Energy Matters

Overcoming air drag, which makes all land transport more energy intensive at higher speeds, takes up the most energy. Power for maglev trains is used to accelerate the train, and may be produced when the train slowed (so called "regenerative braking"), it is also usually used to make the train fly, and to stabilise the flight of the train, for air conditioning, heating, lighting and other miscellaneous systems. Power is also needed to force the train through the air ("air drag").

Due to the absence of physical contact between the track and the vehicle, maglev trains experience no rolling resistance, leaving only air resistance and electromagnetic drag, potentially improving power efficiency.

At low speeds the levitation power can be significant, but at high speeds, the total time spent levitating to travel each mile is greatly reduced, giving reduced energy use per mile, but the air drag energy increases as a square law on speed, and hence at high speed dominates. Some systems (notably the Swissmetro system) propose the use of vactrains — evacuated (airless) tubes used in tandem with maglev technology to minimize air drag. This has the potential to increase speed and efficiency greatly, as most of the energy for Maglev trains is lost in air drag.

In some maglev systems, the drive mechanism lies in the guideway, so it doesn’t have to be carried in the vehicle. This is a radical departure from traditional transport systems of every other type. In addition, with maglev trains, propulsion power only needs to be provided for short stretches as the vehicle passes through an active propulsion section. Thus, the primary energy needs of the maglev trains are significantly reduced, compared to wheel/rail systems at the same speed.

The weight of the large electromagnets in many maglev designs is a major design issue. A strong magnetic field is required to levitate a massive train. For this reason one research path is using superconductors to improve the efficiency of the electromagnets, and the energy cost of maintaining the field. Another research path is implementing advanced light-weight materials to reduce the weight of the vehicles.

The German Transrapid, Japanese HSST (Linimo), and Korean Rotem EMS maglevs levitate at a standstill, with electricity extracted from guideway using power rails for the latter two, and wirelessly for Transrapid. If guideway power is lost on the move, the Transrapid is still able to generate levitation, using the power from onboard batteries. This is not the case with the Japanese High Speed Maglev System (Linear Motor Car MLX / LO1), the HSST Linimo or the Rotem systems.

A scientific report about the energy consumption of high speed trains and maglev systems can be downloaded in pdf format here:

"Energy Consumption of Track-Based High-Speed Transportation Systems: Maglev Technologies in Comparison with Steel-Wheel-Rail". Edition: Research Series Volume 3, 2018.
Publisher: The International Maglev Board
ISBN: 978-3-947957-02-6