Putting Brutus size motors in perspective, the largest diesel engine in the world is the
Finnish 14 cylinder, 2,300 ton ship-moving, oil burner Wärtsilä RT-flex96C. This turbocharged two-stroke unit generates 109,000 horsepower - 81,205 watts - and is used to move huge container ships.
As powerful as these mega-machines might be, most earth moving is done by fleets of smaller excavators.
The Hybrid Excavator
The modern electric excavator is typified by the Komatsu Hybrid. The Komatsu Hybrid System PC200LC-8 uses a diesel engine to turn a power generator which operates the swing motor.
As the boom of the excavator swings around, it needs to brake. Similar to regenerative braking in the Toyota Prius hybrid, the PC200LC-8 uses motor braking, but captures the energy in ultra capacitors. This energy is then ready for instant reuse. The result is fuel use and emissions reductions of 25-40%. This is a great idea.
In terms of power, the PC200LC-8 diesel is a turbocharged 138 hp unit. The rig weighs in at about 44,000 pounds with a bucket capacity of 1.5 cubic yards. The hybrid excavator has all the capabilities of a diesel-only excavator.
In the mini-excavator market, there is the IHI 9VX Electric. This little machine runs on a 5 hp (continuous) electric motor. Remember that 5hp is 3,725 Watts (745 watts/hp x 5 hp). This little digger needs a 220 volt outlet minimum, and comes with a 75-foot long power cord.
Its empty weight is 2,060 pounds, and the EV will haul 1,885 pounds. The maximum digging depth is 5'2" with a top speed of 2.2 mph. All in all, this EV excavator is comparable to other mini-excavators like the Cat 301.
The Catapillar 301 has a 18.1 hp motor with a base weight of 1,700 pounds and an operating weight of 3,550 pounds. The Cat can dig to a depth of 6.8 feet and travel at a top speed of 2.8 mph.
Actual Heavy Equipment Emissions
Researchers from the University of CA, Riverside Bourns College of Engineering Center for Environmental Research and Technology (CE-CERT). have measured emissions from new hybrid and diesel excavators and dozers. The results were surprising.
Hybrid makers claim 20 percent reduced CO2 emissions with NOx reductions of 30 percent. The actual measurements were from 7-28 percent reduced CO2, but an increase
in NOx of 21 percent. The problem lies in tuning diesel engines for both fuel efficiency
and nitrogen oxide reductions.
The Electric Excavator takes advantage of the instant torque provided by the electric motor. In the process, this excavator operates with less air pollution than a diesel rig.
While most excavators and heavy equipment are diesel powered, the very biggest rigs
Earth, dirt and rock are heavy. It takes a lot of power to move large volumes of earth. Excavating huge volumes takes huge power. Big diesels cannot supply the power needed. Huge shovels, draglines, and excavators tie into the grid to pull down in the neighborhood of 6,000,000 watts (4,500,000 horsepower) at 20,000 volts!
One of the biggest of all is Big Brutus. This Bucyrus Erie 1850B EV shovel stands 160 feet high and weighs in at 5,500 tons or 11 million pounds! The bucket holds 90 cubic yards (CY), or a weight of 150 tons. Compare this to 3-5 CY for an average excavator.