In this work a self-contained solar heating forced water cooling unit was selected and assembled. It consists of three flat-plate solar collectors, each of area 1.2 m2, a d.c. pump, a photovoltaic module and a storage tank. The electrical power produced by the photovoltaic module operates the d.c. pump, which circulates the cooling water through the solar collectors to transfer the heat to the storage tank. The electrical voltage and current, the water rate of flow, and water temperature at inlet and outlet of the collector were all measured. Solar irradiation, wind speed and ambient temperature were also measured. Daily distribution of electrical current, water mass rate of flow, module efficiency and collector efficiency were plotted in figures. Module efficiency, pump efficiency and collector efficiency were taken as dependent variables, while the solar irradiation, ambient temperature and time were the independent variables. Optimum values were graphically indicated and related to each other in a clear discussion. An economic study and comparison of three different systems were carried out: a common thermosyphon system; an a.c. pump circulating system; and this system, which is a d.c. pump circulating system. Results revealed that collector efficiency reached a daily average value of 47% due to d.c. pump installation powered by photovoltaic electric output.
