The Eaton Corporation will be offering retrofit versions of its Hydraulic Launch Assist (HLA) hybrid power system for refuse trucks later in 2010.  This program will be offered through select, qualified partners and installers throughout North America.

The HLA system is a parallel hybrid system that works in tandem with the truck’s existing, conventional power train.  This hybrid system is especially well-suited to refuse trucks because of their continual start-stop operation.

Eaton’s HLA system works by adding hydraulic compression and capturing to a conventional truck to harness braking energy.  The kinetic energy of the slowing vehicle is transferred to hydraulic pressure, which is then released again during acceleration.  This takes pressure off the engine during its most strenuous loads, reducing its power requirements, resulting in lower emissions and fuel use.

Eaton plans to offer the hydraulic hybrid system on several platforms, targeting refuse trucks first and then moving to other commercial vehicles with similar start-stop duty cycles.

Here’s how the system works:

During braking, the HLA system absorbs the kinetic energy of the slowing vehicle with a hydraulic pump on the drive train, slowing the vehicle and compressing hydraulic fluid into a high-pressure accumulator.  The fluid compresses nitrogen gas, pressurizing the system.  This system captures about 70% of the vehicle’s braking energy.

When the vehicle accelerates again, fluid in the accumulator is released to match the rate of acceleration, driving through the pump in reverse, transferring energy back to the drive line.  This takes load from the engine, assisting it in accelerating the vehicle, lowering engine use and need.  This reduces fuel consumption by 20-30% in most active duty, start-stop applications.

What’s more, the system can be set for “economy mode” in which the engine does not accelerate the vehicle until all hydraulic pressure is spent first, thus accelerating the vehicle by stored hydraulic power alone, initially.  This results in significant fuel savings.

For many commercial truck applications, this type of system is not only much more economical to install (retrofit), but it is also a significant way to improve fuel economy and lower emissions.

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