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Young scientists give a thumbs-up to ethanol's efficiency

Agriculture.com Staff 10/07/2015 @ 2:32pm

Recently, Agriculture Online carried a story about E85 fuel (85% ethanol, 15% regular gasoline) which discussed claims about the effect of the corn-based fuel on gas mileage in cars. Ethanol proponents generally claim that ethanol, because of its lower energy value, will reduce efficiency by 5-15%. Others say the reduction in mileage for E85 may be closer to 30%.

Leave it to kids to come up with the scientific answer to a question about new technology. Agriculture Online received a response to that story from Mark Seetin, Hayfield, Virginia. His daughter, Tressa, a sophomore in high school, recently won the Virginia State Science and Engineering Fair, Research and Innovation area of the Engineering Division, with a project measuring the fuel efficiency of various blends of ethanol in a small electric generator. Earlier, the project won first place awards at her high school and the Northern Virginia Regional Science and Engineering Fair.

Here's how her dad summarized the project:

"Tressa and her chemistry lab partner, R.J. Hartman, did an interesting experiment involving the use of various blends of gasoline and ethanol in a Coleman Powermate Model 1850 portable generator. They had decided to use an off-the-shelf, unmodified portable electric generator (gasoline powered) to test the effect of various fuel mixtures of gasoline and ethanol.

"Their experiment led to a couple of interesting areas of thought. While we did not even know if the generator would run on mixtures in excess of 20% ethanol, it performed well, including running on pure ethanol. I believe the reason was that the engine had a manual choke, so we could adjust the richness of the fuel mixture, but it ran well on all mixtures (E10, E20, E40, and E85).

"To allow for statistical analysis, four replications of each fuel mix were prepared and used -- with the exception of pure ethanol. We ran out of our 100% laboratory pure ethanol after two replications of pure ethanol, so the pure ethanol data was not used in the analysis.

"Among the most interesting of the results dealt with the use of a blend of 15% gasoline and 85% ethanol, commonly known as E85 and increasingly marketed throughout the U.S. The E85 fuel mix consistently provided a longer than expected running time. [Each run of the experiment involved putting exactly 50 ml of fuel in the tank, and measuring the running time with a stopwatch.] The expected running time was calculated by comparing the relative energy contents of each fuel mix (expressed as a percentage of the control, pure gasoline). Using gasoline as the base with 116,090 Btu/gallon, and ethanol at 76,330 Btu/gallon (65.8% of the energy content of gasoline) the E85 should run roughly 71% as long as pure gasoline. But it consistently ran at 79-80% as long as the gasoline, representing a boost of roughly 12% above the expected running time.

"Because we had a uniform load of 800 watts on the generator, we were able to calculate the relative efficiency achieved by each fuel, by converting the KWH output to Btus and dividing the energy output by the energy input in the form of the fuel mix. The efficiency of the gasoline came out to 10.17%, while the E85 came out at 11.40%, a gain of 12% over the efficiency of pure gasoline.

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E85 AIN'T E85 09/15/2015 @ 12:05pm First, 100% ethanol-free gasoline(E0) has been made rare by the EPA & often NOT available in cities for testing. Second, labeled E85 is normally a mixture of 60% to 70% ethanol(E0 content, 40% to 30%). At its worst, labeled E85 could be as low as 52% ethanol(E0 content, 48% gasoline). Almost never, will you find labeled E85, to be 85% ethanol, 15% E0. Third, I suspect, your compared 116,090Btu/gallon(E0) 100% gasoline, is actually E10. My own decade(s?) of comparison of E10 compared to true E0, in five from-the-factory standard setting 87octane, low compression ratio(9:1 to 10.5) gasoline engines, show that E0 mpg is superior to E10 mpg by 8%, 8%, 7%-8%, 7% & 5%.

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