Interpretable probabilistic forecasting of building multi-energy loads using residual learning and global attention-enabled transformer: A case study for residential buildings in South Korea Hyung Joon Kim, Dongwoo Kim, Hyunwoo Tak, Jae Yong Lee Energy and Buildings, 2026 • Interpretable probabilistic multi-energy load forecasting for building-level IES. • A global attention-enabled Transformer models inter-load and temporal dependencies. • Gaussian-based residual learning improves error calibration and prediction intervals. • Deep SHAP quantifies feature contributions and cross-validate the PMELF results. Accurate forecasting of building-level multi-energy loads is essential for artificial intelligence (AI)-supported design and resilient operation in residential u-IESs, enabling risk-aware planning under uncertainty. However, despite recent advances, existing multi-energy load forecasting (MELF) models still face two key challenges. First, existing models, which are primarily designed for regional-level integrated energy systems such as university campuses with relatively stable operating patterns, lack explicit mechanisms to capture complex coupling relationships among multi-energy loads and often overlook localized building-level load behaviors, thereby reducing sensitivity to subtle demand variations and degrading the quality of the resulting prediction intervals. Second, current MELF models offer limited interpretability, making it difficult to validate model behavior and elucidate the impact of multi-energy interactions on forecasting performance. To address these issues, this study proposes a new interpretable probabilistic MELF (IPMELF) framework that integrates global attention mechanisms with a residual learning-enabled multiple-decoder Transformer architecture for building-level u-IESs. First, a global attention mechanism that integrates feature-wise and time-wise attention with a fusion layer is employed within the Transformer network to explicitly capture the interrelationships among multiple loads as well as the temporal dependencies of multi-energy loads. Gaussian Process Regression-based residual learning is then integrated to enhance local sensitivity, calibrate forecasting results, and produce high-quality prediction intervals by modeling the discrepancy between deterministic predictions and the ground truth with a composite kernel. Finally, Deep Shapley Additive Explanations are applied as a cross-validator, offering clear rationale for PMELF predictions. Case studies conducted on real-world residential buildings in South Korea demonstrate the superior performance of the proposed IPMELF framework, achieving the highest average forecasting accuracy with an R 2 of 95.84%, the lowest pinball loss of 3.34, and improved coverage with narrower prediction intervals, while enhancing the interpretability and trustworthiness of the PMELF results.
Field evaluation of a soft actor–critic-based control strategy for a centralized geothermal heat pump system Dongwoo Kim, Hyung Joon Kim, Hyunwoo Tak, Jae Yong Lee Energy Conversion and Management, 2026 Reinforcement learning (RL) has attracted increasing attention for building energy system control. However, its real-world application remains limited owing to sensor constraints, legacy hardware, and operational uncertainties. This study presents the development and field evaluation of a Soft Actor–Critic (SAC)-based optimal control strategy for a centralized ground-source heat pump cooling system in an existing commercial building. The proposed controller optimizes the number of operating heat pumps and chilled-water supply temperature by considering the outdoor conditions, ground-source temperature, buffer-tank temperature, and Time-of-Use electricity pricing without relying on real-time indoor temperature measurements or hardware modifications. A physics-informed simulation environment was constructed using simplified thermal models of the building, buffer tank, and geothermal loop. The SAC policy was trained using historical summer weather data representative of the study site. The trained controller was then deployed in a real building and evaluated through field A/B testing conducted over multiple months against a conventional rule-based control strategy. Fair comparison was ensured by normalizing weather-induced performance variations using the outdoor air enthalpy. Field results demonstrated that the SAC-based control reduced electricity consumption by 11.75% and electricity costs by 13.27% compared with the rule-based baseline, while maintaining comparable cooling energy delivery. The results confirm that reinforcement learning-based control can be effectively implemented in legacy ground-source heat pump systems and can deliver tangible energy and cost benefits under real operating conditions.
