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No Electricity? New Cooling System Uses Sunlight & Salt Water

KAUST scientists have developed a simple cooling system based on solar energy and the cooling effect of saltwater evaporation that could be used for refrigeration in hot regions with limited access to electricity.
KAUST scientists have developed a simple cooling system based on solar energy and the cooling effect of saltwater evaporation that could be used for refrigeration in hot regions with limited access to electricity.
KAUST; Veronica Moraru

A new experimental electricity-free cooling system is under development at the Saudi Arabia’s King Abdullah University of Science & Technology (KAUST), a press statement reveals. All the system requires is salt & sunlight to cool a space or refrigerate food at temperatures of 3.6 degree celsius.

Large parts of Middle East lack resources like drinking water & electricity. This problem involves innovative solutions, often utilizing abundant alternative resources or new technologies like drones. Case in point: United Arab Emirates (UAE) started using “rain drones” to kick-start storms to increase rainfall in the region.

Cooling system designed by KAUST engineers could be used to cool rooms in households
Cooling system designed by KAUST engineers could be used to cool rooms in households KAUST; Wenbin Wang

The KAUST electricity-free cooling system, detailed in a paper in journal Energy and Environmental Science, is another solution that tackles the problem of heat from abundance of sunny days. Surprisingly, it uses that very sunlight to cool buildings-down. The experimental KAUST set up uses a mixture of salt & sunlight to produce its cooling effect for interior spaces, crucially, no electricity is required. The machine takes advantage of a natural “phase-change” phenomenon that sees energy absorbed, when salt crystals dissolve in water. In other words, if salt is added-to warm water, water rapidly cools as the salt dissolves.

A highly reusable, electricity-free cooling method

The KAUST researchers picked ammonium nitrate for its high-water solubility & its cooling power, which is 4 times greater than ammonium chloride, subsequent best-performing salt during tests. Ammonium nitrate is not expensive and is already widely used in fertilizers, meaning, it’s also a commercially viable option. In their experiments, scientists found that ammonium nitrate might be used to cool the space surrounding an ammonium nitrate filled metal cup from room temperature (approx. 77ºF/25ºC) to 38 ºF, (3.6ºC) in about 20 minutes. The temperature-then remained below 59ºF (15ºC) for more than 15 hours. The KAUST team believes their system can be often used for cooling rooms also for food refrigeration. The salt can be often crystallized & reused once again after it’s dissolved by evaporating the water via solar heat. The water also can be reused via a solar still.

Researchers world-wide also are looking to develop alternatives to the traditional air conditioner worldwide in a bid to tackle global climate change, consistent with the IEA, technology spews many tons of CO2 worldwide daily. Researchers from Singapore, for instance, recently developed a “cold tube” radiative cooling system that would replace the air conditioner and allows users to keep their windows open, while the system cools down their interior space. Purdue University researchers, meanwhile, developed a Guinness World Record-breaking white paint that’s so reflective, it can cool buildings down and vastly-reduce the need for air conditioning units.

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