| A photovoltaic pumped, closed-loop solar domestic hot water (SDHW) system was built and investigated experimentally. The SDHW system comprised two 1.2 m by 2.4 m flat plate collectors, a positive displacement vane pump driven by a permanent magnet direct current (D.C.) motor, a photovoltaic (PV) module and a shell-and-coil natural convection heat exchanger (S-C NCHE). Two pumps and two motors were tested to determine electrical and hydraulic performance. The collector flow rate and PV power were found to vary linearly with insolation. The pressure drop in the supply line, return line, collectors and heat exchanger were measured. The system was tested with the two collectors connected in parallel and series. The pressure drop across the collectors dropped significantly for parallel collectors and higher flow rates were obtained for each PV module tested. The optimum collector flow rate was found to be 0.2 L/min-m{dollar}sp2.{dollar} A 20 W{dollar}sb{lcub}rm P{rcub}{dollar} PV module was found to be appropriate for the SDHW system. The motor starting insolation level was determined for each PV module, pump and motor tested. The necessity of a linear current booster (LCB) in providing the required motor starting current was established.; Thirteen (13) PV modules ranging in size from 10 W{dollar}sb{lcub}rm P{rcub}{dollar} to 75 W{dollar}sb{lcub}rm P{rcub}{dollar} were mounted on the roof and connected to the experimental set up to operate the SDHW system. The performance of the PV modules was tested four times in four different seasons. The operating voltage and current as well as the open-circuit voltage and short-circuit current were tested for all PV modules. Different types of PV modules were found to degrade at different rates due to aging and temperature rise. |
