and now has more than 100 registered users. The ADVISOR model runs quickly, requires modest computer resources, and is useful for concept development and evaluation. The PSAT computer code incorporates more sophisticated dynamic models of component behavior and readily allows analysis of transient vehicle performance and control system development. PSAT has been upgraded and improved during the past year in accordance with the PNGV systems-analysis team’s work plan, and that process is continuing. An advanced training class for PSAT held in January 1999 was attended by more than 50 people. PSAT has been used to examine the benefits of improved control algorithms (Oakland University) and optimization techniques (University of Michigan) on HEV performance.

The new structure for the coupled development of these two models through joint management and funding by DOE, with industry in a consulting/advisory role, makes excellent sense. Based on different logics, these models are suited to different objectives, and the similarities in many of the subsystem component models will allow developments that improve these subsystem models to be used in both PSAT and ADVISOR.

ASSESSMENT OF THE PROGRAM

The HEV propulsion system, which combines an engine, such as the four-stroke CIDI engine, with energy-storage devices, such as batteries, in a lightweight vehicle, is essential to meeting the 80 mpg fuel economy goal within the time frame of the PNGV program. There are many ways to configure an HEV power train system, and developing and then optimizing such systems with their many interactive components is a challenging task.

The recent announcement by EPA of its proposed Tier 2 emissions standards starting in 2004 has made the modeling of the emissions of HEVs an urgent task for the PNGV systems-analysis team so that extensive emissions/fuel economy/ performance/cost trade-off studies can be carried out. Part of this task is to ensure that the emissions models in PSAT and ADVISOR are sufficiently complete and accurate for this purpose. A key issue here is modeling the performance of CIDI engine exhaust catalysts for NOx and traps for PM and validating these models against experimental data. Because the HEV uses a smaller engine and can control transients through the battery/electric motor propulsion system component, the models should explore whether the HEV configuration provides significant additional opportunities for emissions reduction beyond the lowest emissions levels provided by a stand-alone CIDI engine power train.

A second important task for the PNGV systems analysis team will be to develop a more complete model for fuel-cell power train systems. The fuel-cell-based propulsion system, with its inherently low-emissions characteristics and potential for high efficiency, is a promising longer term technology being pursued by the PNGV program and automobile companies. An unresolved question for



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