A theoretical analysis of solar collector/storage panels

A theoretical model for the evaluation of the transient performance of combination solar energy collection and heat storage panels is derived and analyzed. Beginning with the MIT II House (1947) and including several houses built in the 1960's by the CRNS Solar Energy Laboratory in Odeillo, France, published experimental studies of CS systems have shown considerable variance in determined operating effectiveness. Economic advantages have led to commercial exploitation of these systems, although design criteria are absent from the literature.

Use is made of an analytical method for determining fully developed natural convection in a vertical, symmetrically heated channel derived by Ostrach (1952), further developed by Bodoia and Osterle (1962), and modified and empirically verified for simple, uniform, asymmetrically heated boundary conditions by Aung (1972). This method is then further expanded for use with numerically implicit boundary conditions involving glazing wall heat conduction. A simulation program is used to establish CS panel operating characteristics and design criteria for performance optimization.

Results indicate that solar thermal efficiencies of up to approximately five percent are obtainable during mild weather with useful heat being recoverable up to about 50 percent of the time, depending on ambient temperature, selected design criteria, and incident solar energy. In cooler weather, excessive heat loss out of the cover glazing prevents any useful heat gain from being obtained.