Experiments were divided into two stages, in the first one we used 1 g/l marine salted water (1500­2000 pS/cm) in the feed hot channel and deionised water as coolant. In the second stage a

concentration of 35 g/l (40-46 mS/cm) was used as feed water and the same deionised water in the cooling channel. In both stages the pilot plant was evaluated during solar hours, one day of operation comprised about 7 hours. Normally the experiments were started when the solar filed was delivering a minimum temperature, so the feed was heated up gradually. The modules start to distil, although depending greatly on hot inlet temperature, when a difference of 20 °C in temperature between hot and cold inlet is achieved, and that is when measurements of conductivity and production started.