|The DEUTZ hybrid unit.|
Engine manufacturer DEUTZ has developed a mild hybrid drive system for off-road construction equipment that has the potential to reduce fuel consumption by as much as 30%. The hybrid drive consists of a DEUTZ four-cylinder diesel engine, an electric motor, a lithium-ion battery pack and a control unit. The electric drive serves to assist the main diesel engine drive.
The electrical system provides a nominal 15 kW output, with a peak capacity of up to 30 kW, almost doubling the power of the DEUTZ engine. The electric motor/generator is situated where the engine’s flywheel and flywheel housing is normally located.
Constantly energized when the engine is running, the system produces electrical energy that is stored within a lithium ion battery pack. In response to high engine loads, the system reverses its operating mode and turns into an electric motor to assist the engine in driving the machine’s hydrostatic transmission.
The hybrid power unit has the following functions:
Start and stop: automatic engine stop during idling phases, automatic engine start in the case of continued operation, the usual starter is omitted.
Battery charging: if the diesel engine has excess power, the electric unit can charge the battery while operating as a generator.
Recuperation: part of the braking energy is refed into the battery by the electric unit.
|An AR65 wheel loader.|
A prototype unit has already been fitted to an Atlas Weyhausen wheel loader. While the standard AR65 loader is powered by a 68 hp (51 kW) DEUTZ TCD 2011 diesel engine, the hybrid version has been replaced by a smaller 50 hp (37 kW) D 2011 non-turbo-charged oil-cooled version.
Currently, all functions on the Weyhausen loader’s equipment side are still hydraulically driven. The next step will be to power the loader totally by a full hybrid drive system, delivering eventual emission-free operation.
DEUTZ developed the hybrid drive has been developed in conjunction with Heinzmann, a manufacturer of engine control systems and a long-term DEUTZ partner and supplier. Commercial production is unlikely before 2010.
A leading independent diesel and gas engine manufacturers, DEUTZ produces around 286,000 units annually, with a turnover in excess of €1.5 billion. It has an overall engine range extending from 9 kW to 500 kW for markets and applications including construction, quarrying, mining, materials handling, agricultural, groundcare, industrial and airport ground handling equipment.
(DEUTZ’s roots go back to N. A. Otto & Cie, started by Nicolaus August Otto and Eugen Langen, the world’s first engine factory.)
|Cat’s new D7E electric drive tractor. Click to enlarge.|
Caterpillar’s D7E Series-Hybrid Tractor. On a larger off-road scale, Caterpillar earlier this year announced the D7E—the first electric drive track-type tractor using modern technology. The D7E is in the 60,000-pound (27,000-kilogram) weight range and is powered by a Cat C9 engine producing 235 hp (175 kW) that drives a generator to produce electricity to power two AC electric drive motors connected to a differential steering system.
The C9 engine with ACERT Technology meets US Tier 3 emissions standards, and the tractor has been designed with Tier 4a in mind.
A traditional mechanical transmission is not needed, because the variable speed electric motors serve the function of a continuously variable transmission. The electric drive train has 60 percent fewer moving parts compared to previous D7s. The electric system also provides power to auxiliary components so that no engine belts are needed.
Compared to the Caterpillar D7R Series II, the D7E will deliver 25% more material moved per gallon of fuel, 10% greater productivity and 10% lower lifetime operating costs. Caterpillar plans to commercially introduce the D7E in select markets during 2009.
Cat will provide additional information about the D7E in 2009 when the electric drive tractor nears commercial availability.