A group of scientists from the Oregon Center for Electrochemistry (OCE) and Arizona-based zero-emission vehicle company Nikola has investigated whether electrolyzers and fuel cells powered by intermittent wind and solar may become economically competitive in providing seasonal energy storage in the U.S. energy market. “Our paper investigates multiple end-uses of fuel cells for grid power and shipping,” the research’s corresponding author, Paul Kempler, told pv magazine. “It remains to be seen whether electrolyzers will be able to operate under intermittent availability provided by both wind and solar. The cost of electrolyzers is also certain to fall over the next ten years due to the widespread scale-up of production capacity and intermittently-powered electrolyzers and fuel cells is a new idea here that could be quite important by 2040-2050 in a U.S. grid powered primarily by wind and sunlight.”
In the study “Research priorities for seasonal energy storage using electrolyzers and fuel cells,” published in Joule, Kempler and his colleagues defined long-duration energy storage (LDES) as storage solutions with energy capacities equivalent to over 10 hours of rated power, with optimal levels reaching 100 hours. “The low lifetime number of charge-discharge cycles associated with seasonal storage makes storage capital costs over $10/kWh uncompetitive with existing sources of firm generation,” the paper reads.
They modeled a US energy system relying 100% on wind and solar and supported by 200GW of LDES with a storage capacity of 80,000GWh. “For comparison, electrification of the entire fleet of light-duty vehicles in the US would require 200 times less power capacity but 83 times greater energy storage capacity,” they also explained, noting that hydrogen stored in caverns or pipes may reach costs that may be 10 times below the capital cost of pumped-hydro storage or vanadium redox flow batteries.
The academics reported that hydrogen can currently be produced at over $10/kg and emphasized the need for the hydrogen industry to improve the efficiency and costs of both electrolyzers and fuel cells. According to them, the U.S. Department of Energy (DoE) target hydrogen price of $1/kg may only be achieved through the availability of very low cost electricity, at less than $0.05/kWh. “Low prices for wind and solar in regions such as California and Texas are available today and will become increasingly available over the next decade,” Kempler stated, noting that the bottom range of wind and solar levelized energy costs is now around $0.03/kWh, according to US-based Lazard. “Power purchase agreements have already been signed for $0.02/kWh in California and costs for direct use of wind and solar are likely to continue to decline as the technologies are scaled.”
According to the research group’s calculations, an affordable hydrogen-based system for seasonal energy storage could be achieved at a hydrogen price lower than $3/kg, produced from inexpensive renewable electricity at $0.02/kWh. “For modeled electrolysis stacks available at $200/kW, a hydrogen cost target of $1/kg is met at electricity rates [of] $0.02/kWh by future solid oxide electrolyzer cell (SOEC) electrolyzers operating at 1.2V or at electricity rates [of] $0.01/kWh by future proton exchange membrane (PEM) electrolyzers operating at 1.75V,” it concluded. “Growth of fuel cell markets from applications in back-up power to heavy-duty transportation could be leveraged to satisfy the need for inexpensive, low-capacity-factor power discharge facilities.”
