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Shipping container used to test passive cooling

USA: A shipping container is being employed by researchers to test passive cooling systems in an attempt to find carbon-free ways to keep people cool in extreme temperatures.

Washington State University researchers created the 60ft2 (5.57m2) chamber to test passive systems that use wind towers along with water evaporation instead of electricity to cool spaces. 

Completely independent of the electricity grid, the test chamber is solar powered with battery storage. It can be heated to a temperature range between 125ºF and 130ºF (52ºC to 54ºC) year-round to test cooling innovations, measuring the temperature, humidity and air velocity within and around a cooling system.

The researchers calibrated the chamber using the results of a full-scale experiment that was conducted on a passive, downdraft cooling system tested under the hot dry conditions of Phoenix, Arizona.

“Cooling is increasingly in demand in buildings, especially as the climate gets hotter,” said Omar Al-Hassawi, assistant professor in WSU’s School of Design and Construction. “There might be inclusion of mechanical systems, but how can we cool buildings to begin with — before relying on the mechanical systems?

“With smaller scale models, we can also do much quicker tests and get results sooner than having to wait on large-scale prototype construction,” he added.

One cooling strategy involves capturing breezes from a tower. With a layer of moisture at the top of the tower, evaporation cools the air, which then becomes heavier and sinks by gravity into a living space below. The moisture can be provided by wetted pads, shower heads or misting nozzles. Typically, mechanical fans are only required as a backup.  

Although such systems are occasionally used in hot places like Phoenix, Arizona, people and building professionals are often not familiar with passive cooling techniques or misunderstand them. A passive cooling strategy could make use of old smokestacks in older buildings, for instance, as a cooling tower and could be applicable both for existing or new construction, said Al-Hassawi.

“It’s an older technology, but there’s been an attempt to innovate and use a mix of new and existing technologies to improve performance and the cooling capacity of these systems.”

Students have designed and built some prototype cooling systems which utilise the passive downdraft cooling system. These will be tested starting next semester. Al-Hassawi hopes that industry partners might also be interested in testing passive system designs in the chamber over the coming academic year.

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