Using green hydrogen to power transport in the US would demand three to eight times more energy than batteries, according to a new study by the University of Michigan.

It says that switching all US transportation to green hydrogen would require 10 times more renewable electricity than is currently produced, and three to four times more than the output forecast for 2035.

Whether hydrogen is being used directly in engines or fuel cells, or indirectly in the form of e-fuels, system inefficiencies during production, storage, transportation, dispensing and use lose 80-90% of the energy provided by the initial electrical input.

In a study published in the scientific journal Joule, researchers at the University of Michigan say “green hydrogen pathways for transportation must be carefully prioritised.”

Because electricity produced from renewable sources is limited, it should not be used to generate green hydrogen for modes of transportation where battery-electric technologies are established and effective, they argue.

One example is light-duty vehicles, which account for about two-thirds of US transportation energy consumption and greenhouse gas emissions, Kallanish learns.

Transport is responsible for 22% of global and 37% of US carbon dioxide emissions derived from fossil fuels, according to estimates by the International Energy Agency and the US Environmental Protection Agency.

“Green hydrogen should be used strategically in heavy-duty road, rail, aviation and marine transportation where electric alternatives are constrained by load and range,” says Tim Wallington, first author on the report and a research specialist in the Center for Sustainable Systems at the university.

Using hydrogen as a direct fuel source would need significant changes in fuelling and infrastructure, which can be avoided by using hydrogen-based e-fuels. However, these tend to be 20-50% less energy efficient than direct uses of green hydrogen.