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A Bright Sun Shine Can Bring a lot of Coolness

Cooling does not always have to consume electricity. Solar heat can even power an air conditioner.

The air conditioning is advancing, also in the America. Only few percent of the homes have air conditioning, but the popularity of the devices is steadily increasing. In do-it-yourself shops they are waiting in piles for a buyer.

‘If the demand for air conditioning continues to increase, we will also have a problem on our electricity grid. Those devices consume energy. The American work during the day in a cool office, get in their car and turn on the air conditioning, and then don’t want to be in the heat at home.

Is there no other way to think of cooling that is less dependent on electricity? Yes. Researchers are busy designing and refining a solar cooler that cools using the heat of the sun. Handy, because when the sun shines brightly, the need for cooling is greatest.

It sounds rather contradictory: use heat for cooling. But it is possible with a technique called adsorption cooling. Water is under very low pressure in the cooling machine. So low that it already evaporates when lukewarm water flows from the building that needs to be cooled. That principle must be known to those who have boiled a pan of water in the mountains, where the air pressure is low: the water is already bubbling well below 100 degrees.

Once the water evaporates, it is absorbed by silica gel. That stuff is also in small bags in, new bags, and sucks up water. It works just like salt that you sprinkle on spilled red wine: that also absorbs the liquid.

When the silica gel is full of water, a valve closes and another valve opens, allowing the evaporating water to access a new silica gel package. Thus the evaporating water is constantly absorbed by the silica gel. The water that in the meantime has been heated by solar controllers on the roof is led along the filled silica gel. Like a kind of fire, this water fires the silica gel dry again, so that it can be reused and the process can start again. The residual heat is released on the outside of the building.

The big advantage of this process is that it requires almost no electrical energy. No refrigerant needs to be mechanically compressed, which does happen in an air conditioner or refrigerator.

Due to the lack of such a mechanical process, a solar cooler also requires less maintenance. The final advantage are the refrigerants – silica gel and water – that are in the solar cooler. They are a lot less harmful to the environment than the refrigerants in traditional air conditioning.

To date, more than hundred thousands solar cooling systems have been installed in United States. Especially in southern Europe, solar cooling and use of solar coolers has started to rise. Together with Germany, Spain now holds the largest number of solar cooling systems.

For the time being mainly institutions and companies are opting for solar cooling. Solar cooling systems or Solar coolers do not yet exist in the many States of America.

“The following applies to schools and offices: buy a cooling machine, connect solar controllers to it, and go,”. For a long time that was difficult for houses: only cooling machines could be made with a much too large capacity for a household.

In a dry place, we should not focus on the supply of water that has been heated by the sun. Other heat sources are also suitable. There is also a lot of residual heat from industrial processes. District heating runs on this in the winter. In the summer you could cool houses with the same city network.


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