Gasoline-fueled hybrid vs. conventional vehicle emissions and fuel economy

摘要

This paper addresses the relative fuel economy and emissions behavior, both211u001emeasured and modeled, of technically comparable, contemporary hybrid and 211u001econventional vehicles fueled by gasoline, in terms of different driving cycles. 211u001eCriteria pollutants (hydrocarbons, carbon monoxide, and nitrogen oxides) are 211u001ediscussed, and the potential emissions benefits of designing hybrids for grid 211u001econnection are briefly considered. In 1997, Toyota estimated that their grid-211u001eindependent hybrid vehicle would obtain twice the fuel economy of a comparable 211u001econventional vehicle on the Japan 10/15 mode driving cycle. This initial result, 211u001eas well as the fuel economy level (66 mpg), made its way into the U.S. press. 211u001eCriteria emissions amounting to one-tenth of Japanese standards were cited, and 211u001esome have interpreted these results to suggest that the grid-independent hybrid 211u001ecan reduce criteria emissions in the U.S. more sharply than can a conventional 211u001egasoline vehicle. This paper shows that the potential of contemporary grid-211u001eindependent hybrid vehicle technology for reducing emissions and fuel consumption 211u001eunder U.S. driving conditions is less than some have inferred. The importance 211u001e(and difficulty) of doing test and model assessments with comparable driving 211u001ecycles, comparable emissions control technology, and comparable performance 211u001ecapabilities is emphasized. Compared with comparable-technology conventional 211u001evehicles, grid-independent hybrids appear to have no clear criteria pollutant 211u001ebenefits (or disbenefits). (Such benefits are clearly possible with grid-211u001econnectable hybrids operating in zero emissions mode.) However, significant 211u001ereductions in greenhouse gas emissions (i.e., fuel consumption) are possible with 211u001ehybrid vehicles when they are used to best advantage.