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2024
2

Excellent presentation paper by The Society of Air-conditioning and Refrigerating Engineers of Korea (SAREK)

We received the Excellent Presentation Paper Award at the 2024 Summer Conference of the Society of Air-conditioning and Refrigerating Engineers of Korea.
Congratulations!
Excellent presentation paper award at the summer conference of SAREK 2024
2024/06/21
Awards and Honors
We visited Tokyo city university and had a meeting with professor Shukuya for about 20 days.
We discussed how to simplify from the complex building model to the simple RC(Resistance capacitance) model to get insight before the main modeling by simulating the simplified model.
By deriving the energy balance equation from the physical model and solving it using matrix calculations, we were able to understand the overall process of RC model numerical calculation.
We discussed thermodynamics, heat exchange between fluid and pipe, thermodynamic limit temperature, and so on.
We also took the lectures on the role of HVAC systems from a perspective, which gave us the insights to interpret them from an exergy perspective.
We could see that HVAC system works to supply indoor exergy needs but ordinary ones(consisting of evaporators and condensors) work as exergy separators and geothermal heat pump systems work as exergy transportation systems. From an exergy viewpoint, we could understand which system is more work rationally and felt the importance of the exergy concept for understanding more deeply.
From the left to right Student Habin Jo Professor Emeritus Masanori Shukuya, Professor Wonjun Choi
It was an opportunity to expand my knowledge in the exergy field by intensively taking high-quality lectures for a short period of time.
International collaborative research with Prof. Shukuya
2024/01/15 → 2024/02/04
Activity
2023
19

Participation in 2023 SAREK Winter Conference

Location : The Korea Science and Technology Center, Seoul
외피 단열재 위치에 따른 동적 정상상태 엑서지 분석법의 적절성 presented by Habin Jo
복사와 대류 엑서지 전달을 고려한 건물 외피에 대한 계절별 비정상상태 엑서지 분석 presented by Sieun Kim

Presented papers

by Sieun Kim
by Habin Jo
2023 SAREK Winter Conference
2023/11/27
Conferences

Participation in 2023 Autumn KIAEBS Conference

Location : Pusan National University, Busan
지열교환기 설계 파라미터 불확실성에 기인한 지열교환기 출구 유체 온도 변동성 분석 presented by Yoonseong Kim
균일 물질의 열확산계수 및 시스템 길이에 따른 동적 엑서지 분석법의 적절성 검토 presented by Habin Jo

Presented papers

by Habin Jo
by Yoonseong Kim
2023 KIAEBS Autumn Conference
2023/11/10
Conferences
Excellent presentation paper award at the autumn conference of KIAEBS 2023

Participation in 2023 KSES Autumn Conference

Location : Sono Calm Convention Center, Yeosu
Prof. Wonjun, Student Euntak, Sieun and Suhyun
전역 민감도 분석 기반의 지열교환기 설계 길이 불확실성 분석 presented by Euntak Shin
복사와 대류를 고려한 건물 외피에 대한 비정상상태 엑서지 분석 presented by Sieun Kim

Presented papers

by Euntak Shin
by Sieun Kim
2023 KSES Autumn Conference
2023/11/07
Conferences

Participation in 2023 Autumn KSGHE Conference

Location: Chosun University, Gwangju
ASHRAE 지열교환기 설계법에 대한 전역 민감도 분석 Euntak Shin
토양 열응답 함수 불확실성에 의한 지열히트펌프 입구 유체 온도 변화의 확률론적 분석 Yoonseong Kim
The latest research trends and technological advancements in the geothermal and hydrothermal fields were actively shared at the 2023 KSGHE Autumn Conference. There were a total of 33 oral presentations and 43 poster presentations.
Me and Yoonseong presented in the Ground Source Heat Pump session. It was a unique experience because we had previously presented in the same session with other researchers in same field at another conferences like SAREK.
In the past, I couldn't fully concentrate on the presentations of other researchers in the same field because of nervousness about my upcoming presentation. However, meeting them again in the same session made me more focused on their research methodologies and directions.
Moreover, I felt that I could learn more about the aspects I didn't know through the presentations of others.
I also felt that it was essential to pay close attention to the feedback that follows the presentations. Knowing what questions other researchers have about my research can provide valuable hints for preparing future presentations and is an excellent opportunity to critically evaluate what I might have missed. Therefore, even if busy, active participation in conferences is considered essential for expanding one's research capabilities.
After the conference, thanks to Professor Wonjun Choi's consideration, we had the opportunity to participate in a dinner. Although it felt a bit awkward, I was delighted to receive advice and words of encouragement from senior researchers in similar fields during the meal.
Additionally, it was a time to realize the importance of networking through interactions with various professors and industry professionals.
Written by: Euntak Shin

