Integration of a Solar Parabolic Dish Collector with a Small-Scale Multi-Stage Flash Desalination Unit: Experimental Evaluation, Exergy and Economic Analyses

Abstract

In this study, a small-scale two-stage multi-stage flash (MSF) desalination unit equipped with a vacuum pump and a solar parabolic collector (PDC) with a conical cavity receiver were integrated. To eliminate the need for heat exchangers, a water circulation circuit was designed in a way that the saline feedwater could directly flow through the receiver of the PDC. The system’s performance was examined during six days in July 2020, from 10:00 a.m. to 3:00 p.m., under two distinct scenarios of the MSF desalination operation under the vacuum (−10 kPa) and atmospheric pressure by considering three saline feedwater water flow rates of 0.7, 1 and 1.3 L/min. Furthermore, the performance of the solar PDC-MSF desalination plant was evaluated by conducting energy and exergy analyses. The results indicated that the intensity of solar radiation, which directly affects the top brine temperature (TBT), and the values of the saline feedwater flow rate have the most impact on productivity. The maximum productivity of 3.22 L per 5 h in a day was obtained when the temperature and saline feedwater flow rate were 94.25 °C (at the maximum solar radiation of 1015.3 W/m2) and 0.7 L/min, respectively, and the MSF was under vacuum pressure. Additionally, it was found that increasing the feedwater flow rate from 0.7 to 1.3 L/min reduces distillate production by 76.4% while applying the vacuum improves the productivity by about 34% at feedwater flow rate of 0.7 L/min. The exergy efficiency of the MSF unit was obtained as 0.07% with the highest share of exergy destruction in stages. The quality parameters of the produced distillate including pH, TDS, EC and DO were measured, ensuring they lie within the standard range for drinking water. Moreover, the cost of freshwater produced by the MSF plant varied from 37 US$/m3 to 1.5 US$/m3 when the treatment capacity increased to 8000 L/day.

Solar desalination: A review of recent developments in environmental, regulatory and economic issues

“…For water production of 100, 1000 and 50,000 m 3 /day, the associated costs were 12, 1.7, and 0.9 $/m 3 . This was a 93% reduction because of scaling up and was like that reported by Babaeebazaz et al, [51].…”

“…The economics of integrating a solar parabolic collector (PDC) with small-scale MSF desalination plant was examined by Babaeebazaz et al, [51] (Figure 7). The technical part was optimized by varying feedwater flow rates and utilizing vacuum pressure.…”

“…The wood also acts as a thermal insulator which reduces heat loss in the system. (from Dong et al, [31]) (adapted from Babaeebazaz et al, [51])…”

“…Stream flows throughout the MSF desalination unit (0: Feedwater, 1-2: Preheated feedwater, 3-4: Hot water at TBT, 5-6: Discharged brine, 7-8: Produced distillate water). (adapted from Babaeebazaz et al,[51])…”

Enhancing Fresh Water Production in Solar Parabolic Dish Desalination System

“…The solar parabolic dish desalination system was evaluated based on the experimental data obtained during the testing phase. The system's performance was measured in terms of solar radiation intensity, water production, and efficiency [16].…”