Integration of Electrodialysis with Renewable Energy Sources for Sustainable Freshwater Production

This thesis performs an analysis on electrodialysis for desalination and its integration with renewable energy systems. Firstly, a literature review is performed, which summarizes the fundamental concepts of electrodialysis and its integration with renewable energy sources. It covers photo electrodialysis, photovoltaic-assisted electrodialysis, reversible electrodialysis and wind energy-driven electrodialysis. Secondly, a thermodynamic model of a combined photo-electrodialysis-chloralkali system for desalination is developed. The waste brine stream from an electrodialysis unit is sent to a chloralkali reactor to produce H2, Cl₂, and NaOH. Photoactive materials and photovoltaic panels are utilized to provide the required energy for the process. The specific energy requirements for the electrodialysis and chloralkali units are found to be 1.225 kWh/m³ of freshwater and 2.5 kWh/kg Cl₂. The overall combined system energy and exergy efficiencies are found to be 23.93% and 33.14%, respectively. Additionally, a solar pond-assisted reverse osmosis-electrodialysis system to produce freshwater and a hydroponic fertilizer solution for sustainable desalination and waste recovery is designed and thermodynamically modelled. The electrodialysis unit is integrated to recover Mg²⁺, Ca²⁺ and SO₄^2- ions from the reverse osmosis waste. A solar pond with an organic Rankine cycle is also integrated to produce the electricity required. The overall energy and exergy efficiencies of the integrated system are found to be 20.36% and 2.546%, respectively. Finally, a life cycle assessment is carried out on a photo-electrodialysis process to quantify the environmental impacts for producing 1 m³ of freshwater. The life cycle impact assessment results are found to be 0.127 kg CO2-Eq, 6.41 x 10^-4 kg SO₂-Eq, 4.04 x 10^-5 kg phosphate-Eq, 1.01 x 10^-3 kg DCB-Eq and 33.7 kg DCB-Eq for global warming potential, acidification, eutrophication, freshwater aquatic ecotoxicity and marine aquatic ecotoxicity, respectively. Finally, a sensitivity analysis is performed to observe how various energy inputs (conventional and renewables) into the process affect the selected environmental impacts.