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This 'Cold Tube' can beat the summer heat without relying on air conditioning:
"Air conditioners work by cooling down and dehumidifying the air around us—an expensive and not particularly environmentally friendly proposition," explains project co-lead Adam Rysanek, assistant professor of environmental systems at UBC's school of architecture and landscape architecture, whose work focuses on future energy systems and green buildings. "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 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.
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.
A new cooling system for your home?
(Score: 2) by RS3 on Thursday August 20 2020, @02:22PM (12 children)
Article doesn't mention it but the (air) fan in ACs uses quite a bit of energy, and air isn't a great heat container compared to water. You could incorporate an efficient compressor / refrigerant system into the water cooling panels if needed and overall would consume much less energy than air-based ACs. Yes, condensate and mold are problems but can be dealt with by cleaning and anti-mold coatings.
(Score: 2) by JoeMerchant on Thursday August 20 2020, @03:31PM (10 children)
I designed (but only partially built) an off-grid cabin with - potentially - a ground water chiller system of pipes in the ceiling of the sleeping area. My idea was to use copper pipe installed on a slope that would drain the condensate over to a gutter that would carry it outside, and yes, if you slam the door it might well rain inside.
We had a naturally flowing spring (4" borehole), and were already using it to feed a waterfall pond-filler, so the supply and discharge were taken care of, and would flow without any pump energy. The question remained: was it worth the effort and expense to install all that copper pipe as compared to slapping in a $200 window rattler that would chill the room faster and to a lower final temperature? For the money side of the equation, the window rattler wins hands down, even if you need a $1000 generator to drive it. Where that solution loses is in listening to a window rattler all night long - if you're going to the woods to sleep in a cabin, who wants to listen to the same A/C noises you hear at a Motel 6?
🌻🌻 [google.com]
(Score: 2) by RS3 on Thursday August 20 2020, @03:47PM (9 children)
Super-cool! Yes, pun intended, but great project. Yeah, that condensate is a difficult problem if you don't want indoor rain.
You're poisoned by capitalism- not all worthwhile projects are the least cost. You've learned, and are now sharing some of that. Imagine if everyone compiled what they learn!
But yes, copper has become quite expensive over the past 50 or so years.
I live in higher latitudes but still need (er, want) the window rattler occasionally but can't sleep with the noise, so I run it full-on for a couple of hours, get the bedroom down to 70 or so and I'm good for the night.
Thermodynamics is a favorite of mine- did very well with it in college. Didn't like partial differential equation analysis, but the bottom-line natural logarithm that it boils down to (another pun!) is pretty easy and makes sense to me.
Years ago I had seen in a Popular Science mag. where someone had 2 holes dug, insulated, and installed septic tanks, filled with large rocks, to act as hot and cold energy storage. Combined with solar panels, graywater heat reclamation, all integrated into an efficient control system with counter-flow heat exchangers is some of my dream system.
I'm really big on insulation. And, keeping the humidity OUT.
Does your cabin have good plastic moisture barrier under it? If not, can you add it? Maybe diminishing returns?
(Score: 2) by JoeMerchant on Thursday August 20 2020, @05:01PM
It's not only the money, it's also the time cost - which, ultimately, is why the cabin was never finished: not enough time to build it. Capitalism means you can just go to WallyWorld and buy a $200 AC unit and have it installed in less than an hour - as opposed to sourcing a truck full of copper pipe and sweating joints in the ceiling for 6 days before it's all assembled.
🌻🌻 [google.com]
(Score: 2) by JoeMerchant on Thursday August 20 2020, @05:09PM (7 children)
Hit send quick before joining a conference call, but it's a 99% listen conference, so....
Cabin is built on an elevated deck, interior floor is ~8' above outside ground - quite a bit more breeze up off the ground. I built the deck, almost built the stairs, then life happened. Sold the property a couple of years ago, not sure if I want to know if the buyers finished the cabin or not, they thought they were going to.
The big idea of the cold tubes was to get the radiant cooling while being able to leave the windows open for breeze at night, sort of like sleeping under a 64F cloudy sky, but one that doesn't rain or let the bugs in.
