
“Cold Tube” cooling system uses half the energy of an air conditioner - bornelsewhere
https://newatlas.com/energy/cold-tube-cooling-air-conditioner/
======
sparker72678
> 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 right back out into the
environment.

~~~
eggsnbacon1
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 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.

~~~
dylan604
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.

~~~
sparker72678
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
if not cycled regularly.

~~~
londons_explore
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.

~~~
MaxBarraclough
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...](https://www.theguardian.com/cities/2018/mar/27/china-clean-air-
indoor-quality-shanghai-cordis-hongqiao-filters)

------
ladberg
The author doesn't really explain it well because his explanation breaks some
physics laws, so it doesn't "suck" your body heat away.

Instead, it lowers the amount of heat radiating onto you from your environment
by replacing hot walls with cold walls, which will lower the temperature of
your skin.

It's efficient specifically because it _doesn 't_ cool by convection (like
every other cooler). This allows the designers to insulate it so they only
have to offset temperature gained by incoming heat radiation when keeping it
cool. That also means it won't cool the air, just the objects near it.

~~~
labawi
Thermal radiative coupling is bidirectional. Sucking away is appropriate and
important as you do actually have to displace the energy somewhere. It works
the same way when sucking air.

A simpler non-radiating equivalent would be a reflective foil, or a polished
metal - you could enclose yourself within it, get no radiating heat from
environment, yet it wouldn't help cool you, because your radiation has no
place to go.

~~~
taneq
> It works the same way when sucking air.

This is a good analogy because (being pedantic) you can't suck air either. You
can only make a region of lower pressure, into which the higher-pressure air
pushes itself.

~~~
labawi
May I then ask what can you suck, by your definition?

~~~
taneq
Good question! 'Sucking' here is a bit like 'centrifugal force' \- it's a real
thing, but only in the right frame of reference.

In the case of centrifugal force, it's a real thing in a rotating reference
frame, but doesn't exist in an inertial reference frame (because in that frame
the acceleration is towards the center, ie. centripetal).

In the case of suction, it's a real thing when your zero-pressure reference
point is above 'absolute zero' pressure, such as when you're measuring gauge
pressure. In this case you can have an area of 'negative pressure' which is
'sucking' the surrounding fluid into it.

------
heisenzombie
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 thermal conduction, and
this 'magic mirror' on top, to effectively refrigerate its contents by
radiation to space. This uses no power, and works in direct sunlight [^1].

So weird, probably not very practical (what about cloudy days?), but very
cool!

[^1] in fact, if you put it in the shade then it would warm up because it
could no longer radiate to space.

~~~
mkl
> [^1] in fact, if you put it in the shade then it would warm up because it
> could no longer radiate to space.

If I understand correctly, this isn't quite right. If it's in the shade, then
whatever is shading it is radiating more heat onto it (because the shading
object is hotter than space) and possibly reflecting its own radiated heat
back. If it's under a clear sky then it's receiving less heat, so what it
loses by radiating has more effect. Does that sound right?

~~~
hajimemash
I agree with your description, OP possibly concised his words a little too
much as to imply the wrong thing.

~~~
heisenzombie
I agree too :)

------
klyrs
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 AC units for an inefficient
thermal interface -- you need to stand next to it to feel cooled?

~~~
tripletao
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 for the same heat transfer in the opposite direction,
thus their big tunnel instead of a little filament. Even with their cold
source at absolute zero, they'd still need >100x.

~~~
sparker72678
_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.

~~~
URSpider94
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.

------
kristopolous
I saw a very promising AC technology at CES in january that people may find
interesting: [https://www.oxicool.com/](https://www.oxicool.com/)

I don't have the material science or chemistry background to know how
effective it is, but I hope everything they claim holds water, it sounds
pretty good.

There's also a DIY water based AC with pipes and a cheap pump you can find
widely on the internet, but I haven't done it yet. Here's an example
[https://www.instructables.com/id/Hollis-homemade-
AC/](https://www.instructables.com/id/Hollis-homemade-AC/) ... In the comments
one poster suggested a toilet tank as a reservoir, that sounds promising.

~~~
yourapostasy
That's neat and I'm going to keep an eye on it. The -15° F ambient
differential somewhat limits its usefulness, and I'd like to see an induction-
powered heater as an option instead of conduction-based heating. I'm guessing
the 10-year lifespan is due to the fan bearings and the molecular sieve
lifetime, and I'd like to see the overall system lifespan increased by 10X.

