Syllabus:

GS-3: Achievements of Indians in science & technology; indigenization of technology and developing new technology. 

Context:

Recently, researchers at the Indian Institute of Science (IISc) have developed a siphon-powered thermal desalination system that can transform salty seawater into clean drinking water faster, cheaper and more reliably than existing methods.

Thermal Desalination System

• A thermal desalination system that leverages the principle of siphonage to continuously draw seawater, enabling its evaporation and subsequent condensation into potable water.

Key Challenges of Traditional Solar Stills

• Salt Accumulation: During the evaporation process in traditional solar stills, salt present in seawater crystallizes and deposits on the heated evaporator surfaces. This salt accumulation forms crusts that obstruct water flow, significantly diminishing the effective evaporation area. 
• Capillary Wicking Limitations and Scaling Constraints: Solar stills use wicking materials to move saline water to the evaporation surface, but their limited lifting height (10–15 cm) restricts system scale and water output per stage.

Siphon

• A siphon is a device that allows the transfer of a fluid from one reservoir to a second at a lower level even though the first part of the journey is up-hill.
• A siphon is effectively an inverted U-tube with unequal length tubes.

Technology and Working Principle of Siphon Desalination System

Composite Siphon Mechanism: The core component of the system is a composite siphon which is consisting of a fabric wick combined with a grooved metallic surface. 

• The fabric wick draws saline water from the reservoir, while gravity facilitates a continuous and steady flow, effectively flushing away salt deposits before they can accumulate.

Thin Film Evaporation and Condensation: The water is distributed as a thin film across the heated metallic surface, where it undergoes evaporation. The resulting vapor then condenses on a proximate cooler surface positioned just two millimetres apart.

Enhanced Efficiency via Ultra-Narrow Air Gap: The ultra-narrow air gap greatly improves thermal efficiency of the system. It enables production of over 6 litres of potable water per square metre per hours, several times higher than conventional solar stills.

Advantages of the Siphon-Powered Thermal Desalination System 

• Multistage heat recycling: By stacking multiple evaporator-condenser pairs, the system recycles heat repeatedly, maximizing output from solar energy.
• Salt resistance: The siphon flushes salt before crystallization, enabling the system to handle highly saline water up to 20% salt concentration, including brine.
• Low cost and scalability: Made of simple materials like aluminium and fabric, the system is affordable and scalable.
• Sustainability: It runs on solar energy or waste heat, well-suited for off-grid communities, disaster zones, and arid coastal regions.
• Drinking Water for water-stressed regions: It could help secure safe drinking water for millions in water-stressed regions. From small villages to island nations, the siphon-powered desalination system may finally make the ocean a dependable source of fresh drinking water.

Sources:
Tribune India
PIB
DD News
science demonstrations