Equipment World Digital Magazine
Issue link: https://read.dmtmag.com/i/102855
innovations | continued Two machines, two paths to fuel efficiency A s manufacturers continue to squeeze the remaining fuel efficiency from today's emissions-compliant engines, they are looking for game-changers in other components. This past year Caterpillar announced two ways it is going beyond the en- gine to accomplish double-digit fuel consumption reductions: excavator electric hybrid approach worked well, it was still difficult to meet all cost goals for this size of machine. There was a clear winner between the cost of the two systems." (Cat does, however, use electric hybrid technology on its 6120B H FS mining shovel.) 336E H excavator W hen Cat unveiled the 336E H to the press in October, two announcements got immediate attention: one, the use of a hydraulic hybrid system instead of electric, and two, a 25-percent reduction in fuel consumption compared to the current 336E. When placed side by side with the previous generation 336D, the hybrid's fuel reduction goes up to 33 percent. Considering all factors, Cat says the total fuel efficiency of the hybrid could be as high as 50 percent, measured in tons per liter, compared to the D Series machine. Cat took a dual path approach in exploring hybrid options: one engineering team looked at electric hybrids and another examined hydraulics. Randy Peterson, with the Advanced Component and Systems division at Caterpillar, hesitates to use the term "competing" when talking about the teams. "Both were working toward a common goal," he says. "While the 22 January 2013 | EquipmentWorld.com Conserve, optimize and reuse From the outside, the hybrid machine looks just like the current 336E, but there are significant changes under the hood. Caterpillar promotes "conserve, optimize, and reuse" terminology when explaining the hybrid system, with each term showcasing a key component: Conserve: The Electronic Standardized Programmable (ESP) pump is designed to ensure smooth transition between power sources to conserve fuel. It uses a solenoid-operated proportional control valve to control the pump displacement via the engine's electronic control module. The ESP pump enables a reduction in engine speed, allowing fuel savings and quieter operation by matching engine and pump load. Cat applied an in-house-developed algorithm to the ESP pump controls to ensure smooth transition between the hydraulic hybrid power sources, engine and accumulator (see "reuse" below). "We can seamlessly transfer between one or the other power source, and the operator doesn't feel it," says Aleksandar M. Egelja, engineering manager, Advanced Component and Systems division. Optimize performance: The Adaptive Control System valve is "the brain of our hydraulic system," Egelja says, directing flow from both the pump and accumulator. The valve serves as a logistics center, managing hydraulic restrictions and flows, sending energy to where it's needed with no loss of power. This, in turn, reduces fuel consumption by reducing pressure losses within the hydraulic system. Reuse: Energy is generated when an excavator swings