Abstract: The disclosed invention is a solar still utilizing recirculating air driven by natural convection to evaporate pure water from saline water. The pure water evaporated into the air is removed by a condenser and the condenser also cools the air thereby causing its density to increase. The air density difference within the still, due to temperature differences, causes the air to flow in the desired pattern. This natural convection may be augmented by a fan or fans, if desired, to increase the output of the still. The same air is continuously circulated thereby reducing the thermal losses that occur when moist air is removed from the still. A recirculating pump is the only mechanical device required when the still is in the natural convection mode of operation.

Abstract: A multi-purpose solar energy collector is disclosed. The collector is a flat plate type of collector that is designed to heat either air or water, or both, and is portable so that it can readily be moved from one place to another. In the air heating mode, the collector is ideally suited for drying grain. After the grain drying season, the collector can be converted to the liquid heating mode to heat agricultural process water or domestic water, for example. In the combined air-liquid heating mode, the collector can be used to provide both heated air and heated liquid.

Abstract: Recirculating natural convection solar energy collectors are disclosed. In one species of the invention, the collector comprises an insulated housing, a cover of glass or other suitable transparent material, a transparent plate of glass or other suitable material mounted inside said housing and spaced apart from the cover, a heat absorber mounted inside the housing and spaced apart from the transparent plate, an air separator mounted inside the housing and spaced apart from the absorber and cover, and a heat exchanger located inside the housing at the top of the housing. The heat absorber is made from a thin sheet of suitable material such as aluminum foil that has a surface coated with a heat absorbing material such as black paint, solar selective black chrome and the like. As the air inside the housing flows over the heat absorber, it is heated and rises to the top of the housing. The heat exchanger at the top of the housing absorbs heat from the hot air thereby cooling the air.