@article{seo_yoon_lee_cho_2023, title={Comparative Analysis of ANN and LSTM Prediction Accuracy and Cooling Energy Savings through AHU-DAT Control in an Office Building}, volume={13}, ISSN={["2075-5309"]}, DOI={10.3390/buildings13061434}, abstractNote={This paper proposes the optimal algorithm for controlling the HVAC system in the target building. Previous studies have analyzed pre-selected algorithms without considering the unique data characteristics of the target building, such as location, climate conditions, and HVAC system type. To address this, we compare the accuracy of cooling load prediction using ANN and LSTM algorithms, widely used in building energy research, to determine the optimal algorithm for HVAC control in the target building. We develop a simulation model calibrated with actual data to ensure data reliability and compare the energy consumption of the existing HVAC control method and the two algorithms-based methods. Results show that the ANN algorithm, with a CV(RMSE) of 12.7%, has a higher prediction accuracy than the LSTM algorithm, CV(RMSE) of 17.3%, making it a more suitable algorithm for HVAC control. Furthermore, implementing the ANN-based approach results in a 3.2% cooling energy reduction from the optimal control of Air Handling Unit (AHU) Discharge Air Temperature (DAT) compared to the fixed DAT at 12.8 °C in a representative day. This study demonstrates that ML-based HVAC system control can effectively reduce cooling energy consumption in HVAC systems, providing an effective strategy for energy conservation and improved HVAC system efficiency.}, number={6}, journal={BUILDINGS}, author={Seo, Byeongmo and Yoon, Yeobeom and Lee, Kwang Ho and Cho, Soolyeon}, year={2023}, month={Jun} }
 @article{yoon_seo_mun_cho_2023, title={Energy savings and life cycle cost analysis of advanced double skin facade system applied to old apartments in South Korea}, volume={71}, ISSN={["2352-7102"]}, DOI={10.1016/j.jobe.2023.106535}, abstractNote={South Korea is one of the most densely populated countries in the world, and the population density in urban areas is much higher among others. Apartments are the most common form of residential buildings due to their high population density. More than 60% of domestic residential buildings are apartments, with more than 10 million households. The high population density is a problem that has long plagued South Korea because more than 45% of apartments are old apartments that are more than 20 years old. Old apartment buildings have low thermal performance that results in lots of energy consumption. Balconies, which worked as a thermal buffer, are also being removed by residents to expand indoor space. According to the green remodeling project supported by the Korean government, the typical retrofitting method is replacing external windows with the high-efficiency window in old apartments in South Korea. This paper proposes a retrofitting method using an extended double-skin façade (DSF) system that replaces exterior windows and acts as a thermal buffer. The simulation model is developed with the EnergyPlus simulation program to conduct energy performance analyses. The simulation model has been calibrated using actual experimental data collected between October 1, 2019, and January 15, 2020. Results show that the cooling, heating, and lighting energy can be reduced up to 44.1% by fully utilizing electric energy generated by solar PV panels integrated with the DSF system. The payback period is about 15 years based on the energy price provided by the utility company. Although the payback period is long, it has great potential of energy savings and CO2 emission reductions. The DSF system should be considered as a way of renovation, considering other factors such as increased real estate values and energy cost increases in the future.}, journal={JOURNAL OF BUILDING ENGINEERING}, author={Yoon, Yeobeom and Seo, Byeongmo and Mun, Junghyun and Cho, Soolyeon}, year={2023}, month={Jul} }
 @article{yoon_seo_cho_2023, title={Potential Cooling Energy Savings of Economizer Control and Artificial-Neural-Network-Based Air-Handling Unit Discharge Air Temperature Control for Commercial Building}, volume={13}, ISSN={["2075-5309"]}, DOI={10.3390/buildings13051174}, abstractNote={Heating, ventilation, and air-conditioning (HVAC) systems play a significant role in building energy consumption, accounting for around 50% of total energy usage. As a result, it is essential to explore ways to conserve energy and improve HVAC system efficiency. One such solution is the use of economizer controls, which can reduce cooling energy consumption by using the free-cooling effect. However, there are various types of economizer