Nov 3, 2020

14 min read

Wearable Air Conditioning - Yes, That’s a Thing Now

Wouldn’t it make more sense to cool individual human bodies rather than use exorbitant amounts of energy to cool down entire buildings? Is that even possible? In our previous post, we explored the strange and futuristic world of smart clothing. Carrying on from that, in this post, we’ll take a look at the equally interesting and strange history of wearable air conditioning technology.

For many years now, there have been mounting concerns about climate change and global warming. Many solemn voices have called humanity out on our ways and implored us to clean up our act. Air conditioning is seen by many as a viciously ironic cycle - air conditioners tend to make their surroundings hotter - and as global temperatures seem to rise and more people command significant disposable incomes, there is an increase in the number of air conditioning units - which again contributes to increasing temperatures. 

As of 2020, there are upwards of 1.2 Billion AC units chugging away around the world, pumping cool air into and hot air out of people’s homes. Popular estimates claim that this figure will go up to a grim 50 billion units by the year 2050! That’s definitely not good news. It has apparently been observed that the 2010-2019 has been the hottest decade in recorded human history. And 2019, scientists claim, was the 2nd hottest year recorded by humans. Let’s face it - not many of us like being cooped up indoors in sweltering heat - It’s no surprise then that bright minds have applied themselves to this problem for ages. Cooling solutions of one variety or the other, believe it or not, have existed right from the times of Ancient Egypt and China. 

The Egyptians hung reeds on their windows and had water trickle down over it in order to keep it wet - The evaporating water cooled down the air flowing in through the windows. A number of other recognisable scientific names such as Faraday and Benjamin Franklin also had a go at devising their own versions of a mechanical cooling device. 

The first modern electrical air conditioning unit was invented in 1902, by American inventor Willis Carrier. Since then, the modern AC has become an indispensable part of modern life, with a 2015 estimate claiming that over 87% of American households had air conditioning systems. 

But make no mistake, air conditioning is not just an indulgent excess of our decadent times - In many areas, it is an inescapable necessity- there are a number of health conditions, including cancer, that make hot temperatures intolerable for patients. A wide range of commercial settings such as drug stores, ATMs and many others, need air conditioning in order to operate optimally. Art galleries, laboratories and research centres have a legitimate need for cool, controlled internal environments. 

Today, the market has finally started seeing wearable air conditioning products in the earnest for the first time. Although the idea has existed in theory for several years, viable, market-ready solutions are only just starting to emerge. In case you just reacted to that with raised eyebrows and skeptical disbelief, you are not alone. The idea of air-conditioned clothing does sound too good to be true. 

But hey, we live in a world where you can point your phone into the sky and an app names the planets and stars you’re looking at! Could it be that we’re really onto something with air-conditioned clothes and wearable air conditioning technology? 

The problem with air conditioning as we know it

Before we get to wearable air conditioners and air-conditioned tee shirts, we need to wrap our hands around why they are even being looked into so seriously in the first place. 

It’s quite simple really - the fact that we have upwards of a billion AC units globally represents a major environmental threat. The reason for this is inherent to the design and working principle of air conditioning units.

For those who are not familiar with how an air conditioner works, here goes - an air conditioning unit works by drawing heat from the air-conditioned room, pushing it outside, and returning the cooled air back into the room.

Obviously, there are more nuances to it. But this is essentially the basis for modern air conditioning. Now, the problem should be as obvious as daylight - the price we pay for cooler homes is a hotter planet. If this effect was unnoticeable and more or less theoretical 50 years ago, today, thanks to the sheer ubiquitousness of air conditioning, it’s a glaringly obvious problem that seriously contributes to climate change. 

And that’s not all - like we said earlier in this post and in earlier articles (like this one), there is another worrying component to this - energy. Keeping our homes cooler than the outside environment requires a lot of energy. Again, you don’t need to be a scientist to figure this out. And as it is, energy is getting harder to come by. With the global population exploding like never before and an increasing number of people commanding unprecedented amounts of disposable wealth, energy demand is shooting up at a breakneck pace. With energy supply not really being able to keep up, we’re looking at a somewhat bleak forecast, energy-wise, in the near future. 

Long story short - if the number of air conditioners in use continues to rise in keeping with the current trend, we’re looking at nothing short of a full-on ecological disaster. 

