Let the sun cool the beers

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Danish students build a solar powered system to keep the beers as cool as Roskilde festival's music. The concept behind is called 'evaporative cooling'.

Danish students build a solar powered system to keep the beers as cool as Roskilde festival's music.

You can hence let the cooler in the sun without killing the party!

Three teams of DTU (Technical University of Denmark) students have therefore set out to ensure cold drinks without using of energy-consuming refrigerators. All three apply the principle of ‘evaporative cooling’, which has been used for centuries to keep food cold using solar heat.

We are all familiar with the principle: If you suck on your finger and stick it up in the air, your skin feels cool when the water evaporates from the finger. Evaporative cooling is most effective in dry weather, so how cold the beers get depends a lot on the weather. Therefore, there are many good reasons to hope for a dry and sunny festival.
With their ‘Coolbox’ project, four students have opted for a very simple model that consists of a ventilation pipe covered with polyether foam. When the foam is kept wet, evaporation of the water will cool down the contents of the container.

At the festival, we will give the festival-goers the opportunity to build their own beer cooler with room for 12 beer cans. In addition, we will tell festival-goers about the principles behind evaporative cooling and its perspectives,” says Magnus Held, one of the four DTU students behind Coolbox.

‘The natural fridge’ project, which DTU student Anders Kjær Huntley is involved in, is a bit more complicated:

“Our concept is a box-in-a-box, where the inner box is covered with a wet cloth and where channels allow air to flow in the space between the inner and outer box. A steady flow is maintained by means of PC fans that use a minimum of power. The entire device is insulated to prevent penetration by the sun’s rays,” says Anders Kjær Huntley.

The third cooling project is simply called ‘cool down’. Here, cooling takes place under a low pressure of 0.01 bar, which means that the system can work under lower temperatures. Under the right conditions, it will be able to cool down 10 beers from 20 to 10 degrees Celsius in less than 30 minutes.

“In order to be able to demonstrate the project for the festival-goers, we will offer a swap-a-warm-beer-to-a-cold-beer service at different locations every day,” says DTU student Kasper Hjorthær Nielsen.

The team’s system consists of two containers connected by a pipe, one that holds beers in water, and one that contains salt which absorbs water vapour from the first container in which the beers are cooled as a result of the evaporation. The by-product is salt water which a solar panel heats up, so that the water evaporates and the salt can be re-used.

Adapted from article by Henrik Larsen for DTU online news

Photography Ditte Valente

Follow-up: Roskilde: ChillCan putting a stop to lukewarm beer, telling us how the students have improved the concept, based on their first experience in 2015.


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