Article: Hydrogen Cars

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A hydrogen car is an automobile which uses hydrogen as its primary source of power for locomotion. The hydrogen can be obtained from decomposition of methane or from water and electricity using electrolysis. A primary benefit of using pure hydrogen as a power source is that it uses oxygen from the air to produce only water vapor as exhaust, moving the source of atmospheric pollution from many cars back to a single power plant, where it can be more easily dealt with. (The hydrogen car has absolutely nothing to do with fusion of hydrogen.)

Hydrogen is not a pre-existing source of energy like fossil fuels, but a carrier, much like a battery. It is renewable in a realistic time scale, unlike fossil fuels which can take millions of years to replenish. The largest apparent advantages are that it could be produced and consumed continuously as well as cleanly using solar, wind and nuclear power for electrolysis. However, hydrogen production methods currently utilizing hydrocarbons would actually be more pollutive than direct consumption of the fossil fuels. To reduce pollution and reliance on fossil fuels, sustainable methods of hydrogen production would have to be invested in.

Some hydrogen cars currently exist, and a significant amount of research is underway to make the technology more viable. The common internal combustion engine, usually fueled with gasoline (petrol) or diesel liquids, can be converted to run on gaseous hydrogen. However, the most efficient use of hydrogen involves the use of fuel cells and electric motors instead of a traditional engine. Hydrogen reacts with oxygen inside the fuel cells, which produces electricity to power the motors. One primary area of research is hydrogen storage, to try to increase the range of hydrogen vehicles while reducing the weight, energy consumption, and complexity of the storage systems. Two primary methods of storage are metal hydrides and compression.

High speed cars, buses, submarines, and space rockets already run on hydrogen, in various forms. The Fuel Cell Car Kit is a working toy model car that runs on solar power, using a reversible fuel cell to store energy in the form of hydrogen and oxygen gas. It can then convert the fuel back into water to release the solar energy. They are available online.

While fuel cells are potentially highly efficient, and working prototypes were made by Roger E. Billings in the late 1960s, three major obstacles exist in the development of a fuel cell-powered hydrogen car. The first problem is that hydrogen has a very low density. Even when the fuel is stored as a liquid in a cryogenic tank or in a pressurized tank as a gas, the amount of energy that can be stored in the space available is limited, and hydrogen cars therefore have limited range compared to their conventional counterparts. Some research has been done into using special crystalline materials to store hydrogen at greater densities and with better safety margins.

Instead of storing molecular hydrogen on-board, some have advocated using hydrogen reformers to extract the hydrogen from more traditional fuels including methane, gasoline, and ethanol. Many environmentalists are irked by this idea, as it promotes continued dependence on fossil fuels (at least in the case of gasoline). However, given an efficient reforming process, vehicles using reformed gasoline or ethanol to power fuel cells would still be more efficient than vehicles running internal combustion engines.

The second major problem that used to plague hydrogen fuel cells involves the high cost of making reliable fuel cells that would provide electric power in a hydrogen car. Scientists are also working hard to figure out how to produce inexpensive fuel cells that are also robust enough to survive the bumps and vibrations that all automobiles have to handle. Most fuel cell designs are fragile and can't survive in such environments. Also, many designs require rare substances such as platinum as a catalyst in order to work properly, and the catalyst can be contaminated by impurities in the hydrogen supply. However, within the past few years, a nickel-tin catalyst has been developed which drastically lowers the cost of a hydrogen fuel cell car to make it an economically viable car.

The third "problem" is due to the fact that while hydrogen can be used as an energy carrier, it is not an energy source. It still must be produced from fossil fuels, or from some other energy source, with a net loss of energy (since the conversion from energy to hydrogen storage and back to energy is not 100% efficient). But Hydrogen is nearly twice as efficient than traditional combustion engines, which only have an efficiency of 15-25%. Hydrogen has a thermodynamic efficiency of 50-60%. The percentage will never be 100% because of the second law of thermodynamics. The US Energy Department has already announced plan to produce hydrogen directly from nuclear power plants. One of the main ideas of Generation IV nuclear power plant is to produce at the same time electricity and hydrogen. Since all energy sources have drawbacks, a shift into hydrogen powered vehicles will require difficult political decisions on how to produce this energy. Recently, alternative methods of creating hydrogen directly from sunlight and water through a metallic catalyst have been announced. This may provide a cheap, direct conversion of solar energy into hydrogen, a very clean solution.

An existing conventional car cannot easily be converted to run from hydrogen, due to a number of inherent differences in the technologies. Other renewable energy sources, like biodiesel, are more practical for existing automobile conversions, but come with their own host of problems.

Despite these problems, United States President George W. Bush is optimistic that these problems could be overcome with research. In his State of the Union address, he announced the U.S. government's hydrogen fuel initiative, which complements the President's existing Freedom CAR initiative for safe and cheap hydrogen fuel cell vehicles--even though some scientists around the US explain that his plan requires taking hydrogen from fossils, natural gas, and coal rather than renewable sources.

Hydrogen internal combustion engine cars are different from hydrogen fuel cell cars. The hydrogen internal combustion car is a slightly modified version of the traditional gasoline internal combustion engine car. Hydrogen internal combustion cars burn hydrogen directly, with no other fuels and produce pure water vapor exhaust. The problem with these cars is the hydrogen fuel is used up rapidly. A full tank of hydrogen gas, in the gaseous state, would last only a few miles before the tank is empty. However, methods are being developed to reduce tank space, such as storing condensed (liquid) hydrogen or using metal hydrides in the tank.

In 1807, Isaac de Rivas built the first hydrogen-fueled internal combustion vehicle. However, the design was very unsuccessful.

BMW's internal combustion hydrogen car has more power and is faster than hydrogen fuel cell electric cars. A BMW hydrogen car (H2R) broke the speed record for hydrogen cars at 300 km/h (186 mi/h), making automotive history. Mazda has developed Wankel engines to burn hydrogen. The Wankel uses a rotary principle of operation, so the hydrogen burns in a different part of the engine from the intake. This reduces pre-detonation, a problem with hydrogen fueled piston engines.

However the major car companies like DaimlerChrysler and General Motors Corp, are investing in the slower, weaker, but more efficient hydrogen fuel cells instead. Hydrogen fuel cells run directly on hydrogen fuel, or on hydrogen produced in the vehicle from reforming methane or gasoline (this from petroleum), or natural ethanol, while hydrogen internal-combustion cars run on hydrogen only.

Some claim to have devices that convert water to hydrogen gas directly in the car using the engine's output, making a car that runs on water and produces water as exhaust. Since this is a closed loop exhibiting net energy output (perpetual motion), it is widely regarded as a hoax.

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