An illustration depicting how a large-scale version of the system could be used to cool an entire room - Wenbin Wang/KAUST
There are many parts of the world which lack infrastructure but get a lot of sunlight ... which makes buildings uncomfortably hot. A new system could help, as it uses a combination of sunlight and salt water – but no electricity – to produce a cooling effect.
Currently being developed at Saudi Arabia's King Abdullah University of Science and Technology (KAUST), the experimental setup takes advantage of a natural "phase-change" phenomenon in which energy is absorbed as salt crystals dissolve within water. This means that if salt is added to warm water, that water rapidly cools as the salt dissolves.
After some experimentation with different types of salt, it was found that one known as ammonium nitrate worked best. Mainly because it's highly water-soluble, its cooling power is four times greater than that of the next-best salt, ammonium chloride. As an added bonus, ammonium nitrate is already widely utilized in fertilizer, and is quite inexpensive.
Besides its use in cooling systems for buildings, the system could also be utilized to refrigerate food. In lab tests, water with added ammonium nitrate was placed in a metal cup, which was in turn put inside a sealed polystyrene foam box.
As the salt dissolved and the water cooled, the temperature of the cup dropped from room temperature (about 25 ºC/77 ºF) to 3.6 ºC (38 ºF) within approximately 20 minutes. It proceeded to stay below 15 ºC (59 ºF) for over 15 hours - link - Ben Coxworth - link -more like this (Saudi Arabia) - link - more like this - link
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