The power of salinity gradients

Abstract

The development and exploitation of sustainable and environmentally friendly energy sources are required in order to resolve global energy shortages and to reduce the reliance of many countries on fossil fuel combustion. Salinity gradient energy has been considered a potential candidate for renewable energy due to the abundance of saline waters that could be combined with less saline solutions across the globe. Pressure Retarded Osmosis (PRO) is one of the technologies to harness salinity gradient energy. Apart from zero carbon dioxide emission, PRO is capable of producing power with less periodicity, abundance and low environmental impacts. One of the preconditions for the technical and financial feasibility of PRO, however, is the development of a PRO-specific membrane - one that meets the conditions that none of the current commercially-available membranes have met so far. The current paper discusses the progress made in PRO membrane development, particularly during the past decade, and analyses the challenges that are still hindering the implementation of PRO at large scales. Also, this paper explores possibilities for the implementation of PRO by analysing various combinations of existent solutions of various salt concentrations. Australia has been chosen to demonstrate some potential applications of PRO. This vast country has extensive reserves of saline waters that could be paired with less concentrated solutions to generate power. For each combination of solutions, a conceptual idea is presented, and an estimate of power production is given. Also, advantages and disadvantages of each scheme are discussed. The ideas and estimates can be easily extrapolated, with minor adjustments, to other countries with similar conditions. It is hoped that this publication will be valuable to those nations that have similar policies as Australia's, with government incentives for the development and implementation of new technologies to explore new renewable energy sources.