A novel methodology of round-year thermal performance evaluation for solar heaters in real weather conditions

Abstract

Currently, there is limited information regarding the performance of solar heaters in a round-year period under real weather conditions and the determination of their characteristic equation following standard methods. Therefore, this study presents a methodology to determine the characteristic equation of the annual thermal performance under real conditions based on uncertainty and linear regression analysis estimation. With this methodology, it is possible to analyze daily experimental data in a collector that has not been restricted to any particular requirement of evaluation standards. This methodology was applied to evaluate a flat plate solar heater operating in Mexico over a period of one year in two operating modes: thermosyphon and forced circulation. In the case of forced circulation, a small submersible pump was implemented, the activation of which was controlled by using a thermostat, thereby providing an effective control of the flow and temperature of the collector. The results indicated that the methodology was adequate to identify the level of uncertainty in a line of the best fit, which allowed the determination of a characteristic equation that reflects the operation of the heater under real conditions, in a round-year period. As a result of the application of this methodology, it was observed that the use of a submersible pump and a thermostat increases the efficiency throughout a whole year by 0.06, whereas the continuous use of a pump increases efficiency by 0.17, with respect to the operation in the thermosyphon mode.