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Posted by David Sherman [72.47.9.228] on Monday, July 26, 2010 at 21:22:26 :
In Reply to: ethanol cheaper than gasoline posted by clueless [201.202.22.114] on Monday, July 26, 2010 at 19:37:01 :
In the long run, an engine should be designed to run strictly on alcohol. In that case the compression ratio could be raised considerably due to the higher octane rating, and you're really see an improvement in efficiency. I've never understood the point of trying to run an unmodified gas engine on alcohol, since you have less BTU/pound with the alcohol (an alcohol molecule contains oxygen, which means you're buying and storing an element that a gasoline engine gets for free out of the air) and therefore less efficiency in terms of lbs of fuel per BHP-hr. The current politics and subsidies for alcohol are unsustainable and it's not clear if alcohol is always going to be available at gas-like prices.
As for the questions, I suspect that the main reason they don't sell neat alcohol at the filling stations is that some people would enjoy drinking it. 15% gasoline added to the alcohol is enough to dissuade even the most die-hard alcoholic from drinking it. Ethanol is merely one of many alcohols. The two other common ones are isopropanol (rubbing alcohol) and methanol (wood alcohol). Some less-common alcohols like sterol and menthol aren't even liquids. Ethanol happens to be the one that's best for fuel simply because it's the cheapest to make, thanks to yeast.
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