The floor, as I left it, was 6" deck boards with 1/4" to 1/2" gaps - never tested it myself but common wisdom is that mosquitoes and other noxious flying insects tend not to fly up through floor gaps like that. Easy enough to put in a solid finished floor, if needed. Just time and money.
🌻🌻 [google.com]
(Score: 2) by RS3 on Thursday August 20 2020, @07:26PM (6 children)
If I live 3x normal I still won't have enough time to do all the projects I envision. I need to win a big lottery and hire a team. Guess I have to play to win...
I envisioned you using soft copper tubing- no soldering.
Now they make those nice aluminum heat spreaders for under-floor PEX heating. Probably work great for cooling overhead, or in walls too. Nice sweat stains on the walls... Would need to finish walls with FRP and condensate troughs along the bottom. Some might object... More engineering needed...
(Score: 2) by JoeMerchant on Thursday August 20 2020, @09:22PM (5 children)
That would be a quicker install, but you're going to be looking at those pipes. Now, you made me think of putting a thin copper foil catchplate underneath, that could be practical, but would still dampen the radiant properties... When I thought about soft copper, in addition to appearance I also thought about irregularities in the "straight" sections leading to drip points...
I did learn about those heat exchangers later - when it had already become pretty obvious that the cabin wouldn't be happening. They'd work well, but I don't think you'd want to pay for enough of them to cover a ceiling.
I was going to go for Hawaiian style single-layer wall construction, maybe sprayed with ceramic insulation on the inside - the insulation could also semi waterproof the wall, but even Killz loses its anti-microbial action after a few years. There are some "nanotech" companies proposing shark-skin inspired antimicrobial surfaces, but I'm skeptical of their longevity: they use silver in their formulation, and I suspect that as the silver oxidizes the antimicrobial action dissipates.
🌻🌻 [google.com]
(Score: 2) by RS3 on Thursday August 20 2020, @09:45PM (4 children)
https://www.amazon.com/Ft-Aluminum-Transfer-Radiant-Heating/dp/B009KT7PO6 [amazon.com]
Pretty inexpensive. I was envisioning them behind something decorative. Again, maybe FRP?
(Score: 2) by JoeMerchant on Thursday August 20 2020, @10:55PM (3 children)
Nifty, and cheaper than the ones I was looking at... still, would work best for radiant heating/cooling if exposed. I think these are made to underlay concrete for hot water systems.
🌻🌻 [google.com]
(Score: 2) by RS3 on Friday August 21 2020, @02:27PM (2 children)
I've mostly seen them tacked up under wooden floors- between joists, up flat against subfloor. Again, these kinds of things are more common at higher latitudes like mine.
I'll have to think about this whole thing a lot more, but condensation seems like a huge problem for any chilled surface inside a structure. TFA talks about treated surfaces. I almost remember something about a coating that resists water, maybe ionically repels water? Not even sure if that's possible. Drip drip drip.
My personal preferred system, and they exist, would involve an air to liquid heat exchanger with fan and temp. control for each room. Water / anti-freeze would circulate to a central heating / cooling system, often located outside. That system can take or give heat to rooftop panels (which could radiate heat away at night), ground loop, air, graywater, underground thermal storage tanks, whatever.
The master heat pump doesn't need an efficiency-robbing refrigeration reverser- just a control system with solenoid valves to control what goes where. 2 master heat pumps might be needed, or would be more efficient- one for higher temps and one for lower temp ranges.
Control system is the fun part. :)
(Score: 2) by JoeMerchant on Friday August 21 2020, @04:13PM (1 child)
In a home you could probably control the mold better - my entire high school was air conditioned using a chilled water system, no opening windows anywhere, about 2 acres of flat roof. I had chronic bronchitis for 4 years, only cleared up in the summer months, and when I went to college it disappeared permanently.
🌻🌻 [google.com]
(Score: 2) by RS3 on Saturday August 22 2020, @01:18AM
Legionella...
(Score: 0) by Anonymous Coward on Thursday August 20 2020, @04:50PM
Even worse if they're the portable type that have everything inside the building with an exhaust vent to the outside. Rather than proper ones where the hot side of the machine is located outdoors with the energy being dissipated outside, rather than inside where it has to be cooled.