Fortescue Metals Group has found a fast train to a greener future – and it’s all downhill.

Perpetual motion has been discovered in Western Australia’s Pilbara. Well, kind of. Fortescue mining has found its new ore-hauling electric trains will generate more power than they need.

There’s no smoke or mirrors. No laws of physics are broken.

It’s all thanks to gravity.

It’s not a new concept – it’s in the nature of an electric motor to also be an electric generator. Regenerative braking is a feature of almost all electric vehicles, though they don’t operate at the same scale as a train.

It’s about the immense weight of an iron ore cargo needing to be kept under control on long, gentle downhill slopes. The brakes that keep the 2.8km, 35,000 tonne load stable regenerate that friction into electricity – and prime the locomotives’ batteries.

An example of a regenerative electric locomotive. Credit: GE transportation

By the time they’ve reached their destination, the batteries are full.

It’s an idyllic win-win situation for corporate cost efficiency and climate mitigation.

Perpetual motion machines

Fortescue Metals Group chairman Andrew Forest has announced plans to embrace electric trains – and profit from the process.

Fortescue currently operates 16 trains with 54 locomotives that burn through some 82 million litres of diesel a year. It says that’s 11 per cent of the company’s total carbon emissions.

It plans to build a fleet of “Infinity Trains” to exploit the energy potential of four of its rail routes from the Pilbara. These have sufficient slopes down to their Port Hedland destination.

Such terrain immensely simplifies the process.

“The regeneration of electricity on the downhill loaded sections will remove the need for the installation of renewable energy generation and recharging infrastructure, making it a capital-efficient solution for eliminating diesel and emissions from our rail operations,” says Fortescue CEO Elizabeth Gaines.

“Battery-electric locomotives offer significant potential for emissions reduction in the near term as we seek to reduce our carbon emissions in the Pilbara by 50 per cent by 2030,”

Richard Cohen, Rio Tinto

All four Pilbara routes are to be equipped with regenerative trains by 2030. Any excess electricity will be offloaded to support the company’s other regional operations.

“The commercial opportunities are obvious for FFI [Fortescue Future Industries] as it pioneers this technology, captures its value and distributes it globally,” says Forest. “Less obvious is that we have an opportunity to not only lower our operating costs, eliminate the cost of diesel from our company but of course eliminate our rail system carbon emissions.”

Read also: Steel making is critical – and a critically bad carbon problem.

Other Australian miners are embracing the idea – even if the routes don’t all offer a net energy gain.

Every bit counts. Especially when every train has three locomotives hauling some 250 cars.

Rio Tinto has announced intentions to buy four battery-electric trains for use in the Pilbara. What power they don’t recover through their brakes will be replaced through purpose-built recharging stations.

The first is due to be delivered in 2023.

“Battery-electric locomotives offer significant potential for emissions reduction in the near term as we seek to reduce our carbon emissions in the Pilbara by 50 per cent by 2030,” says Rio Tinto executive Richard Cohen.

Gravity-assisted generation

The potential of gravity-assisted power generation was the subject of a recent study published by the Elsevier science journal Energy.

It proposes creating transport systems carrying water from high altitudes to fill reservoirs for coastal or plains cities, “converting the potential energy of water into electricity with the regenerative braking systems of electric trucks and storing it in the truck’s battery”.

Electric truck hydropower system. Axial description of the system where the empty truck moves up the mountain to collect the containers filled with water, and the truck with the full container goes down the mountain generating electricity. Credit: Julian David Hunt et al / Energy Volume 248

The empty truck would not need all that electricity to return to its start point. Nor need it be a specifically designed or dedicated piece of infrastructure.

“The energy stored in the electric truck can be sold to the grid or used by the truck to transport other goods,” the study reads.

It estimates electric truck hydropower would cost some $US30-$US100 per MegaWatt hour. This, it says, compares to the $US50 to $US200 per MegaWatt hour of conventional hydroelectric dams.

“Apart from being a low-cost and impact electricity generation technology, electric truck hydropower can operate in combination with solar and wind resources and provide energy storage services to the grid,” it concludes.

Fortescue’s Forrest agrees: “Business leaders and politicians globally (must come) to the realisation that fossil fuel is just one source of energy and there are others now, like gravitational energy, rapidly emerging, which are more efficient, lower cost and green. The world must, and clearly can, move on from its highly polluting, deadly if not stopped epoch of fossil fuel.”

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