Experimental study of a solar thermal desalination unit

Scarcity of potable water causes a serious problem in arid regions of the world where freshwater is becoming insufficient and expensive. Warm regions in the Middle East and North Africa are considered among the severest water shortage places. The objective of this project is to study the potential of using solar energy to run existing multi-stage flash (MSF) desalination units in the Arabian Gulf. One problem with MSF is the low efficiency of the system because of the bulk energy required for heating. Exploitation of solar energy in thermal desalination processes is a promising technology because of the ubiquitous nature of sun's energy. Experimental studies were conducted on a single flash desalination unit. The pilot unit demonstrates the use of solar radiation as the thermal energy input. The process starts by preheating seawater through a vacuumed condenser. Seawater, then, flows inside a circulation tank to be indirectly heated by a heat transfer fluid. The heat transfer fluid circulates inside a flat plate solar collector facing south to absorb solar energy. After raising its temperature, seawater goes through an expansion valve and flashes in a vacuumed chamber to form brine and vapor. The vapor transfers to the condenser and condenses to form potable water by losing its latent heat of vaporization to incoming seawater. The flow rate of the working fluid is controlled via a control valve based on a set point temperature reference. The experiments were carried out using different values of the controlling variables to enhance analysis and validate results.