Parametric study and thermal performance assessment of a new solar desalination unit coupled with heat pump

Developing conventional solar stills has been given a wide interest being a solution for the water shortage and world energy crises because of simplicity and low energy consumption. As a contribution to these innovation efforts, a 250 W heat pump unit was integrated with a single-slope solar distiller to provide two functions: heating the basin water (by a part of the heat pump condenser) and cooling effect for the extracted vapor from the distiller cavity (via the heat pump evaporator). The other part of the heat pump condenser is subcooled in a separate container via water. The effects of extracted vapor speeds (by varying the fan speed) and different subcooling container temperatures were studied to select the best performance for the modified distiller. The vapor speed tests included 4 variable speeds from 9.33 to 17 m/s. The selected vapor speed was 14 m/s due to its higher corresponding daily cumulative yield of about 10.14 L/m², which means a 152.63% increasing ratio than that of the reference distiller. Additionally, at a subcooling temperature range of 45 – 50 °C, the enhancement ratio increased to 158.5% with a daily water productivity of 10.263 L/m². The thermo-economic performance was also assessed. From the thermal performance point of view, augmentation ratios of 89.18% and 33.57% were obtained for energy and exergy efficiencies, respectively. Also, for the economic part, the results showed that the freshwater price was 0.0136$/L (for the modified device), which exhibits a reduction of 8.1% than that of the conventional distiller.