An efficient combination of transcritical CO2 refrigeration and multi-effect desalination: Energy and economic analysis

This paper presents a novel combination of transcritical carbon dioxide refrigeration with Boosted-MED (Multi-Effect-Desalination) system to provide cooling and fresh water simultaneously. In the combined system a part of gas cooler in refrigeration system is replaced by the first effect and Booster module of Boosted-MED; so that a significant amount of waste heat would be recovered. Thermodynamic and economic analyses are carried out in order to investigate the proposed system's performance. Since institution of CO2 as a heating medium in MED systems is a novel topic; so, the heat transfer process between CO2 and seawater is studied. Results show that the supercritical CO2 presents an effective heat exchange process. Therefore, the specific heat transfer area would be reduced 135% and 25% compared to conventional MEDs and sensible heat source MEDs, respectively. The proposed combined system can save 57% of energy and 37.8% and 29.1% of total annual cost in Iran and Toronto respectively, compared to a stand-alone CO2 refrigeration system and an MED-Boosted.