Energy and exergy analyses of a solar PV/T driving hybrid reverse osmosis-thermal distillation system

Abstract

Solar desalination holds significant promise for providing freshwater to remote and off-grid areas, which includes solar thermal distillation (STD) and solar photovoltaic reverse osmosis (PV-RO). To achieve higher efficiency via full-spectrum utilization of solar energy, this paper proposes a hybrid reverse osmosis-thermal distillation system driven by a solar photovoltaic-thermal collector (PV/T-RO-TD). To evaluate the conversion of solar energy, electrical energy, thermal energy and chemical energy in these three systems, both the first-law and second-law based analyses are adopted. Results show that while PV/T-RO-TD systems only have moderate energy and exergy efficiencies in the desalination process, it achieves better utilization of solar energy. Meanwhile, the energy and exergy efficiencies are 83%, 81%, 13%, and the exergy efficiencies are 20%, 3%, 13% in the solar harvesting process of PV/T-RO-TD, STD, and PV-RO, respectively. In addition, the specific water productivity under one-sun of 26.94–73.92 L/m2 h in the PV/T-RO-TD system surpasses it in STD and PV-RO systems, which are 3.79–9.89 L/m2 h and 22.74–69.63 L/m2 h, respectively. With better performance, the PV/T-RO-TD system can be regarded as an effective choice for boosting the water productivity of solar desalination.