Cost Analysis of an Autonomous Low-Temperature Solar Rankine Cycle System for Reverse Osmosis Desalination D. MANOLAKOS, S. KYRITSIS Dept. of Natural Resources & Agricultural Engineering Agricultural University of Athens 75, Iera odos street 11855 Athens GREECE http://www.aua.gr J. KARAGIANNIS, P. SOLDATOS Dept. of Agricultural Economics & Rural Dev'nt Agricultural University of Athens 75, Iera odos street 11855 Athens GREECE http://www.aua.gr Abstract: The present paper regards the design outlines and cost analysis, of a low temperature solar organic Rankine cycle system for Reverse Osmosis (RO) desalination. The thermal processing taking place is described briefly below: Thermal energy produced from the solar collectors array evaporates the working fluid (HFC-134a) in the evaporator surface, changing the fluid state from sub-liquid to super heated vapour. The super-heated vapour is then driven to the expanders where the generated mechanical work produced by the processing drives the High Pressure pump of the RO unit, circulation pumps of the Rankine cycle (HFC-134a, cooling water pump), and the circulator of the collectors. The saturated vapour at the expanders’ outlet is directed to the condenser and condensates. HFC-134a condensation is necessary in the Rankine process. On the condenser’s surface, seawater is pre-heated and directed to the seawater reservoir. Seawater pre-heating is applied to increase the fresh water recovery ratio. The saturated liquid at the condenser outlet is then pressurised by the HFC-134a pump. Such system can be considered as an alternative to PV-RO system or other thermal processing distillation methodologies since it is reliable, environmentally friendly, with low O&M cost and it is ideal to exploit low temperature thermal sources in a most efficient way. Key-Words: Solar energy, ORC, RO desalination, solar collectors, cost analysis 1. Introduction The present work regards the cost analysis of a Low Temperature Organic Solar Rankine system which generates energy for RO desalination. The cost analysis is based on the simulation results provided by the application of suitable softwares. A prototype system is going to be installed within the framework of COOP-CT-2003-507997 project, partly financed by EC. 2. Technical description of the system The Low Temperature Solar Organic Rankine Cycle (LTSORC) system for RO desalination consists of the following sub-systems and components (Fig.1): (1) High efficiency vacuum tube solar collectors’ array, (2) Circulator, (3) Evaporator, (4) Condenser, (5) Expanders, (6) HFC-134a pump, (7) RO unit, (8) Insulated seawater reservoir, (9) Fresh water reservoir, (10) RO energy recovery system The system operation is described briefly below: Thermal energy produced by the solar array (1) preheats and evaporates the working fluid (HFC-134a) in the evaporator surface (3). The water temperature at collector inlet is about 70 o C and the outlet temperature about 77 o C. The super-heated vapour is driven to the expanders (5) where the generated mechanical work drives the RO high pressure pump high pressure pump, cooling water pump, HFC-134a pump (6) and circulating pump (2). The saturated vapour at the expanders’ outlet is directed to the condenser (4). On the condenser surface, seawater is pre-heated and directed 2005 WSEAS Int. Conf. on ENVIRONMENT, ECOSYSTEMS and DEVELOPMENT, Venice, Italy, November 2-4, 2005 (pp266-271)