Residential heating energy usage patterns under the COVID-19 pandemic in Korea Chihye Bae, Jae Yong Lee, Dongwoo Kim, Chungyoon Chun Indoor and Built Environment, 2025 This study examined the impact of the COVID-19 pandemic on residential heating energy consumption in South Korea, focusing on space heating and hot water production. Using data from smart meters and surveys in the Y Apartment Complex, the research analysed consumption patterns before COVID-19 (2019), during the early stages (2020) and the spread period (2021). The findings reveal significant variations in heating energy usage due to increased time spent at home and heightened hygiene awareness. During the spread period, there was a shift to consistent space heating throughout the day, with reduced night time heating and increased daytime and minimal control patterns compared to the pre-COVID-19 period. Hot water consumption was also increased overall, particularly in the early pandemic period, due to heightened hygiene awareness. Cluster analysis shows that households maintaining lower indoor temperatures pre-pandemic experienced higher consumption growth post-pandemic. Households with children and students had significantly higher increases in hot water usage. These findings enhance our understanding of the impact of COVID-19 on residential energy consumption and underscore the need for adaptive energy management strategies that can dynamically adjust practices in response to changes in occupant behaviour during significant social upheaval such as the pandemic.
Optimization of Centralized-Distributed cooperative heat pump systems for Performance, Costs, and environmental benefits in electrified buildings Dongwoo Kim, Jae Yong Lee, Hyunwoo Tak, Hyung Joon Kim Applied Thermal Engineering, 2025 • Electrified systems with heat pumps outperform traditional gas boilers. • Centralized–distributed cooperative systems optimize energy, costs, and emissions. • Cooperative systems cut costs and CO 2 by 16.43% and 19.39%, respectively. • Cooperative systems reduce reliance on oversized equipment and storage. Heat pumps play a critical role in electrified building systems, yet their performance and reliability often degrade significantly during cold winter conditions, challenging their broader implementation. This study evaluates the performance, economic feasibility, and environmental impacts of a novel centralized–distributed cooperative heat pump system compared to a baseline gas boiler and two electrified configurations: decentralized and centralized systems. While the cooperative system addresses winter performance degradation and enhances heat pump stability, its potential is limited under rule-based operation. To overcome this limitation, an optimization model was developed considering the actual annual heating, cooling, and domestic hot water demands of a 100-household residential apartment complex. Results show that the cooperative system outperforms decentralized and centralized systems in energy efficiency, cost savings, and CO 2 emissions reduction. The optimized cooperative system reduced total costs and CO 2 emissions by 16.43% and 19.39%, respectively, compared to the baseline, while reducing the rated capacity of the equipment and minimizing reliance on thermal storage. These advantages were maximized with optimization, dynamically adjusting intermediate temperatures and operational modes to suit varying load conditions. Heat pump systems can potentially redefine residential energy systems in electrified buildings, with cooperative configurations enhancing performance, flexibility, and sustainability.
Experimental study of flash tank injection on a heat pump system with a rotary compressor Acra 2016 8th Asian Conference on Refrigeration and Air Conditioning, 2016
A theoretical model for a gas injection heat pump used in electric vehicles Acra 2014 Proceedings of the 7th Asian Conference on Refrigeration and Air Conditioning, 2014
RECENT SCHOLAR PUBLICATIONS
Offline Reinforcement Learning for Optimal Control of a Greenhouse with Ground Source Heat Pump C Jang, D Kim, R Yun Energy, 141404 , 2026 2026
