Next Stop: Fuso Aero Star Eco Hybrid
TOKYO 33°N/103°W ——— “Omori, Omooori,” sings the computer-generated female voice as it calls out the subway station of that name, after which a special chime sounds to indicate the stop. Anyone who uses public transportation in Tokyo immediately notices the love the Japanese have for electronic gadgetry – not to mention their talent for organization. Rail and bus systems in this huge metropolis are surprisingly efficient, and even the taxi drivers seem relaxed, despite the fact that cars, buses, and trucks transport huge numbers of people and goods each day through the streets of Tokyo, whose greater metropolitan area is home to nearly 35 million people. As a result, every reduction in fuel consumption here benefits the global climate. | ||||||||
“Our new hybrid bus can reduce fuel consumption by as much as 30 percent,” says the engineer Yuta Susuki. “The amount of savings depends on how the vehicle is employed by the respective bus operator.” We’re standing at a test rig in front of a shiny brand-new Aero Star Eco Hybrid bus. It’s the latest bus model from Mitsubishi Fuso Truck and Bus Corporation, the Japanese pioneer in hybrid technology and member of the Daimler Trucks division of Daimler AG.
The bus and rig are at the Mitsubishi Fuso Proving Ground north of Tokyo. While a test driver starts the bus up on the rolling test rig, Susuki explains the vehicle’s technology to us. The Mitsubishi Fuso Aero Star Eco Hybrid operates with a series hybrid drive, in which the diesel engine doesn’t drive wheels directly but instead is used solely to drive an electrical generator. The generator charges a large battery and powers two high-performance electric motors with a combined output of 158 kW (215 hp), which propel the vehicle. “The bus drives like a tram,” Susuki says. Susuki knows a little German as a result of his business trips to Stuttgart, and he likes to tell us funny stories about his visits to Germany.
“Instead of a big diesel engine with more than eight liters of displacement, we were able to install a much smaller 4.9-liter engine in the hybrid bus,” Susuki says. The diesel unit can be smaller because it doesn’t bear the strain of propelling the vehicle from a standstill, a job the electric motors can do much better because, unlike internal combustion engines, they transfer their entire output to the wheels from the get-go. With its reduced workload, the small engine can be continuously run at an optimal speed, which further decreases fuel consumption. Because it’s so light, it also makes up for most of the excess weight of the hybrid drive components.
The bus is now running in its impressively quiet electric mode on the test rig, which rolls as the wheels turn. Power is supplied by a large lithium-ion battery, whose tiny cousins can be found in digital cameras and cell phones, and whose exceptional performance capability is what enables the combustion engine/electric drive combination to compete with conventional systems. The battery is housed under a prominent air scoop on the roof of the Aero Star Eco Hybrid, which immediately identifies this vehicle as a hybrid bus to those in the know.
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