How to beat the summer heat without relying on air conditioning

A so-called ‘Cold Tube’ could fight rising summer temperatures while using less energy than conventional air conditioning. Researchers say the chilled panels can work both indoors and outdoors.  

Exterior of the Cold Tube demonstration pavilion. Credit: Lea Ruefenacht/ University of British Colombia

Many people beat the summer heat by cranking up the air conditioning. However, air conditioners guzzle power and spew out millions of tons of carbon dioxide daily. They’re also not always good for your health – constant exposure to central A/C can increase risks of recirculating germs and causing breathing problems.

There’s a better alternative, say a team of researchers from the University of British Columbia, Princeton University, the University of California, Berkeley and the Singapore-ETH Centre, in a statement. They call it the Cold Tube, and they have shown it works.

The Cold Tube is a system of rectangular wall or ceiling panels that are kept cold by chilled water circulating within them. Since heat naturally moves by radiation from a hotter surface to a colder surface, when a person stands beside or under the panel, their body heat radiates towards the colder panel. This creates a sensation of cooling like cold air flowing over the body even if the air temperature is quite high.

Not new yet unique

Although these types of cooling panels have been used in the building industry for several decades, what makes the Cold Tube unique is that it does not need to be combined with a dehumidification system. Just as a cold glass of lemonade would condense water on a hot summer day, cooling down walls and ceilings in buildings would also condense water without first drying out the air around the panels.

The researchers behind the Cold Tube conceived of an airtight, humidity-repelling membrane to encase the chilled panels to prevent condensation from forming while still allowing radiation to travel through.

The team built an outdoor demonstration unit last year in Singapore, inviting 55 members of the public to visit and provide feedback. When the system was running, most participants reported feeling “cool” or “comfortable,” despite an average air temperature of 30 degrees Celsius (86 degrees Fahrenheit). The panels also stayed dry, thanks to the special membrane.

“Because the Cold Tube can make people feel cool without dehumidifying the air around them, we can look towards shaving off up to 50 per cent of typical air conditioning energy consumption in applicable spaces,” said Eric Teitelbaum, a senior engineer at AIL Research who oversaw the demonstration project while working at the Singapore-ETH Centre.

Keeping indoor air healthy during the pandemic

There’s another aspect of the Cold Tube that is particularly relevant in 2020, says project co-lead Adam Rysanek.

“The COVID-19 pandemic has brought to the public’s awareness how sensitive our health is to the quality of the air we breathe indoors. Specifically, we know that some of the safest spaces in this ‘new normal’ are outdoor spaces,” said Rysanek. “As the climate changes and air conditioning becomes more of a global necessity than a luxury, we need to be prepared with alternatives that are not only better for the environment, but also our health. The idea of staying cool with the windows open feels a lot more valuable today than it did six months ago.”

The team is currently using the data collected in Singapore to update their projections of the Cold Tube’s effectiveness in indoor spaces globally. They plan to demonstrate a commercially viable version of the technology by 2022.

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