
Sony’s wearable air conditioner is pretty cool - randyzwitch
https://www.theverge.com/2020/7/22/21333837/sony-reon-pocket-hands-on-wearable-air-conditioner-japan
======
easytiger
It might be worth the author noting that the reason this works is that the
area that it's placed at the base of the neck changes perceived thermal
strain. it is an ancient trick that when one holds an ice cube there it makes
you feel temporarily cooler. The brain gets false information as to the
surface temperature and makes slightly different cooling decisions.

So your body can get to higher temperatures whilst you have a longer period of
tolerance of it. There is some question as to the safety of this for people
who might not be of athletic ability etc. It likely will allow increased,
often significantly, blood pressure. In older people this could be dangerous
if that is the case.

[https://link.springer.com/article/10.1007/s10072-020-04349-x](https://link.springer.com/article/10.1007/s10072-020-04349-x)
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3017491/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3017491/)
[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968886/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968886/)

~~~
kace91
>So your body can get to higher temperatures whilst you have a longer period
of tolerance of it. There is some question as to the safety of this for people
who might not be of athletic ability etc. It likely will allow increased,
often significantly, blood pressure.

Is it possible to use this effect to get the opposite result? that is, fooling
the brain to perceive itself to be hotter than it is to overcharge the cooling
mecanisms at the cost of an unpleasant feeling of heat?

~~~
superhuzza
Yes that's often given as a possible explanation for the popularity of hot
drinks and hot spices in warmer climates.

[https://www.npr.org/sections/thesalt/2012/07/11/156378713/co...](https://www.npr.org/sections/thesalt/2012/07/11/156378713/cool-
down-with-a-hot-drink-its-not-as-crazy-as-you-think)

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ani-ani
For a heavy duty version of this, check out phase change material (PCM) vests.
They are generally lined with pockets holding small PCM packs that maintain a
near-constant temperature for 3-4 hours (then you have to swap the packs).
There are several companies making these but here is one example:
[https://www.texascoolvest.com/](https://www.texascoolvest.com/)

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Someone1234
The thermal camera picture in the article doesn't make sense.

If this is using the Peltier Effect the cold surface would be against the skin
to cool you, and the hot surface would be pointing out towards the thermal
camera which is the opposite of what it shows.

If we take that photo at face value, the device is actually heating the person
and yet their skin is somehow cooler (which isn't actually something this
device can do anyway, it makes you FEEL cooler, but doesn't actually cool you
over a wider area, or worse actuall makes you even hotter as you will sweat
less due to misleading signals).

~~~
slipheen
The article doesn't show the original context for the photo, but I imagine
it's an image of the body after using it, not while the cooler is attached.

~~~
StillBored
Right, but then the question remains why is the lower back cooler in the
picture as well. Is the blood flow through ones entire back flow through that
area first?

Which of course made me think the correct placement for it would be somewhere
with a lot of blood flow near the skin that could be cooled a couple degrees.
I was thinking the inner thigh might be a good place, but the device isn't
shaped correctly for that, given your just going to cool one side, and cook
the other.

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Robotbeat
Doesn’t mention either the power consumption or the amount of heat (in watts)
removed from the skin.

At rest, the body produces about 100 Watts of heat. Pettier coolers aren’t
that efficient... from what I can tell, their energy consumption is roughly
equal to the amount of heat they can remove in situations like this...

So in an order of magnitude calculation, to reject all the body’s heat on a
hot day would require about 100Watts... so about eight 18650 Lithium ion cells
for an hour, so maybe about half a kilogram of cells.

Plus a fan and radiator assembly (roughly the size of a CPU fan and heatsink).
Probably adding about another half a kilogram for a total of 1 kilogram.

EDIT: I think phase change material might be a cheaper and less noisy
option... about a kilogram ice packs will also absorb about 100Wh of heat
before reaching body temperature.

Now if you can get a miniaturized mechanical heat pump that has higher
efficiency (day a coefficient of performance of 2-4) and you need to last for
much longer than an hour, I think you can significantly beat the weight of an
ice pack.... and, of course, water has a heat of vaporization of 627Wh/kg,
beating both options, so simply sweating (and drinking water to replenish) is
the most efficient option per kg... Evolution wins again! (Provided it’s not
too humid that you can no longer evaporate sweat, in which case you can die
even while resting, naked, in the shade, healthy, young, and next to a fan...
which can happen if the “wet bulb” temperature exceeds 35C or 95F ie 100%
humidity at 95F or 50% humidity and 115F on a sustained basis.)

~~~
rapjr9
If you removed all 100W of body heat you'd likely be dead after a while! A
wearable cooling device doesn't have to remove all the heat your body
generates, it just needs to remove enough to make you feel cooler, in addition
to the heat your body already sheds naturally.

