Arriva, one of the largest bus operators in the UK, conducted the trial on the midi bus on a standard bus route in Gillingham, Kent, from March last year (2015).
According to Ian Tarran, engineering director at Arriva UK Bus, the Flybrid KERS demonstrated its performance under real-world operating conditions, successfully capturing, storing and releasing energy from the brakes.
Adam Robson, Torotrak Group CEO, adds that findings from the trial have already proven invaluable in selecting the operating strategy for the volume production system – which will be a second generation design. And he adds that Tier 1 and Tier 2 manufacturing partners are now working on production tooling.
“This is a very exciting time for the group, with the bus KERS project that started in 2012 going into commercial production from the middle of this year,” states Robson.
“I am delighted with the progress we have made and we look forward to delivering our first systems to Wrightbus during Q3 2016.”
“After 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,” comments Brian Maybin, Wrightbus engineering director.
“Production vehicles will be able to be delivered into service late in 2016,” he adds.
And Arriva’s Tarran says: “Having collaborated with Torotrak and Wrightbus on the flywheel project since 2012, we are looking forward to installing Flybrid KERS across our bus fleet from Q3 2016 onwards.
“As one of the largest bus operators in the UK with over 5,900 buses, improving the efficiency of our bus fleet and reducing emissions is important to us and our customers.”
Flybrid KERS is an efficient and robust hybrid technology, well suited to the long service life and repeated stop-start duty cycles of public service buses.
Torotrak argues that using common materials and manufacturing methods, as well as eliminating any need for replacement batteries during service life, its flywheel-based technology offers exceptional value and an opportunity for widespread hybridisation.
The system itself captures kinetic energy normally wasted when the bus is braking, storing it in a steel and carbon fibre flywheel weighing 8.5kg and spinning at up to 30,000 rpm. This energy is then delivered back to the wheels, reducing engine power required to accelerate the bus and hence also fuel consumption.
Robson says that detailed testing is currently underway on rigs and in a new Euro 6 StreetLite bus – with expectations including further improvements in bus fuel efficiency and reduced KERS weight and cost.
He states that the new design has reduced parts count and system weight by 30% and 80kg respectively, and that incorporates a simpler 2x2x2 clutched flywheel transmission system has also reduced ‘coast down’ losses while improving efficiency during torque transfer.