|MadSci Network: Engineering|
Aaron; My favorite alternative fuel is food. It is used, with a bicycle, to make a very energy-efficient and cost-effective transportation system. Unfortunately, there are not many other alternatives. Petroleum-based fuels are very cheap, fewer than twenty cents a pound before taxes, they are very well established, and generally are well accepted. We all know that some other fuel will be needed for the future. Presently, we do not know what it will be. Hydrogen has been used to power several research vehicles, mostly by Ford. No one has found a cost-effective way to assure its safe use. Hydrogen leaks are potentially explosive. Hydrogen is odorless, so leaks are not readily detected. In addition, storage containers and fuel lines for hydrogen appear to need more work to be crashworthy. Compressed natural gas (CNG) powered cars and light trucks are available, primarily for special fleet usage. Conversion kits are available for many vehicles. Natural gas powered vehicles have very long engine life, even in difficult usage and weather conditions, since there is no fuel dilution of the engine oil. CNG appears to provide the best choice at this time as an alternative to liquid petroleum fuels. Brazil is unique in that it has alcohol fuel available at service stations. The Brazilian government subsidizes usage of alcohol. Without this subsidy, alcohol would not be an economically attractive fuel choice. Electric vehicles have been around for a long time. Presently, no battery has the energy density and power density needed for general acceptance by most drivers. Energy density is needed to give acceptable vehicle acceleration, primarily passing ability. Power density is needed to provide acceptable driving range between recharges of the batteries. Early battery powered vehicles were slow, had no air conditioning, heating, or other power-consuming accessories. Future vehicles may use electric propulsion, with fuel cells to generate much of the electricity for long trips. Energy efficiency will be improved by use of regenerative braking and higher efficiency motors and controls. This appears to be the most promising of the current choices. Unfortunately, it will take some time to bring fuel cell costs down to acceptable levels. I hope this helps to answer your questions, Aaron. People such as you should help our industrial and governmental stay motivated to find a better fuel for transportation. The reference below may be used to provide more details, and much more background material. http://www.google.com/search?q=cache:www.ucsusa.org/transportation/advanced.html http://www.pprc.org/pprc/pubs/topics/altfuels.html http://www.ncsl.org/programs/energy/ALTFUEL.htm
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