Process Heat
_____________________________________________________________________________________________

Solar thermal technologies can provide process heat for drying food and clothes, driving high temperature chemical reactions and melting metals.

A solar pond is a pool of salt water (usually 1-2 meters deep) that collects and stores solar energy. Solar ponds were first proposed by Dr. Rudolph Bloch in 1948 after he came across reports of a lake in Hungary in which the temperature increased with depth. This effect was due to salts in the lake's water, which created a "density gradient" that prevented convection currents. A prototype was constructed in 1958 on the shores of the Dead Sea near Jerusalem.

The pond consisted of layers of water that successively increased from a weak salt solution at the top to a high salt solution at the bottom. This solar pond was capable of producing temperatures of 90 °C in its bottom layer and had an estimated solar-to-electric efficiency of two percent. Current representatives of this technology include a 150 kW pond in Ein Bokek, Israel, and another used for industrial process heat at the University of Texas El Paso.

Transpired air collectors are highly efficient and cost effective.Salt evaporation ponds use solar energy to concentrate brine solutions used in leach mining, remove dissolved solids from waste streams, or obtain salt from sea water. An evaporation pond consists of a shallow layer of water that can evaporate at a rate of 3-6 mm/day. The use of evaporation ponds to obtain salt from sea water is one of the oldest applications of solar energy, and evaporation ponds remain one of the largest commercial applications of solar energy used today.[46]

A transpired air collector is a perforated sun-facing wall first introduced in the early nineties. The wall absorbs sunlight and pre-heats air as much as 22 °C as it is drawn into the ventilation system. These systems are highly efficient (up to 80 percent) and can pay for themselves within 3 to 12 years in offset heating costs. Representatives include an 860 m² collector in Costa Rica used for drying coffee beans and a 158 m² collector in Quebec, Canada used for drying chicken manure.