2016 Toyota Mirai hydrogen fuel-cell car, Newport Beach, CA, Nov 2014Enlarge Photo
California's plan to reduce carbon emissions from transportation anticipates a mix of battery-electric and hydrogen fuel-cell vehicles.
Recharging batteries from the electric grid is relatively simple, but producing hydrogen fuel requires a good deal of energy to split pure hydrogen out of other compounds.
To ensure that the carbon footprint of fuel-cell vehicles is significantly lower than that of gasoline or diesel cars, the state mandates that one-third of the energy used to produce hydrogen fuel be from renewable sources.
Under Assembly Bill 8 (AB8), passed in September 2013 by the California Legislature, the state will fund at least 100 publicly-available hydrogen fueling stations over several years.
The state has committed $20 million a year through 2024, and thus far, 48 hydrogen stations are planned and funded.
Light-duty vehicle type scenario, now-2050 (California Air Resources Board)Enlarge Photo
But using 1 kilowatt-hour of grid electricity to recharge an electric car will get you 3 or 4 miles of travel, whereas you'll get a lot less than that from a fuel-cell car.
Both vehicles use electricity to power electric motors that drive their wheels, but on a wells-to-wheels basis, there are more steps--and hence greater reductions in efficiency--to get the electricity from hydrogen than from the power grid.
In addition to the carbon footprint of the electricity generation itself, there's carbon associated with the hydrogen feedstock.
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And, there are energy losses at every stage as that 1 kWh of electricity is used to separate the hydrogen, which must then be compressed, transported, pumped into the vehicle's tank, and finally used to run a fuel-cell stack whose output is water and ... electricity.
Renewable hydrogen requirement
The stations funded by the California Energy Commission are required to dispense hydrogen that is at least 33 percent renewable, under an Addendum to the terms of the funding contracts it signs with private providers like First Element Fuel.
2015 Hyundai Tucson Fuel Cell at hydrogen fueling station, Fountain Valley, CAEnlarge Photo
That gets the wells-to-wheels carbon footprint of a hydrogen vehicle below that of gasoline vehicles, on average, despite the other two-thirds being mostly sourced today from natural gas, a fossil fuel.
"All applicants ... must provide a plan for dispensing at least 33% renewable hydrogen," says the CEC's contract language.
"This plan must describe how each station or portfolio of stations in the application expects to dispense at least 33 percent renewable hydrogen on a per kilogram basis over the applicant’s portfolio of Energy Commission-funded stations."
Eligible feedstocks include biomethane or other biogases, including biomass, digester gas, landfill gas, sewer gas, or municipal solid waste gas.
Eligible energy sources to crack hydrogen out of those feedstocks include electricity from:
Separate Senate bill
The commission notes that this requirement is independent of a mandate in a Senate bill (SB1505) that permits the California Air Resources board to regulate the renewable content of hydrogen fuel.
That bill puts two mandates on hydrogen dispensed for use in fuel-cell vehicles.