Field evaluation of a soft actor–critic-based control strategy for a centralized geothermal heat pump system D Kim, HJ Kim, H Tak, JY Lee Energy Conversion and Management 354, 121248 , 2026 2026
Interpretable probabilistic forecasting of building multi-energy loads using residual learning and global attention-enabled transformer: A case study for residential buildings … HJ Kim, D Kim, H Tak, JY Lee Energy and Buildings, 117424 , 2026 2026
Global-local attention-enabled multiple decoder Transformer for multi-energy load forecasting in user-level integrated energy system HJ Kim, D Kim, H Tak, JY Lee Applied Energy 396, 126255 , 2025 2025 Citations: 18
Empirical analysis of the demand-based heat supply system in district heating buildings D Kim, H Tak, JY Lee Applied Thermal Engineering 277, 127031 , 2025 2025 Citations: 8
Heat demand response of end users based on energy awareness level and energy-monitoring app usage D Kim, C Bae, JY Lee Journal of Building Engineering, 113721 , 2025 2025
Residential heating energy usage patterns under the COVID-19 pandemic in Korea C Bae, JY Lee, D Kim, C Chun Indoor and Built Environment 34 (7), 1422-1444 , 2025 2025 Citations: 1
Optimization of Centralized-Distributed cooperative heat pump systems for Performance, Costs, and environmental benefits in electrified buildings D Kim, JY Lee, H Tak, HJ Kim Applied Thermal Engineering 272, 126464 , 2025 2025 Citations: 6
Deep reinforcement learning-based residential building energy management incorporating power-to-heat technology for building electrification HJ Kim, JY Lee, H Tak, D Kim Energy 317, 134601 , 2025 2025 Citations: 15
Understanding Residents’ energy consumption Profiles: Behavioral segmentation analysis of heat energy consumption in Korean apartment residences C Bae, JY Lee, D Kim, C Chun Energy and Buildings 319, 114482 , 2024 2024 Citations: 12
A study on the impact of residents' energy usage behavior on heating energy consumption based on smart meter data and surveys C Bae, JY Lee, D Kim, C Chun Energy and Buildings 300, 113634 , 2023 2023 Citations: 18
Analytical study on changes in domestic hot water use caused by COVID-19 pandemic D Kim, T Yim, JY Lee Energy 231, 120915 , 2021 2021 Citations: 54
Energy performance evaluation of two-phase injection heat pump employing low-GWP refrigerant R32 under various outdoor conditions D Kim, DC Lee, M Lee, HJ Chung, Y Kim Energy 214, 119098 , 2021 2021 Citations: 28
Two-phase flow patterns and pressure drop of a low GWP refrigerant R-1234ze (E) in a plate heat exchanger under adiabatic conditions DC Lee, D Kim, S Yun, Y Kim International Journal of Heat and Mass Transfer 145, 118816 , 2019 2019 Citations: 36
Novel optimized operating strategies of two-phase injection heat pumps for achieving best performance with safe compression D Kim, S Myeong, D Cha, Y Kim Energy 187, 115925 , 2019 2019 Citations: 21
Evaporation heat transfer and pressure drop characteristics of R1234ze (E)/R32 as a function of composition ratio in a brazed plate heat exchanger DC Lee, D Kim, W Cho, Y Kim International Journal of Heat and Mass Transfer 140, 216-226 , 2019 2019 Citations: 37
Composite fouling characteristics of CaCO3 and CaSO4 in plate heat exchangers at various operating and geometric conditions KS Song, J Lim, S Yun, D Kim, Y Kim International Journal of Heat and Mass Transfer 136, 555-562 , 2019 2019 Citations: 74
Comparative thermal performance evaluation between ultrathin flat plate pulsating heat pipe and graphite sheet for mobile electronic devices at various operating conditions DS Jang, D Kim, SH Hong, Y Kim Applied Thermal Engineering 149, 1427-1434 , 2019 2019 Citations: 58
An experimental study on the evaporation heat transfer and pressure drop of R-1234ze (E) in a shell and plate heat exchanger CU Jo, DC Lee, D Kim, Y Kim 25th IIR International Congress of Refrigeration, ICR 2019, 474-479 , 2019 2019
극저온 지역난방시스템에서의 캐스케이드 열 공급에 대한 연구 이민우， 김동우， 이상헌， 이정훈， 김용찬 대한기계학회 춘추학술대회, 1935-1938 , 2018 2018
MOST CITED SCHOLAR PUBLICATIONS
Performance comparison between R410A and R32 multi-heat pumps with a sub-cooler vapor injection in the heating and cooling modes IY Cho, HJ Seo, D Kim, Y Kim Energy 112, 179-187 , 2016 2016 Citations: 111
