Energy assessment of a dish-Stirling system powering a reverse osmosis plant for seawater desalination

Abstract

Water scarcity in many regions of the world and the global demographic growth make the desalination of seawater and/or brackish an effective solution to meet the growing demand for freshwater. Nowadays, reverse osmosis has the largest share of the global installed desalination capacity. The impelling need to reduce greenhouse gas emissions has been pushing the search for sustainable technologies to produce the electricity needed to power reverse osmosis plants. Among solar technologies, little attention has been paid to the possibility of powering reverse osmosis with electricity from the dish-Stirling concentrator. To fill this knowledge gap, this paper assesses the energy-saving potential of a reverse osmosis plant coupled with a cogenerative dish-Stirling concentrator on a small island in the Mediterranean Sea. A model of the integrated systems was developed based on data measured on a real dish-Stirling concentrator, and variation of the energy consumption of the reverse osmosis plant with the temperature of the feedwater solution was also accounted for. Hourly simulations showed that almost 36% of the annual water demand could be covered by driving the plant using electricity from the concentrator, and the solar fraction of the electricity consumed by the reverse osmosis plant accounted for 57%. Finally, the analysis revealed that only a 1% decrease in solar fraction resulted when the heat recovered from the concentrator is not used for the feedwater preheating.