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Electric Vehicles Research
Posted on October 23, 2012

Caterpillar unveils first hybrid excavator

Caterpillar unveiled the first model in its new line of hybrid excavators, the Cat® 336E H, at its Mossville Industrial Design Center last week at a special trade press event. The new 336E H will be sold and serviced exclusively through the global Cat dealer network following the machine's official launch at bauma 2013 in Munich, Germany. The order board opens in Feb. 2013, with factory shipments beginning in March 2013.
 
The excavator uses a new hydraulic hybrid technology developed by Caterpillar. "A hybrid is independent of any particular technology—it doesn't have to be electric," said Ken Gray, global product manager for large hydraulic excavators for Caterpillar's Excavation Division. "There are many ways to store and reuse energy, including our patented hydraulic hybrid system featured on the Cat 336E H."
 
"Caterpillar has developed, built, and tested electric hybrid excavators, but—until now—we had not found a hybrid approach that would actually lower our customers' owning and operating costs," Gray said. "Large excavators operate in high-production applications in which fuel is a very significant operating cost for our customers. So, the 336E H, the hybrid version of our workhorse 336E, is ideal for introducing our new hydraulic hybrid technology, with its more than 300 filed patents."
 
Gray added, "No other commercially available technology has higher power density than hydraulics, and that's why we selected a hydraulic solution to help our customers achieve substantial fuel savings. The 336E H also meets stringent Tier 4 Interim/Stage IIIB emission standards. It is extraordinarily quiet, too. So it's a socially responsible machine for our customers to own, and they will sacrifice nothing in terms of performance, power, force, speed or production. Once more, the owning and operating costs for the 336E H are actually lower than the standard machine."
 
"The 336E H is a game-changer—the most revolutionary excavator to come to market in decades," said Gary Stampanato, vice president of Caterpillar's Excavation Division. "Customers aren't going to choose the 336E H simply because it is sustainable. They will select it because it actually lowers their owning and operating costs, and maintains the performance of our industry leader, the 336E. Caterpillar has the most productive and fuel-efficient excavator product line in the industry."
 
Technology
 
"Caterpillar's corporate technology strategy centers on research and development in advancing technology to meet customers' needs today, which is what the 336E H does," said Tana Utley, Caterpillar's chief technology officer and vice president of the Product Development and Global Technology Division. "We're also continuously working on innovations that we anticipate will meet their future needs. That's why we're continuing our research and development in electric hybrid technology too, which actually began our hybrid development path several years ago."
 
Since the introduction of the 300 Series in 1994, the family of excavators has become the industry standard in a large variety of general, quarry and heavy construction applications. Caterpillar introduced the standard 336E in 2010 as a direct replacement for the 336D. The 336E was introduced primarily to meet Tier 4 Interim/Stage IIIB emissions standards, and like any new Cat machine, the 336E includes several enhancements over its predecessor, including more horsepower with greater fuel efficiency, more lift capability, higher digging force and automatic aftertreatment regeneration.
 
The 336E H has all of the same powerful advantages of the 336E with the biggest difference between the two models being even greater fuel efficiency. To achieve added fuel savings, the design of the 336E H uses three building block technologies that:
 
1) Conserve fuel with engine power management via the Cat Electronic Standardized Programmable (ESP) pump, which smoothly transitions between the hydraulic hybrid power sources, engine and accumulator.
2) Optimize performance using restriction management via the patented Cat Adaptive Control System (ACS) valve, which intelligently manages restrictions and flows to seamlessly control machine motion with no loss of power, and to ensure operators experience no difference in control, hydraulic power or lift capability.
3) Reuse energy via the hydraulic hybrid swing system, which captures the excavator's upper structure swing brake energy in accumulators, and then releases the energy during swing acceleration.
 
Fuel Savings
 
The 336E H delivers industry-leading productivity with up to 50 percent greater fuel efficiency, which is measured in tons per liter, over the 336D. Customers can expect the 336E H to use up to 25 percent less fuel compared to a standard 336E, and up to 33 percent less fuel than the 330/336D. All three of the technology building blocks, Conserve, Optimize and Reuse, are integrated together to maximize fuel savings in a variety of applications. Even in low-intensity swing applications, customers will still experience significant fuel savings because of the Conserve and Optimize technologies. (Additional factors, such as operator skill and jobsite conditions, also affect fuel savings.)
 
Return on Hybrid Investment
 
Because the 336E H burns less fuel and reduces regulated engine emissions, owning and operating costs will be dramatically lower compared to the standard machine, and its carbon footprint will be smaller, as well. Precisely when customers will recoup their initial investment in a 336E H depends on fuel prices and their applications. Assuming today's fuel prices and a high-production application for a 336E H, Caterpillar estimates customers can realistically expect to see a return on their investment for the hybrid excavator model in as little as one year.
 
Validation
 
Customers have been using field follow machines, which are first production machines built for customer acceptance testing, to validate fuel burn, controllability, reliability and performance of the 336E H. In a formal production study completed in August 2012, results were impressive, including greater fuel efficiency, and lower cab and spectator noise levels than the 336E and 336D. Additionally, the ACS valve, which intelligently manages restrictions and flows to seamlessly control machine motion, has been in the field since 2008 with superior performance and reliability. The ACS and hybrid system have also proven to work well together to maximize performance and controllability of work tools, including hammers, shears and grapples.
 
IDTechEx comment
 
Large and heavy duty industrial and commercial vehicles are rapidly adopting hybrid electric powertrains including Toyota and Mitsubishi outdoor forklifts and the new John Deere hybrid electric heavy agriculture vehicles. Caterpillar has taken a parallel approach to this.