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Komatsu to Introduce Hybrid Excavator

A rendering of a hybrid excavator. Source: Kobe Steel.

Nikkei. Komatsu Ltd. plans to introduce a hybrid hydraulic excavator in Japan and overseas this fall. The machine is powered by a combination of an electric motor and diesel engine.

The midsize excavator consumes 30% less diesel than the company’s existing model of comparable size driven only by a diesel engine. It will be priced around ¥12 million (US$99,000) in Japan, 20% higher than the current model.

Komatsu, the world’s second-largest maker of construction machinery, plans to sell a total of 1,500 units in Japan and overseas in fiscal 2010 according to the report in the Nikkei. The company has been working on hybrid construction machinery for a number of years, and was awarded a US Patent on its efforts in 2004.

The excavator uses an engine; a hydraulic pump powered by the engine; hydraulic actuators activated by discharge oil from the hydraulic pump; an electric motor that works in conjunction with the engine to assist in driving the hydraulic pump; an electric generator powered by the engine; and a battery for storing generated electric power.

If the work load of the hydraulic actuators is low and the absorbed torque (the torque of the engine which the hydraulic pump requires in order to drive the hydraulic actuators) of the hydraulic pump is smaller than the output torque of the engine, the extra output torque of the engine actuates the generator so that electric power is generated for storage in the battery.

Komatsu is not alone in its efforts to deliver hybrid construction machinery.

  • Japan’s Kobe Steel and NEDO (New Energy Development Organization) are undertaking joint development of a prototype hybrid excavator.

  • New Holland has unveiled a prototype hybrid excavator (called the Hybrid) which offers fuel savings of up to 40% compared to diesel-only units.




A bit like a series hybrid. Hope Case, Caterpillar, and Deere catch on too.


I know the "umbilical" cord would be a pain, but I can't help wondering if excavators in urban settings could be electric (using ultracaps for peak power requirements).


Gotta wonder if an hydraulic hybrid would make sense for this application, eliminating the electric motor, batteries, etc.



Beyond being a pain, I would suspect that an "umbilical" might post a safety hazard in an active construction site. With all sorts of cranes, excavators, vehicles, structures and manpower milling around, a severed umbilical could easily create a shock hazard, as well as bringing work to a sudden halt at an inconvenient moment.

Moreover, the power demands of such heavy-duty equipment may overtax the local electric grid connections, and there is little reason to beef up an infrastructure for an admittedly temporary usage.

At the same time, diesel construction equipment used in a dense urban setting can create noticeable local emissions impacts -- Boston during the Big Dig comes to mind. A good solution to this problem, though, would probably involve hybrids, and other low sulfur / clean diesel technologies.


how big is this thing? $100k seems like a small price.

Michael McMillan

I did the math a while ago, I may have been wrong, but pound for pound, hydraulic fluid has the same energy density at 5000 psi as lead acid batteries.

They already have a hydraulic system. Why not add a few accumulators for high pressure, and make it a hydraulic hybrid. When the engine is not in use, they can turn off the engine, and use the stored hydraulic energy.

If they put some work into it, they can even recover hydraulic energy as the excavator lowers a weight.


In Canada we have a huge electric digging machine (P&H 9020 Dragline) that digs for coal, but it doesn't move around much (it walks very slowly) so the "umbilical" isn't much of a problem.

Roger Pham

Nick & Michael,
I was wondering the same thing, whether it would be simpler or cheaper to use hydraulic set up instead?

And then it dawn on me that:
1) hydraulic hybrid requires storage of energy via compressed nitrogen gas tank at 1000-5000psi, meaning that there is not a steady pressure required to operate the hydraulic actuators directly from the nitrogen pressure storage tank. This means that you will need a separate hydraulic pump and hydraulic motor, both having variable displacement mechanism to account for the high variation in storage pressure. You cannot use the single hydraulic pump to both charge the tank and power the actuators at the same time. This implies no major cost nor complexity reduction from using generator-motor electric route. The displacement of the pump & motor must be constantly adjusted, and that increases complexity, whereas the generator simply charges the battery at the same voltage, and the motor simply runs from the battery at the same voltage each time.

2) "hydraulic fluid at 5000psi has equal energy pound for pound with lead acid battery..."

While this may be true, have you calculated the weight of the high-pressure nitrogen tank strong enough to hold 5000 psi of pressure? It probably will weigh >200 lbs if made out of carbon fiber, but may cost $1500 or more, or will weigh much higher if made out of steel...And the battery type used will be either NiMH or Li-ion which will be much lighter than lead-acid at much smaller volume requirement.

I'm sure that Komatsu engineers must have considered these and many more factors before they settled for this type of parallel hybrid drive.


If there is no infrastructure to support a plug-in excavator, you can just get a portable power generator that runs on diesel and plug it into that. :)

Ed Danzer

If the picture is of the size machine they are planning on building it would be a 150 size or smaller. The reason for electric hybridization is in many cases an excavator the power usage is under 10 hp in standby or light usage.
Current hydraulic technology is not very efficient at lower power levels.
As to accumulators, revisit the EPA hydraulic hybrid info. They have better energy densities than batteries of ultra capacitors for high power short duration demands.


I wana use MSC. MD. ADAMS V2005R2 in simulation calculating of Hydraulic Construction Machinery. Will it work or not?

yaghob hazrati

Hi happy new year i am komatsu excavators specialist dearsir Plase send me your heydrolic & electronic manual for excavator (pc 2oo lc-7) if it is possible farsi or englesh deta. very thanks


I saw more of this staff at

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