Would be interested in the papers behind this tech, as I think there are a lot
of caveats they're glossing over.

[1] seems to be a paper on adjacent technology.

[2] seems to indicate the service lifetime of the molecular sieve is the
controlling factor in the estimated lifecycle. 10 years sounds like the upper
range.

[1]
[https://aip.scitation.org/doi/abs/10.1063/1.4822041?journalC...](https://aip.scitation.org/doi/abs/10.1063/1.4822041?journalCode=rse)

[2]
[http://www.yyindustry.com/news_show.asp?id=28](http://www.yyindustry.com/news_show.asp?id=28)

~~~
kristopolous
They're trying to get version 1 out the door. Hopefully there's a dramatic
improvement and optimization curve still available given it's such early days
still

------
abrowne0
This is just a regular hydronic radiant system which is very efficient because
it doesn’t need to heat the air. The thing is, hydronic systems have been
around for 70 years or more but they typically are not used for cooling
because of the humidity issues that arise which are damaging to the building.
So this can only be implemented in buildings with materials resistant to water
damage. Hydronic radiant systems are the best around it terms of heating
efficiency but very expensive to install. This article seems like hype and bs.

~~~
abrowne0
It does say that there is a Novel membrane to prevent humidity build up, but
there isn’t a lot of information about the membrane and what conditions it
will work in. For instance, Will it work in a wooden structure with drywall?

------
andor
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](https://de.wikipedia.org/wiki/K%C3%BChldecke)

~~~
justinclift
Is this the same kind of thing? (english wikipedia)

[https://en.wikipedia.org/wiki/Chilled_beam](https://en.wikipedia.org/wiki/Chilled_beam)

------
csours
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.

------
zbyte64
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.

~~~
sparker72678
There are some "radiant cooling" installations out there. Most use either the
ceiling or the floor, for the reasons you point out.

~~~
stephen_g
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](https://en.wikipedia.org/wiki/Chilled_beam)

Apparently it works pretty well.

~~~
istjohn
That uses a different mechanism. It cools the air and relies on convection.
TFA specifically avoids cooling the air.

------
infogulch
This is pretty neat. It lets you (somewhat) decouple the temperature and
humidity of the air from how cool it feels to be in the room, by only removing
_radiative_ heat coming from inside the room. You could choose to exchange air
with the outside more rapidly without losing efficiency because you aren't
putting as much energy into conditioning the air itself. I wonder if there are
any infrared-transparent wall paints.

------
b0rsuk
Circulating fan uses tenth the energy of an air conditioner.

The Revenge of the Circulating Fan
[https://www.lowtechmagazine.com/2014/09/circulating-fans-
air...](https://www.lowtechmagazine.com/2014/09/circulating-fans-air-
conditioning.html)

------
username505
This is just a geothermal unit with the evaporator built around the load and
instead of air to air transfer through convection it is air to air transfer
through radiation... nothing but smoke and mirrors. The problem with
efficiency and A/C is the excess heat generated by the compression element of
the Refrigeration Cycle. The closest thing to 100% efficiency is achieved
through absorption chillers that utilize an internal chemical reaction based
off of external heat to produce compression through a metered system... neat
idea though. Heating systems that utilize the same process are different
though - you can achieve greater than 100% efficiency with the use of flash
gas bypass designs that will say for example produce 1.5 tons of heat in a 1
ton system.

------
adrianmonk
This sounds expensive to install. For it to work as well as regular AC,
wouldn't this have to be built into basically all the walls in your home?

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

------
tobyhinloopen
Description seems like a thing from a science fiction.

------
OminousWeapons
This sounds like they reinvented a swamp cooler. Am I missing something?

~~~
pengaru
There is absolutely nothing resembling a swamp cooler going on here.

------
growlist
Pretty cool

(sorry)

------
Stierlitz
> .. 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.

~~~
thefiregecko
This confused me for a bit. The point of the system is to prevent energy from
being reflected or radiated from a surface. Systems like this have been around
for a while ([https://www.energy.gov/energysaver/home-cooling-
systems/radi...](https://www.energy.gov/energysaver/home-cooling-
systems/radiant-cooling)), the news here is that this works with temperatures
below the dew point because they have solved the condensation issues.

