Technical feasibility comparison of off-grid PV-EDR and PV-RO desalination systems via their energy consumption

Abstract

To explore the techno-economic feasibility of powering remote, rural desalination systems with renewable energies, this study conducted pilot-scale experimental work and software modeling to identify the energy consumptions of two common brackish water desalination technologies – electrodialysis reversal (EDR) and reverse osmosis (RO) – when operated with different water salinities, flow rates, and temperatures. The pilot-scale experiments were conducted in parallel at the Brackish Groundwater National Desalination Research Facility in Alamogordo, New Mexico; for the software modeling, WATSYS software was used for EDR, and WinFlows software was used for RO. The experimental results showed that product flow rate and the salinity of feed water significantly affected the specific energy consumptions (SECs) of EDR and RO. The SEC of EDR is more sensitive to feed water salinity variations, as compared to the SEC of RO. The SEC sensitivities of EDR and RO to product flow rate were slightly different. The SEC of EDR was not significantly influenced by temperature variations, while the SEC of RO was affected significantly by temperature variations. With the energy requirements for these systems identified under a range of operating conditions, HOMER software was used to identify optimal renewable energy systems for powering the desalination technologies under each combination of operating conditions. Lastly, the total net present cost of each renewable energy system was calculated, and the most economical systems were identified. As determined by measured energy consumption and modeled energy production, solar energy can feasibly power off-grid ED/EDR and RO systems in regions with meteorological conditions similar to Alamogordo, New Mexico. For low-salinity water with solar power, EDR was far more efficient than solar-powered RO, with a total net present cost difference of 48–159%, if the blending is not an option for RO. For higher-salinity water, solar-powered RO was more efficient than solar-powered EDR, with a lower total net present cost.