The research regards the development, application testing and performance evaluation of a low temperature solar organic Rankine cycle system for Reverse Osmosis (Ro) desalination. Below a technical description of the system to be developed is given: Thermal energy produced by the solar array evaporates the working fluid (HFC-134a) in the evaporator surface. The super-heated vapour is driven to the expanders where the generated mechanical work drives the RO unit pumps (high pressure pump, cooling water pump, feed water pump) and circulating pump. The saturated vapour at the expanders' outlet is directed to the condenser and condensates. On the condenser surface, seawater is pre-heated and directed to the seawater reservoir. Seawater pre-heating is applied to increase the fresh water recovery ratio. The seawater tank is insulated. The use of seawater for condensation purpose on the condenser surface decreases the temperature of "Low Temperature Reservoir" of Rankine cycle thus a better cycle efficiency is achieved. The saturated liquid at the condenser outlet is pressurised in a special pressurisation arrangement consists of two vessels and three valves, substituting a pump. The sub-cooled liquid at the pressurisation arrangement outlet is driven to the economiser. The economiser acts as working fluid pre-heater. In the economiser outlet saturated liquid is formed, which is directed to evaporator inlet and the cycle is repeated. For the prototype system 240 m2 of vacuum tube solar collectors will be deployed. The evaporator and condenser capacity is estimated about 100 kW. For these systems' characteristics and considering a water recovery ratio of seawater RO desalination unit of 30%, the average yearly fresh water production is estimated at 1450 m3 (or 4 m3 daily). Specific innovations of the system are: Low temperature thermal sources can be exploited efficiently for fresh water production; solar energy is used indirectly and does not heat seawater; the RO unit is driven by mechanical work produced from the processing; development of a special control system; the components of the system will be tuned to each other so that to achieve higher efficiency and consequently fresh water production rates; the system condenser acts as sea water preheated and this serves a double purpose; (1) increase of feed water temperature implies higher fresh water production
(2) decrease of temperature of "low temperature reservoir" of Rankine cycle implies higher cycle efficiencies.