NSTU-NETI is developing a flywheel energy storage drive to save fuel and reduce environmental stress

The flywheel drive is an efficient energy storage device. It is capable of operating in a wide temperature range (from -25 to +50 °C), and its specific energy consumption significantly exceeds that of chemical batteries. Another positive aspect of using FES is the possibility of instant transmission or reception of almost any power, limited in the case of mechanical transmissions only by the strength limit of structural materials, says Yuri Pankrats, associate professor of the Department of Electric Drive and Automation of Industrial Installations at NSTU-NETI.

"The flywheel acts as a kinetic energy accumulator, converting it into electrical energy during braking and returning it to the vehicle's on-board network. The stored energy can be used during peak loads, for example, during intensive acceleration or climbing. This will significantly reduce the load on the engine, fuel consumption and the amount of harmful emissions into the atmosphere. Such a system is most effective in the urban cycle with frequent acceleration/deceleration of transport," said Anatoly Sapsalev, an engineer at the NSTU-NETI Research Laboratory for Testing Electric Drives, Doctor of Technical Sciences, Professor.

NSTU-NETI proposed using a magnetic coupling to drive the flywheel, a non—contact device for transferring mechanical energy (torque) between shafts using a magnetic field. On the primary (leading) and secondary (driven) coupling halves, separated by an air gap, there are permanent magnets oriented poles to each other. When the motor rotates the primary, the magnetic lines of its poles interlock with the poles of the secondary, forcing the flywheel located on the same shaft with the secondary coupling half to unwind without mechanical contact between the rotating parts. This ensures an almost complete absence of friction, which minimizes energy loss, reduces wear on parts, and increases equipment life. The absence of a rigid mechanical connection dampens vibrations and protects against overloads — during sudden load surges or jamming, the coupling halves begin to slip relative to each other, preventing damage to the electric motor and other drive elements.

Semi-couplings can use not only permanent magnets, which require alloys based on rare earth metals, but also electromagnets that provide flexibility and high power control, adds Anatoly Sapsalev. When using electromagnetic excitation, the coupling force (transmitted torque) is directly regulated by the amount of current passing through the windings. Unlike permanent magnets, electromagnets require a continuous supply of electricity to maintain a magnetic field. 

A promising area of application of the proposed device, which is based on contactless magnetic transmission of mechanical power and flywheel energy storage devices, are rail vehicles (railway trains, subways, trams, cable cars). It takes a lot of energy to brake them, and if you don't waste it by heating the brakes and untwisting the flywheel, the accumulated energy can be spent on gaining speed. This method will save up to 30% of the energy consumed by the vehicle.

The use of a flywheel energy storage device in unmanned aerial vehicles (UAVs) is promising because electric motors coupled with such a flywheel heat up much less compared to an internal combustion engine. Reducing the heat footprint makes the drone less visible to IR sensors. In addition, the high energy output rate of the flywheel drive is important for fast takeoff or sudden maneuvers. The scope of application of the device, except for urban transport and UAVs, are wheeled, tracked and floating unmanned vehicles.

This year, NSTU-NETI scientists have filed an application for registration of the intellectual property object "Flywheel energy storage drive".