Optimizing the big machines
While more cars are running on biofuels and electricity, their off-road cousins—specifically in agriculture, construction, forestry, and mining—have not changed much. Most of them still run on fossil fuels.
Off-road vehicles represent 10 percent of transportation CO2 emissions in the United States, and this number will keep climbing if attention remains with on-road vehicles.
“There are many universities in the U.S. that work on passenger cars and new technology for them, but there are very few who work on medium and heavy equipment or off-road vehicles. That is what we’re focused on,” said Kim Stelson, founding director of the Center for Compact and Efficient Fluid Power at the University of Minnesota.
One reason that off-road vehicles are difficult to decarbonize is their demanding energy and power requirements.
“Carbon-based fuels like gasoline or diesel have 40 times more energy per unit mass than batteries—and that factor of 40 is what has made them necessary in these machines,” he explained. “All a car has to do is move itself along a road. But something like an excavator also has to dig soil and dump it. So its power levels as you dig goes up and down, and the engine has to go fast or slow, while fully loaded or lightly loaded. All of this variation reduces the efficiency of the engine and it increases the emissions.”
Stelson is part of a multidisciplinary team looking to achieve net-zero carbon emissions for off-road vehicles by 2050. Since 2019, the U.S. Department of Energy has invested more than $8 million into studies at CSE on this topic.
“We believe it’s possible to cut their greenhouse gas footprint in half with things that are not exotic, using technology that could be developed and commercialized within years,” he said.
“To potentially save 1.2 quads (351 billion kilowatt-hours) of energy,” Stelson added, “we must operate the engine efficiently, eliminate the throttling valves, store and release energy better, and install smarter controls to manage everything.”
Simply put, Stelson and the other main investigators—Perry Li, Will Northrop, Zongxuan Sun, and Jim Van de Ven—are building a better system.
Close industry partnerships have been vital in progressing the team’s research. CNH Industrial has been a key partner in recent projects. In addition to providing an engine for experiments aimed at learning how to operate a wheel loader most efficiently, the company gave a compact track loader to a study on optimally pairing hydraulic and electric power
transmission.
“The University of Minnesota is well-positioned to lead in this area because we have significant research expertise in fuels, energy conversion, actuation, sensing, and control for target applications,” said Stelson.
So, what’s the best net-zero solution for off-road vehicles? Is it going to be green hydrogen, green ammonia, or biofuels? Will we combust it or use fuel cells? Will some of these vehicles be fully electric, or will they combine electricity with other power sources?
“The answer probably is yes to all of those options,” said Stelson. “There’s not a simple answer. What’s right for working in a mine might be different from what’s right for working in a corn field.”
