If you thought that to solar lanterns can are expensive and that it needs a complicated process of manufacturing, then you are wrong!. Here is an article about how a group of students designed  solar lanterns from a PET bottle.All they need was an electric switch,a solar panel , a PET bottle filled with a special liquid and a bulb attached to the top half of the bottle.

Using a PET bottle, a solar panel and a switch, students of the Social Entrepreneurship and Consulting Cell (SECC) from Symbiosis Institute of Business Management (SIBM) have innovatively lit up homes of almost 75 villagers in Nande village. Now, they will do the same for others in Lavale, Chande and Mulkhed. These solar lanterns cost about INR 450 only.

Solar Lanterns -How does it work?

The students named it "Ashadeep" meaning light of hope.During the day, the bottle light does two things. It traps energy in its solar panel and can be used as a source of light as light is captured from the top half of the bottle and shines through the chemical liquid.

When the device is switched on, the solar energy is used to power an LED bulb that is positioned in the bottle. The light from the bulb is diffused through water to brighten up a home

source:http://www.punemirror.in