Multi-effect evaporator desalination powered by geo-solar thermal energy

Abstract

The abundance of solar energy in Saudi Arabia makes it the most promising option for use in water desalination. A salinity gradient solar pond (SGSP) is one of the most encouraging direct solar heat collectors. Increasing the gradient zone depth of the SGSP to 0.6m allows it to sustain the low operating temperature of single-or multi-effect evaporators (MEE) for 9 months of the year. The unique innovation of utilizing the heat of deep well water to support the operation of a system with such a low operating temperature provides feed water at up to 55°C, which means only 11.2kJ of heat energy is required to heat each 1kg of water to the MEE’s evaporation temperature. This is 9.7% of the energy required when using surface seawater. A MATLAB simulation tool was developed to model the coupling of an SGSP with an MEE and was validated with experimental data collected for the climatic conditions of Saudi Arabia. It is well known that a conventional thermal desalination plant is cost-intensive, but the coupling model study of SGSP–MEE shows its operational feasibility at much lower costs.