June 12, 2007

Ethanol Boosting Systems for Automobiles

Biofuel naysayers have a wealth of criticisms to use if they really want to derail the renewable energy juggernaut. "The EROIE is not as good as petroleum" "The feedstock is better used as food" "The emissions from ethanol is more toxic than gasoline" "Subsidies are the only reason that ethanol producers make any profits", etc.

Well the oil industry "wasn't built in a day" either (and the resemblance to Rome is pretty apt). The reality is that if Henry Ford had succeeded in encouraging the use of ethanol when he produced the first Model T, engines would have developed much differently than they did and the EROIE, toxicity, feedstock diversity, and subsidy issues would have been solved a long time ago. Give ethanol a hundred years and lets see how efficient and clean it and other biofuels can be.

Here are excerpts from an October 2006 article in Green Car Congress that demonstrates the potential for redesigned combustion engines that exploit the high octane of ethanol.

Startup Working to Commercialize Direct Injection Ethanol Boosting + Turbocharging
Ethanol boost with turbocharging promises a cost-effective means to obtain high fuel efficiency in gasoline and flex ethanol/gasoline powered engines.

MIT scientists and engineers earlier this year founded a company—Ethanol Boosting Systems, LLC (EBS)—to commercialize their work on direct-injection ethanol boosting combined with aggressive turbocharging in a gasoline engine. (Earlier post.) The result is a gasoline engine with the fuel efficiency of current hybrids or turbodiesels—up to 30% better than a conventional gasoline engine—but at lower cost.

EBS has a collaborative R&D agreement with Ford, and anticipates engine tests in 2007 with subsequent licensing to Ford and other automakers. If all goes as expected, vehicles with the new engine could be on the road by 2011.

The foundation of the approach is the enhanced knock suppression resulting from the separate, direct injection of small amounts of ethanol into the cylinder in addition to the main gasoline fuel charge.

The injection of a small amount of ethanol into the hot combustion chamber cools the fuel charge and makes spontaneous combustion much less likely. According to a simulation developed by the MIT group, with ethanol injection the engine won’t knock even when the pressure inside the cylinder is three times higher than that in a conventional SI engine. Engine tests by collaborators at Ford Motor Company produced results consistent with the model’s predictions.

With knock essentially eliminated, the researchers could incorporate into their engine two operating techniques that help make today’s diesel engines so efficient: a high degree of turbocharging and the use of a higher compression ratio.

The combined changes could increase the power of a given-sized engine by more than a factor of two. But rather than seeking higher vehicle performance, the MIT researchers cut their engine size in half. Using well-established computer models, they determined that their small, turbocharged, high-compression-ratio engine will provide the same peak power as the full-scale SI version but will be 20 to 30% more fuel efficient.

The ethanol-boosted engine could provide efficiency gains comparable to those of today’s hybrid engine systems for less extra investment: about $1,000 as opposed to $3,000 to $5,000. The engine should use less than five gallons of ethanol for every 100 gallons of gasoline, so drivers would need to fill their ethanol tank only every one to three months. The ethanol used could be E85.

Given the short fuel-savings payback time—three to four years at present US gasoline prices—the MIT researchers believe that their ethanol-boosted turbo engine has real potential for widespread adoption.

To actually affect oil consumption, we need to have people want to buy our engine, so our work also emphasizes keeping down the added cost and minimizing any inconvenience to the driver.
—Daniel Cohn, MIT senior research scientist and CEO of EBS

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