Parker Hannifin's patented RunWise advanced series hydraulic hybrid drivetrain makes its production debut on a garbage collection truck.
During a month of real-world testing in south Florida, an Autocar E3 class 8 refuse collection truck with the RunWise system tallied a 42% reduction in diesel fuel consumption. Over a 12-month span that would translate to approximately 4000 gal (15,150 L) of fuel saved per truck per year, according to Vance Zanardelli, Business Unit Manager for Energy Recovery at Parker Hannifin Corp.
Parker's hybrid drivetrain technology provides other paybacks.
"The RunWise system also can absorb twice as much braking power vs. competitive hydraulic assist systems. And it can provide three to four times more braking power than electric parallel hybrid systems. This means drivers can drive without going easy on the brakes. And because more of the braking energy is recovered with RunWise, brake maintenance intervals can be extended up to eight times vs. a non-hybrid truck," Zanardelli explained.
Instead of a conventional automatic transmission, the proprietary software-controlled RunWise system operates in hydrostatic mode—meaning the engine is decoupled from the wheels—during low to medium speeds. During higher speeds, RunWise operates in a mechanical mode with the engine directly coupled to the wheels.
Key technical features of the RunWise system include hydraulic pumps/motors, accumulators, and a Power Drive Unit (PDU).
Hydraulic pumps/motors charge the accumulators, slow the vehicle during braking, and propel the vehicle during acceleration. "The Parker C24 piston pump/motor was custom-designed in a variable bent-axis configuration for heavy truck applications. A single C24 with its over-center operating capability can seamlessly switch from pumping to motoring mode," explained Zanardelli.
High-pressure, nitrogen-charged accumulators store energy recovered during braking. "The Parker accumulators, made of a carbon-fiber composite, operate at between 3000 and 5000 psi," Zanardelli said.
The PDU functions in hydrostatic low (0-25 mph [0-40 km/h]), hydrostatic high (25-40 mph [40-64 km/h]), as well as mechanical drive (40 mph [64 km/h] and above). "The PDU also serves to drive the cooling and lubrication pumps as well as the power takeoff unit," according to Zanardelli.
A cradle assembly houses the major RunWise components. "The assembly is an easy-to-service package, which can be removed and replaced in less than 90 minutes," said Zanardelli.
Parker had strength in component technology when R&D activities began in 2003 for the RunWise system. However, the company initially lacked the know-how necessary to develop a complete hybrid vehicle drive system (namely powertrain system engineering and integration experience) because this represented an entirely new line of business.
"Parker addressed this challenge by leveraging its global component and system capabilities; developing public and private technology partnerships; investing in state-of-the-art simulation, design, and test facilities; and by integrating all vital components into a stand-alone assembly that could be tested independently before vehicle installation," explained Zanardelli.
Yet this year, 11 Autocar E3 low-cab forward heavy-duty trucks with RunWise technology will be delivered to three Florida locales (Miami-Dade County, Hialeah, and the City of Miami).
"The first full production model year for the E3 will be the 2012 model year with build commencement in the second quarter of 2011," according to Mark Neale, Director of Vocational Vehicles for Autocar LLC.