Renault range08 June 2012

A diesel-electric hybrid 26-tonne three-axle Renault rigid has joined the UK fleet of Norbert Dentressangle. Dave Young reports from the handover of this innovative trial vehicle

Renault Trucks' new 26-tonne gvw Premium Distribution hybrid has begun a four-year operational trial with Norbert Dentressangle. Using what Renault Trucks' executives describe as Volvo group drivetrain technology, the new truck exhibits many similarities – but is not identical to – an FM Volvo hybrid previously featured in Transport Engineer, and follows a prototype released in 2010.

The truck manufacturer says the hybrid can save up 20% on fuel and reduce C02 emissions by a similar amount, via its parallel Hybrys Tech system. Like most of the others to date, this allows the truck to start using the electric motor, an continue up to 20km/h before the diesel engine takes over. The system also cuts out idling by turning it off when the vehicle is at a standstill.

With an 8.4m Cartwright box body and full-height Dhollandia tail-lift, the payload of 11.63 tonnes is said, by Renault engineers, to be around 800kg less than a conventional rigid. The additional unladen weight comprises around 200kg for the batteries and 150kg for the electric motor, with the rest taken by ac/dc converters, additional electric motors and cooling systems.

This hybrid has been optimised for start-stop urban use and has a six-cylinder DXi7, Euro5, SCR (selective catalytic reduction), common-rail diesel engine, rated at 310bhp and 1,153Nm of torque. As for motive electric power, that comes from a 70kWh permanent magnet synchronous motor, mounted behind the diesel and producing 120kW of power, 800Nm (peak) of torque and 400Nm of retardation. The 600V lithium-ion battery pack, comprising 384 cells and rated at 1.2kW, has been mounted on the offside of the chassis, with diesel and AdBlue tanks on the nearside.

Adapted equipment
In a little detail, software for the truck's Optidrive 12-speed automated gearshift has been re-optimised for hybrid use. Further, primary retardation is now through the hybrid MDU, with integrated Optibrake engine braking. Essentially, the electric motor has been integrated with the EBS (electronic braking system) and is used preferentially to maximise kinetic energy recovered into the electrical storage system (ESS).

Making that work, the driver is encouraged to slow the vehicle via the electric motor, acting as a retarder/generator. In fact, foot brake application functions sequentially – first through the electric motor, next Optibrake and only then the air disc brakes. A dashboard display advises the driver in real time of energy saved or wasted during retardation.

On the conventional brakes, the main modification appears to be an enlarged brake compressor tank, reflecting the fact that refill times may be limited, with the diesel engine not running. However, if low air pressure is sensed the engine automatically restarts to run the compressor.

Looking at the steering, front and rear axles are actuated hydraulically, and independently of the diesel engine, by ac motor-driven pumps with mechanical back up. One pump supplies the front steering axle and a second the rear steer. The front axle circuit also employs a mechanical pump located on the rear of the gearbox. The cab heater pump is also electrically powered.

Although neither Renault nor Norbert Dentressangle revealed the terms of this deal, it's believed that the hybrid truck is leased (in common with alternative fuel vehicles from most European truck makers), because of the high capital cost and untried residual market. Renault is certainly taking responsibility for the batteries. Unlike some other parts of Europe, there is no UK government financial support – direct or indirect – for this environmental initiative.

At the hybrid's handover last month, Renault executives stressed that this is an operational trial, and not yet a commercial launch – with both parties pledged to share data (although they were coy about benchmarks and what would constitute success).

Dave Young

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