Yeah, but aren’t air conditioners these days smart?

You might be tempted to make the case that AC manufacturers have been tackling this problem by reducing the energy consumption of air conditioning units. While it is true that modern AC units have dramatically better energy efficiency than their predecessors, the sheer number of units more than offsets higher energy ratings. Moreover, in developing countries, especially those with extremely hot weather, higher rated ACs are still unaffordable to most and are commonly ignored in lieu of cheaper, lower rated units. 

With the advent of devices such as tablets and smartphones, manufacturers started moving towards “smart” air conditioning units which used these devices as smart sensors. Today we have more recent iterations of smart ACs which come with a laundry list of “smart” capabilities like temperature sensing, intelligent internal climate control etc. These smart ACs contain IoT-based sensors which use AI to offer a much more customised and less wasteful solution. 

There is no doubt that the advent of the Internet of Things has made air conditioners less power-hungry and more intelligent in their power use. In the global scheme of things however, considering the reality of our ecological and energy situation, these are mere breadcrumbs. 

The problem with wearable air conditioning

Cooling individual human bodies is inevitably going to be cheaper than cooling entire buildings. This was the idea that led some smart, a couple of decades ago, to wonder if we could air conditioners altogether. 

The idea of air conditioned clothing, in principle at any rate, is not a new one. So, why haven’t we actually seen any viable air conditioned clothes hit the market you ask?

First of all, that’s not the case, as we’ll see in just a little bit. The main reason why the idea of wearable air conditioners hasn’t really been able to take off is because the laws of physics are seemingly in conflict with it - Let us explain - Think about your window or split AC unit; Inevitably, they have a large component that’s placed outdoors. This is because, to cool something down, you have to make something hot. The heat has to be transferred onto another object. This is the first and possibly the most serious challenge when it comes to making air conditioned clothes. As you reduce the size of such a device, it becomes increasingly harder to find a way to dissipate the heat. Also, when said device is sitting on a person’s skin, it’s an altogether different challenge. 

Then, there is the second problem - cooling things down takes a lot more energy than heating things up. This is why cooling devices (refrigerators or air conditioners) tend to be bulky, loud and large. This is by design - cooling is an inherently energy inefficient process. 

The interesting thing with air conditioned clothing is this - they don’t need to work like regular air conditioners in that, we’re dealing with a biological system here. With wearable air conditioning, it’s not so much about absolute temperature values as it is about a perceived increase in comfort, for the wearer. After all, human temperature perception is subjective - what we perceive to be cold is very much a function of the relative temperature gradient between our bodies and the environment. So, a wearable air conditioning device doesn’t necessarily have to work like a scaled down split AC unit - they just need to create a sensation of cold that is substantial enough for the wearer to feel some respite from the heat. At any rate, that’s exactly what the personalised air conditioning devices in the market today are able to manage. 

Working between the two limitations of preserving battery life (due to typically small sizes) and creating a discernible cooling effect, it has to be said that some manufacturers have come out with surprisingly competent offerings. Before we check out some of the more promising personalised air conditioning products out there in the market today, let’s take a brief look at the principle on which most of them are based.

Cooling through the Peltier effect

Today’s air conditioned smart clothes are based on a phenomenon called the Peltier effect. All the way back in the 19th century, a French Physicist named Jean-Charles Peltier observed that when he passed a current through a junction point comprising a metal and a semiconductor, a cooling effect was produced. Much to his amazement, reversing the direction of the current resulted in a heating effect - this is called the Peltier effect. 

Today, the Peltier effect is used in a wide range of devices, which are collectively termed as “thermoelectrics” - Wine coolers, heated bar grips and heated car seats are just some of the everyday applications of this phenomenon.

There are a host of studies presently underway to study potential applications of the Peltier effect in personalised thermoelectric cooling devices. 

Sony’s air conditioned undershirt

Japanese electronics giant Sony made a lot of waves earlier this year when they released their wearable air conditioning product Reon Pocket

The reon pocket, which is based on the Peltier effect, is a little plastic device that weighs less than a hundred grams. Sony claims that the device can simply be used by holding it in your hand, but it is recommended to use it with Sony’s special undershirt which retails separately.

The undershirt, which has been specially designed with the Reon Pocket in mind, has a neat little pocket at the back, that the device slips into. There’s also an app that goes with, to help you control the cooling settings. 

