Scientists use only salt and sunlight to counteract the heating planet  

A one-slide summary of this article with questions to use with your 14–16 students: rsc.li/3az989B

Researchers have developed a system that uses endothermic dissolution of a salt in water to cool its immediate surrounding area. Solar energy can then regenerate the solute and this means the cyclic system can work without requiring an electricity supply, making it well-suited for users in remote areas.

The system has two stages. The first stage involves dissolving ammonium nitrate salt in water in a metal cup, which requires energy. This energy is drawn from the immediate environment, cooling the air surrounding the cup as well as the solution. The second stage regenerates the solute by evaporating the water solvent and is achieved by wicking the solution vertically onto the surface of a 3D structure, which, when exposed to simulated sunlight, offers a large area over which the solvent can evaporate. This leaves behind a compact crystalline salt layer on the surface, from which larger crystals can drop-off over time, to be collected underneath the structure for re-use.

The system can deliver cooling whenever needed, all day long and all year round, while the solar solute regenerator works during daytime when solar energy is present. This system is not at all expensive as both the dissolution cooling system and solute regenerator are cheap. However, there are some limitations to consider. Compared to conventional air conditioning, this system still has a low cooling power, and it is only suitable for cooling small spaces.

Read the full story in Chemistry World.

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