- What is hydrogen?
- What is a fuel cell?
- How is hydrogen produced and converted to power?
- Is hydrogen safe?
- Will we ever run out of hydrogen?
- What are the advantages of using hydrogen and fuel cell energy?
What is hydrogen?
Hydrogen is the lightest and most abundant element in the universe. It is an energy carrier, not an energy source, meaning that it stores and delivers energy in a usable form. In its pure form (H 2), hydrogen is a colorless and odorless gas. Since it combines easily with other elements, however, hydrogen is rarely found by itself in nature and is usually found as a part of other compounds, including fossil fuels, plant material, and water.
What
is a fuel cell?
A fuel cell is an energy conversion device similar to a battery. Unlike a battery, fuel cells are designed for continuous replenishment, meaning it must be fueled, rather than recharged like a battery. Fuel cell technology can be used to power cars, buses, homes, businesses and even cellular phones and computers.
Fuel cells use a chemical reaction rather than combustion to produce electricity. Hydrogen and oxygen are combined in the fuel cell to produce electricity and water. There are several major types of fuel cells (Alkaline, Phosphoric Acid, Solid Oxide, Regenerative, etc) and most use hydrogen to create energy. Hydrogen can be generated using solar and wind powered electrolysis of water, or can be extracted from hydrocarbon fuels.
Fuel cells are more efficient than traditional power technologies. An internal combustion engine converts about 15 percent of the energy in gasoline to power a car. Fuel cell vehicles are expected to achieve efficiencies of 40 to 45 percent. Fuel cell powered vehicles are also much cleaner than non fuel cell powered vehicles. The only emission from the tailpipe of a fuel cell vehicle operation on hydrogen is water vapor.
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animation of a functioning hydrogen fuel cell.
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How
is hydrogen produced and converted to power?
Hydrogen does not exist alone in nature. Natural gas contains hydrogen, as does biomass and hydrocarbons like coal. Another source of hydrogen can be harnessed from water from sources such as wind, solar, geothermal, nuclear and hydropower energies. All hydrogen production processes are based on the separation of hydrogen from hydrogen-containing feedstock. Today, we use two primary methods to separate hydrogen: thermal and chemical.
About 95 percent of the hydrogen produced in the United States uses a thermal process with natural gas as the feedstock. This process is called steam methane reformation, or SMR. The United States also produces hydrogen electro-chemically from water when higher purity hydrogen is needed. This process, called electrolysis, passes electricity through water in an ionic transfer device to separate water into its hydrogen and oxygen parts.Once hydrogen is extracted through one of these methods, it can be used in a fuel cell to convert into electrical energy. For more information on fuel cells, see “What is a fuel cell.”
Is
hydrogen safe?
Yes. Hydrogen is lighter than air and diffuses rapidly, which means that when it is released, it dilutes quickly into a non-flammable concentration. To become a fire hazard, hydrogen must be confined, but since it is so light, that is very difficult to do.
Hydrogen is also odorless, colorless and tasteless. Humans probably won’t be able to detect a hydrogen leak, but given hydrogen’s tendency to diffuse quickly, an indoor hydrogen leak would briefly collect on the ceiling and eventually move away from where anyone might detect it. Hydrogen, however, can cause asphyxiation. In most situations, hydrogen’s buoyancy makes it unlikely to be contained where asphyxiation might occur.
Like any flammable fuel, hydrogen is combustible. In order for a hydrogen fire to occur, an adequate concentration of hydrogen, the presence of an ignition source and the right amount of an oxidizer must be present at the same time. We already know that hydrogen disperses quickly, making this difficult. An explosion cannot occur in any contained location that contains only hydrogen. Hydrogen flames also have low radiant heat and the combustion of hydrogen primarily produces heat and water. A hydrogen fire has significantly less radiant heat compared to hydrocarbon fires, though the flame itself is just as hot. Overall, the rise of secondary hydrogen fires is lower.
Finally, hydrogen is non-toxic and non-poisonous. It will not contaminate groundwater, nor will a release of hydrogen contribute to atmospheric pollution. Hydrogen does not create “fumes.”
Will
we ever run out of hydrogen?
Probably not. Hydrogen is everywhere, making up more than 90 percent of all matter. It is the most abundant element in the universe and it is the third most abundant element in the Earth’s surface. Hydrogen can be found in water and all organic matter. Without the existence of hydrogen, it would be very difficult to sustain life.
What
are the advantages of using hydrogen and fuel cell energy?
Widespread use of hydrogen as an energy carrier could help address concerns about energy security, global climate change and air quality. Fuel cells are an important enabling technology for the hydrogen future and have the potential to revolutionize the way we power our nation.
Hydrogen and fuel cell technology have the potential to reduce our dependence on foreign sources of energy such as oil. Hydrogen can be derived from a variety of domestically available resources including fossil fuels, renewable and nuclear power.When we drive our cars and power our homes, we generate greenhouse gases, which are thought to be responsible for a change in global climate. If we used hydrogen to generate power, we could significantly reduce the greenhouse gas emissions, especially if the hydrogen is produced using renewable resources.
Furthermore, fuel cells powered by pure hydrogen emit no harmful pollutants. For instance, the only emission from the tailpipe of a fuel cell vehicle operation on hydrogen is water vapor. Hydrogen power could significantly reduce air pollution.
Fuel cells are also significantly more energy efficient than combustion-based power generation technologies. Conventional combustion-based power plants typically generate electricity at efficiencies of 33 to 35 percent, while fuel cell plants can generate electricity at efficiencies of up to 60 percent. Internal-combustion engines in today's automobiles convert less than 30 percent of the energy in gasoline into power that moves the vehicle. Vehicles using electric motors powered by hydrogen fuel cells are much more energy efficient, utilizing 40-60 percent of the fuel's energy.