ALTERNATE FUELS

Most important alternative fuel candidates are: ethanol, methanol, natural gas, liquefied petroleum gas (LPG), vegetable oil esters commonly called as ‘biodiesel’ and hydrogen  High petroleum prices during 1980’s provided motivation for development programmes for use of ethyl alcohol produced from agricultural products  as motor fuel in countries like Brazil. During the same period, clean burning properties of methanol and its easy production from natural gas led to technological development activities on methanol in the USA. Methanol being liquid it is better suited than natural gas for storage on-board of vehicles. However, due to its toxicity and its corrosive nature towards fuel system materials, interest in methanol as automotive fuel has gone down although a number of demonstration fuel cell vehicles (FCV) using methanol have been developed. Presently, natural gas and biodiesel have attracted maximum attention of the governments, vehicle manufacturers and fuel suppliers. Hydrogen is considered as an alternative transport fuel in the long term especially for the fuel cell powered vehicles. .

Properties of Alternative Fuels

Some of the key properties of the main alternative fuel candidates are compared in Table 8.13 with those of conventional petroleum fuels. Key properties to be considered for :

• Combustion and Performance: Heat of combustion, heat content of stoichiometric mixture, octane number (SI engine) , cetane number (CI engine), boiling point ( esp., cold start), flammability limits
• Emissions: Chemical composition and nature, adiabatic flame temperature
• Storage and Handling: Boiling point, volumetric energy density, vapour pressure, flammability limits

Keeping the above in view the main alternative fuels are being discussed below

LHV= Lower heating value