SNU College of Mechanical and Aerospace Engineering Professor YOON Byung Dong and his research team have developed ‘EH Skin’ to convert waste energy into electricity.

"While commuting home, I take out my smart-phone and turn on the air conditioner at home, A few minutes later, there’s a pop-up notice which informs me that the air at home is quite cool enough. In spite of wireless sensors which transmit information from home, the total cost of the electricity bill is reduced. This reduction is mainly caused by higher electricity efficiency utilizing waste energy."

This is possible due to"Energy Harvesting (EH)" technology that harvests waste energy and converts it into electricity. EH technology recycles waste energy without any development devices. Any waste energy such as air conditioner trembling, automobile exhaust heat, and foot pressure against the floor can be used to generate electricity.

Recently the breakthrough device which harvests energy from the air conditioner by pasting thin little piezoelectric elements on the machine was developed. Professor Yoon Byung Dong of the College of Mechanical and Aerospace Engineering Laboratory for System Health & Risk Management and his research team developed a new ‘EH skin’ to paste upon a trembling machine surface such as an air conditioner. The traditional ‘EH skin’ took the shape of sticks which took up lots of space and had low durability. The newly developed one can harvest much more energy by being pasted upon the right spot without taking up any additional space.

The research team members pasted the new ‘EH skin’ upon the most trembling spot of the air conditioner surface. They succeeded in harvesting 70% of total waste energy and converting it into 3.7 milli-watts of electricity. That amount of electricity is sufficient to operate the wireless sensors. In fact, the research team confirmed the real-time temperature information by remote. Professor YOON mentioned, “when the EH skin is attached to a KTX train or airplane airfoil, much more electricity can be generated.” He also explained that the recharging costs of wireless sensor batteries can be reduced greatly with further research.

The team’s research paper ranked among the top ten most-read research papers in March 2011, after being published in international academic journals such as Smart Materials & Structures. Furthermore, it was mentioned as noteworthy research on the respected U.S. Web-based science news portal PhysOrg in April 2011.

Automobiles, vessels and airplanes produce a significant amount of waste energy. The Korea Institute of Machinery and Materials (KIMM) is now engaged in research on how to produce highly-efficient automobiles by harvesting exhaust heat. KIMM System Dynamics Research Center Manager KIM Young Chul mentioned at the ‘EH Research Conference’ held in Daejeon on May 18 that “EH technology contributes to an increase in fuel consumption efficiency by 10%.” Since the automobile exhaust heat reaches several hundred degrees Celcius, the waste energy can be converted into tens of watts of electricity.

This EH technology can be used in factories, plants and buildings to save energy. Professor Yoon said that the new EH device can save up to half of current energy consumption. To harvest waste energy, thermoelectric element efficiency should be raised. The current thermoelectric element converts 5% of heat into electricity, which indicates the level of ‘heat-electricity index 1’. Recently, U.S. CalTech Department of Materials Science Professor Jeffrey Schneider and his research team published their findings on a new thermoelectric element material with high conversion efficiency in the May 5, 2011 issue of Nature, The research team observed the result of heat-electricity index 1.8 at 576 degrees Celcius (850K) through nano-structure improvement. This material can convert 9% of heat into electricity.

Written by JUNG Yu Jin, SNU English Editor, yjjung0503@snu.ac.kr
Proofread by Brett Johnson, SNU English Editor, morningcalm2@gmail.com