Advancing Grids With Highway Levitation

How retrofitting roadways with superconductors could be an energy-transport win-win

3 min read

Illustration of a car and bus on a road, shown in cross-section, which also leads off to a home and a factory.

This schematic shows in cross section a proposed superconducting highway system that could transmit both grid power and liquid hydrogen (as an energy-storage medium) as well as provide infrastructure for a possible superconducting maglev transportation grid.

University of Houston

Superconductors have long promised advanced power grids and transportation networks. However, the threat of high costs has long held back these dreams. Now a new study argues that one way to make such projects a reality is to combine them into a unified system, one that could both help cars and trucks zip around faster than a bullet train and deliver electricity without losses. It could also shuffle around liquid hydrogen fuel, a key future source of clean energy, scientists say.

Regular electrical conductors all resist electron flow to some degree, resulting in lost energy. In contrast, superconductors conduct electricity with zero resistance. As such, they can lead to significantly more efficient power grids. The way in which superconductors can host powerful electric currents also means they can generate powerful magnetic fields to enable incredibly fast maglev trains.

“As soon as I had the idea, I realized the huge potential, and the more I thought about it, the more I found new benefits. I am extremely excited because I feel it is really a world-changing concept.”
—Zhifeng Ren, University of Houston

However, the high costs linked with superconductivity have limited the daily use of both long-distance maglev trains and long-distance superconducting power-transmission cables. Now, a new study argues, one way to reduce the costs of both these applications is to unite them into one system so their expensive parts can pull double duty.

In addition, this proposed combined system would store and transport liquid hydrogen. Fuel cells can convert the chemical energy stored in fuels such as hydrogen into electricity, typically performing more efficiently and sustainably than a car’s internal combustion engine. Liquid hydrogen would also help cool the superconductors in this system, reducing the need for specialized pipelines.

“I have been studying clean energy, superconductors, hydrogen, and so on for many years,” says study lead author Zhifeng Ren, a materials physicist and director of the Texas Center for Superconductivity at the University of Houston. “I know the potential of each technology, but each one of them is expensive. If multiple functions can be realized in a single system by combining all the relevant technologies together, the cost of each function will not be that expensive.”

Maglev trains typically float on a guideway of high-cost permanent magnets, with superconductors incorporated into each train’s undercarriage. The new concept flips this design, embedding superconductors into existing highway infrastructure and adding magnets to the undercarriages of vehicles. This avoids the complex machinery needed to cool superconductors in each vehicle. Instead, the liquid hydrogen in the design would help cool the superconductors in the system. Relatively cheap liquid nitrogen and a vacuum layer would help thermally insulate the liquid hydrogen.

This supersystem uses superconductors to move people, cargo, and energy.

In this design, vehicles with magnetic undercarriages—trucks, trains, and even personal vehicles—would enter the superconductor guideway to levitate and move at speeds of 500 to 800 kilometers per hour to reach their destinations, or even 1,000 km/h when the system is built inside a tube where air can be pumped out. After leaving the guideway, vehicles could continue their journeys using conventional internal combustion or electric motors.

“As soon as I had the idea, I realized the huge potential, and the more I thought about it, the more I found new benefits,” Ren says. “I am extremely excited because I feel it is really a world-changing concept.”

The researchers built a model to show they could levitate a magnet above a superconductor guideway. They used liquid nitrogen to cool the model but noted that future models will use liquid hydrogen.

All in all, the new design could help move people, cargo, and fuel in an energy-efficient manner, they say. Ren says they have received outside interest in further developing this concept.

“We are trying to build the next-step demonstrator to further show the feasibility of the concept,” he says. “The most important issue is financing.”

The scientists detailed their findings 24 April in the journal APL Energy.

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