Sony claims that the Reon Pocket can reduce the wearer’s temperature by about 13°C. The device is already available in the Japanese market and retails for just over $120 US. It is yet to hit the shelves in the global market.

Floodgates open

It’s not just Sony that’s come to the wearable air conditioning party - a number of other wearable air conditioning solutions have been gaining popularity in recent times. Embr, a startup founded by MIT students, has come out with a pocket-sized air conditioner called the Embr Wave. 

Much like Sony’s reon pocket, the embr wave employs the Peltier effect. The device is a wristband which retails for about 300$. When you strap it onto your wrist, a ceramic plate that sits on the inside portion of your wrist gets really cold - the company claims that the site was very much chosen deliberately, as this portion of the human anatomy is extremely rich in thermosensitive nerve receptors. 

Again, like we mentioned before, the idea here is not to actually cool the person down like an air conditioner does to a room, but to create a subjective sensation of cold. And to this end, the embr wave seems to live up to its founders’ tall claims - a study conducted by UC Berkeley found that test subjects felt upto 5 degrees cooler using the device. 

This prototype device created by a team of engineers from the University of San Diego goes even further - it’s a small, flexible patch that sticks onto the user’s skin and manages to perform both heating and cooling functions. It brings the skin’s temperature up or down to a comfortable pre-set point, and keeps it there, even as the ambient temperature fluctuates. The patch is made from thermoelectric alloys

“This kind of device can greatly improve your personal thermal comfort, whether you are commuting on a warm day or freezing in your office,” said Renkun Chen, a professor of mechanical and aerospace engineering at UC San Diego who led the study.

Although the device is just in its proof of concept stage, it could be truly revolutionary, if it ever makes it to the market. Even though there are many personal air conditioning devices out there, no manufacturer has really been able to crack the code in terms of usability, portability and ease of integration. Most devices contain large moving parts like a fan or use water as a coolant, which makes integrating them into clothing a nightmare. This patch developed by Dr.Chen and his team is lightweight, flexible and as such, is the solution that is most suited for integration into clothing.

This project, which was funded by the US Department of Energy, has earned several accolades for its ingenious design, which helps it overcome some of the more common shortcomings that plague cooling devices which are based on the thermoelectric effect - Much like most other devices of its ilk, Dr.Chen’s flexible patch, although based around the same principle, does not use a heat sink. Instead, the patch contains an “insulating” layer which is sandwiched between the part that is in contact with the skin surface and the part that is meant to dissipate heat out and away from the body. 

This is the feature that makes the device so versatile in its potential for integration - Dr.Chen hopes to be able to integrate the device into functional clothing intended for labourers who work under extreme conditions like miners and construction workers, although it’s already nearing market viability in its original armband form.

Dr.Chen is confident that the product will be able to find full commercial viability in the nearest future. 

Can we use energy harvesting to power air conditioned clothing?

At ONiO, we live and breathe energy harvesting. Energy harvesting, for those who aren’t in the know, refers to any modern technology that enables a device to operate on energy drawn from its surroundings. 

So then, having examined the most significant challenges that wearable air conditioning technology is faced with, we see the battery problem raise its head once again. This is nothing ne

w. It is no longer a secret that batteries are by far the most crude and unsophisticated power solution out there for portable devices and the sensors they house. They are cumbersome, expensive and worst of all, they are toxic to the environment.

But, unfortunately, energy harvesting is a newly developing area within semiconductor technology and is only just taking its first bold steps. Although energy harvesting technologies are so well suited for wearable devices like health trackers, implants and skin patches, HVAC devices are an entirely different ball game. 

They require enormous amounts of power and as things stand, even batteries are barely up to the task. In the future, maybe we will be able to develop more energy-efficient air conditioning solutions or maybe energy harvesting modalities will offer radically higher energy outputs - we just don’t know yet. 

In the meantime, we’ll leave you with a link to a video where the possibilities for HVAC (heating, ventilation and air conditioning) devices to use energy harvesting, have been discussed.

About the author

Abishek Swaminathen

Senior Content Manager

Abishek is ONiO’s senior content manager. A medical doctor by profession, he stumbled onto a writing career almost by accident, as it were. Words have enthralled Abishek since the day he first held a book and at ONiO, he channels his inner wordsmith towards providing our subscribers with regular doses of fun and informative content.

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