not yet been defined or validated. In summary, concept cars represent a major milestone toward meeting PNGV Goal 3, and each contributes significantly to our understanding of the challenges this goal represents. The committee congratulates the USCAR partners for their outstanding efforts and the demonstrated results.


The GM concept vehicle, the Precept, is designed to meet all of the Goal 3 functional targets (with the exception of luggage space) and is expected to achieve 80 mpg using a dual-axle regenerative parallel hybrid power train (GM, 2000). In addition to this design, GM has built a fuel-cell version of the Precept packaged in the same basic chassis and body. The fuel-cell vehicle uses a hydride hydrogen storage system and is expected to achieve a gasoline equivalent fuel economy of more than 100 mpg and have a range of 500 miles without refueling. A fully functional version of this car is expected by the end of 2000.

The Precept hybrid is a very complex vehicle and represents state-of-the-art performance in all of its design parameters and components. The body structure is an aluminum-alloy space frame with both aluminum and plastic exterior panels. Every component has been designed to fulfill its function with minimum weight. The aerodynamic drag coefficient has been reduced to 0.163, the lowest known value for a five-passenger automobile and lower than that of any production vehicle. The propulsion system consists of a 1.3-liter, three-cylinder, CIDI, turbocharged, 44-kW aluminum engine coupled with a 10-kW peak power electric motor and alternator mounted in the rear of the car, plus a 25-kW peak power electric motor and alternator in the front. The rear unit employs a four-speed, automatically shifted, manual transaxle. This configuration permits regenerative braking on all four wheels, the energy is stored in either a lithium-polymer or a NiMH battery pack, with a 3-kWh usable energy capacity. Curb weight of the vehicle is 2,590 lbs (1,176 kg); the wheel base is 112 in (2,839 mm); the overall length is 193 in (4,906 mm); and overall width is 68 in (1,726 mm).

The sophistication evident in the overall design and electronic controls for energy management, thermal management, chassis systems, and climate control for the Precept hybrid show how challenging meeting the PNGV Goal 3 is. This vehicle demonstrates what can be achieved with today’s technology but raises significant questions about the affordability of meeting the 80-mpg fuel economy target. Since the inception of the PNGV program, significant progress has been made in reducing the cost of many components, especially the power electronics, but a very significant cost challenge still remains.

The Precept fuel-cell vehicle is designed with 105-kW peak, 75-kW continuous power, hydrogen-air PEM fuel cell operating at 1.5 bar, together with two hydride storage tanks expected to hold a total of 4.9 kg of hydrogen, all within the vehicle structure described above. In addition to the fuel-cell stack, the system

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