“Cold Tube” cooling system uses half the energy of an air conditioner • Hacker News Board

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

#21

Post by aaron695 » Thu, Aug 20, 2020, 7:07 AM UTC

LifeIsThermal wrote: post #20

Notice how the system cools by absorbing heat from a body, but the greenhouse theory says that the earth surface warms from air absorbing heat from it. The GHE is pseudo-science.

My new rule is upvote anyone who segues into anti-global warming statements on articles that don't mention Global Warming.

Because I'm sick to death of every time an efficiency is mentioned people have to bring out their favourite religion because we all forgot about Global Warming since a hour ago.

I'm also impressed you waited 3 years to comment.

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

#22

Post by m463 » Thu, Aug 20, 2020, 9:40 AM UTC

klyrs wrote: post #2

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…

Gaining or losing heat via radiation isn't as easy as conduction, but it does work.

It's possible to make ice at night in temperate climates by taking the equivalent of a solar concentrator, putting water at the focus and pointing it at a dark patch of clear sky.

You know, probably standing in the sun vs shade is probably the opposite analogy. In the sun you get radiative heating from the sun, in the shade you just get heating from the nearby air.

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

#23

Post by finphil » Thu, Aug 20, 2020, 4:48 PM UTC

This sounds promising. I wonder if such can be implemented in small dwellings.

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

#24

Post by marcinzm » Fri, Aug 21, 2020, 12:32 AM UTC

eggsnbacon1 wrote: post #13

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…

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…

[I was wrong]

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

#25

Post by mrfusion » Fri, Aug 21, 2020, 12:42 AM UTC

foxyv wrote: post #5

klyrs wrote: post #2

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…

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.

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

#26

Post by roywiggins » Fri, Aug 21, 2020, 12:42 AM UTC

marcinzm wrote: post #24

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…

[I was wrong]

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)

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

#27

Post by stephen_g » Fri, Aug 21, 2020, 12:45 AM UTC

marcinzm wrote: post #24

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…

[I was wrong]

But heat pump heating and cooling has coefficient of performance / energy efficiency ratios around 3-4 (or even higher than 5 for certain applications!), so you more than make back your efficiency loss there.

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

#28

Post by dylan604 » Fri, Aug 21, 2020, 12:45 AM UTC

eggsnbacon1 wrote: post #13

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…

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 purpose something about helping help control humidity as well as regulation to bring in "fresh" air to mix with the "stale" air in the building.

So some parts of construction techniques and building materials have improved significantly. However, when comparing the framing lumber used today to what was used in the 60s, I'm shocked that new construction doesn't fall over the first time the wolf huffs and puffs.

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

#29

Post by stephen_g » Fri, Aug 21, 2020, 12:49 AM UTC

sparker72678 wrote: post #12

zbyte64 wrote: post #9

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.

There are some "radiant cooling" installations out there. Most use either the ceiling or the floor, for the reasons you point out.

Yeah, my brother used to work in a building that was cooled like this with a 'chilled beam' system - https://en.wikipedia.org/wiki/Chilled_beam

Apparently it works pretty well.

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

#30

Post by csours » Fri, Aug 21, 2020, 1:03 AM UTC

I'm not an expert, if one is available please comment.

Human perception of temperature is mostly based on 5 things: Ambient air temperature, Radiant Heat (infrared radiation), humidity, direct conduction of heat, and air movement.

It seems like this addresses Radiant Heat. Another way to address this is to add more insulation, install low-emissivity windows, plant shade trees in your yard.

Half of my house feels much warmer in the afternoon because it lacks shade. I used a thermometer to see the difference between the ambient air temperature in the two halves; the hot side was only 2 degrees F hotter. I don't have an IR thermometer, but I imagine that the walls in the hot side are at least 10 degrees F hotter.