Thermal comfort and energy saving in a vehicle compartment using a localized air-conditioning system MS Oh, JH Ahn, DW Kim, DS Jang, Y Kim Applied Energy 133, 14-21 , 2014 2014 Citations: 107
Evaporation heat transfer coefficient and pressure drop of R-1233zd (E) in a brazed plate heat exchanger DC Lee, D Kim, S Park, J Lim, Y Kim Applied Thermal Engineering 130, 1147-1155 , 2018 2018 Citations: 100
Performance comparison among two-phase, liquid, and vapor injection heat pumps with a scroll compressor using R410A D Kim, Y Jeon, DS Jang, Y Kim Applied Thermal Engineering 137, 193-202 , 2018 2018 Citations: 97
Flow patterns and heat transfer characteristics of flat plate pulsating heat pipes with various asymmetric and aspect ratios of the channels DS Jang, JS Lee, JH Ahn, D Kim, Y Kim Applied Thermal Engineering 114, 211-220 , 2017 2017 Citations: 83
Composite fouling characteristics of CaCO3 and CaSO4 in plate heat exchangers at various operating and geometric conditions KS Song, J Lim, S Yun, D Kim, Y Kim International Journal of Heat and Mass Transfer 136, 555-562 , 2019 2019 Citations: 74
Comparative evaluation of flow boiling heat transfer characteristics of R-1234ze (E) and R-134a in plate heat exchangers with different Chevron angles D Kim, DC Lee, DS Jang, Y Jeon, Y Kim Applied Thermal Engineering 132, 719-729 , 2018 2018 Citations: 73
Comparative thermal performance evaluation between ultrathin flat plate pulsating heat pipe and graphite sheet for mobile electronic devices at various operating conditions DS Jang, D Kim, SH Hong, Y Kim Applied Thermal Engineering 149, 1427-1434 , 2019 2019 Citations: 58
Effects of ejector geometries on performance of ejector-expansion R410A air conditioner considering cooling seasonal performance factor Y Jeon, J Jung, D Kim, S Kim, Y Kim Applied Energy 205, 761-768 , 2017 2017 Citations: 58
Performance characteristics of an R600a household refrigeration cycle with a modified two-phase ejector for various ejector geometries and operating conditions Y Jeon, S Kim, D Kim, HJ Chung, Y Kim Applied Energy 205, 1059-1067 , 2017 2017 Citations: 58
Optimization of the injection-port geometries of a vapor injection scroll compressor based on SCOP under various climatic conditions D Kim, HJ Chung, Y Jeon, DS Jang, Y Kim Energy 135, 442-454 , 2017 2017 Citations: 57
Analytical study on changes in domestic hot water use caused by COVID-19 pandemic D Kim, T Yim, JY Lee Energy 231, 120915 , 2021 2021 Citations: 54
Condensation heat transfer characteristics of R245fa in a shell and plate heat exchanger for high-temperature heat pumps J Lim, KS Song, D Kim, DC Lee, Y Kim International Journal of Heat and Mass Transfer 127, 730-739 , 2018 2018 Citations: 53
Comparative performance evaluation of self-humidifying PEMFCs with short-side-chain and long-side-chain membranes under various operating conditions D Cha, SW Jeon, W Yang, D Kim, Y Kim Energy 150, 320-328 , 2018 2018 Citations: 47
Evaporation heat transfer and pressure drop characteristics of R1234ze (E)/R32 as a function of composition ratio in a brazed plate heat exchanger DC Lee, D Kim, W Cho, Y Kim International Journal of Heat and Mass Transfer 140, 216-226 , 2019 2019 Citations: 37
Comparative performance evaluation of conventional and condenser outlet split ejector-based domestic refrigerator-freezers using R600a Y Jeon, D Kim, J Jung, DS Jang, Y Kim Energy 161, 1085-1095 , 2018 2018 Citations: 37
Two-phase flow patterns and pressure drop of a low GWP refrigerant R-1234ze (E) in a plate heat exchanger under adiabatic conditions DC Lee, D Kim, S Yun, Y Kim International Journal of Heat and Mass Transfer 145, 118816 , 2019 2019 Citations: 36
Performance evaluation of a gas injection CO2 heat pump according to operating parameters in extreme heating and cooling conditions HJ Chung, C Baek, H Kang, D Kim, Y Kim Energy 154, 337-345 , 2018 2018 Citations: 32
Energy performance evaluation of two-phase injection heat pump employing low-GWP refrigerant R32 under various outdoor conditions D Kim, DC Lee, M Lee, HJ Chung, Y Kim Energy 214, 119098 , 2021 2021 Citations: 28
Analysis of two-phase injection heat pump using artificial neural network considering APF and LCCP under various weather conditions D Kim, KS Song, J Lim, Y Kim Energy 155, 117-127 , 2018 2018 Citations: 26
