The Hydraulic Hybrid

Last October, Caterpillar announced a game-changer in the excavator business — the 336E Hybrid. This innovative 37-ton excavator is by no means compact, but its use of an ingenious “hydraulic hybrid” system to capture and reuse energy is a technology that all machine categories should be discussing. The 336E H is an excellent excavation machine yes, but its power is balanced with efficiency, fuel conservation, money savings, emissions and noise reduction and the introduction of a new breed of machine to the construction industry. Wait a second. Hydraulic hybrid? Not electric. Is that right?

“There’s a lot of debate about how to define a hybrid,” explained Ken Gray, global product manager for large hydraulic excavators, in a press conference in early April. “A hybrid in our mind is a machine that’s equipped to collect, store and reuse energy. We don’t care how we save it. We just want to save it.”

So, how does the 336E H collect, store and reuse energy? It takes a number of technologies, but basically the machine saves and reuses energy from the machine’s swinging, collected in the hydraulics of the unit’s unique hybrid system. According to Cat, this energy conservation boasts fuel savings up to 25 percent, compared to its sister machine — the regular 336E.

To achieve fuel savings, the design of the 336E H is relatively straightforward, said Cat, using three building block technologies: 1) Conserve fuel with engine power management via the Cat Electronic Standardized Programmable (ESP) pump; 2) Optimize performance using restriction management via the patented Cat Adaptive Control System (ACS) valve; and 3) Reuse energy via the hydraulic hybrid swing, which captures the excavator’s upper structure swing brake energy in accumulators and then releases the energy during swing acceleration.

“We conserve — we use a different pump that allows us to turn that engine at a lower speed, so we can actually save a significant amount of fuel,” explained Brian Stellbrink, product application specialist at Caterpillar Inc. “We optimize by using the Adaptive Control System — ACS — taking that hydraulic flow and power and distributing it and doing that as efficiently as possible. Then we reuse, collecting, storing and reusing energy that’s normally been wasted in standard excavators.”

As mentioned, the 336E H was unveiled in October 2012, and its order board opened this February with factory shipments beginning in March. According to Gray, customers have shown tremendous enthusiasm for the 336E H since the day it was unveiled. “Customer interest has been off the charts,” Gray said in a press release. “They’re not only reaching out to Cat dealers to learn more about the 336E H, they are placing orders. In fact, we received our first signed orders October 17, the day after the reveal.”

There are also two additional hybrid excavators on the way. Both the 336F H and 336D H models will have the same hybrid Cat Electronic Standardized Programmable (ESP) pump as the 336E H. The 336F H will feature a Cat C9.3 ACERT engine that meets Tier 4 Final/Stage IV emissions standards; the 336D H will feature a Cat C9 ACERT engine designed to meet the needs of customers in those countries with emissions standards different than Tier 4 Final/Stage IV.

It’s all about fuel savings and saving money overall. Customers can expect the 336E H to use up to 25 percent less fuel compared to a standard 336E and up to a 50 percent improvement in fuel efficiency compared to a 336D in a wide variety of operating conditions. All three of the technology building blocks, 1) Conserve, 2) Optimize and 3) Reuse, are integrated together to maximize fuel savings in a variety of applications. Precisely when customers will recoup their initial investment in a 336E H depends on fuel prices, a customer’s specific application and the number of hours the machine operates in a year.

“Payback can be in as little as one year, assuming today’s fuel prices and being in a high production application,” said Gray. “But most likely, we’re looking at an 18-month payback in North America — maybe 24 months. If it’s longer, than maybe you need a smaller machine, or it’s a situation where you’re not getting enough work. But typically I think you’re going to see an 18-month payback.”

The best part: I actually got to operate the 336E H alongside the 336 E, and I could not tell the difference. I guess that’s the point. The two machines are nearly the same, except for this exciting new hydraulic hybrid system.

“The majority of the 336E H machine is the same machine we’ve had for the last two years,” explained Gray. “We started with a very strong foundation and carried over what customers are looking for and what has been proving itself out in the marketplace.”

We’ll keep you updated on this amazing new machine, as well as its next generation of excavator offspring.

Keith Gribbins is managing editor of Compact Equipment, based in Brecksville, Ohio.