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April 14, 2007
Ethanol and Compression ratios
If you listen to members of the radical right in this country, Ethanol is the greatest scam ever conceived of by ecologists. I often find this line of reasoning weaker than their standard mindless drivel. Their arguments are based on data from the late 70's to come to the conclusion that there are more BTU's going into the production of corn than we are getting out in BTU's of Ethanol. Once again it's what happens when you put your ideology before your science, you go off making erroneous statements like that one. The reality is that there is an issue that should be looked at which is the fact that per gallon we are packing a third less BTU's into Ethanol. So we'd have to make a third more fuel available to make Ethanol a replacement for gasoline, which could pose a challenge, but just because it represents a challenge doesn't mean it's time to pack up and bury our heads in the sands like our radical right wing friends would have us to believe.
This is where the topic of compression ratios comes up. Here's the text book sort of Compression ration definition.
It is the ratio between the volume of the combustion chamber, when the piston is at the bottom of its stroke, and the volume when the piston is at the top of its stroke.
In a gasoline engine the compression ratio has to be around 10 to 1. Any higher than that and the fuel being sprayed into the combustion chamber starts to explode prematurely and causes a knocking sound to start. Which brings us back to Ethanol...The optimal compression ratio for it is at 15 to 1, hence the problem. We are running Ethanol in a motor optimized for gasoline leading to unoptimized Ethanol energy output. In engines designed to run for Ethanol, the higher octane of Ethanol offsets the lower amount of BTU's and you end up with the same fuel economy per gallon. Plus all the advantages of the much greater environmental and energy returns from Ethanol, unfortunately an engine optimized to run on Ethanol, no longer will run on regular gasoline properly.
Now there are experiments running that will allow the creation of dynamic compression ratios for motors allowing them to switch to optimize whatever kind of fuel ratios that they have to deal with, so when you were running with Ethanol you get maximum performance or if you are running with gasoline it runs at a lower compression ratio to give it maximum performance. These kinds of motors are also referred to as VCR (variable compression ratio) engines. There is also a movement to use the high vaporization energy level of Ethanol to act as a coolant for regular gasoline engines to allow them to function at higher compression ratios during high performance maneuvers, which is interesting I guess, but I'm not sure why you just don't go all Ethanol in the first place. I'm thinking that's likely built on the assumption of a scarcity of Ethanol, which is only a current situation and not a longer term prospect.
Ultimately corn based Ethanol is merely a stepping stone on the way towards a cellulose Ethanol fuel system. People have been raising concerns about the fact that we just can't grow enough corn to supply our fuel, which is a true statement, but remember the same facilities that can make corn based Ethanol can make cellulose based Ethanol as well. What we are doing right now is building the infrastructure of Ethanol for ourselves. We are changing the American mindset and the easiest thing to do right now is to use corn until we perfect the cellulose technologies that will replace it in likely a few short years.
The problem is that we can't keep waiting for the change to happen. We've got to start taking the leap and quick. America is in the mess that we are in now, because we've been tricked by big oil and the automakers that fuel cells are going to be just around the corner for 30 years, so nothing at all should change. The short answer is that time is up and it's time for action instead of excuses. We can combine Ethanol and plug-in hybrid technologies together, and provide America with energy independence in next decade before we even will see the first affordable fuel cell car on the market and even better Ethanol is a great source of hydrogen so we can just covert it on board to run the fuel cells anyway. So the future is here now, it's time to act, it's time for both sides of the ecological debate to stop whining about the solution and start helping us build the fuel economy of the future.
Posted by Jamison at April 14, 2007 9:42 PM
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