A Simplified Test for Solar Water Purification

Pure water is one of the most important resources the country has; however, as the demand for water increases, its availability is decreasing. Recent court actions to force states to export ground water graphically illustrate the competition for this diminishing resource. The depleting of the Ogallala aquifer and the accompanying loss of valuable irrigated farmland is another example of the serious pure water problems facing New Mexico and the country.

Vast quantities of brackish and salt water are available; however, the normal purifying techniques such as reverse osmosis, electrodialysis, and, to a minor extent, evaporating salt ponds are not sufficiently economical except where the demand outweighs price considerations.

In this project, “A Simplified Test for Solar Water Purification,” conducted by the New Mexico Solar Energy Institute, on-hand equipment was used to determine if a solar-driven, low-pressure system would be technically and economically practical. This technique used a low-cost unglazed FAFCO solar panel as a heater during periods of insolation and as a vapor condenser during cooler periods of no insolation. It used a 30-gallon insulated hot water tank for water storage. The test sequence used domestic water in the tank to simulate brackish, gray, or salt water. Plumbing was added to allow solar heating of the water via thermosiphon and nocturnal low-pressure evaporation by means of a hydrostatic column of water.