By Gokulan Kumarananthan
Have you ever wondered how you can stay warm even when it’s freezing cold outside? That you could be shivering with chilliness, place a hand on your neck and still feel warmth? Internal chemical processes like metabolism and circulation help ensure the core temp of our body remains around 36°C. The excess heat given off dissipates quickly in the cold weather... but what if we could harness that lost energy?
This may seem like something out of The Matrix, with humans connected to the National grid and being used as a power source, but it's an incredibly simple concept. Thermoelectric fabrics is fundamentally the idea of being able to harness your body heat through gadgets in clothing to provide an electricity source. Imagine just simply walking around in chilly weather and your t-shirt producing electricity to charge your phone with.
The future of wearable technology.
How it works is by the use of appliances called thermoelectric generators (TEGs) that generate power by converting temperature differences into electric voltage. In this case, where you wear the TEG, the temperature differential is between your body heat and the surrounding air. This is most efficient in very cold climates where the ambient air is chilly, so your body works hard to heat itself up, resulting in a high ratio between the hot area and the cold area, which leads to the most electricity produced.
The gadget would comprise a three-layered structure containing two flat, copper heat spreaders sandwiching the thermoelectric generator. This design is proven to have the highest efficiency and lowest form factor (the physical size and shape of the hardware). Copper is utilised due to its durability and conductivity.
Addressing the idea of integrating the TEG into clothing, the options explored by researchers include placing the gadget in armbands (for the upper arm and wrist), a simple piece of cloth (to be stuck to the chest under a t-shirt) and the t-shirt itself. The researchers measured how much power is produced through TEGs in each of these spots at normal walking speed.
As seen in the table above, the armband on the upper arm has the highest power production because of good contact with the skin and variability of the air flow. However, one could argue the most convenient of these to wear would be a t-shirt. For reference, a phone usually needs around 2-6 watts to charge, so all of these options could charge a phone if that was its intended purpose.
Of course, charging a phone isn’t the only function your body heat can do.
Uses have a wide variety, be it for charging electronics like your phone, powering up sensors to gather data, or even making sure your pants stay smooth and wrinkle free, (a garment called Kinetic Pants).
Let’s dive into more detail. These sensors embedded in the clothes, that would get their energy from the power-harnessing garments, can be used for a multitude of purposes: -In a hospital, to measure the heart rate and blood pressure of a patient. -In space, to measure the oxygen and carbon dioxide percentage in a spacesuit. -In the military for soldiers, to check for the presence of deadly chemical gases in a conflict/warzone.
All of this, with the added benefits of working in the day and night (unlike compact solar panels), and without replacement/recharging (unlike a battery pack).
Taking all these pros into account, there are certainly going to be some pressing issues. There’s a fine line that has to be observed between ensuring enough energy is taken to produce a substantial amount of power, and making sure not too much body heat is taken so that the person doesn’t feel too cold.
In addition, there are questions considering how the clothing can be washed and if there are any health and safety issues that may arise from toxicity after extended use over a long period of time.
We still have a long journey to go before thermoelectric clothing utilising body heat can be mass produced, but that day is steadily coming closer and closer. Eventually, maybe even you, the reader, can scroll through your phone, all while it’s charging with electricity made from the clothes on your back.
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References:
https://news.ncsu.edu/2016/09/wearable-teg-heat-harvesting-2016/ https://phys.org/news/2018-11-harnessing-body-power-electronic-devices.html https://www.sciencedirect.com/science/article/abs/pii/S0306261916312594 https://www.theengineer.co.uk/shirt-capable-of-converting-body-heat-into-electricity/#: ~:text=Belgian%20researchers%20have%20created%20a,power%20low%2Denergy% 20wearable%20electronics
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