Development of a modal emissions model for a hybrid electric vehicle

With the growing market share of hybrid electric vehicles (HEVs), new methods are needed for estimating their actual energy use and emissions in order to support emission inventories. This research quantifies criteria associated with startup and shutdown of the internal combustion engine (ICE) for a 2001 Toyota Prius HEV and develops a modal tailpipe emissions model under hot stabilized conditions. The engine is found to be off below thresholds of engine power demand that are speed and acceleration dependent. Vehicle specific power (VSP) is used as the basis for modeling emissions. The predicted cycle emissions of CO, NO(x) and HC for individual cycles are subject to large relative errors, but the overall emission predictions for the average of multiple cycles have relative errors within 10% for each selected pollutant. The ICE engine status identification method is recommended for application to model HEV emissions under actual driving conditions. (C) 2011 Elsevier Ltd. All rights reserved.