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Reverse electrodialysis (RED) represents one of the most promising membrane-based technologies for clean and renewable energy production from mixing water solutions. However, the presence of multivalent ions in natural water drastically reduces system performance, in particular, the open-circuit voltage (OCV) and the output power. This effect is largely described by the “uphill transport” phenomenon, in which multivalent ions are transported against the concentration gradient. In this work, recent advances in the investigation of the impact of multivalent ions on power generation by RED are systematically reviewed along with possible strategies to overcome this challenge. In particular, the use of monovalent ion-selective membranes represents a promising alternative to reduce the negative impact of multivalent ions given the availability of low-cost materials and an easy route of membrane synthesis. A thorough assessment of the materials and methodologies used to prepare monovalent selective ion exchange membranes (both cation and anion exchange membranes) for applications in (reverse) electrodialysis is performed. Moreover, transport mechanisms under conditions of extreme salinity gradient are analyzed and compared for a better understanding of the design criteria. The ultimate goal of the present work is to propose a prospective research direction on the development of new membrane materials for effective implementation of RED under natural feed conditions.

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Ethiopia is one of the fastest-growing economies in the world despite immense challenges towards access to sustainable energy supplies and modern energy technologies. The country is undertaking great effort towards the development of renewable energy technologies and green legacy. However, the largest share of energy consumption (≈87%) in Ethiopia is dominated by traditional fuels (charcoal, fuel wood, dung cakes, and agricultural residues) which pose various health and environmental risks. The country has an enormous amount of renewable energy potentials (e.g., solar, hydro, wind and geothermal), but only 5% of its full hydropower potential is exploited and others are not fully harvested or not well developed to date. This review paper provides a comprehensive assessment on renewable energy availability, potential, opportunity, and challenges in Ethiopia. We believe the information provided in this review will enlighten the current and future prospects of renewable energy deployment in Ethiopia.

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Membrane-based energy technologies are presently gaining huge interest due to the fundamental engineering and potentially broad range of applications, with economic advantages over some of the competing technologies. Herein, we assess the potential deployability of the existing and emerging membrane-based energy technologies (MEnT) in Ethiopia. First, the status of the current energy technologies is provided along with the active energy and environmental policies to shape the necessary research strategies for technology planning and implementation. Ethiopia is a landlocked country, which limits the effective extraction of energy, for instance, from seawater using alternative, clean technologies such as reverse electrodialysis and pressure retarded osmosis. However, there exists an excess off-grid solar power (up to 5 MW) and wind which can be used to drive water electrolyzers for hydrogen production. Hydrogen is a versatile energy carrier that, for instance, can be used in fuel cells providing zero-emission solutions for transport and mobility. Although Ethiopia is not among the largest CO2 emitters, with more than 90% energy supply obtained from waste and biomass, the economic and industrial growth still calls for alternative CO2 capture and use technologies, which are highlighted in this work. We believe that the present work provides i) the status and potential for the implementation of MEnT in Ethiopia ii) and basic guidance for researchers exploring new energy pathways toward sustainable development in developing countries. Ion-exchange membranes; fuel cells; electrolyzers; salinity gradient power; CO2 capture and use