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://www.ncbi.nlm.nih.gov/pmc/articles/PMC3017491/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968886/

>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?

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...

Yes, there is a bracelet that does both heating and cooling effects:

https://embrlabs.com/

Maybe it's a placebo but I wash my hands with cold water in the summer and I believe it makes a small, but noticeable, difference in cooling me.

Wouldn't you simply put a warm object on the neck instead of a cool object?

It does seem like shoes are a better place for this technology -- the feet see a huge amount of bloodflow, and shoes tend to trap heat so there's a bigger thermal differential to exploit.

Because the only way for one side of the device to be cooler is for the other side to be hotter, this particular device must be positioned where the heat from the hot side will dissipate away from the person. (Apparently, heat dissipates fairly well through the kind of shirts people wear in hot weather.) So, putting this particular device in a shoe would not cool down the foot because shoes don't dissipate heat well.

What would cool down the foot would be a device consisting of 2 parts connected by a hose, which would carry liquid from the part in the shoe to the other part (which could be strapped to the bottom of the leg). The liquid would carry heat away from the part in the shoe. A second hose would be needed to return the liquid to the part in the shoe. Call the part outside the shoe the radiator.

Oh god no, don't seal them in the shoes! The device would require custom shoes with venting to dump heat out of the top of the toebox. Or as you say, an external leg-mounted heatpump, but that sounds quite uncomfortable

>The device would require custom shoes with venting to dump heat out of the top of the toebox. Or as you say, an external leg-mounted heatpump

Sounds like a job for Sietch Tabr!

There is already a device like this which uses the wrist: https://embrlabs.com/

I seriously doubt the author was aware of that.

Regarding the ice cube technique, I found some freezable bandanas on Amazon that have the same effect as holding an ice cube or using this Sony device.

Interesting.

Are the dangers still significant for shorter durations? For example, a 10 minute subway journey.

My first thought was “this would be useful for mountain biking in the desert”. But if much of the effect is perception, it seems like it could be very dangerous in an athletic situation.

I don't think the dangers are significant at all. The danger would come from changing how you perceive your level of heat, causing overheating related issues to come without you noticing the warning signs. If you ride the subway for a 10 minute commute every day, and it's a little warm, you will have virtually no side effects from this.

There aren't new side effects, there is just a hiding of symptoms.

would it be safe to wear this while exercising heavily?

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/

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).

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.

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.

I would guess, if it is a real thermal image, that it was taken just after the device was removed to show the users _skin_ temperature.

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.)

> 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...

Adam Savage did a video where he and someone who appears ridiculously well-qualified built one of these https://www.youtube.com/watch?v=z_Ti4GP0ntE

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.

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.

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

>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..

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.

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

Have you heard of their infamous How to Build a PC video? The Verge has a very low reputation for a reason.

> I've heard that peltier coolers aren't very efficient or powerful, so this isn't surprising

Yes, the ones you can buy under $1000 apiece are only %3-%5 efficient.

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?

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.

The device uses the "Peltier effect" to cool: https://en.wikipedia.org/wiki/Thermoelectric_effect#Peltier_...

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=...)

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.

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

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.

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.

This is awesome, thank you!

Would something like this work? I'm not sure how portable they are: https://coolshirt.com/

Have you looked at motorcycle cooling vests?

I have now! Thank :)

Me too. It seriously lowers my quality of life. Have you found any other hacks that make things better?

# 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). 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!

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

https://sg.news.yahoo.com/device-hugs-neck-personal-air-cond...

https://www.japantrendshop.com/usb-forehead-neck-cooler-p-29...

https://www.ebay.com/c/1708057939

https://shinning.en.made-in-china.com/product/lCmxOdKYfhVi/C...

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

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...

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.

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.

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.

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

ThermaZone makes a product for that. Good for migraines, sinus infections, and body aches. It takes A/C and distilled water to make something cold or hot.

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

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 :)