12-06-2014, 12:02 PM
SOLAR PONDS
SOLAR PONDS.ppt (Size: 1.11 MB / Downloads: 64)
INTRODUCTION
The sun is the largest source of renewable energy and this energy is abundantly available in all parts of the earth. It is in fact one of the best alternatives to the non-renewable sources of energy [1].
Solar energy has been used since prehistoric times, but in a most primitive manner. Before 1970, some research and development was carried out in a few countries to exploit solar energy more efficiently, but most of this work remained mainly academic [2].
After the dramatic rise in oil prices in the 1970s, several countries began to formulate extensive research and development programmes to exploit solar energy [2].
One way to tap solar energy is through the use of solar ponds. Solar ponds are large-scale energy collectors with integral heat storage for supplying thermal energy. It can be use for various applications, such as process heating, water desalination, refrigeration, drying and power generation [1]
WHAT A SOLAR POND IS
A solar pond is a body of water that collects and stores solar energy. Solar energy will warm a body of water (that is exposed to the sun), but the water loses its heat unless some method is used to trap it. Water warmed by the sun expands and rises as it becomes less dense. Once it reaches the surface, the water loses its heat to the airthrough convection, or evaporates, taking heat with it. The colder water, which is heavier, moves down to replace the warm water, creating a natural convective circulation that mixes the water and dissipates the heat. The design of solar ponds reduces either convection or evaporation in order to store the heat collected by the pond. They can operate in almost any climate [3].
WORKING PRINCIPLE
The solar pond works on a very simple principle. It is well-known that water or air is heated they become lighter and rise upward. Similarly, in an ordinary pond, the sun’s rays heat the water and the heated water from within the pond rises and reaches the top but loses the heat into the atmosphere. The net result is that the pond water remains at the atmospheric temperature. The solar pond restricts this tendency by dissolving salt in the bottom layer of the pond making it too heavy to rise [1]. You can see a shematic view of a solar pond in Figure 1.
APPLICATIONS
Salt production (for enhanced evaporation or purification of salt, that is production of ‘vacuum quality’ salt)
Aquaculture, using saline or fresh water (to grow, for example, fish or brine shrimp)
Dairy industry (for example, to preheat feed water to boilers)
Fruit and vegetable canning industry
Fruit and vegetable drying (for example, vine fruit drying)
Grain industry (for grain drying)
Water supply (for desalination) [4].
CONCLUSION
Solar ponds can be effectively used as replacements in industries that use fossil fuel to generate thermal energy. Solar ponds can be used for process heating, refrigeration, water desalination, production of magnesium chloride, bromine recovery from bittern, enhancement of salt yield in salt farms. It will be the future energy source.