Is there a way to achieve a cooling effect for buildings without turning on air-conditioners, fans, or any power? Saudi Arabian scientists have recently proposed a cooling system that does not require any power, and can attain a cooling effect through water and salt. The blazing sunlight also serves as a helping hand for the system.
The research team of King Abdullah University of Science and Technology (KAUST) uses the cooling effect of salt to establish this non-power cooling system. Salt absorbs heat when melting that reduces the temperature, which is why a sprinkle of salt in warm water would lower the temperature swiftly alongside the melting of salt. The research team believes that such natural phenomenon may perhaps be applied in buildings that are “heated” by sunlight.
However, which salt exerts the best effect? The experiment of KAUST pointed out that the best option is ammonium nitrate as it contains a high water solubility and four times the cooling effect of the second best option ammonium chloride. Ammonium nitrate is also an affordable component that is widely utilized in fertilizers. (Note)
（Source：KAUST）
The research team believes that the ammonium nitrate cool system can also be used for food preservation since it possesses excellent performance in refrigeration and constant temperature, apart from cooling buildings.
The research team first poured ammonium nitrate water into a metal cup, before placing the cup in a sealed Styrofoam box, and the temperature of the cup is reduced from 25ºC to 3.6 ºC within 20 minutes as the salt melts and the water gradually cools down. The temperature can be kept under 15 ºC for more than 15 hours.
The ammonium nitrate cooling system can be recycled and reused since the crystallization of salt after water evaporation can be collected and put back into the system. A solar distiller can also be installed to allow the water to return to the cooling system, if you wish to preserve water.
Doctor Wenbin Wang commented that refrigeration demand is rising exponentially amidst climate change and global warming, though power is not widely available in all regions. The research team believes that the ammonium nitrate cooling system is able to provide low cost food refrigeration and space cooling for off-grid remote areas, where the powerful cooling effect of brine can be perceived even without power.
Note: ammonium nitrate is the cause for the 2020 Beirut explosion, and can also be used to make improvised explosive devices. Many countries are considering about removing this particular chemical compound from consumer applications in fear of misuses.
(Cover photo is a sketch, source: Flickr/Dyniss Rainer CC BY 2.0)