Thermoelectric generators convert heat or cold to electricity (and vice-versa). Normally solid-state devices, they can be used in such things as power plants to convert waste heat into additional electrical power, or in small cooling systems that do not need compressors or liquid coolant. However the rigid construction of these devices generally limits their use to flat, even surfaces. In an effort to apply thermal generation capabilities to almost any shape, scientists at the Ulsan National Institute of Science and Technology (UNIST) in Korea claim to have created a thermoelectric coating that can be directly painted onto most surfaces.
Variously known as the Peltier, Seebeck, or Thomson effect, the thermoelectric effect is seen in semiconductor devices that create a voltage when a different temperature is present on each side or, when a voltage is applied to the device, it creates a temperature difference between the two sides.
The specially-formulated inorganic thermoelectric paint was created using Bi2Te3 (bismuth telluride) and Sb2Te3 (antimony telluride) particles to create two types of semiconducting material. To test the resultant mixture, the researchers applied alternate p-type (positive) and n-type (negative) layers of the thermoelectric semiconductor paint on a metal dome, generating an average power output of 4 mW per square centimeter.
Though not quite up to the 40 mW per square centimeter of some flexible thermoelectric generators, such as KAIST's wearable device (or even close to the high-power delivered by Northwestern University's thermoelectric material), the major advantage of the UNIST prototype is that it can be applied to almost any surface with just a paintbrush.
"By developing integral thermoelectric modules through painting process, we have overcome limitations of flat thermoelectric modules and are able to collect heat energy more efficiently." said Professor Son of UNIST. "Thermoelectric generation systems can be developed as whatever types user want and cost from manufacturing systems can also be greatly reduced by conserving materials and simplifying processes."
According to the UNIST researchers, it should one day be possible to convert heat to electricity by simply painting the external surfaces of buildings, on roofs, and on the exterior of cars, and open the way to many other materials and devices easily transferred to many other voltage-generation applications.
"Our thermoelectric material can be applied any heat source regardless of its shape, type and size." said Professor Son. "It will place itself as a new type of new and renewable energy generating system."
The results of this research were recently published in the journal Nature Communications.