Tag Archives: Conditioning

Researchers develop a new, more efficient way to keep cool — the ‘Cold Tube’

With the world getting hotter, finding energy-efficient ways to cool down is more important than ever. A team of researchers from the University of British Columbia, Princeton University, the University of California, Berkeley and the Singapore-ETH Centre plan to help us do just that with the ‘Cool Tube’.

The experimental pavilion setup in Singapore.
Image credits Lea Ruefenacht.

Air conditioning can be a blessing in the hot summer months, but they also consume a lot of power. Added up on a city- or country-wide scale this translates to a huge drain on our grids and vast quantities of CO2 emissions. Air conditioning can also contribute to respiratory complications by keeping germs in suspension in the air (by keeping it in constant motion).

The team behind Cold Tube wanted to change how we manage our personal temperature during such times, and their approach doesn’t involve cooling or moving air at all.

Cool cooling ideas

“Air conditioners work by cooling down and dehumidifying the air around us—an expensive and not particularly environmentally friendly proposition,” explains co-lead author Adam Rysanek, assistant professor of environmental systems at UBC’s school of architecture and landscape architecture.

“The Cold Tube works by absorbing the heat directly emitted by radiation from a person without having to cool the air passing over their skin. This achieves a significant amount of energy savings.”

The system consists of a series of rectangular panels that can be fitted to walls or ceilings. These elements are kept cool by chilled water being circulated through them.

The idea behind the Cold Tube is that heat naturally radiates from hot surfaces to colder ones — that’s how heat from the Sun makes it to Earth. When you sit under or near one of these elements, your body heat will radiate towards it. The team describes this effect as similar to the sensation of cold air flowing over your body, even when ambient temperatures are high.

It’s not a new concept — in fact, it’s been in use in industrial settings for several decades now. What Cold Tube does differently, however, is to use a special coating that does away with the need to dehumidify air.

A look inside a pavilion incorporating the Cold Tube system
A look inside the pavilion.
Image credits Lea Ruefenacht.

Humidity in the air condenses on cold surfaces, which can cause hygiene issues and damage surfaces and materials. The team developed an airtight, water-repellent membrane that encases their panels, and prevents condensation from forming (but still allows the system to function as intended).

The researchers tested their system in an outdoor setting in Singapore last year. The temperature outside during the test was 30 degrees Celsius (86 degrees Fahrenheit) on average. Yet, participants reported feeling ‘cool’ and ‘comfortable’ despite the heat, and the panels remained dry throughout the day.

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

“This design is ready. It can obviously be used in many outdoor spaces—think open-air summer fairs, concerts, bus stops, and public markets. But the mission is to adapt the design for indoor spaces that would typically use central air conditioning.”

The system doesn’t rely on cooling air, like a traditional air conditioner, so it can even be used with an open window, or in open spaces. The team hopes that its low operating cost will make the Cold Tube an attractive option for both developed and developing countries. A commercially viable version of the system is expected for 2022.

The paper “Membrane-assisted radiant cooling for expanding thermal comfort zones globally without air conditioning” has been published in the journal PNAS.

Wall fans.

New paper proposes we use air conditioners to make fuel out of thin air

Cool down your home and the climate at the same time.

Wall fans.

Image credits Sławomir Kowalewski.

New research from the Karlsruhe Institute of Technology and the University of Toronto wants to put your air conditioning unit to work on fighting climate change. The idea is to outfit air conditioners — devices which move huge amounts of air per day — with carbon-capture technology and electrolyzers, which would turn the gas into fuel.

Crowd oil

“Carbon capture equipment could come from a Swiss ‘direct air capture’ company called Climeworks, and the electrolyzers to convert carbon dioxide and water into hydrogen are available from Siemens, Hydrogenics or other companies,” said paper co-author Geoffrey Ozin for Scientific American.

Air-conditioner units are very energy-thirsty. As most of our energy today is derived from fossil fuels, this means that air conditioners can be linked to a sizeable quantity of greenhouse emissions. It’s estimated that, by the end of the century, we’ll be using enough energy on air conditioning to push the average global temperature up by half a degree. Which is pretty ironic.

The team’s idea is pretty simple — what if heating, ventilation, and air conditioning (or HVAC) systems could act as carbon sinks, instead of being net carbon contributors? Carbon-capture devices need to be able to move and process massive quantities of air in order to be effective. HVAC systems already do this, being able to move the entire volume of air in an average office building five to ten times every hour. So they’re ideally suited for one another. The authors propose “retrofitting air conditioning units as integrated, scalable, and renewable-powered devices capable of decentralized CO2 conversion and energy democratization.”

“It would be not that difficult technically to add a CO2 capture functionality to an A/C system,” the authors write, “and an integrated A/C-DAC unit is expected to show favourable economics.”

Modular attachments could be used to add CO2-scrubbing filters to pre-existing HVAC systems. After collection, that CO2 can be mixed with water to make, basically, fossil fuels. As Ozin told Scientific American, the required technology is commercially available today.

But, in order to see if it would also be effective, the team used a large office tower in Frankfurt, Germany, as a case study. HVAC systems installed on this building could capture enough CO2 to produce around 600,000 gallons of fuel in a year. They further estimate that installing similar systems on all the city’s buildings could generate in excess of 120 million gallons of (quite wittily-named) “crowd oil” per year.

“Renewable oil wells, a distributed social technology whereby people in homes, offices, and commercial buildings all around the world collectively harvest renewable electricity and heat and use air conditioning and ventilation systems to capture CO2 and H2O from ambient air, by chemical processes, into renewable synthetic oil — crowd oil — substituting for non-renewable fossil-based oil — a step towards a circular CO2 economy.”

Such an approach would still take a lot of work and polish before it could be implemented on any large scale. Among some of the problems is that it would, in effect, turn any HVAC-equipped system into a small, flammable oil refinery. The idea also drew criticism as it could potentially distract people from the actual goal — reducing emission levels.

“The preliminary analysis […] demonstrates the potential of capturing CO2 from air conditioning systems in buildings, for making a substantial amount of liquid hydrocarbon fuel,” the paper reads.

“While the analysis considers the CO2 reduction potential, carbon efficiency and overall energy efficiency, it does not touch on spatial, or economic metrics for the requisite systems. These have to be obtained from a full techno-economic and life cycle analysis of the entire system.”

The paper “Crowd oil not crude oil” has been published in the journal Nature Communications.