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“Cold Tube” cooling system uses half the energy of an air conditioner

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Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#101

Post by Tade0 »

heisenzombie wrote: post #45

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…

There's even a cost-effective solution available:

https://mse.umd.edu/news/story/cooling-wood-an-ecofriendly-b...

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#102

Post by cyberdrunk »

londons_explore wrote: post #47
sparker72678 wrote: post #32

Earlier quoted context omitted.

The outdoor fresh air intakes are typically via ERVs (Energy recovery ventilation systems). These systems bring in fresh air, filter it, and typically run it through a heat exchanger to minimize energy losses as the fresh air comes and and the stale air goes out. The purpose is to prevent buildup of harmful gasses and VOCs (everything from CO2 to CO to regular out-gassing of furnitures, etc) that can become dangerous…

2020: ”Poisonous stuff in our houses... Bad! Let's vent it to the environment!” 2120: The environment is all full of poisonous gasses from the people of 2020. Each house needs its own air purifier to make the outdoor air safe to breathe.

> 2120: The environment is all full of poisonous gasses from the people of 2020. Each house needs its own air purifier to make the outdoor air safe to breathe.

That's the case in much of the world already... I live in area where there's tons of smog in the colder months and consider installing a system for bringing in filtered air from the outside, so that I won't have to open windows for the 6+ months smog period.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#103

Post by CorrectHorseBat »

ants_a wrote: post #98
ladberg wrote: post #95

Earlier quoted context omitted.

I still feel like "sucking" is misleading because it doesn't change how much heat you radiate, only how much heat is radiated on to you. A better analogy would be like a curtains for heat.

I think that the analogy is used because people underestimate how much heat is lost to radiation. Human body radiates energy away at about 800W. It's not noticeable, because normally it is balanced by a similar flux of thermal radiation coming in from the environment. If the apparent radiative temperature of the environment is reduced it can indeed feel like it is sucking heat out.

You're off by about an order of magnitude there. The human body uses ~10MJ per day which is ~100W. This not only includes radiation losses but also convection and evaporation.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#104

Post by MaxBarraclough »

londons_explore wrote: post #47
sparker72678 wrote: post #32

Earlier quoted context omitted.

The outdoor fresh air intakes are typically via ERVs (Energy recovery ventilation systems). These systems bring in fresh air, filter it, and typically run it through a heat exchanger to minimize energy losses as the fresh air comes and and the stale air goes out. The purpose is to prevent buildup of harmful gasses and VOCs (everything from CO2 to CO to regular out-gassing of furnitures, etc) that can become dangerous…

2020: ”Poisonous stuff in our houses... Bad! Let's vent it to the environment!” 2120: The environment is all full of poisonous gasses from the people of 2020. Each house needs its own air purifier to make the outdoor air safe to breathe.

This is already a reality.

> the first Cordis hotel on mainland China boasts something that is genuinely rare in big Chinese cities: clean indoor air.

https://www.theguardian.com/cities/2018/mar/27/china-clean-a...

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#105

Post by ants_a »

CorrectHorseBat wrote: post #103
ants_a wrote: post #98

Earlier quoted context omitted.

I think that the analogy is used because people underestimate how much heat is lost to radiation. Human body radiates energy away at about 800W. It's not noticeable, because normally it is balanced by a similar flux of thermal radiation coming in from the environment. If the apparent radiative temperature of the environment is reduced it can indeed feel like it is sucking heat out.

You're off by about an order of magnitude there. The human body uses ~10MJ per day which is ~100W. This not only includes radiation losses but also convection and evaporation.

I am not. As I said this outgoing radiation is mostly balanced by incoming radiation. But it does illustrate the theoretical maximal capacity for radiative cooling, when stuck naked in interstellar space.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#106

Post by contravariant »

ekianjo wrote: post #89
sparker72678 wrote: post #7

> 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…

> The notoriously bad energy efficiency of air conditioners Their efficiency is based on thermodynamics, so there's not much you can do to break the physical barriers.

I'm fairly certain air conditioners aren't operating anywhere near the thermodynamic limit. At ordinary ambient temperature you could maintain a temperature difference of 10C with about 3000% efficiency.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#107

Post by julienfr112 »

ants_a wrote: post #105
CorrectHorseBat wrote: post #103

Earlier quoted context omitted.

You're off by about an order of magnitude there. The human body uses ~10MJ per day which is ~100W. This not only includes radiation losses but also convection and evaporation.

I am not. As I said this outgoing radiation is mostly balanced by incoming radiation. But it does illustrate the theoretical maximal capacity for radiative cooling, when stuck naked in interstellar space.

That's a bit misleading. It's like saying i can blow at a pressure of 16 psi in the void, but when I blow into a balloon whith the atmospheric pressure of the environnement, I can only reach 2 psi. The 16 psi is purely theorical.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#108

Post by froj »

CorrectHorseBat wrote: post #103
ants_a wrote: post #98

Earlier quoted context omitted.

I think that the analogy is used because people underestimate how much heat is lost to radiation. Human body radiates energy away at about 800W. It's not noticeable, because normally it is balanced by a similar flux of thermal radiation coming in from the environment. If the apparent radiative temperature of the environment is reduced it can indeed feel like it is sucking heat out.

You're off by about an order of magnitude there. The human body uses ~10MJ per day which is ~100W. This not only includes radiation losses but also convection and evaporation.

> normally it is balanced by a similar flux of thermal radiation coming in from the environment

The parent comment wasn't talking about net power dissipation. 800W radiation would be the case if the environment was at 0K. Usually, the environment radiates about 800W back at you.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#109

Post by froj »

julienfr112 wrote: post #107
ants_a wrote: post #105

Earlier quoted context omitted.

I am not. As I said this outgoing radiation is mostly balanced by incoming radiation. But it does illustrate the theoretical maximal capacity for radiative cooling, when stuck naked in interstellar space.

That's a bit misleading. It's like saying i can blow at a pressure of 16 psi in the void, but when I blow into a balloon whith the atmospheric pressure of the environnement, I can only reach 2 psi. The 16 psi is purely theorical.

That seems like a false analogy. In the case of thermal radiation you actually are emitting photons with a total power of 800W independent of your environment.

Re: “Cold Tube” cooling system uses half the energy of an air conditioner

#110

Post by taneq »

CarbyAu wrote: post #41
eggsnbacon1 wrote: post #13

Earlier 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…

Best marketing voice : "Why migrate to the sunbelt? Burn gas and wait for climate change to bring the warmth to you!" ...sigh. I really hope it doesn't go this way.

Any time I buy property I check how far above sea level it is, so I can estimate when I'll be able to sell it as beachfront property...
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