Thanks to high-tech system costs, an eDumper costs about twice as much as a diesel-powered truck. But it never needs fuel – saving 11,000 to 22,000 gallons of diesel per year, plus its carbon emissions – and it almost never needs recharging. Road tests show that it generates about as much electricity going downhill as it uses going uphill. Miauton said the company is now making three more eDumpers for mines in Germany and is planning even larger electric dump trucks.
The idea of downhill power generation will soon get an even bigger boost. Australian mining company Fortescue, a major producer of iron ore, announced in March that it would build “Infinity Trains” to generate electricity while hauling loads of ore from mines in the Outback.
The company currently operates 16 trains in Western Australia driven by 54 locomotives which use a total of approximately 20 million gallons of diesel fuel each year. Each train has up to 244 cars. They can be nearly two miles long and carry over 37,000 tons of ore.
Fortescue’s managing director, Elizabeth Gaines, said four routes from mines in the inland Pilbara region are far enough upstream from their final destination – Port Hedland on the north coast – to be suitable for Infinity trains. The company plans to have them running on all four routes before 2030 by developing the dynamic braking feature that many locomotives already have to convert gravity into electricity, she said in an email. Some routes will generate even more power than they need for the return trip, and the company will use the extra electricity elsewhere in its operations.
The most innovative proposal to generate electricity from gravity could be hydroelectricity by electric truck. According to a study published in March, a fleet of electric trucks filled with water high up in the mountains can generate electricity as they descend on regular roads. The empty trucks can then be driven back to fetch more water or be used elsewhere.
The study’s lead author, Julian Hunt, a Brazil-based researcher at the International Institute for Applied Systems Analysis, said the system is about as cost-effective in generating electricity as wind power. , solar and regular hydro.
For starters, electric truck hydro can be much cheaper than the alternatives.
“You just have to buy electric trucks and be able to connect them to the grid – that’s all the cost,” he said. “But for hydropower plants you need huge dams, tunnels, turbines and many other different components that have very high capital costs.”
Depending on conditions, the electric water-carrying trucks could also be deployed to generate electricity from different stages of a mountain descent, or even from different rivers on different routes. “It’s very flexible, very modular,” he said.
The system will not always be suitable — how much truck drivers are paid, for example, will affect the price of its electricity. But Hunt said it can be useful where regular storage of hydropower in mountain lakes isn’t possible and where rivers dry up in the summer. It will also eliminate many of the environmental and social impacts caused by large hydropower plants, such as the need to flood large swathes of land for reservoirs or relocate communities, he said.
Christopher Knittel, a professor of energy economics who directs the Center for Energy and Environmental Policy Research at the Massachusetts Institute of Technology, who was not involved in the study, said he was concerned that the costs of such system are higher than estimated.
But “it’s an interesting idea, for sure,” he said in an email. “Given how quickly things change and the need for new technology, I’m always happy to see things outside the box.”