What is a Wearable Thermoelectric Generator

Thermoelectric generators are solid state devices that convert difference in temperature between two faces of solid state materials into an electrical energy, the value of the produced energy is proportional to the temperature difference  between the two sides. this is an application of a discovery  by German scientist Thomas Johann Seebeck in 1821.

One of the active and progressing fields of use for theses generators is as a power source for wearable digital electronic devices such as intelligent watches, calculators, wireless , medical sensors and pacemakers. Designing and manufacturing miniature thermoelectric generators for wearable’s is very challenging as the device need to be very small, reliable and durable , it is required to use the human body temperature as the hot side and the surrounding temperature as the cool side, also need to produce sufficient power to keep the wearable working under all weather conditions . Thermoelectric generators  has a preference over photo voltaic in this case as it is not affected by change in weather conditions , if suitable materials are found which can produce very small and reliable generator capable of providing enough power, it is definitely preferred over other types of alternative energy sources.

Fortunately a team of The Korea Advanced Institute of Science and Technology (KAIST) researchers headed by Byung Jin Cho, a professor of electrical engineering, proposed a solution to this problem by developing a glass fabric-based thermoelectric generator that is extremely light, flexible and produces electricity from the heat of the human body. His detailed study can be found using the link in resources below.

Professor Cho came up with a new design technique to build a flexible thermoelectric generator that minimizes thermal energy loss but maximizes power output. His team synthesized liquid-like pastes of n-type (Bi2Te3) and p-type (Sb2Te3) TE materials and printed them onto a glass fabric by applying a screen printing technique. The pastes permeated through the meshes of the fabric and formed films of thermoelectric materials in a range of thickness of several hundreds of microns. As a result, hundreds of thermoelectric material dots (in combination of n and p types) were printed and well arranged on a specific area of the glass fabric.

When using KAIST’s TE generator (with a size of 10 cm x 10 cm) for a wearable wristband device, it will produce about 40 mW electric power based on the temperature difference of 31 °F between human skin and the surrounding air.

Prior to Professor Byung Jin Cho findings, two types of thermoelectric generators have been developed based either on organic or inorganic materials. The organic-based thermoelectric generators use polymers that are highly flexible and compatible with human skin, ideal for wearable electronics but produce a low power output and hence can not be used efficiently. Inorganic-based thermoelectric generators produce the right level of electrical energy, but they are heavy, rigid, and bulky , so not suitable as power source for wearable digital electronic devices .

Professor Cho explained about the research saying ” Our technology presents an easy and simple way of fabricating an extremely flexible, light, and high-performance TE generator. We expect that this technology will find further applications in scale-up systems such as automobiles, factories, aircrafts, and vessels where we see abundant thermal energy being wasted.”

As time pass by , we expect many successful research results and findings using other different materials and techniques to develop an alternative to the above mentioned studies. Wearable digital electronics are expected to be used on a wider scale than at the present time, perhaps by using new suitable power sources.

 

 

Resources

http://www.energyharvestingjournal.com/articles/6444/wearable-thermoelectric-generator#comment-form

http://www.kaist.ac.kr/html/en/

https://need.kaist.ac.kr/index.php?mid=Research03

http://www.eurekalert.org/pub_releases/2014-04/tkai-tgo041014.php

http://www.innovationtoronto.com/2014/04/lightweight-power-generator-wearable-electronics/

 

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