PPT OF SOLAR POND

SOLAR PONDS: 

SOLAR PONDS SUBMITTED BY Ankita churoria Roll no:085568 HERTAGE INSTITUTE OF TECNOLOGY

INTRODUCTION: 

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 . 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.

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After the dramatic rise in oil prices in the 1970s, several countries began to formulate extensive research and development programmes to exploit solar energy. One way to t r ap solar energy is through the use of solar ponds. Solar ponds are large-scale energy collectors with integral heat storage for supplying thermal energy .

WHAT A SOLAR POND IS:-: 

WHAT A SOLAR POND IS :- A solar pond is a body of water that collects and stores thermal energy. A solar pond can be used for various application such as process heating desalination, refrigeration, drying, and solar power generation .

WORKING PRINCIPLE: 

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 . You can see a shematic view of a solar pond in Figure 1.

Fig. 1 Shematic View Of A Solar Pond.: 

Fig. 1 Shematic View Of A Solar Pond.

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The solar pond possesses a thermal storage capacity spanning the seasons. The bottom of the pond is generally lined with a durable plastic liner made from material such as black polythene and hypalon reinforced with nylon mesh.Salts like magnesium chloride, sodium chloride or sodium nitrate are dissolved in the water, the concentration being densest at the bottom (20% to 30%) and gradually decreasing to almost zero at the top. Typically, a salt gradient solar pond consists of three zones.

The Three Zones: 

The Three Zones An upper convective zone of clear fresh water that acts as solar collector/receiver and which is relatively the most shallow in depth and is generally close to ambient temperature, A gradient which serves as the non-convective zone which is much thicker and occupies more than half the depth of the pond. Salt concentration and temperature increase with depth, A lower convective zone with the densest salt concentration, serving as the heat storage zone. Almost as thick as the middle non-convective zone, salt concentration and temperatures are nearly constant in this zone.

TYPES OF SOLAR PONDS: 

TYPES OF SOLAR PONDS There are two main categories of solar ponds : nonconvecting ponds, which reduce heat loss by preventing convection from occurring within the Pond convecting ponds, which reduce heat loss by hindering evaporation with a cover over the surface of the pond.

NONCONVECTING SOLAR PONDS: 

NONCONVECTING SOLAR PONDS Classification S alt gradient :- A salt gradient pond has three distinct layers of brine of varying concentrations. Because the density of the brine increases with salt concentration, the most concentrated layer forms at the bottom. Membrane pond :-It inhibits convection by physically separating the layers with thin transparent membranes. As with salt gradient ponds, heat is removed from the bottom layer .

Fig. 2 Salt Gradient Solar Pond.: 

Fig. 2 Salt Gradient Solar Pond.

PROCESS : 

PROCESS As sunlight enters the pond, the water and the lining absorb the solar radiation. As a result, the water near the bottom of the pond becomes warm up to 93.3°C. Although all of the layers store some heat, the bottom layer stores the most. Even when it becomes warm, the bottom layer remains denser than the upper layers, thus inhibiting convection. Pumping the brine through an external heat exchanger or an evaporator removes the heat from this bottom layer. Another method of heat removal is to extract heat with a heat transfer fluid as it is pumped through a heat exchanger placed on the bottom of the pond.

APPLICATIONS: 

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).

Desalination : 

Desalination Drinking water is a chronic problem for many villages in India. In remote coastal villages where seawater is available, solar ponds can provide a cost-effective solution to the potable drinking water problem. Desalination costs in these places work out to be 7.5paise per litre, which compares favourably with the current costs incurred in the reverse osmosis or electrodialysis/desalination process.

Refrigeration : 

Refrigeration Refrigeration applications have a tremendous scope in a tropical country like India. Perishable products like agricultural produce and life saving drugs like vaccines can be preserved for long stretches of time in cold storage using solar pond technology in conjunction with ammonia based absorption refrigeration system.

BHUJ SOLAR POND: 

BHUJ SOLAR POND It was the first experiment in India, which successfully demonstrated the use of a solar pond to supply heat to an actual industrial user. The 6000-square-metre solar pond in Bhuj, the first large-scale pond in industrial environment to cater to actual user demand, supplied totally about 15 million litres of hot water to the dairy at an average temperature of 75 ° C between September 1993 and April 1995.

Fig. 3 The Bhuj Solar Pond.: 

Fig. 3 The Bhuj Solar Pond .

ADVANTAGES: 

ADVANTAGES Low investment costs per installed collection area. Thermal storage is incorporated into the collector and is of very low cost. Very large surfaces can be built thus large scale energy generation is possible . They are environmental friendly. Cost free operation.

DISADVANTAGES: 

DISADVANTAGES The evaporated surface water needs to be constantly replenished. Expensive cleaning of large collector surfaces in dusty areas is avoided. It requires a flat open area of land which is exposed to sunlight to produce maximum energy. The accumulating salt crystal is to be removed which is expensive.

CONCLUSION: 

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.

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