the potential to recover a fraction of the vehicle's kinetic energy during braking. Not only were the concept cars demonstrated by the PNGV partners in 2000 a great technological achievement, they also helped clarify the remaining hurdles to achieving success for the PNGV program. It is apparent that the fuel cell will not be feasible in a production-prototype vehicle by 2004. This leaves the internal combustion engine as the primary energy converter, and even using the most efficient one, the CIDI diesel engine, the three-times fuel economy target remains a stretch goal. If maximization of fuel economy is the design target, the diesel engine is the first choice; however, meeting the mandated emission standards is a major challenge for the diesel engine. Therefore, a critical consideration to maximize fuel economy is reduction of nitrogen oxides (NOx) and particulates, the two emission standards that are most difficult for the diesel engine to meet.
Reducing the cost for manufacturing and moving the concept technology into current and future vehicles has now become a central factor, so there has been a notable shift in emphasis during 2000–2001 to cost reduction and manufacturability. Resources are being focused on continued development of enabling technologies, such as exhaust-gas after-treatment systems, fuel composition effects on system performance, advanced battery energy storage systems, and power electronics and component cost reduction. The investigations of promising longer-term prospects, such as advanced combustion systems and fuel cell technologies, are also continuing.
The PNGV presented to the committee an overview of the status and critical development issues of the candidate energy-conversion and energy-storage technologies that survived the 1997 technology selection process. Overviews of candidate electrical and electronic systems and advanced structural materials for the vehicle body were also presented.
This chapter addresses the following technology areas and related issues:
Four-stroke internal-combustion reciprocating engines;
Electrochemical storage systems (rechargeable batteries);
Power electronics and electrical systems;
Vehicle safety; and
The committee reviewed R&D programs for each of these technologies, along with related vehicle safety and fuels issues, to assess progress so far and the developments required for the future. In the committee's opinion the PNGV continues to make significant progress in developing the candidate systems and identifying critical technologies that must be addressed to make each system viable. The committee is pleased that, since the introduction of the concept vehicles in 2000, there has been a shift in program focus to include affordability.