Experimental set-up
The system has two independent loops, the solar loop that supplies the thermal energy to the desalination unit and operates with osmosed water in order to protect solar collectors from corrosion and scaling and the desalination loop, which is in turn divided in two circuits, the cold and the hot
respectively. The solar loop, installed and designed for a former project (AQUASOL Project: Development of an advanced hybrid solar-gas multi-effect distillation system), is composed of a 500 m2 stationary CPC solar collector field and a 24 m3 thermal storage system based on water. Only half of the solar field is used in the case of MEDESOL.
The desalination loop consists of two separated 2 m3 polypropylene tanks (PP-H) used as hot and cold water reservoirs. Feed solution, prepared with deionised water and marine salt crystals, at both concentrations of 1 and 35 g/l is pumped, depending on the experiment, into the three AGMD modules connected in series or into one of them (in the case of “real sweater experiments” we only used one of the modules) by means of a centrifugal pump. Before entering the modules, feed is heated by way of the solar loop which is connected to the pilot plant trough a 10 plates titanium heat exchanger (HRS spiratube) coated with an advanced non-fouling layer to protect it from seawater aggressiveness. The maximum hot temperature achieved during the experiments was 90-95 °С. Likewise, deionised water is used as refrigerating fluid and can be cooled down if necessary, passing it through an air cooler. After AGMD process, both cold and hot water are returned to their corresponding tanks thus closing both circuits. The inlet and outlet temperatures of each of the modules are monitored using thermocouples type E. Electromagnetic flow meters are used to measure the feed and cooling stream mass flow rates. Conductivity probes are installed in both hot feed circuit and distillate line. Finally, pressure of both hot and cold channels is also measured at the entrance of the AGMD modules avoiding values higher than 0.2 bar, which is the maximum LEP[4] allowed to prevent from membrane wetting.
