Hydrogen is the simplest and most abundant element on earth—it consists of only one proton and one electron. Hydrogen can store and deliver usable energy, but it doesn’t typically exist by itself in nature and must be produced from compounds that contain it.
Sources of Energy
Diverse domestic resources can be used to manufacture hydrogen. The majority of hydrogen produced today comes from natural gas and other fossil fuels. Hydrogen is currently made with electricity that comes from the grid or renewable sources like biomass, solar, wind, and geothermal energy. As new technologies make alternative production methods more cost-effective, solar energy and biomass can be used more directly to generate hydrogen in the long run.
The majority of hydrogen can also be produced through the high-temperature process known as steam methane reforming, in which steam reacts with a fuel made of hydrocarbons to produce hydrogen.
Hydrogen is produced in another common way by electrolyzing water to separate the molecule H2O into oxygen and hydrogen. An electrolyzer, like a fuel cell, produces hydrogen from water molecules rather than using the energy of a hydrogen molecule, as in a fuel cell. This is how electrolysis takes place in an electrolyzer.
Utilizing microorganisms like bacteria and microalgae, biological reactions can also produce hydrogen. Microbes consume plant material and produce hydrogen gas during these processes.
The photobiological, photoelectrochemical, photovoltaic-driven electrolysis, and solar thermochemical processes are just a few of the many ways that sunlight can be used to produce hydrogen.
Hydrogen can transport and store a significant amount of energy; it is not an energy source. In fuel cells, hydrogen can be used to produce heat and power in addition to electricity. Hydrogen is currently primarily utilized in the production of fertilizer and petroleum refining, with transportation and utilities emerging as emerging markets.
Uses for Hydrogen
In a fuel cell, hydrogen is a clean fuel that only produces heat, electricity, and water. With the potential to be utilized in a wide range of applications across virtually all sectors—transportation, commercial, industrial, residential, and portable—hydrogen and fuel cells can contribute significantly to our national energy strategy. Fuel and hydrogen cells can provide energy for a variety of uses, such as distributed or combined heat and power; backup energy; systems that enable and store renewable energy; battery power; auxiliary power for ships, trains, aircraft, and trucks; specialized automobiles like forklifts; and automobiles, trucks, and buses that transport passengers and cargo.
Hydrogen and fuel cells have the potential to reduce greenhouse gas emissions in numerous applications due to their high efficiency and emission-free or nearly emission-free operation. According to research supported by the Energy Department, hydrogen and fuel cells have the potential to reduce emissions in the following ways:
- Light-duty highway vehicles: more than 50% to more than 90% reduction in emissions over today’s gasoline vehicles.
- Specialty vehicles: more than 35% reduction in emissions over current diesel and battery-powered lift trucks.
- Transit buses: demonstrated fuel economies of approximately 1.5 times greater than diesel internal combustion engine (ICE) buses and approximately 2 times higher than natural gas ICE buses.
- Auxiliary power units (APUs): more than 60% reduction in emissions compared to truck engine idling.
Systems that combine heat and power (CHP): 35% to more than 50% reduction in emissions compared to conventional heat and power sources (with much greater reductions—more than 80%—if biogas or hydrogen from low- or zero-carbon sources is used in the fuel cell). The greatest obstacle for the production of hydrogen, particularly from renewable resources, is providing hydrogen at a lower cost. Hydrogen must compete with conventional fuels and technologies in terms of cost per mile for transportation fuel cells. This means that the price of hydrogen must be less than $4 per gallon of gasoline equivalent, regardless of the production technology. Research is focusing on lowering the cost of capital equipment, operations, and maintenance, as well as increasing the efficiency and lifespan of hydrogen production technologies, in order to reduce the overall cost of hydrogen.