Solar thermal desalination using the Multiple Effect Humidification (MEH)-method

Solar driven desalination systems based on evaporation of sea water and subsequent condensation of the generated steam have been investigated worldwide for many years'. Starting from simple but sophisticated solar stills working very reliably and self sufficient on small scale drinking water production in the range up to 0.5 m(3) per day, improved concepts have been realized mainly at a research level up to now. The main tasks in term of efficiency of such concepts were the reduction of specific energy consumption and by that requested solar aperture area per cubic meter of water produced daily. One of the concepts is the Multiple Effect Humidification (MEH) method. The enclosure comprising heat and mass transfer is separated from the solar collectors for heat supply of the process. Evaporation and condensation surfaces are oriented to enable continuous temperature stratification along the heat and mass transfer process, resulting in small temperature gap to keep the process running. Most of the energy afforded in the evaporator is regained in the condenser keeping the energy demand on a very low level of less than 120 kWh/m(3). Such systems have been available as an industrial product since November 2005. A demonstration system was installed and commissioned in Jeddah/Kingdom of Saudi-Arabia.