Dezeen article explains. And it can also be charged by urine in emergency situations.
The portable device acts as a mini generator that produces light using ionization by filling it with 500 milliliters of seawater, the salt in the water reacts with magnesium and copper plates inside the device, converting it into electrical energy.
The device emits up to 45 days of light and can also be used to charge a mobile phone or another small electrical device via a USB port.
The WaterLight allows communities to continue to work in the dark. Source: E-Dina WaterLight
The WaterLight was created as part of a collaboration between E-Dina and creative agency Wunderman Thompson, which saw that locals in rural parts of Colombia specifically, the indigenous Wayúu tribe were struggling to keep the lights on at night.