~~~
Robotbeat
Depends on how hot it is outside. If it's hot enough that your body can't
reject enough heat naturally, then you'll die WITHOUT such a device. Also, if
it's hot enough outside, your body can actually absorb heat from the
environment.

Also, your metabolic rate is only 100 Watts if you're resting. Any kind of
exertion would be higher.

If it's hot outside, your body sheds heat by sweat. Non-ideal if you like not
being sweaty.

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PTOB
Pre-Covid, Adam Savage built a portable condensing/evap cooling system using
an old Soviet flight suit. He teamed up with an engineer to make it happen.
Fascinating design/build video.
[https://www.youtube.com/watch?v=z_Ti4GP0ntE](https://www.youtube.com/watch?v=z_Ti4GP0ntE)

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gruez
>I did find, generally, that the Reon Pocket improved matters somewhat, even
on its lowest cooling setting. I was definitely still sweating by the time I
got home, but the cooling sensation does make a difference while you’re
actually out there in the heat.

Sounds like the device is useless then? The impression I got is that it
doesn't meaningfully reduce your overall body temperature, but makes one spot
cooler which presumably distracts you from the heat. I've heard that peltier
coolers aren't very efficient or powerful, so this isn't surprising. Can
someone with who studied physics/engineering calculate what the effectiveness
of this is, vs a block of ice that's about the same size? Given the high
latent heat of water it might be worse than a block of ice..

~~~
stefan_
Sounds like even for a cool unique product like this, Verge authors can't be
bothered to do more original investigation than a leisurely walk to the
supermarket allows for.

~~~
spike021
It's The Verge. They haven't been able to do meaningful journalism in years.

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riedel
I wonder if it is so smart to reduce sweating / skin surface temperature when
your body has difficulties cooling down. Seems like the same word of warning
as for cold leg compress might be reasonable. Has someone done the math if
this can really cool you down?

~~~
easytiger
If you see my other comment, you are right to question the wisdom of this. We
all do it for temporary relief with ice etc. But hours at a time tricking the
brain like this is likely to increase blood pressure.

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josefresco
The device uses the "Peltier effect" to cool:
[https://en.wikipedia.org/wiki/Thermoelectric_effect#Peltier_...](https://en.wikipedia.org/wiki/Thermoelectric_effect#Peltier_effect)

~~~
riedel
Yes, you can do cool stuff with it on the skin: Sophroneo: Fear not. A VR
Horror Game with Thermal Feedback and Physiological Signal Loop
([https://dl.acm.org/doi/pdf/10.1145/3334480.3381659?download=...](https://dl.acm.org/doi/pdf/10.1145/3334480.3381659?download=true))

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dragontamer
Hmmm...

Peltiers are inefficient, but very small. They are pretty simple to use: one
side is hot, the other side is cold (when powered). The Peltier, given a
voltage, will try to set the thermal-difference of the hot-side and cold-side
to a set value. (Lets say a 45 degree difference).

Finally, there's a wattage involved: the amount of heat that the Peltier can
"pump". The Peltier's actual temperature is mostly based on the wattage
(500-units of heat flowing out may result in an actual 10-degree difference,
instead of its theoretical maximum 45-degrees... or whatever the device's
limit is).

An actual air-conditioner with a compressor is more efficient. But a Peltier
is a purely electric device (literally: the electrons flowing through the
wires carries the heat itself and dumps it to the hot side). As such, the
Peltier is small, but inefficient (Electrons moving through wires generate
heat. So the more electrons you send (aka: current), the more waste-heat is
generated). An actual air-compressor would do better in any circumstance where
the additional size / weight is allowed.

\--------------

As such, the only practical use of this "wearable air conditioner" are
situations where a larger, more efficient, air conditioner is not available.

Even then: an ice-pack (ie: using a large refrigerator to cool down a thermal
mass) would be far more efficient, and probably a cheaper, use of electricity.

I'm finding it difficult to think of a situation where ice-packs distributed
from a proper compressor are unavailable. Water / Ice is a surprisingly good
"cold storage" mechanism.

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baybal2
I think, I can make a better version:

1\. Make person wear a thermal jacket

2\. Connect thermal jacket through a heat exchanger to a pack of ice, evap
cooler, or a CO2 bottle.

And if cost, and weight is not an issues, one can go for a vapour compression
system.

I worked on a dumb "smart mini vine cellar" once, and the company whose parts
we were buying was also making this:
[https://youtu.be/WbrytRV_LK8](https://youtu.be/WbrytRV_LK8)

~~~
Blahah
Please design and produce this. I suffer from extreme hyperhidrosis. I would
pay quite a lot of money to be able to keep my skin cool and dry day to day.
The market for this is huge and underserved.