Presented papers

by Euntak Shin
2023 KSGHE Autumn Conference
2023/10/12
Conferences
A new paper titled, has been published in Energy and Buildings.

Paper link

Summary

Data-driven time-series forecasting models for model predictive control of building energy systems have an autoregressive structure that accepts historical data as input. One customary practice is to encode the past 24 h of data to extract daily periodicity information when forecasting 24 h ahead. However, deep learning models have different forecasting mechanisms than traditional time-series models that decompose periodicity. This study focuses on the impact of encoding length in deep learning models used for building energy demand forecasting.
To investigate this, we developed an interpretable deep learning model using an attention mechanism and gated recurrent units. We tested three different encoding lengths: 8 hours, 24 hours, and 168 hours for 24-h-ahead forecasting of zone temperatures and loads.
The findings revealed that the choice of encoding length significantly impacts the model's forecasting behavior and performance. The 24-hour and 168-hour models rely heavily on daily periodicity information, while the 8-hour model depends more on recent state information. This makes the latter more adaptable to sudden changes, providing better accuracy when boundary conditions deviate from typical daily patterns.
The study suggests treating encoding length as a crucial hyperparameter to be optimized based on target characteristics, environmental conditions, and model architecture. It also highlights that an attention weight map can explain a model's inference mechanism which can help improve its performance by adjusting factors like encoding length.

Featured figures

Attention maps of three different encoding length models; (a) 24-h model, (b) 8-h model, and (c) 168-h model
Interpretable deep learning model for load and temperature forecasting: Depending on encoding length, models may be cheating on wrong answers
2023/08/11
Papers
A new paper titled has been published in Case Studies in Thermal Engineering.

Paper link

Summary

This paper presents a novel real-time probabilistic estimation method for determining the thermal properties of backfill material used in underground power transmission lines and ground heat exchangers. The proposed method combines a fast linear analytical model, Bayesian inference, and Jensen-Shannon divergence to enable real-time sequential estimations during field experiments, quantify the estimation uncertainty, and determine the estimation convergence. The method can capture the contextual information affecting the estimation uncertainty, such as the quality of the experiment and the construction state of the backfill. Thus the application of the developed estimation method can lead to significant cost savings by avoiding unnecessary and prolonged experiments.

Featured figures

Illustration of real-time sequential estimation of the probability density function for the backfill thermal conductivity, along with the temporal change in Jensen-Shannon divergence.
Real-time probabilistic backfill thermal property estimation method enabling estimation convergence judgment
2023/06/27
Papers
Excellent presentation paper award at the summer conference of SAREK 2023

Participation in 2023 SAREK

Location : YongPyong resort, Pyeongchang
건축재료의 열확산계수와 시스템 두께에 따른 동적상태와 비정상상태 엑서지 분석법 비교 presented by Habin Jo
복사와 대류를 고려한 건물 외피에서의 비정상상태 엑서지 분석 presented by Sieun Kim
건물 도메인을 포함한 설계 파라미터들의 불확실성이 지열교환기 설계 길이 불확실성에 미치는 영향 분석 presented by Euntak Shin
다양한 지열교환기 클러스터의 열응답 함수 불확실성에 관련된 변수 기여도의 시간적 변화 분석 presented by Yoonseong Kim
From 21 to 23 June 2023, Euntak, Yoonseong, Habin and Sieun had the opportunity to present our paper at the YongPyong Resort in Pyeongchang.
Through this academic presentation, we were able to participate in various knowledge sharing and discussions on building energy use and energy-efficient equipment technologies. It was an opportunity to broaden our knowledge by sharing opinions with various people, not only academics but also those who are working in the field.
In this conference, many researchers specializing in building HVAC systems gathered. In the previous conference, we attended merely as listeners, which felt like to attending a university lecture. However, this conference felt very differen기t. We focused on how other people conducted their research, the methods they used to derive their results, and their presentation skills. Furthermore, the feedback we received after our presentation was beneficial. It helped us prepare for our next presentation and added elements that made our research more sophisticated. Although going to Pyeongchang was not easy, it was definitely worth it.

