http://www.the-hindu.com/2001/01/18/stories/08180007.htm The Hindu on indiaserver.com
Thursday, January 18, 2001 Emerging fuel options for automobiles SURGING OIL prizes as a result of frequent `petro-quakes' and environmental concerns have renewed the interest of the oil industry to seek viable alternatives to substitute petrol and diesel oil for transport vehicles. The gaseous fuels from petroleum sources like compressed natural gas (CNG) and liquid petroleum (LPG) are emerging as first alternatives. While LPG and CNG are proven environmentally cleaner fuels than petrol, fuel supply storage and distribution infrastructure and more importantly safety considerations require closer attention. For equivalent range of distance to be covered, the CNG has an additional fuel volume capacity of nearly 4.3 times than diesel while in terms of additional weight, the factor would be about 3.7 with a corresponding penalty in the passenger or load carrying capacity. For buses and trucks, the diesel engine has been adapted to the new fuel namely CNG instead of the fuel being adapted to the engine. In simpler terms, the diesel engine compression ratio has been reduced to that of the petrol engine, while at part-loads the lean burn characteristics of the diesel engine has been sacrificed. It is no wonder that in a stop and go driving situation seen in a city the engine rejects lot of heat to the exhaust calling for a radiator of extra effectiveness. On the contrary, if the fuel were adapted to the diesel engine, the superior features of the engine would have been retained. There are diesel engines working with neat CNG or with some assistance for ignition with a pilot injection of small quantity of diesel fuel in the production stage. Eventually, the switch over from liquid fuel from petroleum source to the gaseous fuel from the same source is no permanent solution to the ever-spiraling petroleum prices. A renewable source for vehicular use would be a long-range solution. Based on renewable raw materials and ecological balance, the fuel of the future seems to be ethanol. Ethanol for transportation vehicles has been successfully implemented in Brazil. Fundamental and developmental work in U.S., Germany, Japan, Sweden, India and other parts of the world have generated a valuable experience for implementing clean burning and renewable future transportation fuel. Ethanol or ethyl alcohol can be produced from biomass and hence it is called renewable fuel. Variety of feed stocks from agricultural and municipal wastes, cellulose, any starch yielding agricultural products like corn, sugar beets, potatoes and more extensively from sugar cane molasses yield ethanol. In Brazil, where ethanol is the most widely used fuel, the natural source is sugarcane. India too has excellent potential for this resource. Use of corn in the U.S. is the most favoured choice. Ethanol as a sole engine fuel in spark-ignited engines is clean burning with no deposits whatever. Hence particulate emissions associated with petroleum fuels is totally absent ``The blue flame special'' is the apt name for ethanol-powered car given by Professor R. K. Pefley, the former president of Alcohol Fuel Systems in California! The nearly invisible flame may be a source of danger for extinguishing fire in case of inadvertent accident. Hence it is customary to add about 15 per cent of petrol to make the flame luminous for easy visibility. This fuel formulation incidentally helps in cold starting since ethanol has more than three times the latent heat of vapourisation in comparison with petrol. This high latent heat is an advantage as less nitrogen oxides are formed during combustion and therefore low in nitric oxide emissions. Additionally, the high latent heat gives a cooler and denser charge as a cylinder feed and this increases power. Hence alcohol fuels have been favoured for racing engines in the past. It has a high octane number and can permit higher compression ratios promoting increased energy efficiency. Amongst the disadvantages, ethanol has lower heat value slightly less than 70 per cent of the heat value of diesel or petrol. Though this does not affect in terms of thermal efficiency, which is actually higher for alcohol engines, it affects in terms of the range of the vehicle per unit volumetric capacity of the fuel tank. About 1.68 litres of ethanol would have the same energy as a litre of diesel oil. Ethanol is more corrosive than diesel or petrol and hence the fuel system is to be made of ethanol compatible materials. It has poor lubricity and suitable lubricants may be necessary in fuel pumps. On the emission side, it has a tendency to produce more aldehydes, a product of low temperature oxidation. It must be noted that partial oxidation of CNG too can produce formaldehydes. But all these problems have been solved over years of research and development and ethanol technology is mature and ready for implementation. Flexible fuel vehicles (FFVs) are already in the market by the brand names like E-85 meaning 85 per cent ethanol and 15 per cent petrol. Before using as a sole fuel in spark-ignited engine, it can be gradually introduced as an admixture with petrol. Called as gasohol in the U.S., it is a mixture of about 10 per cent ethanol in petrol. This will enhance the octane number also and there is no necessity of blending aromatics in petrol to upgrade the octane number. Aromatics like benzene are known to be carcinogenic. One disadvantage of ethanol when used as a mixture is the problem of phase separation when water is present in alcohol. The presence of water is a blessing in disguise in case of accidental fire. It can be readily extinguished with water. Again, accidental spillage during transit by sea, will not cause damage to marine life because of its ready solubility. In sum, India has a good potential for implementing ethanol as a substitute to fuels from petroleum sources. Far reaching research results have been generated in India and this is the time to take advantage of this valuable human resource and develop self- reliance by using fuels like ethanol from renewable sources. B.S.Murthy Biofuel at Journey to Forever: http://journeytoforever.org/biofuel.html To unsubscribe, send an email to: [EMAIL PROTECTED] Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
