Abstract
A solar-driven membrane distillation system has been built and tested. The system uses PV panel for electricity and solar-thermal collector to generate heat for the operation of the membrane distillation unit to produce water. Hence, this sytem can be considered as a stand-alone system. In order to increase the performance of the MD unit in producing water, a heat pump was coupled with the MD unit. Two of one-day operation based tests were conducted using heat pump (i.e. WHP = With Heat Pump) and without using heat pump ((i.e. WoHP = Without Heat Pump). These two test were conducted to investigate the effect of the heat pump on the system. The test results show that the T.Feed of the WHP test sharply increased (in a very steep slope) from 18°C to about 45°C initially and stable at 49°C. In contrary, the T.Feed of the WoHP test only increase a little of about 6°C only. At higher T.Feed, the feed water will evaporate earlier and faster than at the lower one, which resulted in more production of distillate. While, T.Cond.IN for the WHP test were much lower than that of WoHP test. The temperature difference was approximately 5°C throughout the hours of test. The heat pump successfully increased the temperature of the feed water by pre-heating it and in the same time decreased the temperature of the condenser, especially T.Cond.IN. These two conditions (i.e. higher T.Feed and lower T.Cond.IN) have led to a higher distillate production rate. The results also show that the average distillate output rate of the WHP test was about 11.62 L/h, which is almost twice that of the WoHP test (i.e. 5.98 L/h). Additionally, the total distillate production of the WHP test was about 70.1 which is almost twice that of the WoHP test (i.e. 34.72 L).