Presented papers

by Sieun Kim
by Habin Jo
by Euntak Shin
by Yoonseong Kim
by Wonjun Choi
2023 SAREK Summer Conference
2023/06/21 → 2023/06/23
Conferences

Participation in 2023 IAQVEC

Location : Tokyo Big Sight, Japan
Uncertainty quantification of borehole heat exchanger design length based on a global sensitivity analysis, presented by Euntak Shin
Comparison of dynamic and unsteady-state exergy analyses for materials with different thermal diffusivities presented by Habin Jo
Euntak and Habin had an opportunity to present their academic papers on building energy usage and techniques for the built environment at Tokyo Big Sight during the period of May 20th to 23rd, 2023. This international event offered a diverse range of building physics-related topics, providing a unique platform for knowledge exchange and constructive discussions beyond traditional academic conferences. This presentation opened up new perspectives and insights related to their area of expertise.

Presented papers

by Euntak Shin
by Habin Jo
2023 IAQVEC Conference
2023/05/20 → 2023/05/23
Conferences
Location: Institute of Industrial Science, The University of Tokyo
The IEA Annex 87 meeting was held at the Institute of Industrial Science in Tokyo univ. The topic of Annex 87 was Energy and indoor environmental quality performance of personalized environmental control systems (PECS). During the meeting, the subtask leaders presented their advancements and findings in their subtask. The participants engaged in discussions and shared feedback actively.
Throughout the meeting, it helped to understand the requirements, standards, and guidelines for PECS can vary greatly depending on the use of the building. It was also informative to know about the different technologies required to achieve PECS.
IEA Annex 87 Expert Meeting
2023/05/19
Activity
Location: Institute of Industrial Science, The University of Tokyo
The IEA Annex 37 meeting was held at the Institute of Industrial Science at Tokyo univ. The topic of Annex 37 was Smart Design and Control of Energy Storage Systems. During the meeting, the subtask leaders presented and shared updates on their respective subtasks and actively participate in discussions and feedback.
The meeting provided insights into the energy storage systems, with a particular emphasis on demand-side management strategies. Through Annex 37, helped an understanding of the utilization of phase change materials (PCMs) as a solution for energy storage systems.
After the meeting, we had a tour of the laboratory equipment.
IEA Annex 37 Expert meeting
2023/05/18
Activity

2023 Spring Conference of Architectural Institute of Korea

Date: 2023.04.26 ~ 2023.04.28
Location: BEXCO Exhibition Center 2, Haeundae, Busan
Prof. Wonjun Choi, student Euntak, Yoonseong, and Habin presented at the Spring Conference held at BEXCO Exhibition Center 2 (Haeundae, Busan) from April 26 (Wed) to 28 (Fri), 2023.
전역 민감도 분석을 이용한 지중열 교환기 설계 길이의 불확실성 산정 presented by Euntak Shin
전역 민감도 분석을 활용한 토양 열응답 함수 관련 변수의 시간에 따른 기여도 변화 분석 presented by Yoonseong Kim
열확산계수가 다른 균일물질에 대한 동적 엑서지 분석법과 비정상상태 엑서지 분석법의 비교 presented by Habin Jo

Presented paper

by Euntak Shin
by Yoonseong Kim
by Habin Jo
by Wonjun Choi
2023 AIK Spring Conference
2023/04/26 → 2023/04/28
Conferences
A new paper titled, has been published.