controls available, and their effectiveness may vary depending on the specific climate conditions. To investigate the cooling energy-saving potential of economizer controls, this study employs a dry-bulb temperature-based economizer control approach. The dry-bulb temperature-based control strategy uses the outdoor air temperature as an indicator of whether free cooling can be used instead of mechanical cooling. This study also introduces an artificial neural network (ANN) prediction model to optimize the control of the HVAC system, which can lead to additional cooling energy savings. To develop the ANN prediction model, the EnergyPlus program is used for simulation modeling, and the Python programming language is employed for model development. The results show that implementing a temperature-based economizer control strategy can lead to a reduction of 7.6% in annual cooling energy consumption. Moreover, by employing an ANN-based optimal control of discharge air temperature in air-handling units, an additional 22.1% of cooling energy savings can be achieved. In conclusion, the findings of this study demonstrate that the implementation of economizer controls, especially the dry-bulb temperature-based approach, can be an effective strategy for reducing cooling energy consumption in HVAC systems. Additionally, using ANN prediction models to optimize HVAC system controls can further increase energy savings, resulting in improved energy efficiency and reduced operating costs.}, number={5}, journal={BUILDINGS}, author={Yoon, Yeobeom and Seo, Byeongmo and Cho, Soolyeon}, year={2023}, month={Apr} }
 @article{park_hong_yeon_seo_lee_2023, title={Predictive Model for Solar Insolation Using the Deep Learning Technique}, volume={2023}, ISSN={["1099-114X"]}, DOI={10.1155/2023/3525651}, abstractNote={In this study, prediction performances of a regression model and deep learning-based predictive models were comparatively analyzed for the prediction of hourly insolation in regions located at the temperate climate and microthermal climate with high precipitation. Unlike linear regression models, artificial neural networks (ANN) and long short-term memory- (LSTM-) based models achieved reliable predictive performances with CV(RMSE) of 14.0% and 15.8%, respectively. This study proposed the direction of future research by improving the performance of predicting insolation at 1 hour after the current time-step, which has time-dependent characteristics, by utilizing insolation at 24 hours before the current time-step and insolation at the current time-step in addition to the forecasted weather data. In the proposed models, a large error occurred at sunrise and sunset times, suggesting the possibility of improving predictive performance by utilizing variables related to sunrise and sunset in the future. Along with Cheongju, the proposed model could properly predict the hourly insolation in other regions around the world. The results of predicting other regions derived slightly higher prediction errors than Cheongju. However, it is expected that it will be possible to predict the hourly insolation in other regions with better prediction performance if variables related to geographical location are additionally considered in the future.}, journal={INTERNATIONAL JOURNAL OF ENERGY RESEARCH}, author={Park, Jiwon and Hong, Sung Hyup and Yeon, Sang Hun and Seo, Byeong Mo and Lee, Kwang Ho}, year={2023}, month={Feb} }
 @article{seo_yoon_yu_cho_lee_2020, title={Comparative analysis of cooling energy performance between water-cooled VRF and conventional AHU systems in a commercial building}, volume={170}, ISSN={["1359-4311"]}, DOI={10.1016/j.applthermaleng.2020.114992}, abstractNote={With recent efforts to minimize the energy consumption of heating, ventilation and air conditioning (HVAC) systems in buildings, the variable refrigerant flow heat pump (VRF-HP) system has drawn much attention, replacing the conventional HVAC system in the market. The VRF-HP system has several advantages, such as enhancing the aesthetics of buildings, reducing installation costs and offering high technology products. Although various studies relevant to VRF-HP systems are currently in progress, the evaluation of quantitative energy based on the actual performance information of such systems is still insufficient because it is difficult to accurately reflect various factors affecting their inherent heating and cooling performance in a simulation environment during the design stage. To obtain reliable results for this study, a water-cooled VRF-HP system equipped with a direct expansion air handling unit (DX-AHU) was selected from among various types of VRF-HP systems, and a standardized heating and cooling performance curve in diverse temperatures and part-load conditions based on the heating and cooling field measurement catalog performance data was developed. This paper aims to conduct a comparative assessment of the cooling energy performance between a water-cooled VRF-HP system and a chiller based conventional AHU system through co-simulation between EnergyPlus, MATLAB, and BCVTB after an extensive validation and calibration process. The results indicate that the water-cooled VRF-HP system can reduce cooling energy by up to 15% compared with the chiller based conventional AHU system.