Here is a a sustainable and useful idea for those living near the sea to use ocean water to get pure water. A clever design by Gabriel Diamanti gives 5 liters of fresh water from salt water. The method is very simple. He built a clay pot, a solar plate to heat and vaporize the salt water for desalination (vaporizing salt water) , a metal base and collecting vessel. Sun heats the salt water and condensation takes place. The water vapor is then collected at the bottom where it is cooler than on the top. This water is pure water and drinkable. Salt and other waste is cleaned out from the top for reuse of the same for more water. Five Liters of water can be collected on a good sunlight day. This idea should be made popular in our country since it is very cheap and effective way of collecting pure water in small scale by villagers. The following links gives you the pictures and the idea of how to build one for yourselves.
For more water related resources check the below websites.
For those students who want to do live projects the below resources gives you more ideas. Check them
Refrigeration by sunlight
Science daily carries a article on how sun’s rays are used for cooling food that is kept in a fridge. The process involves heating water to 200 degrees F and then uses the heat to drive a compressor that lowers the temperature of a refrigerant in the fridge. With very hot climate in India I think this is a good solution of keeping farmers vegetable and fruit crops fresh until they are sold in the market. This method is environment friendly, reduces the usage of electricity to minimum.
I’m hoping that somebody takes this idea to implementation stage. The details about this process can be read at http://www.sciencedaily.com/releases/2010/05/100503111531.htm
The MEDISCO project (Mediterranean food and agriculture industry applications of solar cooling technologies) has built several of these solar refrigeration plants in Mediterranean countries where sunshine is plenty. Engineers are using concentrating collectors to direct the sunlight onto an absorber that heats water. check more details at http://www.medisco.org/about/