12 October 2004
General Motors (GM) announced it will build its first hybrid bus in China next year, in cooperation with Shanghai Automotive (SAIC), to promote the technology for cleaner, more fuel-efficient vehicles. The diesel-electric hybrid system by GM will be packaged in a bus manufactured by Sunwin, SAIC’s bus joint venture in Shanghai. The prototype bus will be tested in Shanghai to evaluate the commercial viability of hybrid buses in China.
The joint hybrid bus program will utilize the EPSystem hybrid powertrain developed by GM’s Allison Transmission Division. The EPSystem is a parallel hybrid system, using two sources of power to move the vehicle—(1) diesel engine and (2) dual electric motors powered by a battery-pack. The batteries are charged by a generator driven by the engine. The engine is also coupled to a drive unit which passes mechanical energy directly to the wheels (a feature distinguishing the parallel and series hybrids—in the latter configuration, the engine/generator unit has no mechanical connection to the drivetrain). The EPSystem hybrid also features regenerative braking, to capture braking energy from the wheels in the batteries. The buses are typically fitted with diesel particulate filters, which provide about 90% reduction in PM emissions. Reductions of all regulated emissions are also achieved by the use of a smaller engine and the hybrid duty cycle. According to GM, the buses can bring a 40-60% fuel economy improvement.
GM has sold over 300 hybrid buses in North America, with the biggest order from Seattle, WA. In spite of their potential advantages, however, hybrid buses remain still rather uncommon. One of the problems is high cost of hybrids; with a price premium which can be as much as $200,000 over the cost of an equivalent conventional diesel bus, most hybrid purchases in the USA were helped with government grants. It remains to be seen if the bus prices can be lowered to levels that can be accepted in China.
The announcement was made by GM’s vice-president of environment and energy, Elizabeth Lowery, at the Challenge Bibendum event opened this week in Shanghai.