Torotrak Group and Wrightbus have completed the in-service trial of a Wrightbus StreetLite fitted with Torotrak’s Flybrid mechanical kinetic energy recovery system (KERS). The trial was conducted with Arriva on a standard route in Gillingham, Kent from March 2015. According to its manufacturer, the test successfully demonstrated the performance of the Flybrid KERS under real world operating conditions, including the capture, storage and release of energy from the brakes and the drivability of the system. Torotrak says it is on track to commence production of its bus KERS from mid-2016 onwards.
Already undergoing detailed testing on rigs and in a new Euro6 StreetLite, the new KERS design is intended to further improve bus fuel efficiency and reduce the system’s weight and cost. The new design has reduced parts count and system weight by 30% and 80kg respectively. It also incorporates a simpler 2x2x2 clutched flywheel transmission system, designed to reduce ‘coast down’ losses and improve efficiency during torque transfer. Torotrak describes it as a highly efficient and robust hybrid technology, ideal for the long service life and repeated stop-start duty cycles. The KERS captures the kinetic energy that is normally wasted when the bus is braking and stores it in a steel and carbon fibre flywheel weighing 8.5kg and spinning at up to 30,000rpm. The energy stored in the flywheel is then delivered back to the wheels reducing the energy that is required from the engine to accelerate, reducing the fuel consumption of the vehicle.
Wrightbus Engineering Director, Brian Maybin, said, ‘After the invaluable in-service trials with Arriva, Wrights and Torotrak have confirmed that the next generation of flywheel is now under extensive durability testing, and after successful fuel trials, will be put into service trials from May 2016. Production vehicles will be able to be delivered into service late in 2016.’