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11/06/2017 HYU News > Academics

Title

Making a Heat Storage Device

A piece of contribution to our environment

이창현

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http://www.hanyang.ac.kr/surl/wVKd

Contents
Professor Kim Dong-rip (Electrical Engineering) is one of the many scholars of the field who seek to create a new material that can efficiently store and release heat energy. His new approach of integrating metal or graphene with erythritol, a phase change material, was a significant breakthrough in this endeavor. The details of his research, "Fabrication of three-dimensional metal-graphene network phase change composite for high thermal conductivity and suppressed sub cooling phenomena" were kindly explained to a great length by Kim.


Introduction to Kim’s research field

To simplify Kim’s research, it is conceptually an attempt to create a “heat” battery. Just as the common battery stores and provides electricity, Kim is in the process of creating a heat storage device that can absorb and release heat. The underlying motive of this research was the observation of an irony in two types of industries; one field focuses on cooling temperatures, while the other endlessly work to bring temperatures up. For example, a car factory uses a significant level of heat in shaping and wielding various car parts. However, this heat needs to be constantly in check, since overheating of the factory can cause extreme dangers. On the other hand, a facility that provides heat to households are in forever need of more heat to circulate. Now imagine a device that can absorb the heat from the car factory and deliver it to the heating facility. Kim’s three-dimensional metal-graphene network provides the foundation for what material this device will be made up of.  
 
Kim explaining the details of his research 


This field of technology has received a great deal of attention from the international society in recent decades. Similar to Kim, most scientists turn to the development of a new material for achieving efficient heat storage. The three key standards that a heat storage material or a heat storage device must have, are high energy density, high conductivity, and stability. Historically, the traditional material used for this purpose was water, which lacks efficiency in all three standards for commercial use. To elaborate on these standards, energy density refers to how much energy a material can absorb and retain, which in this case would be heat. High conductivity is the speed at which the material can pass on the energy, vital for efficiency in terms of time. Finally, stability is the ability for the material to maintain its’ initial form after repeated use. As the nature of the material’s task involves repeated heating and cooling, it is imperative that there is no degradation after use. Current research in the field has made somewhat a progress concerning energy density, but has not seen satisfactory achievement in the two other standards.


The distinction of Kim’s breakthrough

The title of Kim’s research explains the breakthrough in this area word by word. Quite bluntly, he has succeeded in the "Fabrication of three-dimensional metal-graphene network phase change composite for high thermal conductivity and suppressed sub cooling phenomena". In the other term, Kim has found a way to create a material (phase change composite) out of metal and graphene, that has high thermal conductivity and stability (suppressed sub cooling phenomena). The term, “three-dimensional” refers to the manner in which metal or graphene is spread throughout this material. The reason for the use of metal was due to its’ high thermal conductivity and general use in the field of mechanics. However, the problem with metal was an inefficient level of energy density. To overcome this limitation, a material called erythritol was introduced. Erythritol is a phase change material (PCM) that is characterized by high energy density and conductivity. It has received a wide range of attention from scholars of various fields for its’ endless potential for utilization.
 
An illustration of how the new material was formed
(Photo courtesy of Professor Kim)


By mixing granules of erythritol with metal paste and subjecting it to hot pressing, a new material composed of 3D metal network was made. This alteration of metal had high energy density, high thermal conductivity, and stability. Furthermore, the same experiment was done using a material called graphene, which had similar results. Specifically, a 3D graphene network had 95% of energy density as pure erythritol, and thermal conductivity was 4.7 time higher than the conventional graphene. As for stability, experiments were carried over 100 times to reveal that the network was stable and the material solid. Furthermore, the metal and graphene network has high flexibility, which indicates a wide scope of utilization methods while maintaining endurance. In fact, this network is stable enough to be put into commercial use right away, and Kim is currently working with different research facilities and companies to explore how this new material can be put into use.
 
The significance of the results

Ultimately, the efficiency of this newfound material will contribute to environmental preservation. As previously mentioned, some industries strive to create heat, while others try to release it. Linking these two fields will create a symbiotic relationship that can also reduce energy costs and help preserve the environment. For example, the average car emits the greatest amount of polluting gases in the process between ignition and waiting for the car to arrive at a certain temperature. If we could use a device that can heat the car up, these gases would decrease significantly. Even electric cars, this heating process is very significant cost of energy. In the end, it all comes down to energy efficiency, which Kim has made a great contribution to.
 
Kim described the positive mind as the ability to find the smallest good thing in the midst of a depressing situation.


In retrospect, Kim pointed out that having a positive mind had been the most helpful support in carrying out his research. When others fall into despair after repeated failures, a person with a positive mind tries to find the silver lining in all of these moments. Kim emphasizes this virtue in all aspect of life. He was especially concerned with many of the students who came to him for counseling. “Today’s students often feel that they are not enough. When writing resumes and giving self-introduction, they feel that they lack fancy achievements to make them stand out”. However, once he gets to know them, they all have distinct talents. Kim explained that seeking room for improvement is indeed important, but to the extent of self-criticism is poisonous. The one thing that he wants to tell his students is that the greatest drive for success is the positive mind.

Lee Chang-hyun        pizz1125@hanyang.ac.kr 
Photos by Choi Min-ju
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