Usuario:Mac/Traducciones/Vehículo de hidrógeno

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An hydrogen vehicle is an automobile which uses hydrogen as its primary source of power for locomotion. These cars generally use the hydrogen in one of two methods: combustion or fuel-cell conversion. In combustion, the hydrogen is "burned" in engines in fundamentally the same method as traditional gasoline cars. In fuel-cell conversion, the hydrogen is turned into electricity through fuel cells which then powers electric motors. With either method, the only byproduct from the spent hydrogen is water.

Hydrogen can be obtained from decomposition of methane (natural gas) or from water using electricity (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 (and very little nitrogen oxides from the nitrogen in the air when burning at high temperatures, 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. (Some dispute this. See Abiogenic petroleum origin.) 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. There is even 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.[1]​

Hydrogen fuel cell[editar]

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 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. Furthermore freezing conditions have to be handled because fuel cells do produce water and utilise moist air with varying water content. 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.

Since all energy sources have drawbacks, a shift into hydrogen powered vehicles may require difficult political decisions on how to produce this energy. The US Energy Department has already announced a plan to produce hydrogen directly from Generation IV reactors. These nuclear powerplants would be capable of producing hydrogen and electricity at the same time. 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.[2]​

Sodium boro hydride (NaBH4) a chemical compound may hold future promise due to the ease at which hydrogen can be stored under normal atmospheric pressures in automobiles that have fuel cells.

Estados Unidos President George W. Bush is optimistic that these problems could be overcome with research. In his 2006 State of the Union address, he announced the U.S. government's hydrogen fuel initiative, which complements the President's existing FreedomCAR initiative for safe and cheap hydrogen fuel cell vehicles.

Hydrogen internal combustion[editar]

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 that can be stored in a normal size tank is used up rapidly. A full tank of hydrogen, 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 1907, Isaac de Rivas built the first hydrogen-fueled internal combustion vehicle. However, the design was very unsuccessful.

It's estimated that more than a thousand hydrogen powered vehicles were produced in Germany before the end of the WWII prompted by the acute shortage of oil.

BMW's CleanEnergy 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 intake backfiring, a risk 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.

An existing conventional car can be converted to run on hydrogen, or a mixture of hydrogen and other gasses as produced in a reforming process. Since hydrogen can burn in a very wide range of air/fuel mixtures, a small amount of hydrogen can also be used to ignite various liquid fuels in existing internal combustion engines under extremely lean burning conditions. This process requires a number of modifications to existing engine air/fuel and timing controls. Roy McAlister of the American Hydrogen Association has been demonstrating these conversions. Other renewable energy sources, like biodiesel, are also practical for existing automobile conversions, but come with their own host of problems.

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 only 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 (see water fuel cell).

In 2005 an Israeli company claimed it succeeded in conquering most of the problems related to producing Hydrogen internal combustion engine by using a device called a Metal-Steam combustor that separate Hydrogen out of heated water. A tip of a Magnesium or Aluminum coil is inserted into the small Metal-Steam combustor together with water where it is heated to very high temperatures. The metal atoms bond with the Oxygen from the water, creating metal oxide. As a result, the Hydrogen molecules become free, and are sent into the engine alongside the steam. The solid waste product of the process, in the form of metal oxide, will later be collected in the fuel station and recycled for further use by the metal industry[3]​

Automobile and bus makers[editar]

Many companies are currently researching the feasibility of building hydrogen cars. Funding has come from both private and government sources. In addition to the BMW and Mazda examples cited above, many automobile manufacturers have begun developing cars. These include:

  • BMW — 7 series (auxiliary power), based on UTC Power fuel cell technology
  • DaimlerChrysler — F-Cell, a hydrogen fuel cell vehicle based on the Mercedes-Benz A-Class.
  • Ford Focus FCV — a hydrogen fuel cell modification of the Ford Focus
  • General Motors — multiple models of fuel cell vehicles including Hy-wire and the HydroGen3
  • Honda is experimenting with a variety of alternative fuels and fuel cells with experimental vehicles based on the Honda EV Plus
  • Hyundai — Santa Fe FCEV, based on UTC Power fuel cell technology
  • Mazda - RX-8, with a dual-fuel (hydrogen or gasoline) rotary-engine[4]​
  • Nissan — X-TRAIL FCV, based on UTC Power fuel cell technology
  • Volkswagen and Toyota also have hydrogen fuel cell cars in development.

A few bus companies are also conducting hydrogen fuel cell research. These include:

  • DaimlerChrysler, based on Ballard fuel cell technology
  • Thor Industries (the largest maker of buses in the U.S.), based on UTC Power fuel cell technology
  • Irisbus, based on UTC Power fuel cell technology

Supporting these automobile and bus manufacturers are fuel cell and hydrogen engine research and manufacturing companies. The largest of these is UTC Power, a division of United Technologies Corporation, currently in joint development with Hyundai, Nissan, and BMW, among other auto companies. Another major supplier is Ballard Power Systems. The Hydrogen Engine Center is a supplier of hydrogen-fueled engines.

Most, but not all, of these vehicles are currently only available in demonstration models and cost a large amount of money. They are not yet ready for general public use.

BMW has recently released to the media information of a new car that has been manufactured and uses hydrogen or petrol and is completely clean. BMW also plans to release its first publicly available hydrogen vehicle in 2008.

Estaciones de servicio (hidrogeneras)[editar]

Since the turn of the millennium, filling stations offering hydrogen have been opening worldwide. Among them:

References[editar]

  1. ↑ Thames & Kosmos kit, Other educational materials, and many more demonstration car kits.
  2. ↑ «Hydrogen's Dirty Secret». Consultado el December 4|fechaacceso= y |Añoacceso= redundantes (ayuda). 
  3. ↑ «IsraCast: THE CAR THAT MAKES ITS OWN FUEL». 
  4. ↑ «NEWS FROM MAZDA». Consultado el December 4|fechaacceso= y |Añoacceso= redundantes (ayuda). 
  5. ↑ Hydrogen-filling station opens ... in Iceland
  6. ↑ Motavalli, Jim (2001). Breaking Gridlock: Moving Towards Transportation That Works. San Francisco: Sierra Club Books. ISBN 1-57805-039-1. : p. 145.

See also[editar]

External links[editar]


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