The United Kingdom has developed a LED Gravity Light recently to solve the lighting problem in the lack of power supply area.
The users only need to raise a twenty pounds( about 9 kg) bag up, then the LED gravity light can work 30 minutes continuously. The gravity light doesn't need charging or other energies, which means it can work without consuming cost.
In addition, the lighting unit can charge for other equipments, such as the radio and rechargeable batteries. The users only need to connect the equipments to the light's interface to adjust the brightness and extend the lighting time according the different needs.