Design Optimization of Shore Based Low Temperature Thermal Desalination System Utilizing the Ocean Thermal Energy

Abstract

A model for calculation and optimization of seawater desalination process is presented. In this process, temperature difference between the upper and the lower strata of the ocean is utilized in producing fresh water, by evaporating the warm surface seawater at a reduced pressure and then condensing the generated steam by using the colder seawater drawn from the depth of the ocean to produce distilled water. In order to make the optimization process realistic, the developed model takes into consideration the characteristics of the proposed location such as temperature and density variation with depth, seabed topography, and subsequently the actual lengths of the cold and the warm seawater intake pipes. This article gives details of the process and investigates on the influence of various parameters on its economics. As electricity is the sole source of energy used, the objective function was taken as the specific energy, i.e., the amount of electrical energy required for producing a unit mass of distilled water. Results indicate that distilled water can be produced at a value as low as 5.5 kWh per ton, which makes the process competitive with most of the existing desalination technologies.