Feasibility and design of solar-powered electrodialysis reversal desalination systems for agricultural applications in the Middle East and North Africa

Abstract

This paper presents photovoltaic-powered electrodialysis reversal (PV-EDR) as a promising desalination technology for agricultural applications in the Middle East and North Africa (MENA). Water scarcity in MENA has led to reliance on brackish water for irrigation of crops. Irrigating crops with high salinity water causes a host of problems including decreased yield and soil degradation. Current solutions are water and energy intensive, leading to overextraction of renewable water resources as well as overreliance on fossil fuels for electricity, which is expensive. Market research in MENA and interviews conducted with farmers in Jordan led to the conclusion that energy cost is the most significant issue facing small-scale desalination systems for agriculture in MENA. PV-EDR was chosen as an improved desalination architecture to meet the needs of farmers by reducing energy costs compared to on-grid reverse osmosis (RO) systems that are currently employed in MENA. A novel time-variant (TV) operational approach is presented for continuous PV-EDR wherein flow rate and EDR stack voltage are varied based on the available solar irradiance such that desalination power matches available solar power throughout a day. This results in a variable product salinity throughout the day, but the presence of large water reservoirs on MENA farms ensures that irrigation water is adequately mixed before being sent to crops. The TV approach enables low-energy, continuous, solar-powered desalination without the need for batteries. Given a case study in Jordan, a TV-PV-EDR system was conceptually designed and compared to current benchmark RO systems in relation to capital cost, energy cost, and total lifetime cost via a theoretical techno-economic analysis. TV-PV-EDR was found to have a levelized cost of water ($/m3) that is 24 % less than current RO systems despite having a larger capital cost. TV-PV-EDR has the potential to provide a mechanism through which more energy-efficient, higher recovery desalination for agriculture can be achieved.