A strange renewable energy source

We don’t normally think of gravity as a renewable energy source, but gravity is what enables the harnessing of hydroelectric power.

Water falls due to gravity, it is then directed into a pipe that increases its pressure and is finally run through a turbine that drives a generator to extract energy from it.

There are also other systems for extracting energy from gravity. For example, Gravity Light is a lamp designed for third-world countries that works with just the use of a 12-kg weight, a dynamo and a speed-reducing gear, and it is able to supply light for 25 minutes on a single charge.

The design’s underlying principles are very similar to those of a weight-driven cuckoo clock or grandfather clock, where the weight’s potential energy is instead transformed into photons, rather than kinetic energy.