Taking economics and the environment into account, what is the best way to store a large amount of energy? Hint: it isn’t an enormous shed full of Tesla Megapack batteries — they’re wildly expensive and require a lot of non-renewable resources to manufacture. Gravity batteries and pumped hydro storage are better, as they can store kinetic energy indefinitely with just the mass of water or heavy stuff. Similarly, you can store kinetic energy in a something spinning and that’s what a flywheel is. To demonstrate that, Erik built his own flywheel battery using water as weight.
Erik runs the Concept Crafted Creations YouTube channel and has posted multiple videos related to physics and energy. But this might just be his most interesting project, because this kind of battery is unknown to most people.
This is a type of kinetic battery, like a gravity battery or pumped hydro storage, except it stores the kinetic energy as rotational inertia in a spinning flywheel. That’s exactly what flywheels are for, but they usually drive mechanisms. In this case, the flywheel provides electricity by turning a motor acting as a dynamo — the same motor that spins up the flywheel in the first place.
Erik’s project is particularly unique because it uses water to weight the flywheel and the water contains can move in and out (relative to the axis of rotation) to decrease the flywheel’s moment of inertia. That’s like when you’re spinning in your office chair with your arms and legs out, then pull them in — you speed up. Erik’s flywheel handles that actuation with two small DC motors in the spindle, which rotate a mechanism that ultimately pivots the arms holding the tubes of water.
Water is an ideal weight because it is very cheap and is easy to adjust. Flywheels perform best when they’re well-balanced and Erik just has to add a bit of water as needed to achieve that balance.
Most of the flywheel parts were 3D-printed and the flywheel rotates on a laser-cut plywood frame. The control box is also laser-cut plywood and it contains an Arduino Nano R3 development board, a potentiometer for adjusting speed, and buttons to control the motor power and arm actuation. The drive motor is a DJI brushless DC motor for drones. A gear reduction in the belt drive increases torque.
When run in reverse, under power from the flywheel, that motor produces power — it is like regenerative braking in an electric car. In fact, when performing regenerative braking, the car itself is acting as a kinetic battery, just as this flywheel does!
