What is Hydrogen?
Hydrogen is the simplest element. A hydrogen atom has only one proton and one electron. It 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, four hydrogen atoms combine to form one helium atom, releasing energy as radiation.
This radiation 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 as a gas (H2), however, doesn’t exist naturally on earth. It is found only in compound form. Combined with oxygen, it is water (H2O). Combined with carbon, it forms organic compounds such as methane (CH4), coal, and petroleum. It is found in all growing things-biomass. It is one of the most abundant elements in the earth’s crust.
Most of the energy we use today comes from fossil fuels. Only seven percent comes from renewable energy sources. But people want to use more renewable energy. Usually it is cleaner, and we won’t run out of it. We won’t run out of hydrogen either.
Every day, we use more 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 TV. Energy carriers make life easier.
Hydrogen is one of the most promising energy carriers for the future. It is a high efficiency, low polluting fuel that can be used for transportation in places where it is difficult to use electricity. Since hydrogen gas is not found in its nature state on earth, it must be manufactured. There are several ways to do this.
How is Hydrogen Made?
Industry produces the hydrogen it needs by a process called steam reforming. High-temperature steam separates hydrogen from the carbon atoms in natural gas (CH4). The hydrogen produced by this method isn’t used as a fuel, but in the manufacture of fertilizers and chemical s and to upgrade the quality of petroleum products.
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. 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 energy. 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.
At the present time, hydrogen’s main use as a fuel is in the NASA space program. Liquid nitrogen is the fuel that has propelled the space shuttle and other rockets since the 1970’s. 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. Hydrogen can be made safely from renewable energy sources and is virtually non-polluting. It is also versatile; it can be 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 5 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 transportation systems we have today? (Just think of the thousands of filling stations across the country, and 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.
For example, hydrogen is a natural as aircraft fuel. Its high-energy contents mean reduced weight and fuel consumption compared to current jet fuel. Plus, it is non-polluting. And converting to hydrogen fuel would be much easier for aircraft-the infrastructure (support system) is simpler. 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 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.
The Future of Hydrogen
Before hydrogen can take its place in 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 to light bulbs. As hydrogen technologies develop, safety issues will be addressed. Hydrogen can be produced, stored, and used as safely as other fuels. The goal of the U.S. Department of Energy’s Hydrogen Program is for hydrogen to produce ten percent of our total energy demand by the year 2030. Hydrogen can reduce our dependence on foreign oil and provide clean, renewable energy for the future.