Investigation of the thermal performance of a solar absorber and nocturnal radiator (SAANR) hybrid panel for summer and winter seasons

Transient analysis and performance prediction of a solar absorber and nocturnal radiator (SAANR) hybrid panel for water heating and cooling in the summer and winter seasons of Gaborone, Botswana is presented. Transient heat transfer models were developed for the panel and the models were then transformed into explicit finite difference forms for numerical analysis using MATLAB. The SAANR panel added up to 7 kWh diurnal heating energy in winter and removed up to 0.5 kWh at night through radiation cooling in summer. The resulting numerical solutions of the model were validated by comparison with experimental results and they showed excellent strength of association with a correlation coefficient of 0.832 and fairly acceptable goodness of fit at an R-squared value of 69%. Sensitivity analysis carried out showed the model to react linearly to panel area changes. From the results, it is concluded that the hybrid panel is robust enough to perform in both the summer and winter seasons of Gaborone, and areas with similar climatic conditions. This implies that the system can be used simultaneously for space cooling and domestic water heating in both summer and winter. This technology can therefore be used instead of electric water heaters and air-conditioners and thus save energy.