https://www.amazon.com/Ruipu-24000ma...+phone+charger
Solar charger Ruipu 24000mah Portable Solar Power Bank With 3 USB Port External Battery Pack Phone Charger With 2 Flashlight and USB Fan For iPhone iPad Samsung HTC Cellphones Tablet And More-Yellow
The hydro generator would work in the dark. This won't. The solar paint idea for very low cost solar panels and new efficient li Ion battery packs seems better for places like in Africa and the tropics that get a lot of sunshine. Interesting concept based on a very old idea -- hydro-power. Continuous hydro-power generation is good as you need no battery storage.