Factors to be considered for development of alternative & renewable fuel systems for motor vehicles:
It is known facts that, motor vehicle contribute adversely towards environment and causes significantly to increase greenhouse gasses. This picture is continuing alarmingly gloomier by the rise of petrol, diesel and kerosene vehicles. Not only do vehicles contribute net carbon gases, mainly CO and CO2, into the atmosphere which contribute to global warming and climate change but the products of combustion also produce additional local pollution causing many physical problems. Besides, the emission of nitrogen oxides, sulfur and carbon particulates (soot) can be very detrimental to health.
We now intend to discuss some imminent developments in running motor vehicles using renewable fuels / systems: We know that, fossil oil and gas are hidden treasures found in the earth crust. Therefore, these fuels are intrinsically cheap, requiring only the costs of finding and extraction from ground. There are three other features that make petroleum based fossil fuels such as petrol, diesel and kerosene uniquely attractive – (a) their very high energy densities, (b) the speed of recharging and (c) the existing world-wide distribution network.
(a) Energy densities are of prime important factor in choosing a particular system of energy-source in motor vehicles. To understand the system, let's take few alternatives of new clean energy sources: (i) rechargeable electric batteries of lead-acid based; (ii) Lithium batteries; (iii) hydrogen gas and Fuel Cells (batteries energized by some form of hydrogen).
(i) Rechargeable batteries are relatively expensive and heavy (due to their low energy densities). Therefore, currently, they are not at all practicable in most of the cases. If we take a comparison between the energy stored per unit weight of petrol and lead-acid batteries the ratio would be about 500:1; even with nickel-metal hydride batteries (another possible contender), the ratio approaches 300:1.
(ii) Lithium batteries are emerging as a practical solution for commercial energy storage device for use in motor vehicles. It has an energy density some 30% to 60% higher than Nickel-Metal hydride, but the supply of Lithium batteries can make the system uneconomic.
(iii) Pure Hydrogen would be ideal, if it is derived in a sustainable way. Unfortunately, this is a gas we would be dealing with and so by definition it has a very low density. Extreme compression or cryogenic temperatures are needed to overcome this problem which poses lot of technological problems to be dealt with, and also the safety aspects. Fuel Cell technology is based on hydrogen, but experts say, liquid compounds containing hydrogen can be used instead of pure hydrogen. Such a system can, theoretically, match energy densities to those of the conventional combustion engine. Again, if using hydrogen means using petroleum compounds then its main advantage is lost.
(b) Speed of recharging is again a very important factor in selecting alternatives. The comparisons regarding speed of charging can be made very easily. How much time does a system take to recharge the vehicle in question in comparison to the time to fill the tank with petrol?(c) A distribution network of conventional oil-based fuels is established world-wide as far the present system is concerned. For any alternative fuels it might take a longer time to build up such infrastructure for distribution.