal.

The DNV GL study also considered hydrogen produced on another continent using solar power, stored either as-is, or after conversion to ammonia or synthetic methane, and shipped to its destination each winter. These options (bars 3 to 5 below) have costs more than double that of locally produced hydrogen (bar 6), as they involve more steps, each with its own costs. All options were compared to wintertime combustion of natural gas with a carbon tax, pegged at 54 euros per metric ton of carbon dioxide (bar 1).

DNV GL projects that a seasonal storage business will be preceded by a market for synthetic fuels. This is the case in the Utah hydrogen storage project, where plans for the early project years call for hydrogen to be mixed with natural gas for combustion in gas turbines.

DNV GL also projects that in 2050, ample short-term storage capacity will be available, in the form of grid batteries, electric vehicle-to-grid applications, and pumped hydro, “to accommodate daily and weekly cycles” in both renewable generation and electricity demand.

DNV GL’s report, The promise of seasonal storage, includes an appendix showing capital and operating costs for all technologies evaluated.