Hydrogen

Like electricity, hydrogen is a secondary source of energy. It stores and carries energy produced from other resources (fossil fuels, water, and biomass).

Hydrogen Basics

What is hydrogen?

Hydrogen is the simplest element. Each atom of hydrogen has only one proton. Hydrogen is also the most plentiful gas in the universe. Stars like the sun consist primarily of hydrogen. The sun is essentially a giant ball of hydrogen and helium gases.

Hydrogen occurs naturally on earth only in compound form with other elements in liquids, gases, or solids. Hydrogen combined with oxygen is water (H2O). Hydrogen combined with carbon forms different compounds—or hydrocarbons—found in natural gas, coal, and petroleum.

Hydrogen has the highest energy content of any common fuel by weight (about three times more than gasoline), but it has the lowest energy content by volume (about four times less than gasoline).

Hydrogen is an energy carrier

Energy carriers allow the transport of energy in a useable form from one place to another. Hydrogen, like electricity, is an energy carrier that must be produced from another substance. Hydrogen can be produced—separated—from a variety of sources including water, fossil fuels, or biomass, and used as a source of energy or fuel.

It takes more energy to produce hydrogen (by separating it from other elements in molecules) than the hydrogen provides when it is converted to useful energy. However, hydrogen is useful as an energy source/fuel because it has a high energy content per unit of weight, which is why it is used as a rocket fuel and in fuel cells to produce electricity on some spacecraft. Hydrogen is not widely used as a fuel for other uses now, but it has the potential for greater use in the future.

How is hydrogen produced?

To produce hydrogen, it must be separated from the other elements in the molecules where it occurs. Hydrogen atoms can be separated from water, hydrocarbons in coal, petroleum, and natural gas, and from biomass.

The two most common methods for producing hydrogen are steam reforming and electrolysis (water splitting).

Steam reforming is a widely used method of hydrogen production

Steam reforming is currently the least expensive way to produce hydrogen, and it accounts for most of the commercially produced hydrogen in the United States. This method is used in industries to separate hydrogen atoms from carbon atoms in methane (CH4). The steam reforming process results in carbon dioxide emissions.

Electrolysis uses electricity

Electrolysis is a process that splits hydrogen from water using an electric current. The process can be used on a large or small scale. Electrolysis does not produce any emissions other than hydrogen and oxygen, and the electricity used in electrolysis can come from renewable sources such as hydro, wind, or solar energy. If the electricity used in electrolysis is produced from fossil fuels, then the pollution and carbon dioxide emissions produced from those fuels are indirectly associated with electrolysis.

Other methods of producing hydrogen

Research is underway to develop other ways to produce hydrogen. These methods include using microbes that use light to make hydrogen, converting biomass into liquids and separating the hydrogen, and using solar energy technologies to split hydrogen from water molecules.

Use of hydrogen

Nearly all of the hydrogen consumed in the United States is used by industry for refining petroleum, treating metals, producing fertilizer, and processing foods.

Rocket fuel is the main use of hydrogen for energy

The National Aeronautics and Space Administration (NASA) is the largest user of hydrogen as a fuel. NASA began using liquid hydrogen in the 1950s as a rocket fuel, and NASA was one of the first to use fuel cells to power the electrical systems on space craft.

Hydrogen fuel cells produce electricity

Hydrogen fuel cells produce electricity by combining hydrogen and oxygen atoms. This combination results in an electrical current. A fuel cell is two to three times more efficient than an internal combustion engine running on gasoline.

Many different types of fuel cells are available for a wide range of applications. Small fuel cells can power laptop computers, cell phones, and military applications. Large fuel cells can provide electricity for emergency power in buildings and in remote areas that are not connected to electric power grids. Hydrogen use in vehicles is a major focus of fuel cell research and development.

Hydrogen use in vehicles

The interest in hydrogen as an alternative transportation fuel is based on its potential for domestic production, its use in fuel cells for zero-emission electric vehicles, and the fuel cell vehicle's potential for high efficiency.

In the United States, several vehicle manufacturers have begun making light-duty hydrogen fuel cell electric vehicles available in select regions like southern and northern California where there is access to hydrogen fueling stations. Test vehicles are also available in limited numbers to select organizations with access to hydrogen fueling stations.

Most hydrogen-fueled vehicles are automobiles and transit buses that have an electric motor powered by a fuel cell. A few of these vehicles burn hydrogen directly. The high cost of fuel cells and the limited availability of hydrogen fueling stations have limited the number of hydrogen-fueled vehicles.

The refueling challenge

Production of hydrogen-fueled cars is limited because people won't buy those cars if hydrogen refueling stations are not easily accessible, and companies won't build refueling stations if they don't have customers with hydrogen-fueled vehicles. In the United States, about 60 hydrogen refueling stations for vehicles are operating. About 40 of these stations are available for public use, nearly all of which are in California. The State of California has a program to help fund the development of publicly accessible hydrogen refueling stations throughout California to promote a consumer market for zero-emission fuel cell vehicles.