A graphical method of measuring the performance characteristics of solar collectors

A graphical method to measure average and instantaneous efficiencies of a solar concentrator used for heating and boiling liquids and a flat plate collector is presented. The overall heat loss coefficient for the collectors and the optical loss factors: ϱγ(τa)b—the product for a concentrator and (τa)—the product for a flat plate collector, are also obtained. The method involves measuring the temperature of stagnated liquid in the absorber/collector as a function of time at noon. The efficiencies obtained are correct to within 5% of the efficiencies obtained from accurate measurements involving solar radiation data, the design parameters of collectors and the physical characteristics of the materials used in the fabrication of collectors.