Optimized Series Hybrid-Electric System Delivers Best Fuel Consumption Results Yet for Double Deck Vehicle
|The Gemini 2 HEV. Click to enlarge.|
In a recent independent test cycle at the Millbrook Proving Ground in the UK, a Wrightbus Gemini 2 HEV achieved the best results for fuel consumption and CO2 emissions ever recorded from a double deck vehicle: 10 mpg UK (8.3 mpg US, 28 L/100km).
The test was part of the Wrightbus Product Development team’s collaboration with Queens University Belfast and key component suppliers including Siemens, Valence Technology and Ford. The series hybrid-electric drive system also uses an optimized engine management program developed by Revolve Technologies. Revolve Technologies was formerly the UK-based Roush Technologies Limited. An investor group acquired Roush Technologies from its US parent late in 2007, and changed the name to Revolve in December 2008.
The Wrightbus series hybrid system uses a standard 2.4 liter diesel engine—as used in the Ford Transit—as the generator. Revolve engineers have been able to predict load and speed changes in advance, thus allowing greater freedom with injection strategies and EGR (Exhaust Gas Recirculation) rates.
Drawing on its special knowledge of the engine EMS system, Revolve engineers have also been able to utilise some of the existing vehicle based strategies to carry out functions which otherwise would have required significant software changes. This, coupled with a unique CAN interface module, has allowed the full integration of the engine and its controller into the overall hybrid control system, and at a relatively low cost.
Having the engine control as a fully integrated part of the hybrid system is a major advantage – and, coupled with a unique calibration, we have been able to achieve exceptional improvements in fuel consumption. The Wrightbus programme involves optimizing Series Hybrid Drive systems through a detailed analysis of generator load patterns. As a result of this analysis, we have been able to recalibrate the engine to operate at its peak performance throughout the drive cycle, by using smart charging and load control technology. Overall engine performance is significantly improved when compared with normal applications.—Paul Turner, Revolve’s Technical Director of Product Development
In terms of hybrid vehicles in operation, Wrightbus currently has:
- The original Gemini HEV hybrid double deck in operation with Arriva London
- Five Electrocity single deck buses with Travel London
- Seven Electrocity single deck vehicles in operation with Go Ahead Group’s London Central operation
- One Gemini HEV hybrid double deck with London Central
- One Gemini HEV under evaluation with Dublin Bus
- Five Gemini 2 HEV entering service with Arriva London.