Initial evaluation of a phase change solar collector for desalination applications

Although desalination techniques for the preparation of fresh water from seawater and brackish water have been used for decades, they present the problem of high cost, as they are inherently energy intensive processes based on electricity or fossil fuel consumption. Solar thermal collectors could be used in thermal desalination plants in order to overcome some of the issues that they currently present, as long as they become more cost effective and efficient. One of the techniques that are under research in order to achieve this is the use of liquids with low boiling point as heat transfer mediums which minimize thermal losses to the environment by operating in lower temperatures, and utilize the enthalpy of evaporation. In this paper the experimental evaluation of a 2 m2 novel phase change flat plate solar collector is presented. The influence of the ratio of heat carrier volume to available collector volume and of the inclination of the collector, as well as of mass flow rate to the efficiency of the system is assessed in order to find a combination of the above parameters that optimize collector's efficiency and make solar thermal systems more attractive for possible use in desalination applications. A 50% volume filament at a 40° inclination, presented an overall better system efficiency which increased proportionally with increased mass flow rates, leading to an increase of 2 °C per meter of heat exchanger (for a mass flow rate of 5 kg/min) to the heat removal fluid.