Ever thought of the benefits of saving 2 liters of water? Well beside the hundreds of reasons previously listed all over the internet, people looking to reduce their electricity bill now have a reason to store some water.

This Brazilian engineer found a way to light up rooms while reduce electricity bills in countries which come across the sun by simply filling up clear-colored plastic soda bottles with water. All which remains is placing the water-filled bottles in holes drilled in the roof and allow the sun to refract into the room. Of course, this doesn't replace light bulbs, but can be used in a tag-team game: bottles with the sun, bulbs with the moon.