10 new London buses to use clean hybrid system

Ten new Optare Tempo transport buses in London will use a clean hybrid propulsion system. The buses will be run by Transport for London (TfL) and will be equipped with Allison Transmission’s GM-Allison Hybrid EP-System for cleaner and quieter running.

The GM-Allison Hybrid EP-System is a patented “two mode” parallel hybrid technology that combines direct power from an electronically-controlled diesel engine with electric power from an energy storage system for fuel saving, lower emissions, and better performance.

The complete GM-Allison Ep40/50 systems consists of the Ev DriveTM module, which serves as the vehicle transmission; the Dual Power Inverter Module (DPIM); the Energy Storage System (ESS), which is based on advanced Nickel Metal Hydride (NiMH) batteries; two electronic control modules; and the electronic driver interface with integrated display.

From a stationary position, the electrical starter motor draws power from the battery, mounted on the roof of the bus, to set the vehicle smoothly and almost silently into motion. Then, as the vehicle picks up speed, the 250-hp diesel engine comes into action, offering a direct power supply to the drivetrain, as required, and eventually feeding the battery with additional power. An automatic controller ensures that the battery is maintained at optimum charge. At cruising speed, the battery cuts out altogether and operates like a conventional drivetrain.

It also has a regenerative braking system to recapture energy that is normally lost during breaking and transfers it back as usable energy to the electric motor. It is estimated that 40% of the energy used to accelerate a bus with the GM Allison two-mode hybrid system comes from the energy saved during regenerative braking.

Allison estimates that since its system was introduced in 2003, it has contributed to the saving of over 25 million liters of fuel and the elimination of more than 65,000 metric tons of carbon dioxide (CO2). It has been sold into more than 2,200 buses and coaches worldwide and has covered over 200 million kilometers in revenue service.

TfL is testing the buses as part of a study into different hybrid systems. Five of the GM-Allison-equipped buses are with the East London Bus Group to ply the 276 route between Newham General Hospital and Soke Newington. Metroline will operate the other five on the E8 route between Ealing Broadway and Brentford.

The roll-out of these 10 new GM-Allison-equipped buses will contribute to the Mayor’s target of a 60% reduction in emissions across London by 2025. Londoners will notice that hybrid buses are also significantly quieter than diesel buses, making bus travel more pleasant for passengers and reducing noise for local residents along bus routes. TfL currently operates more than 2,500 buses equipped with the smooth fully-automatic transmissions across London.


-  Katrice R. Jalbuena

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Sources:

¹ http://www.allisontransmission.com/international/europe/news/viewitem.jsp?itemno=635
² http://www.allisontransmission.com/international/europe/