Technology – Hydrogen conbustion vehicles

6 05 2009

HowStuffWorks “Hydrogen Fuel”

http://en.wikipedia.org/wiki/Hydrogen_vehicle

http://www1.eere.energy.gov/vehiclesandfuels/avta/light_duty/hicev/index.html

The use of hydrogen as a fuel in motor vehicles offers several advantages over traditional fossil fuels:

  • There exists an unlimited supply of hydrogen — hydrogen is the most abundant element in the universe and the tenth most abundant element on Earth.
  • Hydrogen is renewable — When hydrogen reacts with oxygen, the by-product is water (H2O), which can then be hydrolyzed (broken up into its component parts) to yield more hydrogen.
  • Hydrogen is clean-burning — Unlike the burning of fossil fuels, hydrogen combustion does not produce any destructive environmental pollutants.
  • Hydrogen weighs less and generates more power than hydrocarbon-based fuels.
  • Hydrogen burns faster (and at a lower temperature) than conventional gasoline.

A hydrogen internal combustion engine (ICE) vehicle uses a traditional ICE that has been modified to use hydrogen fuel. The U.S. Department of Energy’s FreedomCAR and Vehicle Technologies Program has identified hydrogen-powered ICE vehicles as an important mid-term technology on the path to the hydrogen economy. One of the benefits of hydrogen-powered ICEs is that they can run on pure hydrogen or a blend of hydrogen and compressed natural gas (CNG). That fuel flexibility is very attractive as a means of addressing the widespread lack of hydrogen fueling infrastructure in the near term. Hydrogen-powered ICEs also have many operating advantages. They perform well under all weather conditions, require no warm-up, have no cold-start issues (even at subzero temperatures), and are highly fuel efficient — up to 25% better than conventional spark-ignition engines.

Burning Hydrogen

Wide Range of Flammability

Hydrogen has a wide flammability range in comparison with all other fuels. As a result, hydrogen can be combusted in an internal combustion engine over a wide range of fuel-air mixtures. A significant advantage of this is that hydrogen can run on a lean generally, fuel economy is greater and the combustion reaction is more complete when a vehicle is run on a lean mixture.

Low Ignition Energy

Hydrogen has very low ignition energy. The amount of energy needed to ignite hydrogen is much less than that required for gasoline This enables hydrogen engines to ignite lean mixtures and ensures prompt ignition. Unfortunately, the low ignition energy means that hot gases and hot spots on the cylinder can serve as sources of ignition, creating problems of premature ignition and flashback.

High Diffusivity
Hydrogen has very high diffusivity. This ability to disperse in air is considerably greater than gasoline and is advanta-geous for two main reasons. Firstly, it facilitates the forma-tion of a uniform mixture of fuel and air. Secondly, if a hydrogen leak develops, the hydrogen disperses rapidly. Thus, unsafe conditions can either be avoided or minimized.

Low Density

Hydrogen has very low density. This results in two problems when used in an internal combustion engine. Firstly, a very large volume is necessary to store enough hydrogen to give a vehicle an adequate driving range. Secondly, the energy den-sity of a hydrogen-air mixture, and hence the power output, is reduced.
Hydrogen

Emissions

The combustion of hydrogen with oxygen produces water as its only product:
2H2 + O2 = 2H2O

The combustion of hydrogen with air however can also produce oxides of nitrogen (NOx):
H2 + O2 + N2 = H2O + N2 + NOx

The oxides of nitrogen are created due to the high tempera-tures generated within the combustion chamber during combustion. This high temperature causes some of the nitrogen in the air to combine with the oxygen in the air. making it a slighly un clear technology.

Un clean production

Not to mention the underlying fact that at this current point in time the production of Hydrogen comes from un clean non renewable resources like coal and methane production. The hydrogen is extracted out of these fossil fuels rather than being made from much more eco friendly re newable technologies such as Geo thermal, solar and nuclear energy production.

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