照亮貧窮的太陽燈 Plastic Bottle Solar Lamp

This is the thing I want to do some time ago - collect innovative ideas.
I am so amazed by the concept of using secondary school physics - Snell's Law and total internal reflection, to make a solar lamp using plastic bottle (though it is not a new thing already). It is an excellent teaching materials for physics students.
Like a mirror used to collect sunlight and reflect on an object to set fire, the plastic water bottle serves as a means to collect sunlight as well.

Through multiple reflections and different paths caused by Snell's Law refraction and internal reflection, light spreads out as it passes through the water column. There should be lots of improvement, to optimize the design and customize to different places. The problem is still how to store the energy.
This project(Liter of light) started in 2002 by Alfredo Moser from Brazil and is has spread throughout the world, especially Philippines.

Source: Alfredo Moser: Bottle light inventor proud to be poor, Solar bottle Superhero