Keywords: deep sea cold water, low pressure boiling, ocean temperature difference, seawater desalination, low-temperature thermal desalination, thermocline
Thermocline-driven desalination: the technology and its potential
Seawater desalination technology is emerging as freshwater requirements are alarmingly increasing all over the world. Conventional technologies such as reverse osmosis and multistage flash evaporation have their limitations, such as chemical treatment and scaling. Low-Temperature Thermal Desalination (LTTD) is an attractive technology with vast potential. It makes use of the ocean temperature difference (thermocline) between surface water and deep seawater. Using the experimental setup established at NIOT, studies were carried out by varying the warm and cold water temperatures. A combination of a roots blower with a water ring vacuum pump was used to generate the required vacuum. Based on the experimental results, a desalination plant for technology demonstration was proposed for one of the island groups in the Indian Ocean. It is intended to draw water from a 350 m depth. This cold water is used to condense the vapour that is being flashed under vacuum from surface seawater. In order to reduce the power consumption, barometric sealing is used by placing the flash chamber and condenser at about 10 m. This paper discusses the design and technical details of the seawater desalination plant for Lakshadweep Islands, along with experimental results.