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In 1995, the acid rain provisions of the 1990 Clean Air Act Amendments went into effect. By year's end, electric utilities had reduced emissions of sulfur dioxide (SO2) far more than required by the new law. According to an MIT Energy Laboratory analysis, the reduction was largely the result of a regulatory scheme that gave utilities the flexibility to trade emissions among units facing higher and lower costs at different places and times.

Under the new law, utilities were issued a limited number of fully tradable permits to emit SO2. Some utilities faced high costs to reduce emissions, so they bought permits from utilities whose costs were lower. Other utilities reduced emissions below their allowable levels, thereby freeing up permits to sell or to save for meeting tighter emissions restrictions in the future.

The result was an unprecedented emissions reduction at a lower-than-expected cost. Judging by the success of this first large-scale experiment, "market-based" environmental regulation could be an effective means of controlling other pollutants, among them carbon dioxide.

The researchers were led by senior lecturer A. Denny Ellerman and Professors Richard Schmalensee and Paul Joskow, all associated with MIT's Center for Energy and Environmental Policy Research and the Sloan School of Management. The work was funded by the National Acid Precipitation Assessment Program and the Environmental Protection Agency.


A major challenge for designers of internal combustion engines is how to seal shut the combustion chamber at the top of the cylinder while the piston is moving up and down. Three rings are mounted on each piston and extend to the cylinder wall to form a seal. But as the piston moves, the rings shift in ways that can contribute to three major engine problems: friction, wear and oil consumption.

A model developed by researchers from MIT and Dana Corp. can help engine designers identify new piston and ring designs that will reduce those problems. For a given engine design and operating conditions, the model describes how the rings move, how much friction and wear occur as they encounter other metal surfaces, and how much lubricating oil escapes into the combustion chamber.

Using the model, the researchers have defined a new friction-reducing shape for the grooves in which the rings are mounted. They have also identified a type of ring behavior that may contribute significantly to oil consumption. The MIT researchers are led by Dr. Victor Wong and Professor John Heywood of the Department of Mechanical Engineering, Sloan Automotive Laboratory and Energy Laboratory. The work was funded by the Energy Lab's Consortium on Lubrication in Internal Combustion Engines.

A version of this article appeared in MIT Tech Talk on September 24, 1997.

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