The sun is the best source of renewable energy available. Solar energy is by far the most abundantly available energy source for this planet.
One way to trap solar energy is by using solar ponds. Solar ponds are large scale solar collectors that have an integral heat storage capability to provide thermal energy. In ordinary ponds, the sun’s rays heat water and this heated water rises upwards and loses its heat to the atmosphere. This results in the pond water remaining at atmospheric temperature. A solar pond dissolves salt in the bottom layer of the pond making the water too heavy to rise.
The solar pond has three zones. The topmost zone is the surface zone or the Upper Convective zone which has little salt content and is at atmospheric temperature. The middle zone is called the Non Convective zone where the salt content increases as the depth increases. Considering a particular layer in this zone, it can be observed that water cannot rise because the layer above this particular layer will have lesser salt content and will be lighter. Also water cannot fall from this layer because the layer below it has more salt content and is heavier. This zone therefore acts as an insulator that permits sunlight to reach the storage zone and also keeps it trapped there in the form of solar energy. The bottom most zone is the most salty one and is called storage zone or Lower Convective zone that collects and stores solar energy in the form of heat.
Solar ponds can be constructed anywhere economically.