In 2009, two designers began working on a battery-free lamp, their idea led to a device powered by a bag of rocks

Martin Riddiford and Jim Reeves, two British designers, began looking for a cheaper way to bring light to families living without reliable electricity, in 2009. So, GravityLight was later developed by them, which was a device that generated electricity as a heavy bag slowly descended. It did not rely on sunlight, batteries, or a connection to the electricity grid, the lamp used gravity to produce light.

It offered an alternative to kerosene lamps. This whole idea later developed into nowlight.

The journey of the idea

The UK charity SolarAid bought the problem of kerosene lighting to the attention of Riddiford and Reeves in 2009.


The designers decided to explore human power instead. Their work led to GravityLight, which used a raised weight to generate electricity.

How did a bag of rocks power a lamp?

A simple mechanism was used by GravityLight to turn the movement of a falling weight into electricity.

A bag with around 12 kg of material was filled, and as the bag slowly descended, it turned a series of gears connected to a generator.

The generator produced electricity to power LED lights. The system was designed to provide around 20 minutes of light from a single lift of the weight.

GravityLight needed to installed about 1.8 metres above the ground to give the bag enough room to descend. The device produced just under 0.1 watts of electricity, generating light equivalent to 16 lumens.

Batteries or sunlight were not needed for the system to operate. This made it suitable for places where electricity was not consistently available.

How did the designers test their invention?

A working GravityLight prototype was produced in November 2012. The team then used crowdfunding to support further development, manufacturing and trials with families living without electricity in Africa and Asia.

The first crowdfunding campaign attracted 6,219 supporters within 30 days and raised more than seven times its original target, according to the Queen Elizabeth Prize for Engineering.

The team also gathered feedback from users across 26 countries. More than 90% of respondents said they would use GravityLight instead of a kerosene lamp.

Why did GravityLight evolve into nowlight?

As the project developed, the team found that many users also wanted a way to charge their mobile phones. Meanwhile, rechargeable batteries and solar panels were becoming less expensive.

The product had to be later given another thought by the designers. So, nowlight was developed, as they did not wanted to rely on a falling weight, which used a hand-over pulling mechanism connected to a rechargeable lithium-ion phosphate battery.