Green hydrogen pathways, energy efficiencies, and intensities for ground, air, and marine transportation

Green hydrogen produced by electrolysis with renewable electricity can be used directly or in synthetic fuels (e-fuels) to decarbonize road, rail, marine, and air transportation. However, system inefficiencies during hydrogen or e-fuel production, storage, transportation, dispensing, and use lead to approximately 80%–90% loss of the initial electrical energy input. Electric-powered ground, marine, and air transport is approximately 3–8 times more energy efficient than hydrogen alternatives. Renewable electricity sources in the US are insufficient to support hydrogen production for light-duty vehicles. Therefore, green hydrogen should be used strategically in heavy-duty road, rail, aviation, and marine transportation, where electrification alternatives are constrained by load and range. Energy intensity for hydrogen transport measured by renewable electricity per unit of service follows the current trends for petroleum-fueled transport. For freight, ships and rail are the least intensive modes, followed by heavy-duty trucks, then aircraft: 0.04, 0.2, 2, and 20 MJ per t-km, respectively.