An ocean thermocline desalination system using the direct spray method

Abstract

Most of the existing desalination technologies are highly dependent on primary energy, limiting their applications to affluent areas. To address water scarcity in remote areas, it is crucial to exploit the potential of renewable energy sources for desalination. The natural temperature gradient between the surface and deep seabed, i.e., the ocean thermocline, can provide sufficient driving forces for low-temperature thermal desalination. This study presents a thermocline desalination system using the direct spray method. A single-stage spray desalination setup is designed and operated under the temperature ranges that are typical in ocean thermocline. The minimum temperature gradients to drive the system is <5 °C, thus allowing effective integration with thermocline energy. Afterward, thermodynamic and techno-economic analyses are conducted for the thermocline-driven spray desalination system. The major design and operating parameters are observed to have conflicting effects on the water productivity (11–31 m3/day), required heat transfer area (2–4.6 m2 per m3/day of production), and specific energy consumption (2–5.1 kWh/m3). An optimal trade-off of these effects is observed when the system has 2 stages and the cooling water flowrate is 33% higher than the seawater flowrate. Under the optimized conditions, the life-cycle desalination cost ranges from $1–1.5/m3, lower than most decentralized desalination systems operated with solar or ocean thermocline energy.