Store Energy in a Magnetically-Levitated Flywheel to Power Electronics Without Batteries

What is a flywheel?

The engineering challenge of how to best store and retrieve energy has existed for thousands of years. From basic water wheels to the latest battery technology, being able to gather and store energy efficiently has literally powered our societies. However, some methods require expensive/exotic materials or create extra pollution. This is where flywheels can help, as they store energy in the form of rotational inertia within a heavy disk that can be collected when needed or stored when energy is available. Flywheels often lose their momentum due to frictional losses, such as when the wheel encounters air resistance or spins along the central axis, which is why minimizing friction is vital.

YouTuber Tom Stanton has come up with a way to cheaply build a small flywheel that uses magnets around its shaft to levitate with only air resistance to overcome.

Basic magnet physics

"Opposites attract and likes repel" is a common way to memorize how magnets interact with each other's poles, and that is just as true in this case. Inspired by a small toy, Stanton's design uses a pair of stationary bases that contain magnets aligned in one direction while the flywheel's shaft has magnets that are also aligned in this same direction. By giving a slight horizontal offset, these two sets of magnets are able to repel each other and lift the full weight of the flywheel, essentially transforming it into a large sideways spinning top.

Extracting energy

With the mechanics of the flywheel figured out, Stanton moved onto a design for an energy-extracting circuit that would transform the rotational inertia of the disk into electrical energy. In this case, he fitted a second, smaller wheel with a series of magnets on its face further down the shaft. Between these two wheels is a set of four copper coils that have an alternating electrical current (AC) induced in them whenever the magnets pass over, essentially creating an AC generator. However, this form of current is incompatible with most small components, so a bit of extra circuitry was required.

Trying to light a room

To take the AC power from the coils and convert it into more usable direct current (DC), Stanton added a full-bridge rectifier which uses four diodes in a special configuration to make the current flow in only one direction regardless of the alternating current's phase. After adding a smoothing capacitor and increasing the number of turns within the coils, Stanton was able to achieve nearly 10v simply by turning the flywheel with his hand. He then connected the output into a breadboard and added 20 white LEDs in parallel to test the limits. Finally, a small motor with a fan was connected and run, which ran surprisingly fast considering its large current draw.

For more information about this energy storage project, you can check out Stanton's YouTube video here.