The system, also developed in partnership with Arriva, Productiv and Voith Turbo, is anticipated to deliver significant fuel savings and could, says the bus manufacturer, give operators a fuel efficiency payback within five years – compared to the approximately 12 years achievable with conventional diesel-electric hybrids.
An Arriva bus has previously been retrofitted with KERS and tested at Millbrook in its test chamber, but this is the first time the device has gone into full in-service trials.
The flywheel KERS unit, which uses Torotrak's Flybrid technology, captures kinetic energy when the bus is slowing down, and transfers this mechanically back to the drive wheels to accelerate the vehicle, so reducing the engine power required.
The unit is fitted parallel to the transmission on the driveline and linked directly to the rear axle by an additional prop shaft. It also has electronic communications links into the vehicle's transmission to manage shifting and engine torque-down.
"We are excited to see the product in service with Arriva," says Wrightbus engineering director Brian Maybin. The project began two years ago and results have been "very encouraging", he adds. Test track assessments have confirmed predictions of a five-year payback, asserts Maybin.
In a separate announcement, Arriva has confirmed an order for 50 Wrightbus StreetLite and StreetLite Max vehicles, with delivery due in late spring this year.
Following an open tender, Arriva confirmed the order for 34 StreetLite Max 11.5m and 16 StreetLite vehicles (four of which will be 8.8m and the rest 10.8m). All will feature the Cummins Euro 5 engine as well as Wrightbus' Micro Hybrid technology.