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SOLAR PONDS AND ITS APPLICATIONS
PREPARED BY-KUNAL S. MAHAJAN
BE ELECTRICAL, GCOE, JALGAON.
INDEX
INTRODUCTION SOLAR POND WORKING PRINCIPLE ADVANTAGES DISADVANTAGES APPLICATIONS REFRENCES
INTRODUCTION
As we know SOLAR energy is widely freely available, and is said to be future energy as it is renewable energy.
Solar energy is free ,but the devices and methods of storing solar thermal energy are very expensive.
Had you ever thought of storing the solar thermal power without any expensive solar storage devices?
SOLAR POND, is a one of method for trapping and storing solar energy and using it later as the input for thermal power generation plant.
What is a solar pond?
A pool of saltwater which acts as a large-scale solar thermal energy collector
It includes an integral heat storage for supplying thermal energy
Solar pond 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 air through 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.
Construction We know that fluids such as water and air rise up when
heated. Solar ponds stops this process when large quantity of salt
are dissolved in hot bottom layer of the pond, making it too dense to rise to surface and cool down.
Solar pond consists of three main layers. The top layer is cold and has little salt content. The bottom layer is hot,70-80°C , and very salty.
Separating these two layers is important gradient zone. In this salt content increases with increase in depth. Water in gradient zone can’t rise, because water above it has less salt content and is therefore lighter.
Similarly, water can’t fall because water below it has a higher salt content and is heavier.
Thus the stable gradient zone act as a transparent insulator, permitting sunlight to be trapped in the hot bottom layer, from which useful heat is withdrawn.
Working
When solar radiation strikes the pond, most of it is absorbed by the layer at the bottom of the pond.
The temperature of the dense salt layer therefore increases. If the pond contained no salt, the bottom layer would be less
dense than the top layer as the heated water expands. The less dense layer would then rise up and the layers would mix.
But the salt density difference keeps the ‘layers’ of the solar pond separate.
The denser salt water at the bottom prevents the heat being transferred to the top layer of fresh water by natural convection, due to which the temperature of the lower layer may rise to as much as 95°C.
Heat Extraction
For application purpose heat is to be extracted from bottom layer of the pond.
Pumping the brine i.e. saturated hot salt water through an external heat exchanger or an evaporator removes the heat from the bottom layer.
In an heat exchanger there is inlet of cold water and outlet for hot water.
This hot water is then used for various applications, such as thermal power plant, dairy plants,etc.
Solar Pond In Electric Circuit
Energy-Cost Comparison
Advantages
Environment friendly energy – no pollution! Reliable energy source. Stores heat, so it can be used 24*7*365. Can be constructed according to requirements. Low maintenance costs.
Disadvantages
Low efficiency Space availability Salt and water supply needed Low efficiency due to: Heat losses Bottom losses Top losses Radiation losses
Solar Ponds In India
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 Grain industry (for grain drying) Water supply (for desalination) .
References
G.D.Rai,Khanna Publication, 'Energy Sources’. Enersalt website (2011) Solar pond. Available at:
http://www.enersalt.com.au/Local%20Publish/html/more_info.html (Accessed: Mar. 2011)
http://www.ece.utep.edu/research/Energy/Pond/pond.html http://journals.tubitak.gov.tr/physics/issues/fiz-98-22-6/fiz-22-6-6-
97061.pdf http://www.teriin.org/case/solar.htm
For more info contact [email protected]
