Abstract

Reverse osmosis (RO) systems have minimum energy consumption compared to other desalination methods and their energy consumption is only in the form of electric power. However, in addition to fresh water, many buildings and even many factories and industries also need air conditioning, which requires large amounts of energy. The aim of this study was to introduce a new method for combined cold and fresh water (CCW) generation by integration of a RO and a refrigeration system. In this new integrated system, the electrical power consumption of the pumps in the RO system was conserved by preheating the seawater through the waste heat recovery in the condenser of the refrigeration cycle. A further reduction in the electrical power demand of these pumps can be made by replacement of the expansion valve in the refrigeration cycle with a turbo expander. Related coding in energy efficient seawater (EES) software was used to study the feasibility study of the integration of the RO and refrigeration systems to co-generate 10 M³/day fresh water and 3 refrigeration tons of cooling as an illustrative example and the best state for this combined system was determined. The results confirmed that the proposed method provides a reduction of about 7.6% of the power consumption used in the separate production of fresh water and cooling.  

Key words: Reverse osmosis (RO), compression refrigeration cycle, seawater desalination, cogeneration, integration, energy saving.