Regulating body temperature is a problem that humankind has been contending with for millennia. Our physiology adapted to cope with quite a small part of the world, where the climate is a certain way. Once we spread out across the globe, we had to cope with the entire range of weather systems – from hot and humid jungles to icy tundra.
Of course, when it’s too cold, the technological solution is simple: just wrap up warm. But what happens when it’s too hot? That’s the problem which a new wave of wearable devices aim to solve.
Perhaps the most eye-catching of these is the Reon Pocket from Sony – a small piece of plastic, chargeable via USB-C, which is built to sit against your skin, and to cool you down via the Peltier effect. Released exclusively in Japan, where the humidity during summer is a problem in some regions, it functions, basically, like a small cold device which sits against the skin, which, while welcome, is a little more local as a cooling effect than some of the marketing material might suggest.
The Peltier Effect is one of three thermoelectric effects, produced by thermocouples of the sort you might find on the RS Components webstore. It allows the creation of solid-state heat pumps. If we take two junctions, and apply a voltage across them to create a current, heat will be removed from one and be deposited at the other. Note that this only works in the case of DC circuits; otherwise you’d have heat being moved rapidly from one junction to the other without any useful effect.
The traditional means of air conditioning involves pipes of coolant, motors and compressors. Heat is absorbed at one end of a loop and dispersed at the other. This is the function of those big air-conditioning units you might see sprouting from the tops of office buildings. Obviously, this method wouldn’t be practicable in a wearable device. But it’s only very recently that Peltier-based circuitry has gotten small enough that it can be fitted into a wearable device.
On the other hand, we also have devices powered by another thermoelectric effect – the Seebeck effect – which actually allows for smartwatches which don’t ever need to be charged. Wearable devices like the Matrix Powerwatch can be powered by body heat alone, meaning that you never have to worry about charging them ever again.
Naturally, a world where we’re all walking around with air-conditioned jackets is sure to impose a cost on the environment, in much the same way that air-conditioned buildings has done. If the Seebeck effect is properly leveraged, however, then the effect might run in the opposite direction – we’ll have wearable devices that never need to be charged again!
