HEV-96, battery electric and fuel cell propulsion form part of manufacturer’s low-carbon model range
Wrightbus has revealed details of its HEV-96 product, which when combined with the latest iteration of Micro Hybrid delivers up to a 38% cut in fuel consumption over a baseline figure.
“HEV-96 is a parallel hybrid system available in the StreetDeck and StreetLite. Two 75kW motor-generators are attached to opposite sides of the gearbox output shaft. They remove load from the engine when the bus starts from stationary,” says Business Development Director David Barnett.
“That builds on Micro Hybrid, which comes as standard with HEV-96. When slowing, the bus captures kinetic energy by both charging the hybrid package’s lithium-ion battery and also by engaging smart auxiliaries.”
Cost-effective hybrid solution
Engagement of the motor-generators allows the StreetDeck and StreetLite’s Daimler OM 934 engine to work in the most efficient areas of its fuel map at lower road speeds.
Vehicles with HEV-96 are Ultra Low Emission Bus certified. While Wrightbus says that the system delivers a “good” payback period, Mr Barnett expects concerns over air quality to drive its adoption; it may become a standard fitment, as Micro Hybrid has done.
“HEV-96 is not almost as good as a conventional hybrid; rather, it performs at least as well as any full-blown 600v product and it is considerably less expensive,” he adds.
Voith heavily involved
Voith has been heavily involved in developing of HEV-96. Two motors are necessary to avoid a residual imposed load on the output shaft. While zero-emission capability is possible in theory, it will not be offered as components within the gearbox would still be turning.
A control system monitors several parameters when both accelerating and braking to ensure that energy is captured and used most efficiently. In both scenarios, the driver will notice no difference to a conventional diesel.
HEV-96 will be compatible with the the six-cylinder OM 936 engine that is to be offered in the StreetDeck. Wrightbus can offer leasing packages for its battery pack, which is located above the nearside front wheel.
“A further benefit is that if there is a fault with HEV-96, the bus can still be driven and complete its day’s work. It returns to being Micro Hybrid only,” says Mr Barnett.
Fuel cell coming, too
Wrightbus displayed its StreetDeck Fuel Cell Electric Vehicle (FCEV) demonstrator at EBE.
The FCEV bus shares 85% of components with a HEV-96-equipped StreetDeck. It has a 200-mile zero-emission range that can be extended to 265 miles if the operator wishes.
“Battery electric has a place, but with the StreetDeck FCEV we have a double-decker that can take the most demanding city route and convert it to zero-emission operation today and replace diesel buses on a one-for-one basis,” adds Mr Barnett.
The fuel cell generates waste heat that is used to warm the passenger area. A degree of electric heat ‘boost’ is also required, but overall efficiency in the FCEV benefits. The single-deck StreetAir FCEV comes with a base range of 215 miles and, like the StreetDeck, that figure can be extended. A battery-electric StreetDeck will follow in 2019.
