Multi-objective design of reverse osmosis plants integrated with solar Rankine cycles and thermal energy storage

This paper addresses the optimal design of desalination plants that integrate reverse osmosis, a Rankine cycle, parabolic trough solar collectors and thermal energy storage (TES). A multi-objective mixed-integer nonlinear programming model (MINLP) is developed to model such an integrated system and optimize its design and operating conditions according to economic and environmental metrics. The model considers the simultaneous minimization of cost and environmental impact given a specific water demand to be fulfilled. The environmental performance is quantified via life cycle assessment (LCA) principles. Particularly, the CML 2001 methodology, a widely used LCA-based framework, is used to assess the impact, enabling the identification of the main sources of damage across the entire life cycle of the plant. The capabilities of our method are illustrated through its application to a case study considering weather data in Tarragona (Spain). We show that coupling seawater desalination with solar collectors and thermal energy storage leads to significant environmental savings at a marginal increase in cost.The authors would like to acknowledge financial support from the Spanish Government (DPI2008-04099, ENE2011-28269-C03-03, ENE2011-22722, CTQ2009-14420-C02) and to thank the Catalan Government for the quality accreditation given to their research groups SUSCAPE and GREA (2009 SGR 545, 2009 SGR 534)