Hydrogen and Fuel Cells
Hydrogen exists in water, hydrocarbons (such as methane), and organic matter. The energy in 2.2 lb (1 kg) of hydrogen gas is about the same as the energy in 1 gallon of gasoline. Currently, most hydrogen is used for refining petroleum, treating metals, producing fertilizer, and processing foods. Hydrogen can also be used to fuel internal combustion engines (ICEs) and fuel cells, both of which can power low or zero-emissions veihcles such as fuel-cell vehicles. Fuel-cell vehicles are potentially 2 to 3 times more efficient than conventional ICE vehicles and produce no harmful tailpipe exhaust–their only emission is water. Fuel-cell vehicles produce their primary electricity using a fuel cell that is powered by filling the tank with hydrogen. The most common type of fuel cell for vehicles is the polymer electrolyte membrane (PEM) fuel cell. Currently, fuel-cell vehicles and the hydrogen infrastructure to fuel them are in an early stage of development. In Hawaii, General Motors and The Gas Company have partnered (Hawaii Hydrogen Initiative) to bring in fuel-cell vehicles and provide the fueling infrastructure.
Hydrogen is an energy carrier
The production of hydrogen fuel requires energy. For this reason, hydrogen is often described as an energy carrier. Hydrogen can be produced using excess electricity from renewable resources. For example, the wind may be blowing through a wind farm in the middle of the night, when demand for electricity is low. If the electricity production in the middle of the night is greater than the need for electricity, the extra energy can be used to produce hydrogen. The hydrogen can be stored and used later, when electricity demand is at its peak. Or, the stored hydrogen can be used as a transportation fuel.
Where does hydrogen come from?
Hydrogen gas, the “fuel” for fuel cells, does not exist in nature for very long in its pure form (H2). Instead, hydrogen is usually found combined with other elements, such as:
- with oxygen in water (H2O)
- with carbon in “hydrocarbons” (methane: CH4; propane: C3H8; and numerous other carbon-hydrogen chains and rings found in gasoline and diesel)
- with carbon and oxygen in alcohols (methanol: CH3OH; ethanol: C2H5OH)
Hydrogen from water
The hydrogen in water can be separated from the oxygen in a process called hydrolysis. The amount of energy required for the hydrolysis process is more than is ultimately produced by the fuel cell.
However, if renewable energy sources (solar, wind, biomass, etc.) are used for the hydrolysis process, it’s a way to convert available energy from these sources (sunlight, wind, etc.) into a fuel (hydrogen) that can be stored for later use.
Hydrogen from hydrocarbons and alcohol fuels
Hydrogen can be separated from the carbon in hydrocarbons, and carbon and oxygen in alcohol fuels, through a device called a “reformer.” Several companies are developing reformers that will use liquid fuels, such as gasoline, alcohol, or gasoline-alcohol combinations, to produce hydrogen for use in fuel cells.
Reports and Links
- Analysis of Geothermally Produced Hydrogen on the Big Island of Hawaii: A Roadmap for the Way Forward (pdf file; 5 Megabytes; 97 pages) – by Sentech (2008).
- Nuturing a Clean Energy Future in Hawaii: Assessing the Feasability of the Large-Scale Utilization of Hydrogen and Fuel Cells in Hawaii – Report prepared for DBEDT in 2002 by the Hawaii Natural Energy Institute and Sentech (pdf file; 3,302 kb)
- Department of Energy – http://www.afdc.energy.gov/afdc/fuels/hydrogen.html – Hydrogen page
- Hawaii Natural Energy Institute – www.hnei.hawaii.edu/hydrogen.asp – includes information on Hawaii hydrogen and fuel cell activities and partnerships
- International Energy Agency – www.ieahia.org – includes links to renewable-hydrogen case studies and demonstrations
- National Renewable Energy Laboratory – www.nrel.gov/hydrogen/ – hydrogen research
- Renewable Energy Annual - www.eia.doe.gov – current information on renewable energy from the U.S. Energy Information Administration
- Renewable Energy Alliance – www.realliance.org – encouraging the expansion of renewable power markets
- Renewable Energy Policy Project – www.repp.org – articles “strive to be understandable, without glossing over technical issues crucial to well-crafted renewable energy policy”
- Union of Concerned Scientists – www.ucsusa.org – “working for a healthier environment and a safer world.”
- U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy - http://www.eere.energy.gov/