Featuring a passenger-car diesel engine from Audi as a range extender and modular energy storage located beneath the driver’s cab, the MAN Metropolis plug-in hybrid truck concept—developed in cooperation with Benteler Engineering Services and revealed at the recent IAA Hanover Show—will begin a two-year field test as a refuse collection vehicle in the Brussels-Antwerp urban region in January 2013.
There were four main targets for this development project, according to Klaus Feldmann, Project Manager of Hybrid & Electric Vehicle Technology at Benteler Engineering Services B.V., which served as system integrator and worked with MAN for about two years and three months on the project. “One was to get the maximum noise reduction as possible,” he told SAE Magazines at the IAA Show. “If we are driving in pure electrical mode, we get a target of 65 dBa. This compares to 106 dBa for a conventionally powered refuse vehicle. With this noise level, it’s allowed to work through the night in living areas where people sleep.”
The project also aims to reduce CO2 emissions by 60% compared with a conventional diesel vehicle, and to “dramatically” reduce fuel consumption. “The typical garbage truck consumes between 80 and 100 L per day; this truck will consume around 20 L,” Feldmann said.
Another major target was to maintain payload. “Everybody is looking for the payload,” he said. “This is a payload-neutral concept, so [this truck] is not heavier than the conventional one.” The added weight of the hybrid system was offset by removing the standard D20 engine, gearbox, cooling, exhaust, and AdBlue system. The end result is a serial hybrid concept truck that weighs the same as the base truck, according to Feldmann.
MAN and Benteler claim to have created a new type of drive architecture for the Metropolis, which is based on the MAN TGS 6x2-4. The truck’s HVH410 electric traction motor supplied by Remy International delivers 203 kW and drives the truck’s rear wheels via a specially developed two-speed automatic gearbox. The auxiliary units such as power steering, air compressor, and hydraulic pump, as well as the air-conditioning system are also operated electrically and are demand-controlled via the energy-management system.
The drive to lift the refuse containers and compress the waste is electrohydraulic. The truck was fitted with a special hybrid body by Faun. The compression rear loader with lifter was specially designed for fully electrical operation and has a total capacity of 22 m3 (780 ft3).
Energy is supplied by a modular lithium-ion battery with a maximum capacity of 105 kW·h. Located where the diesel engine normally would be, the battery—which weighs exactly one ton, according to Feldmann, “near what the conventional engine weighs”—is thus over the front axle so that as before, the rear axles can bear the weight of the body and of the goods being transported.
The inverter is supplied by Phoenix International, a John Deere company.
“This is a modular system, so the customer can decide what they want to have, which battery capacity,” Feldmann said. “It’s available in 35-kW [increments]… But for the concept truck, we put the maximum in to demonstrate what’s possible.”
Electric operation is designed for a full day shift, comprising two cycles each with four hours’ collection work and a distance of 15 km (9 mi) in stop-and-go operation.
The development team decided to include an onboard range extender because a battery that had to store the entire amount of energy required to operate a heavy-duty truck would take up too much of that vehicle’s payload. The 3-L V6 TDI engine from Audi supplies the battery with electrical energy via a Remy HVH 410 generator whenever it is needed. The diesel engine delivers 150 kW (204 hp), and an engine management program ensures that the engine always operates within its most efficient range.
“Where the normal gearbox was there’s now the Audi V6, which is only producing the energy for the drive mode when we’re driving for example on a highway at 90 km/h,” Feldmann said.
“Packaging layout was definitely a challenge because everybody thinks with an electrified truck it’s a motor, it’s a battery, and it’s some cables,” Feldmann explained. “But it’s more than this because you must integrate a lot of cooling, and then you want to have an onboard charger… You must have a cooling system for the range extender, for the e-motor, for the power electronics—they all must be cooled because we are in a power level which is definitely impossible with air cooling. So everything is water-cooled.
“And then we had a lot of challenges with the auxiliaries—the electrified power steering, electrified air compressor, the brake system, and all of those things—because these are not existing on the market at this moment. You must search for a supplier or develop something by yourself to find the right way to get it electrified.”
The development office of Benteler’s Engineering Services group is based in Helmond, Netherlands. “We have the ability to make proto parts there. We have a proto tool shop, and we work together with the authorities there [on] homologation,” Feldmann said. Benteler Engineering Services has 700 employees in Europe, South America, and China, he noted, including multiple locations in Germany, England, and Sweden.
The Metropolis will be operated in Belgium as a fully operational “frontline” vehicle and monitored by SITA for up to two years. SITA, a subsidiary of Suez Environnement, is a provider of waste management and recovery solutions. MAN and Benteler will receive regular feedback reports on the truck’s performance, according to Feldmann, and likely will discover certain areas that need to be tweaked.
“Definitely we see a huge market,” he replied, when asked of his outlook for serial hybrids in Europe. “First of all, we show the world that it’s possible to electrify a 28-ton truck, with [an all-electric] drive range of more than 30 km. If a customer says, ‘We don’t want to have a garbage truck; we want to have a normal distribution truck,’ then it can drive with this solution approximately 60 km on pure electric. So this shows what is possible in metropolitan areas where you have emission-free zones.”