Hydrogen Power

Hydrogen could be the solution to the world’s energy problem. Hydrogen is nothing new, and in fact it is a large and growing industry. The growth rate for hydrogen consumption is around 10% per year. Within the United States, production was about 11 million metric tons, which in turn created 48 gigawatts of energy. This energy source was about 9% of America’s electric production in 2003. (The total electric production in 2003 was 442 gigawatts.) It does however have many problems that would need to be solved before a widespread changeover could be accomplished.

There are two primary uses for hydrogen today. About half is used to produce ammonia (NH3) via the Haber process, in which Nitrogen and Hydrogen react to produce ammonia gas. The other half of current hydrogen production is used to convert heavy petroleum sources into other fuels.

Much of the popular interest in hydrogen seems to attach to the idea of using fuel cells in automobiles. The cells can have a good power-to-weight ratio, are more efficient than internal combustion engines, and produce no damaging emissions. If cheap fuel cells can be manufactured, they may be economically viable in an advanced hybrid automobile (hybrid in the sense of fuel-cell/battery combination), and there is active research to bring down fuel cell prices.

There are however many problems in simply changing to hydrogen power. Pure hydrogen is not widely available on our planet. Most of it is locked in water or hydrocarbon fuels. Hydrogen can be produced using other high-energy fuels, such as fossil fuels, but such methods generate carbon dioxide to a greater extent than conventional internal combustion engines, and thus contribute to global warming more than if those fossil fuels were used directly to power automobiles. It can also be produced using huge amounts of energy and water. Nuclear power can provide the energy, but has its disadvantages. Currently, hydrogen production is 48% from natural gas, 30% from oil, and 18% from coal; water electrolysis accounts for only 4%.

There is concern how the hydrogen will be manufactured. Manufacturing hydrogen requires a hydrogen carrier such as a fossil fuel or water. The former consumes the fossil resource and produces carbon dioxide, while water electrolysis requires electricity. The required electricity is mostly generated using conventional fuels such as fossil fuels or nuclear power. While alternative energy sources such as wind and solar power could also be used, they are more expensive. Because of this, hydrogen fuel technology can not be called truly independent of fossil fuel dependence, unless a totally nuclear or renewable energy option were considered.

The physical laws of conservation of energy create a situation where the energy needed to create the fuel in the first place may reduce the efficiency of the system. This could reduce the efficiency to below that of the most efficient gasoline internal-combustion engines. This is especially true if the hydrogen has to be compressed to high pressures or liquefied, as it does in automobile applications. The electrolysis of water is itself tends to be a rather inefficient process, usually requiring at least 50% more electricity than the energy stored in the produced hydrogen. However, even the most efficient internal-combustion engines are not very efficient in absolute terms. Gasoline is not a primary energy source either, because crude oil has to be treated in a refinery to obtain gasoline. The inefficiencies are in four main stages: electrolysis, transportation, storage, and oxidation. This requires the production of additional electricity, creating additional pollution, and only worsening the problem the hydrogen fuel cells were meant to relieve. The production problem is a combination of two different problems: one of producing hydrogen efficiently from energy sources, and the other of locating suitable energy sources to do it whether it is renewable or at least less polluting.

The storage of hydrogen produces many problems itself. Although Hydrogen gas has good energy density per weight, it has a poor energy density per volume. Because of this it requires a large tank to store it. Increasing gas pressure would improve the energy density per volume, making for smaller, but not lighter container. Another problem is that compressing a gas will require energy to power the compressor. Higher compression will mean more energy lost to the compression step, and it compounds safety issues. Compressors also have the drawback of adding even more weight.

As an alternative to gaseous hydrogen, liquid hydrogen may be used. Liquid hydrogen is cryogenic, meaning it must be stored at very low temperatures, and boils around -423.188 degrees Fahrenheit. Cryogenic storage cuts weight but requires large amounts of energy to liquefy, and the liquid hydrogen product still does not have impressive energy density per volume.