In November, heavy-equipment giant Caterpillar Inc. unveiled a demonstration of its first prototype all-electric mining truck, built at its Tucson Proving Ground in Green Valley.
The company plans to test a fleet of its electric model 793 haul trucks with mining partners across the globe starting next year, ahead of mass production planned in four or five years, a senior Caterpillar executive said this week.
But Caterpillar doesn’t just plan on selling electric mining trucks.
The company, a longtime supplier of large industrial diesel generator sets for mining and other applications, wants to help its mining customers create their own “microgrids” using renewable energy like solar and wind and battery storage to help fuel its electric trucks.
At the Tucson Proving Ground, Caterpillar is building a demonstration site where solar arrays and wind turbines paired with batteries will generate and store renewable energy to create self-sustaining microgrids, while exploring onsite production of hydrogen for fuel.
“What we’re developing is a mine site of the future, so that we can demonstrate to our customers exactly what they need to transform with their mine sites,” said Denise Johnson, president of Caterpillar’s Resource Industries Group.
“We want to be able to show how it could be done and then validate that it’s something that will work in a setting that is pretty rigorous,” Johnson, who is based in Irving, Texas, said during a visit to the proving ground last week.
Sun, wind and storage
Two solar panel fields were installed in 2016 at Caterpillar’s Tucson Proving Ground in Green Valley.
Caterpillar, which has operated the proving ground in the shadow of Freeport McMoRan’s Sierrita Mine since 1990 and opened a major mining technology center on the west side of downtown Tucson in 2019, has been trying to stay ahead of the technology curve for years.
In 2016, the company installed an initial 500 kilowatts of photovoltaic panels and commensurate energy storage to create a hybrid solar-diesel microgrid at the Tucson Proving Ground — which is not hooked up to local utility power — to cut the off-grid facility’s reliance on diesel generation.
The system was designed to supply much of the power needed to run the off-grid proving-ground site and allow Caterpillar to demo its then-new line of microgrid products, which range from mobile trailer-mounted rigs to scalable custom, on-site installations.
Caterpillar later expanded solar array at the proving ground to 750kW and plans to expand that to 2 megawatts. The company also plans to install two wind turbines by next year that will generate about 3MW, as well as 18 megawatt-hours of on-site battery storage.
The system already is supplying the off-grid Tucson Proving Ground with all of its power, and the new solar, wind and storage capacity will support more electrified machines at the site in the future, the company says.
Johnson said the green microgrid project at the Tucson Proving Ground is an important part of the company’s efforts to reach its sustainability goals, and by extension, the goals of mining customers looking to reduce their carbon footprints.
“At our core, Caterpillar is a technology company, and one that really believes in sustainability,” she said. “It’s one of our core values and certainly something that we see as important to our future as a company. The other piece is certainly the pull from customers, so the combination of the two of them really made sense for us to move quickly and be one of the first to lead in the industry.”
Eye on cost
Making sustainable microgrid technologies affordable for customers also is a priority, Johnson said.
The gigantic model 793 electric haul truck prototype is based on a diesel-powered version with a 256-ton payload capacity that costs about $6 million.
The electric version is expected to cost more, though pricing has yet to be decided and will depend on the final production design, Johnson said, noting that higher upfront costs for electric trucks is partly offset by lower operating costs.
“We’re still working through all the designs of everything so we know they’ll be more expensive, but you’re offsetting that by no longer buying diesel fuel,” she said.
The electric mining trucks also could be outfitted to drive themselves. Caterpillar was one of the first companies to offer autonomously-operated haul trucks and last year said its fleet of more than 500 of such trucks was the largest in the world.
Early learners
Caterpillar developed the electric truck prototype with support from key mining customers participating in Caterpillar’s “Early Learner” customer collaboration program, including Phoenix-based Freeport McMoRan, BHP, Newmont Corp., Rio Tinto and Teck Resources Ltd.
The program, launched in 2021, focuses on accelerating the development and validation of Caterpillar’s battery electric trucks at participating customers’ sites.
By early next year, Johnson said, the electric trucks will begin testing at customer sites in a process expected to go on for couple of years, with production expected by 2027 or 2028.
“The idea here is that we’re going to learn with the mining company, how these machines interact around the site, what it takes to charge them, recharge them, to actually have them move across the infrastructure,” she said.
Caterpillar also offers solar panels supplied through major manufacturers, its own line of battery units for energy storage, backup power and grid stabilization for renewable resources, as well as master system controllers, power inverters and switching equipment.
The company can custom-design microgrids at mining sites by integrating renewables like solar and wind with storage to provide power for when the sun doesn’t shine and the wind isn’t blowing, with diesel generators for backup power.
Highlighting hydrogen
At the Tucson Proving Ground, Caterpillar also will be exploring production of hydrogen fuel for power generation using on-site renewable energy, as well as biofuel made from vegetable oils.
Caterpillar generator units have been capable of burning a partial blend of hydrogen for years, and in 2021, the company began offering custom generator sets capable of operating on 100% hydrogen, as well as gensets that can be configured to operate on natural gas blended with up to 25% hydrogen.
“We will use hydrogen as a storage mechanism, if we have access to wind or solar,” Johnson said. “Instead of just letting that go to waste, we will actually make hydrogen to store energy.”
The company also plans to install a fuel cell to turn hydrogen into electricity, and two gensets capable of running on a blend of natural gas, 100% hydrogen or a blend of both.
Caterpillar also will be exploring renewable biofuels at the proving ground, Johnson said.
“We’ll have standby power that will be leveraged using natural gas and other fuels,” she said. “HVO, hydrogenated or hydro-treated vegetable oil, is a new fuel that is zero-emitting and would be considered a biofuel.”
See how Caterpillar is transforming its Tucson Proving Ground into an all-electric mining site with solar, wind and energy storage.
