Cooling system uses salt and water instead of electricity

Researchers have proposed a passive cooling system that uses salts and water to generate the energy needed for cooling

Spotted: One key challenge for global sustainable development is the need to reduce energy usage, especially in regions which are becoming hotter. As the planet continues to heat up, it is going to become increasingly necessary to develop an inexpensive cooling technology that does not need electricity. A research team at Saudi Arabia’s King Abdullah University of Science and Technology (KAUST) has come with a way to accomplish this, by using sunlight and saltwater – but no electricity – to cool buildings. 

The experimental setup was led by Professor Peng Wang, whose work focuses on photoelectrocatalysis, a process whereby chemical solar cells harvest sunlight and use the energy to upgrade chemicals rather than deliver electricity. The proposed solution takes advantage of the phase change in salt crystals. The crystals absorb energy when they dissolve in water. So, if salt is added to warm water, the water then cools as the salt dissolves. 

Wang’s team experimented with different salts, and found that ammonium nitrate provided the greatest cooling power. In the lab, the ammonium nitrate was added to water and placed inside a sealed, insulated box. As the salt dissolved, the temperature of the water dropped by around 21ºC over a period of 20 minutes and remained cool for more than 15 hours. Solar heat was then used to evaporate the water and recover the ammonium nitrate crystals, which could then be reused. 

In a paper published in the journal  Energy and Environmental Science, professor Wang and the other authors highlight the need for passive cooling systems, especially in lesser-developed regions. They point out that, “globally, there are over 700 million people living in impoverished regions who still do not have access to electricity and thus are unable to enjoy the modern era cooling technologies. In this case, developing an inexpensive cooling technology that operates in the absence of electricity is highly desired and can significantly improve the living standards of those who are left behind by modern human development.” 

As the Earth warms, energy shortages are becoming increasingly common, and the KAUST researchers are not the only ones searching for a solution to these issues. Springwise has recently covered innovations in this space, including a decentralized cooling system and the growing use of passive design in heating and cooling. 

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