'Producing green hydrogen only when wind and solar power is available would be cheaper than 24/7 operation': study
Lower capital costs for renewables & storage and longer lifespan of H2 equipment will offset the latter's higher initial capex, according to scientific paper
The widely accepted view that electrolysers need to operate as close to 24 hours a day seven days a week as possible to produce green hydrogen at the lowest possible cost is false, according to a new scientific study.
Hydrogen: hype, hope and the hard truths around its role in the energy transition
“However, we hypothesize that, at high WWS [wind-water-solar] penetrations and hydrogen penetrations, running this equipment intermittently (with sub-unity use factors) reduces overall system cost.”
The study goes on to explain that “the nameplate capacities of rectifiers, electrolyzers, and compressors must be increased to ensure the same annual quantity of hydrogen is produced as with a unity use factor” and that “higher nameplate capacities mean higher capital costs”.
But it adds: “Fortunately, the impact of higher capital costs on overall hydrogen cost is largely offset by the longer lifetimes of rectifiers, electrolyzers, and compressors with lower use factors.”
“Additional cost is offset because, either a lower nameplate capacity of wind and solar or less hydrogen storage is needed with a lower use factor,” it explains.
“In sum, the lowest cost of hydrogen production integrated with 100% WWS occurs at a hydrogen-equipment use factor below unity, between 0.2 and 0.65 [ie, 20-65%] in the test cases provided.
“As such, it is more cost-effective from an overall system perspective to produce hydrogen intermittently rather than continuously. The results here are subject to model uncertainties, but [the] conclusion appears robust.”
“Economies of scale suggests that interconnecting all WWS generators and adding loads (such as green hydrogen production) that can absorb excess electricity, results in the most cost-effective system.
“Thus, grid operators should incorporate intermittent green hydrogen production in grid planning.”
Assumptions
The 145 countries are responsible for more than 99.7% of global fossil-fuel emissions.
Jacobson et al argue in the paper that biofuel and synthetic aviation fuel are not valid decarbonisation methods for ships or airplanes because they still produce gases and particles that are bad for human health and/or the planet.
“Despite the challenges of implementing green hydrogen for long-distance aircraft and ships, it is important to evaluate this solution because no other clean, renewable energy solution is on the horizon,” they write.