Mercedes-Benz claims fuel cost reductions of up to 60% for its concept Econic natural-gas hybrid garbage truck and reduced diesel consumption of up to 30% for the Econic diesel hybrid garbage truck. The vehicles made their first appearance at the recent IAA Commercial Vehicle Show in Hannover, Germany.
Both vehicles use the same parallel hybrid drive system, a 44-kW ac electric motor producing 420 N·m (310 lb·ft) of torque, located between the clutch and transmission. In the case of the Econic BlueTec diesel hybrid, the system architecture is similar to that used in the Freightliner M2 Hybrid.
The Econic NGT natural-gas hybrid is based on the Econic NGT 2628 three-axle garbage truck chassis, featuring a trailing axle, which has been in series production since 2002. The internal-combustion engine is the turbocharged Mercedes-Benz M 906 LAG inline six-cylinder natural-gas engine with a displacement of 6.88 L. The engine features multipoint gas injection and individual coil ignition for each cylinder. It is Euro 5 compliant and also meets the more stringent EEV (Enhanced Environmentally-friendly Vehicle) emissions requirements. Power output is 205 kW (275 hp) at 2200 rpm, while maximum torque of 1000 N·m (738 lb·ft) is produced at 1400 rpm. Power is transmitted through an Allison WT MD 3060 automatic transmission fitted with a retarder.
The hybrid drive system uses regenerative braking to charge a lithium-ion battery pack with a capacity of 1.9 kW·h. The vehicle can be driven for short distances using electric power only, offering zero-emissions operation in environmentally sensitive areas. Other features include automatic stop/start for the diesel engine and electric drive for vehicle ancillary components.
The vehicle is equipped with a liquefied natural gas (LNG) storage system, which cools the natural gas to -161.5ºC (-258.7ºF) to liquefy the gas. This provides a high-density storage system—600 m3 of natural gas takes up 1.0 m3 of space when stored as LNG. Mercedes-Benz claims that this can reduce the weight of the onboard gas storage system from around 1000 kg (2205 lb) to 500 kg (1102 lb).
For the Econic BlueTec diesel hybrid, the prototype is based on the Econic 2629 NLA chassis. Like the Econic NGT, this is a three-axle chassis with a gross vehicle weight of 26 t (29 ton). The chassis features a steered trailing axle.
Diesel power is provided by a Mercedes OM 906 LA 6.375-L inline six-cylinder turbocharged diesel producing 187 kW (251 hp) at 2200 rpm and maximum torque of 900 N·m (664 lb·ft) between 1400 and 1600 rpm. The engine is downsized compared with regular Econic diesel-powered chassis.
The Econic BlueTec diesel hybrid is equipped with an automated transmission. Mercedes-Benz claims that this hybrid model is now nearing series production. A yearlong series of customer trials is due to begin in early 2009.
Volvo Trucks is set to deliver four hybrid garbage trucks to garbage-handling company Veolia Propreté. The vehicles are to begin trials in London and Paris in fall 2009.
All four vehicles are based on Volvo heavy-duty FE models. These are equipped with Volvo’s 7.0-L, six-cylinder diesel engine. The hybrid package includes a starter motor, 120-kW propulsion motor, alternator, and electronic control unit. Regenerative braking or charging from the diesel engine feeds a lithium-ion battery pack. The trucks are also fitted with Volvo’s I-Shift automated transmission.
Like other parallel hybrids, the diesel engine can be used in combination with the electric drive system, or the two can be operated separately. Volvo claims a 15 to 20% reduction in fuel consumption from hybrid operation. The vehicles also feature plug-in recharging to operate ancillary equipment, which is claimed to reduce fuel consumption by a further 10 to 15%. Reduced noise and exhaust emissions for early morning operations in urban areas offer a useful benefit.
The four pre-production vehicles will be delivered by Volvo complete with bodywork. Maintenance, service, and continuous software upgrades are part of the 24-month lease contract to operate the vehicles.
Volvo says that the hybrid technology is now almost ready to reach the market, and series production is scheduled to begin at the end of 2009. The company claims that there is considerable interest in the market for the technology.