The scheffler cooker is useful for institutional

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The Scheffler cooker is useful for institutional kitchens, hotels, etc. The typical cost of such a cooker is about Rs 40 000 and it yields a saving of 35 to 40 LPG cylinders per year. A series of such cookers can also be used to generate steam which can be used for cooking. Such installations have been made at a few places in India. It may be mentioned that Scheffler reflectors are also used to provide low pressure steam for industrial applications. The world's largest steam cooking system based on Scheffler reflectors has been installed at Tirumala Tirupathi Devasthanam, Andhra Pradesh. 3.13.8 Solar Ponds 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 used for various applications, such as process heating, water desalination, refrigeration, drying and power generation. 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 e.g. a hot air balloon. 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.
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35 A solar pond has three zones. The top zone is the surface zone, or UCZ (Upper Convective Zone), which is at atmospheric temperature and has little salt content. The bottom zone is very hot, 70° 85° C, and is very salty. It is this zone that collects and stores solar energy in the form of heat, and is, therefore, known as the storage zone or LCZ (Lower Convective Zone). Separating these two zones is the important gradient zone or NCZ (Non-Convective Zone). Here the salt content increases as depth increases, thereby creating a salinity or density gradient. If we consider a particular layer in this zone, water of that layer cannot rise, as the layer of water above has less salt content and is, therefore, lighter. Similarly, the water from this layer cannot fall as the water layer below has a higher salt content and is, therefore, heavier. This gradient zone acts as a transparent insulator permitting sunlight to reach the bottom zone but also entrapping it there. The trapped (solar) energy is then withdrawn from the pond in the form of hot brine from the storage zone. Though solar ponds can be constructed anywhere, it is economical to construct them at places where there is low cost salt and bittern, good supply of sea water or water for filling and flushing, high solar radiation, and availability of land at low cost. Coastal areas in Tamil Nadu, Gujarat, Andhra Pradesh, and Orissa are ideally suited for such solar ponds.
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