Many hot and arid regions of the planet need efficient cooling systems due to climate change, but not all communities have access to electricity for air conditioning and refrigeration.
The King Abdullah University of Science and Technology (KAUST) in Saudi Arabia therefore decided to develop an efficient cooling system that works without electricity. New simple cooling system based on solar energy and the cooling effect of salt water evaporation which could be used for cooling in hot regions with limited access to electricity.
The team designed a two-stage cooling and regeneration system, which has no electrical components. Enjoy the powerful cooling effect that occurs when certain salts dissolve in water. This means that if you add salt to hot water, that water cools quickly as the salt dissolves. After each cooling cycle, the system uses solar energy to evaporate the water and regenerate the salt, ready for reuse.
After some experimentation with different types of salt, ammonium nitrate (NH4NO3) turned out to be the most outstanding, with more than four times the cooling power of its closest competitor, ammonium chloride (NH4Cl) . The exceptional cooling capacity of ammonium nitrate salt can be attributed to its high solubility. The other advantage of this salt is that it is quite cheap and is already widely used as a fertilizer.
A simple cooling system powered by passive solar energy capture could provide low-cost food refrigeration and living space cooling for poor communities without access to the power grid.
In laboratory tests, the team showed that the designed cooling system had good potential for a food storage application. When the salt was gradually dissolved in water in a metal cup placed inside a polystyrene box, the temperature of the cup rose from room temperature to around 3.6 degrees Celsius in about 20 minutes. and remained below 15 degrees centigrade for more than 15 hours.
Additionally, once the saline solution reached room temperature, the team used solar energy to evaporate the water using a custom-made 3D cup-shaped solar regenerator. The cup was made of a material designed to absorb as much of the solar spectrum as possible. As the water evaporated, crystals of NH4NO3 grew on the outer wall of the beaker. Crystallized salt can be collected automatically, representing a form of stored solar energy, ready to be reused for cooling when needed.