Caution – A Fresnel lens is powerful light-focusing lens that can produce temperatures over 700+ degrees. Great care must be used when working with these lenses.
Here is an interesting approach to boiling water for purity and then distilling it to remove salts and other impurities.
In this video we use a linear Fresnel lens to boil and distill salt water into drinking water. The goal is to use this simple technology to help people who don't have a clean water source, or live near the ocean and need to desalinate water for drinking and cooking.
http://youtu.be/xJ1qk3HuRiA