~~~
jasonwatkinspdx
Just in case this is a useful suggestion: try checking out auto racing
suppliers. There are undershirts with tubing networks for cool water. They're
meant to go under the fire resistant suit you have to wear under more serious
racing's safety rules. The rigs I've seen have a reservoir with an ice pack
and the equivalent of an aquarium pump that you put in a mini cooler bolted
behind the driver's seat. You could probably macgyver up something similar
with a small hydration bladder style backpack that might give you a few hours
of substantial cooling on the go.

~~~
Blahah
This is awesome, thank you!

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s_gourichon
# Plus sides

Interestingly, this averts the strong issues of evaporation-based air coolers
as explained e.g. on [(67) Personal "air conditioners" aren't what they seem -
YouTube]([https://www.youtube.com/watch?v=2horH-
IeurA](https://www.youtube.com/watch?v=2horH-IeurA)). TL;DW: this works even
if air is pretty humid.

When used outdoors this also even averts the issue of only moving heat very
near.

# Predictable minus sides of the T-shirt option

People with extremely short hair and static position indoor might probably
notice a heat flux rising to the back of their head, in practice this may not
be a problem.

On the contrary, what happens if long hair covers the device? Hair being an
insulator, the device may lose a lot of its efficiency.

Also, resting on your back (e.g. napping) wearing this device would lose its
efficiency.

Apart from those specific situations, this looks like a cool device!

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rapjr9
There have been some other attempts at the same kind of thing:

[https://sg.news.yahoo.com/device-hugs-neck-personal-air-
cond...](https://sg.news.yahoo.com/device-hugs-neck-personal-air-
conditioning-045043008.html)

[https://www.japantrendshop.com/usb-forehead-neck-
cooler-p-29...](https://www.japantrendshop.com/usb-forehead-neck-
cooler-p-2954.html)

[https://www.ebay.com/c/1708057939](https://www.ebay.com/c/1708057939)

[https://shinning.en.made-in-
china.com/product/lCmxOdKYfhVi/C...](https://shinning.en.made-in-
china.com/product/lCmxOdKYfhVi/China-Summer-Neck-Cooler-Soak-in-Water.html)

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rapjr9
I had a system like this more than 10 years ago, sold by Sharper Image, you
can still find them on eBay:

[https://www.ebay.com/c/1708057939](https://www.ebay.com/c/1708057939)

It has metal plates that touch the sides of the neck and a Peltier heat
exchanger with fan on the back. A pack of four C cells was worn on a belt at
your waist or slung over your shoulder. It claimed to work by cooling the
blood in the veins at the side of the neck, so your blood distributed the
cooling throughout your body. When set to High it would cool you down about 5
to 10 degrees F (perceived air temperature, it wouldn't actually cool your
body by that much or you'd be dead). The batteries would only last an hour or
two at the high setting. At a lower setting they'd last much longer but the
cooling effect was much less. It worked but I didn't use it often because it
was uncomfortable to have cold metal plates touching the sides of the neck and
the fan was noisy. After a years use it just stopped working.

Perhaps there is a major vein at the base of the neck to transport the
coolness to other parts of the body? Or maybe the spinal columns fluid does
the heat transfer?

There is indeed research showing that if you cool a persons wrist you can
change their temperature perception, and it has been turned into a product:

[https://www.electronicsweekly.com/news/business/peltier-
effe...](https://www.electronicsweekly.com/news/business/peltier-effect-beats-
heat-2018-07/)

I don't think the principal is the same as this Sony device though. To change
perception requires much less energy than that required to actually cool the
body, and if they could do that on the wrist with a smaller device why build a
bigger device that requires a special shirt to hold the device at the base of
the neck?

For energy efficiency a personal air conditioner makes a lot of sense, why
cool a whole building when you can just cool the people in it? Everyone can
adjust their own temperature then also.

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JoeDaDude
I wonder if this could have a medical application. I'm thinking of those times
when a cold, wet washcloth is placed on the forehead of people with fevers to
cool them down somewhat. Then again, a wet washcloth is a lot cheaper $122.

~~~
jdkrkrkf
The fastest way to bring temperature down in a medical setting is an ice bath,
or injection of cold saline.

They also have cooling blankets, basically a human sized water cooled blanket
connected to a compressor (for cooling the water).

Peltier tech is probably not very useful in this setting, since it's quite
inefficient.

~~~
PTOB
Cold saline really does work. And it's really, really uncomfortable.

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nickpinkston
Some get these for your next Burning Man?

I've been watching Kipp's cooling systems and have wanted to make an AC suit
for some time :-)

[https://www.kippkitts.com/collections/cooling-
systems](https://www.kippkitts.com/collections/cooling-systems)

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haolez
My grandfather was an indian (in Brazil) and he used to wet his ears for the
same purpose. It was a century-old technique from his tribe. I've tried it
once and it does work :)

