Ethanol boosts gas engines.

The gasoline internal combustion engine has more than 100 years of intense development behind it. But now three researchers from the Massachusetts Institute of Technology (MIT) have modified it in a way that elevates efficiency by a remarkable 25%, an advance that could greatly mitigate greenhouse gas emissions and offers compelling advantages over hybrids and diesels. "This has real potential," says David Cole, chairman of the Center for Automotive Research, a nonprofit organization of the University of Michigan.

The design logic is simple. One can alter an engine to create greater compression of the fuel/air mixture within each cylinder, raising thermodynamic efficiency. One can also add a turbocharger, which force-feeds more fuel/air mixture into the cylinders. This makes it possible to get more power out of an engine, or to downsize an engine without losing power, making it still more efficient.

The problem: boosting compression also boosts temperature, and too much heat can ignite the fuel/air mixture prematurely, causing potentially damaging engine "knock." But Daniel Cohn and Leslie Bromberg of MIT's Plasma Science and Fusion Center, and John Heywood of MIT's Sloan Automotive Lab figured out that a little squirt of ethanol into the cylinder from a separate tank could cool it in the same way that rubbing alcohol cools the skin--by vaporizing, then absorbing excess heat. The researchers have formed a company, Ethanol Boosting Systems (EBS), and have drawn several prominent figures on board, including Neil Ressler, former chief technology officer of Ford Motor Company.

How Alternative Engines Stack Up (compared with conventional gasoline engines, except as noted)

                 Clean Diesel         Electric          Ethanol
                                      Hybrid

Cost           $3,000-3,500     $3,500-5,000 +   $1,000-1,500
               (a)              possible         (a)
                                battery
                                replacement
                                cost (a)

Efficiency     20-30% more      30-40% more      20-30% more
Gain           efficient (a)    efficient (a)    efficient
                                                 (a)

Emissions      25% lower        Up to 50% lower  [NO.sub.x]
               [CO.sub.2]       [CO.sub.2]       and PM
               emissions (b)    emissions (c)    reduction,
                                                 compared with
                                                 clean diesel
                                                 (a)

Technological  Better engine     Better engine     Reduced
Advantages     performance (d)   performance (e)   engine
                                                  weight, more
                                                  space in
                                                  engine
                                                  compartment,
                                                  compared with
                                                  electric
                                                  hybrid (a)

               Less complex     Larger battery   Higher torque
               and easier to    means more       and
               install than EH  safety and       horsepower,
               engine (b)       luxury           compared with
                                electronic       clean
                                systems can be   diesel (a)
                                added on (e)

(a) http://www.ethanolboost.com/Technology.htm
(b) http://www.signonsandiego.com/uniontrib/20060207/
news_1n7diesel.html
(c) http://www.ama.ab.ca/cps/rde/xchg/ama/web/advocacy
_safety_envt_hybrid.htm
(d) http://www.discoveralternatives.org/
Alternative_Fuel_Autos_Technology.php
(e) http://www.alliancebernstein.com/CmsObjectABD/PDF/
Research_WhitePaper/R37755_Hybrid.pdf Edward Bruns/iStockphoto

According to Calculations of Knock Suppression in Highly Turbocharged Gasoline/Ethanol Engines Using Direct Ethanol Injection, a 2006 MIT report, bench engine tests by Ford show that the knock limit can be vastly alleviated, and unpublished results indicate that a 25% increase in efficiency should therefore be attainable. That would reduce carbon dioxide emissions by about 20%, says Cohn. The engine's alcohol consumption would be minimal, because the extra cooling is unnecessary under light loads, such as steady driving at low to moderate speeds.

Although not quite as efficient as the best full hybrid systems, the EBS is far simpler, because it needs no electric motor, extra batteries, or complex software. Cohn says those factors would shave $2,000-4,500 off the cost relative to a full hybrid. The EBS and full hybrid systems would have similar emissions profiles.

An EBS engine would also be a couple of thousand dollars cheaper than a diesel engine. The two engines would produce roughly the same amount of greenhouse gas emissions, but the EBS would otherwise be cleaner, emitting fewer nitrogen oxides ([NO.sub.x]) than the diesel engine, and less particulate matter. Many U.S. cities have nonattainment zones for [NO.sub.x], which contributes to ground-level ozone and can damage lung tissue and vegetation.

In a column in the July 2007 issue of Car and Driver, editor-in-chief and engineer Csaba Csere praises the EBS technology and says that if some seemingly manageable problems are solved--for example, maintaining fuel economy under real-world conditions of elevated temperatures and substandard fuel--EBS engines could be powering cars early in the next decade.

RELATED ARTICLE: ehpnet.

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