Paper link

Summary

Buildings and their energy systems are characterized by unique and complex features that can evolve over time. Moreover, building data is highly seasonal, which means that it is subject to variations according to the time of the year. Therefore, an effective deep learning model with exceptional adaptability (i.e., high performance with little data) is required to accurately forecast and control the energy systems of buildings.
Considering the intricate nature of the building-energy field, we conducted a benchmark study to compare the performance of six different deep learning architectures. These included the multilayer perceptron (MLP), simple recurrent neural network (RNN), long short-term memory, gated recurrent unit (GRU), dilated convolutional neural network (DCNN), and transformer. To analyze the effect of data seasonality on forecasting performance, we also developed a data similarity analysis method.
To ensure the reproducibility and accessibility of our benchmark, we utilized a publicly accessible data generator and the open-source Python library DeepTimeSeries. Our forecasting targets were the zone temperatures and thermal loads over a future 24-hour period. The benchmark results, with varying training dataset sizes ranging from 0.3 to 0.9 y, showed that the transformer architecture performed the best, especially on small training datasets. The GRU and RNN came in second and third place, respectively, while the rankings of other architectures varied depending on the training dataset size and forecasting targets.
Additionally, the data similarity analysis revealed that simply increasing the training dataset size does not necessarily improve the model performance. This highlights the importance of model training with highly similar data for the forecasting period.

Featured figure

Matrix plot summarizing the performance rank of six deep learning architectures
Performance evaluation of deep learning architectures for load and temperature forecasting under dataset size constraints and seasonality
2023/04/06
Papers
We visited the University of Tokyo and Tokyo city university and had a chance to look around some research facilities after that we talk with Professors and Doctors
Large facilities used for the wind tunnel experiments in the production technology lab of the University of Tokyo
The Professor Ryozo Ooka and Doctor 오원석
Especially, in Tokyo city university we met Masanori Shukuya who the best expert on exergy and thermodynamics in the world and we learn about the concept of exergy directly.
Professor Masanori Shukuya Teaching Exergy
What I learned the most in the class is the lecture attendees asked so many questions. They are very active about their curiosity and understanding and this attitude made the lecture bilateral. So we can expand our knowledge in many ways.
From the left to right Professor Wonjun Choi, Professor Emeritus Masanori Shukuya, Student Habin Jo
Through this experience, I thought the opportunity interact with researchers was expanded not only domestically.
Visiting University of Tokyo and Tokyo City University
2023/02/20 → 2023/02/24
Activity
We visited the Korea Institute of Energy Research (KIER). We can look around experiment equipments and also know about the Academic Co-op courses.
At the entrance of the KIER
We learned about the purpose of use and how to use the equipment of laboratory by listening to the lab’s Doctor.
Visiting of Korea Institute of Energy Research (KIER)
2023/02/08
Activity
2022
3

Participation in 2022 KIAEBS

Location: Yonsei University, Seoul
Euntak successfully made her first domestic conference presentation.
전역 민감도 분석 기반의 지중열 교환기 설계 길이의 불확실성 산정 presented by Euntak Shin
Yoonseong, Euntak, and Prof. Wonjun

Presented paper

by Wonjun Choi
by Euntak Shin
2022 KIAEBS Autumn conference
2022/11/25
Conferences

Participation in 2022 Autumn KSES

Location: Jeju Oriental Hotel, Jeju
Researchers at the University of Seoul and members of the betlab
We attended the Autumn Conference of Korea Solar Energy Society event on Jeju Island, which took place from October 19 to 21, 2022

Presented paper

by Wonjun Choi
2022 KSES Autumn conference
2022/10/19
Conferences

Participation in 2022 Summer SAREK

Location: Phoenix Park, Pyeongchang
Yoonseong, Euntak, Prof. Wonjun, Yunseon and Habin
From June 22nd to 24th 2022, we attended the Summer Conference of the Korean Society of HVAC (Heating, Ventilation and Air Conditioning) held at Phoenix Park in Pyeongchang, Gangwon Province."

Presented paper

by Wonjun Choi
2022 SAREK Summer conference
2022/06/22 → 2022/06/24
Conferences