Solar Engineering of Thermal Processes, 4th Edition

Chapter 18

Solar Ponds: Evaporative Processes

In this chapter we start with a discussion of solar ponds. These are large, shallow bodies of salt water that are arranged so that the temperature gradients are reversed from the normal, that is, so the hottest layers are at the bottom of the ponds. This allows their use for collection and storage of solar energy, which may under ideal conditions be delivered at temperatures of 40 to above ambient. The first section is a description of ponds and their operation. The next is an introduction to analysis of the thermal performance of ponds (and thus might have been placed in Part I), and in the third section three applications are discussed.

At least two other methods have been noted for maintaining inverted temperature gradients by suppressing convection in ponds through the use of horizontal, vertical, or honeycomb membranes (Hull, 1980) and polymer gel layers (Wilkins and Lee, 1987). These are not treated here.

We then note three evaporative processes: distillation of salt water to produce freshwater, evaporation of salt brines to produce salt, and drying to remove moisture from solids. Evaporation for salt production and drying of crops are many centuries old and are the basis of commercial and agricultural enterprises in many parts of the world. A substantial body of know-how and design information has been developed on evaporation ...