Future of Automobile fuel
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In this part we shall consider prospects of using either pure alcohol or mixture of petrol and alcohol. Petrol engines were in the beginning operated on pure alcohol and as petrol became available in plenty and that to at throwaway prices use of expensive alcohol was permanently discarded. Chemical formula of alcohol is C2H5OH and that of petrol is CnH(2n+2). Value of ‘n’ varies from 6 to 11. You can see that number of hydrogen atoms in petrol is many times (minimum 14 to 24) over those in alcohol (only 5). As a result heat-generating capacity of petrol is far superior to that of alcohol. Grossly we can estimate that one liter of petrol produces energy four times that by alcohol. In other words we can say, engine running on petrol giving 40-horse power; if run on alcohol shall produce only 10-horse power. If we consider this option to replace petrol altogether, we shall have to make engines very bulky and that will make the proposal not acceptable. And so today alcohol is used as a supplement to petrol. Many advantages are sited about mixing alcohol in small percentages. Important amongst them is starting problem is greatly reduced. Alcohol being a good solvent keeps the interior of the engine clean and as a result less down time for engines.
It is recommended that mixing alcohol up to 15 % in petrol works best. Any more addition drastically reduced engine efficiency. The difference in the performance is specially realized when climbing steep roads. Engine remains cooler compared to petrol operated engines even after running the vehicle for a long distance and that too, at higher speeds.
Pollution effect of this fuel is very low. As compared to petrol the carbon dioxide emission is five times less and so it is appreciated as environment friendly fuel. Carbon monoxide is not produced at all when alcohol is burnt and that makes this option more acceptable in city uses. Another advantage, alcohol does not produce nitrous oxide and that is an additional plus point in favor of this fuel option. Other problems with petrol fuel is occasionally knocking is experienced with high ratio engines. This problem is not experienced with alcohol.
Ethyl alcohol can be mixed with water to make good quality alcoholic drink and so it is possible that some may take it and instead of putting in the petrol tank will fill in other place! To solve this problem, methyl alcohol is mixed in this fuel to make it non-potable. Both these alcohols are replaceable as additives in this context.
The claim made that this fuel is eco-friendly is challenged by some experts on the grounds that this fuel is not thermally efficient. Following argument is put up by the experts.
To produce alcohol the fermented mass (wort) is distilled. To distill we need a lot of heat. It is proved that to produce one liter of pure alcohol heat required is about five times the heat that can be got by burning the alcohol. This argument clearly shows that when one liter of alcohol is used in engine, carbon dioxide produced is about one fifth of that produced when that alcohol was distilled. So the simple calculation shows that actually the carbon dioxide emission is to be considered in this context are of the total emission and not of only when alcohol is burnt. With this calculation we understand that the actual carbon dioxide emission is the highest amongst all the options we have considered so far.
We should also consider other processes used in industry to produce alcohol using comparatively lesser amount of heat. In that process, first water gas is produced by heating carbonaceous material in reduced atmosphere up to 300 degrees Centigrade and the exuding flue gases are collected and under pressure passed over catalyst at high temperature. Heat generated during the production of water gas is used. Vapor of various alcohols is collected, cooled, and stored. This is only a brief description of the process. Presently this process is being used in industry to produce varieties of alcohols and afterwards different types of alcohols are separated by fractional distillation. When we want to use this as fuel for engines we need not do the fractional distillation and use the issuing mixture of alcohol after dehydrating to remove residual vapor in the mixture. Since, we can procure large quantities of carbonaceous waste material from industry as well as from other sources such as farming and city waste this process seems to be very attractive in giving fuel. Moreover, the raw material being renewable there will be no difficulty in procuring it in future also.
As we have seen in the previous observation that alcohols having less numbers of hydrogen atoms produces less amount of useable energy as compared with petrol or diesel. Many experts suggest that in case this option is selected as standard fuel for our vehicles, we shall have to modify the engines and make use of larger capacity cylinders. Actually some of them suggest that double the size of cylinders will have to be used to produce same amount of energy. This will make engines more bulky and heavy. Some suggest that alcohol-using vehicles will be in the category of two wheelers and in that case existing engines can be used without any difficulty. Pick up of engines working on alcohol will be of medium to low grade and fast running will not be possible. That means alcohol operated vehicles are not suitable for sport of races.
A comparative study was made in an American university and the results suggested that producing alcohol fuel from molasses is much costlier than producing fuel grade alcohol from buggass, a waste product of sugar industry. Heat generated was also used to produce electricity. It observed that the actual heat required to produce alcohol from water gas is not much and so process units with combined production can be developed with advantages. The catalyst required is not very costly and is easily renewed.
These articles will help you understand the issue in the right perspective so that you will not be fooled by any propagandistic writing supporting any of the options mentioned in the list given above. Final solution is listed in the last article in the 4th part.
In the 4th part we shall consider prospects of using algae called Bytryococcus braunii Kurtz. This is the last and final answer to our problem of vehicular fuel. We shall study this option in greater details. Relation of this alga with our petroleum wells has been established recently and that gives additional weight to this option.
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