power trains with small, turbocharged, compression-ignition direct-injection engines using diesel fuel. All three were start-stop hybrids that shut the engine off when idling. The report from the NRC PNGV committee estimated that dualmode batteries would probably cost $1,000 to $1,500 per battery unit (1.5 kWh), or $670 to $1,000 per kWh (NRC, 2001). Each company took a different route to reduce the vehicle mass and aerodynamic drag and to supply power for auxiliary loads. The high cost of the lightweight materials and electronic control systems made the price target unattainable. In addition, the cost of the compression-ignition direct-injection engine was greatly increased by the exhaust-gas after-treatment systems to control emissions. In the middle of the PNGV program, the Tier 2 emission standard was promulgated, and the NRC PNGV committee believed that the ability of the diesel engine to meet emissions targets was not clear.
The NRC PNGV committee reported that the PNGV program had made significant progress in implementing desirable technologies as fast as possible. Each of the three automobile manufacturers in the PNGV demonstrated a hybrid electric vehicle before the end of the Partnership in 2004. They had developed the concept vehicles by 2000, but the goal of the development of a preproduction prototype by 2004 was not met because of the termination of the PNGV program. Indeed, the manufacturing and engineering innovations that came out of the PNGV program were implemented before 2000. In the end, the three OEMs demonstrated that a production medium-size passenger car could be produced that achieved 80 mpg, and one OEM (DaimlerChrysler) demonstrated that such a vehicle could be produced at a cost penalty of less than $8,000.
The task of the NRC Committee on Review of the FreedomCAR and Fuel Research Program (NRC Freedom-CAR committee) is to assess the FreedomCAR and Fuel Partnership’s management and the research and development activities overseen by the Partnership. The Partnership, started in 2002, built on the earlier PNGV program. FreedomCAR, like PNGV, is a collaboration between the government and industry to support a wide range of precompetitive research in automotive transportation. The Partnership’s goal is to study technologies that will help the United States transition to an automotive fleet free from petroleum use and harmful emissions (NRC, 2005). The vision of the Partnership is to enable a transition pathway that starts with improving the efficiency of today’s internal combustion (IC) engines, increasing the use of hybrid electric vehicles, and supporting research in fuel-cell-powered vehicles so that a decision can be reached in 2015 on the economic and technological viability of hydrogen-powered vehicles. In 2009, a greater emphasis began to be placed on plug-in hybrid electric vehicles (PHEVs). The NRC has thus far reviewed the FreedomCAR and Fuel Partnership twice, with reports published in 2005 and 2008. In the second of these reports, one of the NRC FreedomCAR committee’s tasks was to comment on the balance and adequacy of the efforts and on the progress achieved since the 2005 report. The conclusions and recommendations of the second report focus on the Partnership’s management and oversight but also provide the FreedomCAR committee’s opinion on the readiness of new fuel economy technologies.
The NRC FreedomCAR committee report recognizes that more efficient IC engines will contribute the most to reducing fuel consumption and emissions in the near term. The Partnership focuses research on lean-burn, direct-injection engines for both diesel- and gasoline-fueled vehicles, specifically on low-temperature combustion engines and aftertreatment of the exhaust. The report recognizes that, after completing the research necessary to prove a technology’s viability, there are typically several years of prototyping and developing manufacturing processes before the technology can be introduced into the vehicle fleet. Because of the urgent need to reduce vehicle fuel consumption, the development phase of these technologies has been accelerated while researchers are still studying the controlling thermochemistry of low-temperature combustion. The result is close coordination between those looking to expand the fundamental knowledge base and those investigating applications. The report from the NRC FreedomCAR committee recommends that the Partnership investigate the impact on emissions of combustion mode switching and transient operation with low-temperature combustion, and it questions how much exhaust energy can actually be recovered. Furthermore, the NRC FreedomCAR committee suggests the Partnership closely analyze the cost-effectiveness of the exhaust gas heat recovery research and the potential fuel efficiency benefits before deciding whether to pursue this research further.
Another goal of the FreedomCAR and Fuel Partnership is to develop, by 2015, battery storage for hybrid electric vehicles that has a 15-year life and a pulse power of 25 kilowatts (kW), with 1 kW of pulse power costing $20. This effort focuses on lithium (Li) ion batteries, which are simultaneously in both the research phase, as the knowledge base for specific electrochemical systems is expanded, and the development phase, as the batteries are built and tested. Significant progress had been made since the first FreedomCAR report (NRC, 2005, 2008b). The Partnership has demonstrated batteries that exceed the requirement for a 300,000-cycle lifetime, that have longer calendar lives, and that operate over a wider temperature range than earlier batteries. The NRC FreedomCAR committee recognized that cost is the primary barrier for introduction of the Li-ion battery to the market and commends the Partnership for researching lower cost materials for the cathode and the microporous separator. The report from the NRC