An idea I was told about relatively recently that kind of blew my mind: - Space is cold (~3K) - The atmosphere is really quite transparent in the wavelegth 8-13 μm - If one can construct an optical filter (e.g. grating) which is highly reflective except for a bandpass at 8-13μm, it is possible to reflect most solar energy but still "see" the cold of deep space - It's possible to build a box with sufficiently low ther…
“Cold Tube” cooling system uses half the energy of an air conditioner
51–60 of 137 posts
Re: “Cold Tube” cooling system uses half the energy of an air conditioner
#52> 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…
Portable air conditioners are bad. All the hot components are in the room with you and it takes air from the room and blows it outside. Technology Connections has a good video about this: https://youtu.be/_-mBeYC2KGc?t=355
That's true of the ones that have only one hose to the outside. Those with two hoses are much better, especially if you insulate the hoses:
Re: “Cold Tube” cooling system uses half the energy of an air conditioner
#53An idea I was told about relatively recently that kind of blew my mind: - Space is cold (~3K) - The atmosphere is really quite transparent in the wavelegth 8-13 μm - If one can construct an optical filter (e.g. grating) which is highly reflective except for a bandpass at 8-13μm, it is possible to reflect most solar energy but still "see" the cold of deep space - It's possible to build a box with sufficiently low ther…
Space is without temperature.
Temperature is an attribute of things, space is a lack of things.
What you're referring to is the temperature of cosmic background radiation, which is akin to how you emit infrared radiation at your body temperature. But you certainly don't classify the space where this radiation move through as having your body temperature. The two things are not the same imo.
Re: “Cold Tube” cooling system uses half the energy of an air conditioner
#54Earlier quoted context omitted.
Air conditioners are often more than 100% efficient- they move more heat energy than they consume. (Of course if you start with a fossil fuel, turn it into electricity, and then pipe that into an AC unit, the overall efficiency will be dropped by the efficiency of the power plant, but it's still somewhat made up for by the advantages of heat pumps)
This is false
What is false?
Re: “Cold Tube” cooling system uses half the energy of an air conditioner
#55Earlier quoted context omitted.
New buildings are rather efficient in US. The problem is old buildings that use 5X the energy for HVAC. 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 misconcep…
It is amazing how tight we can make buildings today. I had to learn a lot about HVAC on a remodeling job a few years ago. I had no idea that the drywall can be sealed so tight that when the HVAC system is running it can be next to impossible to open a door without a pressure release duct. Also saw how the HVAC system had vents to bring in air from outside with baffles controlled by the system. Can't remember exact pu…
For regular posts on this topic, see the @buildingsciencefightclub Instagram account. Christine writes delightfully clear posts about modern building science.
Re: “Cold Tube” cooling system uses half the energy of an air conditioner
#56Earlier quoted context omitted.
About 60% of human body heat is lost through radiation. The cooling you would feel would be proportional to the percentage of the area around you that is covered by these cooling walls. Distance wouldn't cause that much loss because the air doesn't absorb much radiation in blackbody range of humans over distances less than 50 meters.(Infrared range with intensity peaking at 93 thousand angstroms)
But when I lose that heat through radiation it would presumably bounce around the room and not much reflects back onto my body. So I’m not seeing how much this really helps. My radiated heat shouldn’t be returning to me anyway.
You lose heat through radiation, but the materials surrounding you are also radiating heat.
You emit thermal radiation at a black-body temperature of 37C or so to the environment, but the average surface nearby (in a non-air-conditioned environment) will be radiating back at 30C or so, for very little net heat loss.
The innovation described here is to replace the local environment with a chilled one that interacts only by radiation. The air with very little mass contributes negligible radiation to the system, so you radiate heat outwards but receive little in return.
Re: “Cold Tube” cooling system uses half the energy of an air conditioner
#57Earlier 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…
And you still have to pump the heat out to somewhere else. The whole premise with this system is that you can keep the temperature higher so you have to pump less heat, which I'm extremely skeptical of, at least for indoor environments.
The biggest gain is that you don’t have to pump out all of the heat of condensation of all of the moisture in the air. Condensing out a pound of water is 200x more energy-consuming than lowering the temperature of a kg of air by 10 degrees C.
Re: “Cold Tube” cooling system uses half the energy of an air conditioner
#58Earlier quoted context omitted.
It is amazing how tight we can make buildings today. I had to learn a lot about HVAC on a remodeling job a few years ago. I had no idea that the drywall can be sealed so tight that when the HVAC system is running it can be next to impossible to open a door without a pressure release duct. Also saw how the HVAC system had vents to bring in air from outside with baffles controlled by the system. Can't remember exact pu…
For regular posts on this topic, see the @buildingsciencefightclub Instagram account. Christine writes delightfully clear posts about modern building science.
I also suggest Matt Risinger’s YouTube channel. Lately he’s been talking about Passive House construction, which supposedly uses only 10% of the energy of a standard built house.
Re: “Cold Tube” cooling system uses half the energy of an air conditioner
#59An idea I was told about relatively recently that kind of blew my mind: - Space is cold (~3K) - The atmosphere is really quite transparent in the wavelegth 8-13 μm - If one can construct an optical filter (e.g. grating) which is highly reflective except for a bandpass at 8-13μm, it is possible to reflect most solar energy but still "see" the cold of deep space - It's possible to build a box with sufficiently low ther…
Space is without temperature. Temperature is an attribute of things, space is a lack of things. What you're referring to is the temperature of cosmic background radiation, which is akin to how you emit infrared radiation at your body temperature. But you certainly don't classify the space where this radiation move through as having your body temperature. The two things are not the same imo.
"Temperature" is a slippery word that has many different definitions depending on what area of physics you're working in.
In this case it is perfectly fine to refer to "the temperature of space" since you're explicitly using it as a cold sink.
As evidence, see the paper (published in Nature no less!) that MengerSponge posted. The authors say "On the other hand, outer space, at a temperature of 3 K, provides a much colder heat sink."
Re: “Cold Tube” cooling system uses half the energy of an air conditioner
#60Earlier quoted context omitted.
This is false
What is false?
The total efficiency of an air conditioner will never be more than 100% based on design; you will never be able to remove more heat than what the system produces in net cooling effect based off of the energy consumption created from compression - this is what would lead you to the eventual path of the theory of the heat death of the universe. You may be able to remove heat from one place to another but never more than what the system produces. Heating systems are completely different regarding efficiency.