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Hydrogen - for 9th through 12th Grade StudentsWhat is Hydrogen?
How Is Hydrogen Made?
Uses of Hydrogen
Future of Hydrogen
Hydrogen is the simplest element known to exist. An atom of hydrogen has only one proton and one electron. Hydrogen has the highest energy content of any common fuel by weight, but the lowest energy content by volume. It is the lightest element, and a gas at normal temperature and pressure.
Hydrogen condenses to a liquid at temperatures of minus 423 degrees Fahrenheit (minus 253 degrees Celsius). It is the coldest liquid known on earth!
Hydrogen is also the most abundant gas in the universe, and the source of all the energy we receive from the sun. The sun is basically a giant ball of hydrogen and helium gases. In a process called fusion, two hydrogen atoms combine to form one helium atom, releasing energy as radiation.
This radiant energy is our most abundant energy source. It gives us light and heat and makes plants grow. It causes the wind to blow and the rain to fall. It is stored as chemical energy in fossil fuels. Most of the energy we use originally came from the sun.
Hydrogen gas is lighter than air, and as a result, it rises in the atmosphere. This is why hydrogen as a gas (H2) is not found naturally on earth and must be manufactured. Natural hydrogen by contrast is always mixed with other elements, in coumpound form. Combined with oxygen, it is water (H2O). Combined with carbon, it makes different compounds such as methane (CH4), coal, and petroleum. Hydrogen is also found in all growing things—biomass.Hydrogen is also one of the most abundant elements in the earth’s crust.
Most of the energy we use today comes from fossil fuels. Only six percent comes from renewable energy sources. Renewable sources are usually cleaner, and can be replenished in a short period of time. We won’t run out of hydrogen either.
Every day we use fuel, principally coal, to produce electricity. Electricity is a secondary source of energy. Secondary sources of energy—energy carriers— are used to store, move, and deliver energy in easily usable form. We convert energy to electricity because it is easier for us to transport and use. Try splitting an atom, building a dam, or burning coal to run your television. Energy carriers make life easier.
Hydrogen has some advantages that may make it a more important energy carrier in the future. Unlike electricity, large quantities of hydrogen can be easily stored (electricity must be produced at the time it is needed.) Hydrogen is also a high efficiency, low polluting fuel that can be used for transportation, heating, and power generation in places where it is difficult to use electricity. In some cases, shipping hydrogen by pipeline can be cheaper than sending electricity over long distances by wire. It can also be stored in a number of different ways. Since hydrogen gas is not found in its natural state on earth, it must be manufactured. There are several ways to do this.
Industry produces the hydrogen it needs by a process called steam reforming. High-temperature steam separates hydrogen from the carbon atoms in methane (CH4). The hydrogen produced by this method isn’t used as a fuel. It is used for industrial processes. This is the most cost-effective way to produce hydrogen today, but it uses fossil fuels both in the manufacturing process and as the heat source resulting in greenhous gas emissions.
Another way to make hydrogen is by electrolysis—splitting water into its basic elements––hydrogen and oxygen. Electrolysis involves passing an electric current through water to separate the atoms (2H2O + electricity = 2H2 + O2). Hydrogen collects at the negatively charged cathode and oxygen at the positive anode.
Hydrogen produced by electrolysis is extremely pure, and electricity from renewable energy sources can be used, but it is very expensive at this time. Today, hydrogen from electrolysis is ten times as costly as natural gas and three times as costly as gasoline per Btu.
On the other hand, water is abundant and renewable, and technological advances in renewable electricity could make electrolysis a more attractive way to produce hydrogen in the future.
There are also several experimental methods of producing hydrogen. Photoelectrolysis uses sunlight to split water molecules into its components. A semiconductor absorbs the energy from the sun and acts as an electrode to separate the water molecules.
In biomass gasification, wood chips and agricultural wastes are super-heated until they turn into hydrogen and other gases. Biomass can also be used to provide the heat.
Scientists have also discovered that some algae and bacteria produce hydrogen under certain conditions, using sunlight as their energy source. Experiments are underway to find ways to induce these microbes to produce hydrogen efficiently.
The U.S. hydrogen industry currently produces about nine million tons of hydrogen a year, enough to power 20-30 million cars or 5-8 million homes. Most of this hydrogen is used for industrial applications such as refining, treating metals, and food processing.
At the present time, hydrogen’s main use as a fuel is in the NASA space program. Liquid hydrogen is the fuel that has propelled the space shuttle and other rockets since the 1970s. Hydrogen fuel cells power the shuttle’s electrical systems, producing pure water, which is used by the crew as drinking water.
In the future, however, hydrogen will join electricity as an important energy carrier, since it can be made safely from renewable energy sources and is virtually non-polluting. It will also be used as a fuel for ‘zero-emissions’ vehicles, to heat homes and offices, to produce electricity, and to fuel aircraft. Cost is the major obstacle.
The first widespread use of hydrogen will probably be as an additive to transportation fuels. Hydrogen can be combined with gasoline, ethanol, methanol, and natural gas to increase performance and reduce pollution. Adding just five percent hydrogen to gasoline can reduce nitrogen oxide (NOX) emissions by 30 to 40 percent in today’s engines.
An engine converted to burn pure hydrogen produces only water and minor amounts of NOX as exhaust.
A few hydrogen-powered vehicles are on the road today, but it will probably be 10-20 years before you can walk into your local car dealer and drive away in one. Finding hydrogen fuel today might be difficult.
Can you imagine how huge the task would be to quickly change the gasoline-powered transportation system we have today? (Just think of the thousands of filling stations across the country, and the production and distribution systems that serve them.) Change will come slowly to this industry, but hydrogen is a versatile fuel; it can be used in many ways.
The space shuttle uses hydrogen fuel cells (batteries) to run its computer systems. The fuel cells basically reverse electrolysis—hydrogen and oxygen are combined to produce electricity. Hydrogen fuel cells are very efficient and produce only water as a by-product, but they are expensive to build.
With technological advances, small fuel cells could someday power electric vehicles and larger fuel cells could provide electricity in remote areas.
Because of the cost, hydrogen will not produce electricity on a wide scale in the near future. It may, though, be added to natural gas to reduce emissions from existing power plants.
As the production of electricity from renewables increases, so will the need for energy storage and transportation. Many of these sources—especially solar and wind—are located far from population centers and produce electricity only part of the time. Hydrogen may be the perfect carrier for this energy. It can store the energy and distribute it to wherever it is needed. It is estimated that transmitting electricity long distances is four times more expensive than shipping hydrogen by pipeline.
Before hydrogen can make a significant contribution to the U.S. energy picture, many new systems must be designed and built. There must be large production and storage facilities and a distribution system. And consumers must have the technology to use it.
The use of hydrogen raises concerns about safety. Hydrogen is a volatile gas with high energy content. Early skeptics had similar concerns about natural gas and gasoline—even about electricity. People were afraid to let their children too near the first light bulbs. As hydrogen technologies develop, safety issues will be addressed. Hydrogen can be produced, stored, and used as safely as other fuels.
Last Revised: December 2006
Sources: Energy Information Administration,Office of Coal, Nuclear, Electric and Alternative Fuels.
The National Energy Education Development Project, Intermediate Energy Infobook, 2005.
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