A serious contender against electric hybrid systems is the hydraulic hybrid, which stores braking energy in a hydraulic fluid instead of batteries.  The energy is then returned to the wheels when the vehicle accelerates, reducing gas consumption and improving performance.  Eaton Corp. has developed a hydraulic hybrid retrofit kit specifically designed for garbage trucks, which can increase fuel efficiency by 30%, while reducing brake wear and improving productivity.

Per the article linked below, the Hydraulic Launch Assist (HLA) hybrid system will be available for installation in Mack LE, MR and Granit chassis later this year, with kits for other makes and models to follow, according to Robert Golin, Business Development Manager for Eaton’s Hybrid Power Systems.

The retrofit is a parallel hybrid system that sits between the transmission and rear axle. It uses the momentum of the truck to compress hydraulic fluid when slowing the vehicle and then releases the stored energy in the fluid to help the truck accelerate on takeoff. It is especially well suited for applications with frequent stops and starts such as refuse collection trucks.

“A Class 8 automated side loader is a great application for HLA because it can make 1,400 stops in a day,” said Golin. It is also simpler than a diesel electric hybrid system and at 1,200 lbs. weighs less than half as much, he said.  Diesel electric systems make sense for applications with less stop and go, but “Why have the cost and complexity (of a diesel electric system) when HLA gives you what you need in a refuse truck?” Golin asks.

The Eaton HLA has two operating modes that can be set by the fleet.  The first provides maximum fuel economy, using only the stored kinetic energy in the hydraulic fluid to start the truck moving from a stop.  That initial boost can be up to 180 hp and can accelerate a stopped refuse truck up to 12 MPH in four to six seconds, according to Golin.

The second operating mode provides maximum productivity, combining the diesel engine’s power with the HLA’s to increase acceleration by 16 to 22% and deliver an overall 10% improvement in productivity.  “That means a truck can handle more bins in a day, and more bins mean more revenue," said Golin.

Installed in a 2- or 3-yr. old chassis, the Eaton HLA should offer refuse fleets a 3-yr. payback, according to Golin.  By taking over much of the vehicle’s braking, it will extend the life of service brakes by four to five times, eliminating up to four brake jobs a year at $1,800 to $2,000 a piece, he estimates.  Fuel savings from using the power stored on braking should save another $3,000 to $4,000 a year, and additional productivity gains should boost yearly savings from the HLA system to about $15,000, Golin said.  (By my math, these conversions must cost around $45,000. - JMH)

The first Eaton HLA retrofit kits are intended for Mack LE, MR and Granite chassis with Allison automatic transmissions, a common combination for side-loader refuse collection trucks.  "They will be installed by a network of service providers trained and certified by Eaton, who will also provide service and warranty support", Golin explained.  Eaton expects to begin delivering the kits to the first certified installers “in the next couple of months,” he said.

Designed for a 10-yr. life and tested up to 3.3 million operating cycles, the HLA hydraulics are self-contained and completely separate from the refuse packer’s hydraulic system.  “Our system is also completely fuel agnostic, so it can even work with CNG-powered trucks to help them regain some of the power lost (with that fuel),” Golin says.

[Source: FleetOwner]