[:: CarEcstasy - Car Technical - Alternative Fuels Information ::]
Advertisments
[ Latest News ]
[ Car Specific ]
[ Audio ]

[0-9] [A] [B] [C] [D] [E] [F] [G] [H] [I] [J] [K] [L] [M] [N] [O] [P] [Q] [R] [S] [T] [U] [V] [W] [X] [Y] [Z]


Back
Alternative Fuels: Because of concerns about fossil fuel reserves, alternative fuels originally gained attention in the 1970s as potential substitutes for petroleum-based fuels. These shortages did not materialize but the environmental advantages of alternative fuels have sustained public interest. The fuels of greatest interest are reformulated diesel fuel, compressed natural gas, alcohols, and biodiesel.
Reformulated diesel fuel
Reformulated diesel fuel is often not considered to be an
alternative fuel because it is still based on nonrenewable petroleum. This fuel is primarily a result of changes in diesel fuel specifications; the specific intention is to reduce emissions without requiring engine hardware modifications. The most common fuel changes in reformulated diesel fuel are lower sulfur, higher cetane number, lower boiling range, and lower aromatics. Lowering the cetane number, aromatic content, and amount of sulfur reduces particulate emissions and raising the cetane number reduces NOx.Achieving these changes at an acceptable cost is a major challenge for refiners.
Fuel additives can assist in achieving at least some of the goals of reformulated diesel fuel. Cetane additives are in common use today and are quite cost effective. Oxygenates can be very effective in reducing particulates but the EPA has expressed reservations about their use due to increases in NOx. To be an acceptable fuel additive, an oxygenate must fall within accepted norms for volatility, solubility with diesel fuel, material compatibility and cost. All of the current oxygenate options present difficulties in one or more of these areas.

Compressed Natural Gas (CNG) (aka. Liquid Petroleum Gas (LPG)))
Compressed natural gas (CNG) is already used in heavy-duty, spark-ignited engines, although its high octane number renders it unsuitable for direct use in compression-ignition engines.
Compressed natural gas is used either with conventional sparkignition technology or as a secondary fuel in dual-fuel engines.
Dual-fuel engines inject a small amount of diesel fuel that ignites a mixture of natural gas and air supplied through a carburetor. While these engines can use diesel fuel if the natural gas supply is interrupted and the dual-fuel equipment can be easily retrofitted
to conventional diesel engines, they are only a transitional technology for automotive use. The heavy-duty natural gas market is moving to dedicated spark-ignited engines.

Alcohol(s)
Alcohol fuels, either methanol or ethanol, can also be used as alternative diesel fuels. Alcohols have low cetane numbers and are difficult to use directly in diesel engines without large amounts of cetane-enhancing additives. By adding cosolvents and emulsifiers, alcohol can be used as a mixture or an emulsion with diesel fuel. This approach can greatly reduce NOx and particulate emissions, but the additives greatly increase the fuel cost and the effect of the fuel on engine durability is still in question. Alcohols can also be fumigated or injected into the intake manifold after the turbocharger compressor and ignited with an injection of diesel fuel similar to the dual-fuel engine described earlier. This approach can also reduce NOx and particulates, but it may require a catalytic converter to control unburned hydrocarbons.

Biodiesel
Biodiesel has received increasing attention during the last several years because it is perceived to be an environmentally friendly fuel. In Europe, it is primarily produced from rapeseed oil, and in the United States, it is derived from soybean oil. Biodiesel is produced by chemically reacting an animal fat or vegetable oil with an excess of alcohol (usually methanol) in the presence of a catalyst to produce alkyl monoesters from the fatty acids present in the oil. These esters are usually referred to as biodiesel. They may be used neat or in blends with diesel fuel.
Biodiesel is nontoxic and biodegradable, and it tends to reduce soot emissions. When used in blends with diesel fuel, the nontoxicity and biodegradability advantages disappear but it still provides lower emissions. Carbon monoxide, unburned hydrocarbons and the carbon portion of particulate are generally lower with biodiesel but NOx and the soluble portion of the particulate increase.
Biodiesel cost fluctuates with the commodity price of the oilseed feedstock, which represents the primary production expense. In Europe, some countries have provided tax incentives to biodiesel that make it price competitive with diesel fuel. In the United States, these tax incentives are not available and biodiesel is four to six times more expensive than diesel fuel.
Biodiesel can be used in existing diesel engines with a minimum of changes. Some elastomers are not compatible with esters, and concerns have been expressed about interactions with the lubricating oil and the thermal and oxidative stability of biodiesel.
:: Recommended Reading / Videos ::
:: Recommended material containing aditional info about Alternative Fuels ::
:: Copyright 2003 - 2012 CarEcstasy.com / All rights reserved ::