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I'm not sure that is an accurate description of the physics. Maybe the air next to the panel is cooler, accounting for the cooling sensation.
I wonder how costly it is to fill your walls entirely with water pipes. Also, one currently ensures there is a stud or lack of electrical when putting nails in a wall. I guess you gotta hang things up differently.
> The notoriously bad energy efficiency of air conditioners Air conditioners are actually pretty fantastically efficient for what they do. The problem with air conditioners is that there's no way to move a ton of heat without using a lot of energy. So, they do use a lot, but they make the most of it. What's truly bad are our buildings that have the minimal insulation and sealing possible, leaking all that cold air ri…
I echo that AC is quite efficient. Far more efficient than traditional heating. There's a misconception that hot areas are less environmentally friendly due to AC. The opposite is true.
Hot areas are only 25 freedom units hotter than humans prefer. Cold areas have months of 50+ temperature difference.
The misconception persists because heat uses gas, which is 5-10X less expensive per BTU of energy than electricity. So it might be cheaper to heat cold areas than run AC in hot ones, but its much more damaging to the environment. Plus, hot climates are using a lot of renewables these days which impacts the environmental friendliness of electric but not gas.
I expect migration to the sun belt to accelerate, at least in the US. It makes a lot of sense from environmental perspectives. In some southern cities there's already long stretches every summer where daytime AC use runs on 70%+ renewable energy.
> .. as a person stands next to or beneath the panel, the body heat radiates towards the chilled panels to create a cooling sensation .. I'm not sure that is an accurate description of the physics. Maybe the air next to the panel is cooler, accounting for the cooling sensation.
> .. as a person stands next to or beneath the panel, the body heat radiates towards the chilled panels to create a cooling sensation .. I'm not sure that is an accurate description of the physics. Maybe the air next to the panel is cooler, accounting for the cooling sensation.
This sounds pretty neat, but their description of cold things sucking thermal radiation doesn't jive with my freshman-physics understanding of thermodynamics. AFAICT they've got cold water circulating in a moisture-repellent membrane, so they're able to absorb heat by chilling the water in the pipes instead of fussing with the humidity in the air like most AC does. So it sounds like trading inefficiency of standard A…
It's the cooling equivalent of a radiant heater, and you need line-of-sight to the walls to feel cooled. The thermal interface is deliberately inefficient for convection (to avoid wasting power chilling the air), but efficient for radiation. Radiation is proportional to absolute temperature T^4. So compared to a glowing radiant patio heater, I'd expect to need maybe (1000^4 - 300^4)/(300^4 - 270^4) ~ 350x the area fo…
Do clothes substantially reduce the effectiveness? Is true line of sight required - visible or near visible spectrum?
Secondly, can you expand a bit about the humidity/condensation aspect? I get the impression that condensation represents inefficiency, and that this somehow avoids having to cool air as a middle layer to cooling a person.
Earlier quoted context omitted.
It's the cooling equivalent of a radiant heater, and you need line-of-sight to the walls to feel cooled. The thermal interface is deliberately inefficient for convection (to avoid wasting power chilling the air), but efficient for radiation. Radiation is proportional to absolute temperature T^4. So compared to a glowing radiant patio heater, I'd expect to need maybe (1000^4 - 300^4)/(300^4 - 270^4) ~ 350x the area fo…
Thanks for explaining. I am also surprised by this possibility given my limited physics knowledge. Do clothes substantially reduce the effectiveness? Is true line of sight required - visible or near visible spectrum? Secondly, can you expand a bit about the humidity/condensation aspect? I get the impression that condensation represents inefficiency, and that this somehow avoids having to cool air as a middle layer to…
It's analogous to the sun shining through a well-insulated window on a winter day--you still feel the radiative heating from the sun, even as the window keeps the warm and cool air separated. Normal window glass wouldn't work for the cooling case, since the heat source isn't the sun (~6000 K) but the human (~300 K), so the wavelengths are much longer, around 10 um, and window glass is opaque there. Plastics with transmission around there are known, though, like the ones used to make the Fresnel lenses for PIR motion detectors. In any case, that membrane lets them keep the cold plate colder than the dew point without condensing water onto it, and also decreases loss of cooling by convection into the air.
It would work best on exposed skin. It should still work with clothes, as long as the clothes aren't too thermally insulating.
1. https://www.energy.gov/sites/prod/files/2013/12/f5/issue7_se...
Not sure why they are researching the mechanism, these systems are commonly installed in Germany and known as "Kühldecke" (cooling ceiling). https://de.wikipedia.org/wiki/K%C3%BChldecke