Good Thinking

Sunlight and salt water join forces in electricity-free cooling system

Sunlight and salt water join f...
An illustration depicting how a large-scale version of the system could be used to cool an entire room
An illustration depicting how a large-scale version of the system could be used to cool an entire room
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An illustration depicting how a large-scale version of the system could be used to cool an entire room
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An illustration depicting how a large-scale version of the system could be used to cool an entire room

There are many parts of the world which lack infrastructure, but that 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.

Additionally, once all of the salt had dissolved, solar heat was used to evaporate the water. The salt was left behind in the form of crystals which formed on the cup – those crystals could then be collected and reused in the cooling system. And while allowing water to evaporate in parched, arid environments might seem wasteful, most of that water could be reclaimed and reused if a solar still was utilized.

A paper on the research, which was led by Prof. Peng Wang, was recently published in the journal Energy and Environmental Science.

Source: KAUST via AlphaGalileo

12 comments
12 comments
Daishi
Ammonium nitrate stored in a warehouse is also what is responsible for leveling Beirut. The downside of using this as a cooling technology is creating easy access to large amounts of ammonium nitrate could have other negative unintended consequences.
minivini
Ammonium nitrate is also a key component in improvised explosives.
Morgan Cadle
Why not start with a solar powered A/C units like a window unit installed into the roof with a 90 degree vent to protect from the weather ,this fed into the house and dispersed using a fan using the electricity

Then adding a water condenser to create the water needed and is part of the unit and you could add salt using a sensor

Some water could be used for creating water and fed through gutters to the fields

As each farm installs one you increase the size of your energy company
Think about the size of the equator and thats where you market as it's solar and these areas have alot of sun

Allows farms to grow with bigger installation and
You could include a remote satellite internet router in the solar panels that allow internet providers more remote access and you get a rental charge and you increase your presence in that market

Just a thought
vince
Simply marvelous use of chemistry. Simplicity rules.
christopher
Because conserving electricity in remote areas flooded with sunlight is essential...
Miro
Why not just use Adiabatic process? Why chemicals? How will be compared?
clay
How did they evap the water without heating the chilled chamber?
Bruce H. Anderson
Would it require distilled or RO water to operate? I wonder if the minerals in regular water would mix with the ammonium nitrate after distillation/evaporation, and if that would degrade the reaction.
Derek
True, Ammonium Nitrate can be used as an explosive BUT it has to be pure. If sold mixed with a few percent of ammonium sulfate or for that matter any other salt it cannot be detonated. So far big chemical companies have resisted making a safe brand but this should not be a roadblock to this project.
Besides that it is already ridiculously easy to get large quantities of Ammonium Nitrate, farmers do it daily.
bahbah
This is all so horribly wrong! Wasting a high energy fertilizer and fresh water for a cooling effect. The technology exists to use salt water both for cooling and humidity, especially suitable for greenhouses in deserts with access to sea or brackish water. There are solar heated to about 30 degrees above ambient the showered into the greenhouse or house.
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