Clean-Fuel Cars in California

One outcome of Russell's clean-fuel work was a set of regulations developed by CARB for California automobiles. The rules mandate a maximum level of ozone production from automobiles. When methanol and other hydrocarbons break down in the atmosphere, they form byproducts, which in turn lead to the formation of ozone. The CARB index uses information on the byproducts of various fuels to compute ozone production per mile traveled.

"We wanted to give the car companies the flexibility to meet those stringent standards, either by changing the technology on the vehicle or by changing the fuel," says Bart Croes, manager of CARB's atmospheric processes research section. "But in reality, the choice of fuels is somewhat limited. For some fuels, there just isn't enough available to fuel all the cars. Other fuels, meanwhile, may have hydrocarbons with lower ozone-forming potential, but are higher in another pollutant."

The regulations are being phased in slowly, and some of the companies are turning to alternative fuels for some of the vehicle fleet by using the new ozone production index. "There are some methanol vehicles, for instance, that have been certified using this reactivity scale," Croes says. "The car companies average the vehicles. They can either have all cars moderately clean, or they can have some cars a little dirtier as long as others are cleaner."

Because CARB's index calculates the maximum amount of ozone potentially produced, one question raised during its development was whether it accurately predicted ozone production in a place like Los Angeles. "That's why we used Ted's model." Croes says, "It's our best representation of what actually goes on in the atmosphere."

Russell used the CRAY C90 at Pittsburgh to study the impact of several alternative fuels, including methanol and reformulated gasoline. And because it's too difficult to study the hundreds of hydrocarbons produced by each fuel, Russell studied only a few hydrocarbons to check the index's accuracy. The results agreed well with the index, within a range of 15 percent, reinforcing the technical validity of the regulations. "We needed to have this test," Croes says, "to give us confidence in what we were doing."

During the coming year, Russell plans to switch this modeling to the center's Alpha Cluster -- a string of 14 workstations using DEC's new Alpha chip -- to study compressed natural gas, liquefied petroleum gas and ethanol. Russell's colleagues Peter Steenkiste, Ed Segall and Naresh Kumar are optimizing the model for distributed application.

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