Hydrogen is the primary source of fuel for internal combustion engines in the New Era. It is a lighter-than-air gas.
Although less dense than the hydrocarbon fuels used for such engines in the Old Era, it produces no harmful emissions, with water vapor as its only combustion byproduct.
It is available for purchase at fuel stations, and used as fuel for some personal vehicles, aircraft, locomotives, power tools, and generators.
Mass production of hydrogen fuel is accomplished with a photohydrogenic reactor, which uses energy from sunlight to induce electolysis and break water molecules apart into hydrogen and oxygen. This process is able to store energy in the form of combustible hydrogen at a much greater energy density than batteries or even supercapacitors can manage. Some hydrogen plants are able to store energy from the electric grid during times of excess by using it to perform the same electrolysis to produce hydrogen.
Due to the very small size of hydrogen atoms, the gas is notoriously difficult to contain. Fuel tanks are constructed from a minimum 2cm thick layer of aluminum and ultra-impermeable carbon fiber.
In many countries, hydrogen fueling stations are common, with even small cities having multiple stations managed by different providers. Hydrogen pumps connect to storage tanks using high-pressure valve connectors and pressurize the tanks using electrically-powered compressors. Completely refilling a vehicle's 12 kg tank takes 5 to 8 minutes.