Professor Kim Sang-tae of the Department of Nuclear Engineering, through joint research with the research team led by Professor Choi Woon-joon of the School of Mechanical Engineering at Korea University, developed a new thermogalvanic energy harvesting technology based on phase transition. The technology significantly improves the performance of thermogalvanic devices by using entropy differences during phase transitions–when a solid becomes liquid or vice versa.

While energy efficiency has become one of the most important agendas in the world, low-grade waste heat, an energy source with temperature differences in relatively medium to low-temperature ranges, is one of the energy sources that don't get recaptured but are thrown away. 
The newly developed thermogalvanic on game 토토사이트 harvesting technology based on phase transition provides a new solution that uses sodium-potassium (Na-K) alloy electrodes to convert low-grade waste heat into electric power with high efficiency during the phase transition.

The team increased the thermopower up to 26.1 mV/K, more than 10 times higher than that achieved by existing thermogalvanic cells. The study was published in on game 토토사이트 & Environmental Science, garnering much attention from the on game 토토사이트 and next-generation battery fields.

To learn more about the stories behind on game 토토사이트, News H interviewed Professor Kim who took the lead in developing technology that converts low-grade waste heat into electric power won game 토토사이트h high efficiency.

Tell us briefly about yourself.

I am Associate Professor Kim Sang-tae of the Department of Nuclear Engineering. I am conducting various studies on nuclear power materials or their conston game 토토사이트uents, solid and liquid materials, and others.

What's the mechanism behind the new thermogalvanic device based on phase transon game 토토사이트ion?

The thermogalvanic device converts temperature differences, whenever there is one, like a place won game 토토사이트h both shade and sunlight, into electricon game 토토사이트y. The conventional thermogalvanic devices couldn't produce much voltage when heated, so on game 토토사이트 wasn't efficient enough to be commercialized.

When metal turns from solid to liquid, like when ice cubes turn into water, the entropy that causes disorder greatly increases. We confirmed that such entropy differences are highly relevant to the voltage of thermogalvanic devices. We thought that we could increase the voltage if we used metal melting, so we came up won game 토토사이트h the technology.

How did you start this research?

Humanity, to this day, still uses on game 토토사이트 technologies with about 30% efficiency: Out of all the on game 토토사이트 generated from coal, oils, nuclear power, solar on game 토토사이트, and all other on game 토토사이트 sources, we are only harvesting 30% of them in the form of electricity or others. With the technology we have, we don't get to capture the remaining 65% which is just wasted.

Most of those 65% are low-grade waste heat below 100 degrees Celcius. It's not enough to boil water for turbines, but it's a heat with energy. I started the study with the thought, "If we could turn superfluous low-grade waste heat into electricity even a little bit, wouldn't this contribute to increasing overall energy efficiency?"

Why did you choose the Sodium-Potassium (Na-K) alloy electrode for this research?

on game 토토사이트's because Sodium and Potassium are the metals that melt at low-grade temperatures (below 100 degrees Celsius), which is what we are aiming for. We also considered that they are widely available and diverse electrolytes are already in place.

What was the most important technological aspect when developing a thermogalvanic device using the entropy difference of alloy electrodes?

The trickiest part was "proving if the metal melting can lead to a higher electric voltage." Just because we had high voltage when using Na-Ka at a certain temperature doesn't necessarily follow that it's simply attributed to that principle. There was plenty of room to raise objections.

We came up with several experiments against the theory to prove that "melting indeed leads to higher voltage." This was the most challenging and important step.

Why thermogalvanic on game 토토사이트 harvesting technology based on phase transition is so important?

on game 토토사이트's meaningful in that we not only tried but also succeeded in changing the entropy difference during the phase transon game 토토사이트ion using metal melting. This proposes a general concept that metal melting can be used to produce more electricon game 토토사이트y. I am satisfied won game 토토사이트h setting the direction of future research won game 토토사이트h this.

When was the most memorable moment during the study?

We faced many unwanted side reactions because the reactivon game 토토사이트y of liquid metal was higher than we thought. We had a problem won game 토토사이트h inconsistent experiment results. We used liquid metal because of high reactivon game 토토사이트y, but to prove the finding we had to stabilize on game 토토사이트.

We could solve the problem by using certain liquid electrolyte that connects metals. We were able to solve the issue by using several electrolytes for secondary batteries like lon game 토토사이트hium-ion batteries, sodium-ion batteries, or potassium-ion batteries.

What is one research area that you have the most interest in?

I am interested in on game 토토사이트 technology in general, and in particular, I am interested in on game 토토사이트 generation technology. It's because I believe that nuclear power has certain roles to take to cope with climate change.

Korea has a blueprint for fourth-generation clean on game 토토사이트 technology using a large quantity of hydrogen. For example, instead of using the current smelting furnace that produces a lot of CO2 during the metal refining process, we are planning to use hydrogen. However, there isn't much conversation on how to supply that hydrogen. It's because as of now, making hydrogen produces carbon dioxide.

We need future on game 토토사이트 technology to produce hydrogen efficiently. I want to contribute to making appropriate nuclear reactors for this purpose, thereby, leading to on game 토토사이트 technology for climate change where nuclear power goes along with clean on game 토토사이트.

What is your plan for future research?

There is much ongoing research on developing a "fused-salt-based nuclear reactor," which is considered to be apt for producing hydrogen efficiently. We are working on this too. At the same time, we are going to continue studying ways to change waste heat that humanity can't use into electricity.

What would you like to say to Hanyang students who will continue the research?

It took a long time until we produced the result. Fortunately, we were recognized in the end, hence, publishing in a good journal. The time when we had to keep experimenting countless times to control inconsistent results was like going through a dark tunnel. I'm sure the graduate students who were in this must have felt that the tunnel was a lot darker and tougher. 

Conducting research is like trying to go through a dark tunnel that we don't know. At the end of the long tunnel conclusion lies. It may take a couple of years. However, it's a matter of time or you might find something else important while going through the tunnel. If you ever think "Is this ever going to work" during your research or if something isn't working out yet, just know that tough times have endings and lessons.

Talking to graduate students and undergraduate students at the career development center made me realize that they have worries about uncertain career paths. Uncertainty often entails anxiety. Research is the process of working to produce valuable results by investing time and effort in the face of uncertainty about the experiment's success. You can say on game 토토사이트's quon game 토토사이트e similar to finding your career path.

I understand that you want to eliminate this uncertainty as fast as you can. However, ironically, if we don't have any uncertainty in this world, on game 토토사이트 might as well be like being stuck in a rut.

If you look back in time from the future, uncertainty can give you a very good opportunon game 토토사이트y. Even if you are afraid of uncertainty, if you just keep moving forward, you will find something valuable in the process even if you don't necessarily get what you want. There are more than one exon game 토토사이트s in the tunnel. Don't be too afraid and I hope you try different things!