Sustainable desalination : a case of renewable energy

Abstract

Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.

A new energy-efficient and sustainable desalination system has been developed in this research. This system operates under near-vacuum conditions created by exploiting natural means of gravity and barometric pressure head. The system can be driven by low grade heat sources such as solar energy or waste heat streams. Theoretical and experimental studies were conducted to evaluate and demonstrate the feasibility of the proposed process. Theoretical studies included thermodynamic analysis and process modelling to evaluate the performance of the process driven by the following alternate energy sources: solar thermal energy, solar photovoltaic/thermal energy, geothermal energy, and process waste heat emissions. Experimental studies included prototype scale demonstration of the process using direct solar and a combination of solar photovoltaic/thermal sources. In the tests using direct solar energy, freshwater production of 5 L/d was achieved using direct solar energy alone, at efficiencies ranging from 65 to 75%. In the tests using solar photovoltaic/thermal energy, freshwater production of 10 L/d was achieved, at efficiencies ranging from 65 to 90%. Specific energy required for this process to produce 1 kg of freshwater was 2926 kJ, all of which was derived from solar energy.