Utility Fleet

Off-Road Hybrids: Technology & ROI

January 2014, Government Fleet - Feature

by Thi Dao - Also by this author

At a Glance

New hybrid off-road equipment includes:

  • John Deere’s 644K electric-hybrid wheel loader costs 15% more than its conventional counterpart and promises to reduce fuel use by 25%
  • Caterpillar’s 336E H hydraulic hybrid excavator costs about 9% more than its conventional counterpart and promises to reduce fuel use by 25%.

While light-duty hybrid vehicles have proven themselves on the streets, hybrid off-road equipment is still relatively new, with few offerings available.

Komatsu claims to have launched the first hybrid excavator in June 2008. Its HB215LC01 electric-hybrid excavator works through regeneration, using the swing momentum to generate energy, which is stored before it is discharged to power the swing motor and engine.

There are a handful of hybrid off-road options available, but two off-road units released in 2013 may be of particular interest to public fleets — an electric hybrid loader from John Deere and a hydraulic-hybrid excavator from Caterpillar; both these units claim a 25% reduction in fuel consumption in comparison to their conventional counterparts. By estimating the incremental cost along with projected fuel savings, fleet managers can estimate if and when they’ll get a return on their investment in a hybrid machine.

John Deere’s 644K electric-hybrid wheel loader utilizes two sources of energy, diesel and electric, capturing regenerated energy as it is being created and using it to power the machine. Photo courtesy of John Deere.
John Deere’s 644K electric-hybrid wheel loader utilizes two sources of energy, diesel and electric, capturing regenerated energy as it is being created and using it to power the machine. Photo courtesy of John Deere.

John Deere Offers Hybrid Loader

John Deere released its 644K electric-­hybrid wheel loader in 2013, advertising a fuel use reduction estimate of 25% over its 644K conventional wheel loader.

The hybrid loader has a smaller engine and maintains a constant 1,800 RPM when it’s in use for improved fuel economy and consistent boom and bucket response. John Chesterman, marketing manager for John Deere’s large wheel loaders, said while the loader does idle down when not in use, this constant in-use RPM means an operator isn’t constantly revving the machine up and slowing it down. The electric motor recaptures kinetic energy to slow the loader when the operator lets off the accelerator, which then drives the generator and hydraulic pumps to save fuel. Additionally, the unit doesn’t have a torque converter, but instead uses a brushless alternating current generator that generates energy. This energy goes into the power electronics, which controls the electric motor.

The benefit here is a much more efficient drivetrain system, Chesterman said. Even for loaders driven down roads for long periods of time, such as driving on roadways to get places or clearing snow, the drivetrain on the hybrid is more efficient than on the conventional drive system.

In performance, Chesterman said the hybrid engine has only 2 hp less than the conventional engine, less than 1% of difference. The bucket capacity is the same for both units.

Caterpillar began selling its 336E H hybrid excavator in early 2013, choosing hydraulic hybrid rather than electric hybrid technology for the machine. Photo courtesy of Caterpillar.
Caterpillar began selling its 336E H hybrid excavator in early 2013, choosing hydraulic hybrid rather than electric hybrid technology for the machine. Photo courtesy of Caterpillar.

Caterpillar Offers Hydraulic Hybrid

Hybrid doesn’t just mean electric hybrid. Caterpillar defines a hybrid machine as one that is equipped with a device to collect, store, and release energy during machine operation. While the company already offers a hybrid diesel-electric powertrain D7E dozer, Caterpillar now offers a hydraulic-hybrid machine — the 336E H  hybrid excavator.

Caterpillar explored both hydraulic and electric systems for excavators and found the hydraulic option was the better choice at this time to ensure lower operating costs and improved return on investment (ROI).

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