This Pendulum Is Actually a Battery

When people hear the word “battery,” they think of a chemical battery, such as lithium-ion or alkaline. But a battery is anything that can store energy for later use, which includes a lot more than just chemical batteries. Gravity batteries store energy by lifting a mass, which can later be recovered by releasing that mass and letting gravity pull it back down — usually actuating some kind of dynamo. Tom Stanton put that into action with this unique pendulum battery.

This is a large pendulum and if Stanton lifts it up to the top of its swing, he has stored the energy from the lifting effort as potential energy in the pendulum (minus efficiency losses). When Stanton releases the pendulum, it will swing back down and offer the opportunity to harvest all of that energy (again, subtracting efficiency losses). But that harvesting part can be done in many ways.

The easiest way to do this would be to connect a dynamo to the axle the pendulum swings on. A dynamo is kind of like an electric motor running in reverse. Rotate the input shaft and the magnets spinning relative to the coil induce electric current in that coil.

In this case, Stanton followed that same basic principle, but “unfolded” the magnets to create something akin to a linear dynamo. In this arrangement, the pendulum is the magnet and it induces current in a series of coils each time it swings past them. That current could be used directly, but isn’t very substantial and so Stanton directed it towards capacitors that charge up over several swings.

The charged capacitors provided enough energy to power Stanton’s electromagnetic RC airplane launcher. That feels like an appropriate use case, because the launcher itself is almost like the linear dynamo running in reverse, so it all came around full circle — or rather, full-line.