Seasonal storage of hydrogen in a depleted natural gas reservoir

• Renewable energy could be seasonally stored as hydrogen in depleted gas reservoirs.
• Hydrogen had 40% of the energy deliverability and 42% of the capacity of natural gas.
• Hydrogen losses from dissolution and diffusion could be reduced to less than 0.1%.
• Losses associated with biological use of CO2 were limited even when CaCO3 dissolved.
• The biological reduction of sulphur minerals to H2S remained a potential problem.

Hydrogen storage in a depleted gas reservoir or in an aquifer offers the potential for the seasonal storage of inherently variable renewable energy, by the electrolysis of water during periods of excess energy production. Here we investigate whether such storage is technically feasible.We compared the respective capacities and deliverabilities of hydrogen to established natural gas in a seasonal storage facility, on the basis of an estimated total volumetric capacity of 48 MMm3, delivery pressures between 5 and 10 MPa and emptying period of 120 days for the Rough Gas Storage Facility (UK). For the modelled scenario, an average power in the order of 4–5 GW would be required during a six month injection cycle to fill the reservoir to capacity. The equivalent hydrogen facility could store and supply 42% of the energy capacity supplied by its natural gas counterpart, and for an emptying period of 120 days could deliver power at an average rate of approximately 100 GWh/day, or ca. 40% of the energy deliverability of natural gas.There appears to be no insurmountable technical barrier to the storage of hydrogen in a depleted gas reservoir. Hydrogen losses from dissolution and diffusion could be reduced to less than 0.1%. Losses from biological conversion of residual CO2 were limited even with calcium carbonate dissolution. However, the biological reduction of sulphur minerals to hydrogen sulphide remained a potential problem.