(Source: Green Car Congress)

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Researchers from the US Department of Energy’s (DOE) National Renewable Energy Laboratory (NREL), Idaho National Laboratory (INL) and Argonne National Laboratory (ANL) are cooperating to develop and test a method for predicting the real-world fuel and electricity consumption of plug-in hybrid electric vehicles (PHEVs) by adjusting dynamometer test results. After examining data on the only PHEV currently available in large numbers, the new adjustment method shows promise for reasonably predicting PHEV average fuel and electricity use, despite differences in design.

Current rules for conventional vehicles do not work for plug-in hybrids because the vehicles run on both electricity and gasoline; industry debate centers on the rules for estimating miles per gallon. This was highlighted by the reaction to GM’s announcement that the Chevy Volt would attain 230 mpg in the city cycle, given a single charge per day, along with combined cycle electricity consumption of 25 kWh/100 miles, based on a draft EPA methodology. (Earlier post.)

PHEV testing is further complicated by the fact that these vehicles operate in two different modes based on the distance they are driven (initially depleting energy from the large vehicle battery, and eventually sustaining the battery charge for longer distance driving). Consensus is building on techniques to handle these first two complications, but one question that remains is how to adjust raw certification cycle test results to best predict a PHEV’s average real-world energy use.

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