Multi-stage solar desalination system for water production in coastal areas of Ecuador

A solar desalination system with heat recovery has been developed for coastal areas of Ecuador with a shortage of freshwater. The prototype consists of a 3-stage distillation tower connected to a flat plate solar collector. The solar energy absorbed by the collector is transferred by natural circulation to the distillation tower, wherein the heat of condensation of water is recovered in each stage to increase distillate output. The modular design of the equipment allows water production to be varied, from a few liters to more than a cubic meter per day. The prototype has few moving parts and can be rapidly disassembled and assembled, greatly facilitating its operation and maintenance. The average monthly production of the desalination unit varies between 4.3 and 5.8 liters per day (2.44 and 3.29 kg/m(2)). A mathematical model was created to analyze system performance. The accuracy of this model was improved by experimentally evaluating the convection heat transfer coefficients in the distillation tower. A simulation program was developed in Matlab-Simulink to predict the temperature profiles, distillate output, and heat flows in the unit. The simulation results for one day of prototype operation were very satisfactory, with a difference of only 77 % between theoretical and experimental data. The simulation was also used to analyze improvements in equipment performance, which determined that freshwater yield could be increased by up to 107 %.