}, journal={APPLIED THERMAL ENGINEERING}, author={Seo, Byeongmo and Yoon, Yeo Beom and Yu, Byeong Ho and Cho, Soolyeon and Lee, Kwang Ho}, year={2020}, month={Apr} }
 @article{yoon_seo_koh_cho_2020, title={Heating energy savings potential from retrofitting old apartments with an advanced double-skin facade system in cold climate}, volume={14}, ISSN={["2095-1698"]}, DOI={10.1007/s11708-020-0801-1}, number={2}, journal={FRONTIERS IN ENERGY}, author={Yoon, Yeo Beom and Seo, Byeongmo and Koh, Brian Baewon and Cho, Soolyeon}, year={2020}, month={Jun}, pages={224–240} }
 @article{yeon_yu_seo_yoon_lee_2019, title={ANN based automatic slat angle control of venetian blind for minimized total load in an office building}, volume={180}, ISSN={["1471-1257"]}, DOI={10.1016/j.solener.2019.01.027}, abstractNote={Windows are the only part of a building that can directly penetrate the solar radiation into the occupied space and thus the shading devices are needed to control the solar penetration. A variety of research have been conducted to develop the optimized slat angle control in the existing literature, but the research incorporating artificial intelligence technique with slat angle control is limited thus far. Therefore, in this study, the ANN (Artificial Neural Network) model was applied to minimize the combined total load consisting of lighting, cooling, and heating loads through automatic slat angle control of venetian blinds. A three-story rectangular office building was simulated using EnergyPlus, and dimming control was applied to control the lighting. The interlocked simulation between Matlab and EnergyPlus was conducted through BCVTB. As a result of comparing automatic blind control via the ANN to fixed blind slat angle, the automatic blind control via the ANN showed 9.1% lower total load than the blind angle fixed at 50°. It was confirmed that the cooling and heating load could be significantly reduced by real-time automatic control via the ANN under various operating conditions, rather than fixing the blinds at one angle.}, journal={SOLAR ENERGY}, author={Yeon, Sanghun and Yu, Byeongho and Seo, Byeongmo and Yoon, Yeobeom and Lee, Kwang Ho}, year={2019}, month={Mar}, pages={133–145} }
 @article{seo_yoon_mun_cho_2019, title={Application of Artificial Neural Network for the Optimum Control of HVAC Systems in Double-Skinned Office Buildings}, volume={12}, ISSN={["1996-1073"]}, DOI={10.3390/en12244754}, abstractNote={Double Skin Façade (DSF) systems have become an alternative to the environmental and energy savings issues. DSF offers thermal buffer areas that can provide benefits to the conditioned spaces in the form of improved comforts and energy savings. There are many studies conducted to resolve issues about the heat captured inside DSF. Various window control strategies and algorithms were introduced to minimize the heat gain of DSF in summer. However, the thermal condition of the DSF causes a time lag between the response time of the Heating, Ventilation, and Air-Conditioning (HVAC) system and cooling loads of zones. This results in more cooling energy supply or sometimes less than required, making the conditioned zones either too cold or warm. It is necessary to operate the HVAC system in consideration of all conditions, i.e., DSF internal conditions and indoor environment, as well as proper DSF window controls. This paper proposes an optimal air supply control for a DSF office building located in a hot and humid climate. An Artificial Neural Network (ANN)-based control was developed and tested for its effectiveness. Results show a 10.5% cooling energy reduction from the DSF building compared to the non-DSF building with the same HVAC control. Additionally, 4.5% more savings were observed when using the ANN-based control.}, number={24}, journal={ENERGIES}, author={Seo, Byeongmo and Yoon, Yeo Beom and Mun, Jung Hyun and Cho, Soolyeon}, year={2019}, month={Dec} }
 @article{lee_hong_seo_lee_2019, title={Application of artificial neural networks for optimized AHU discharge air temperature set-point and minimized cooling energy in VAV system}, volume={153}, ISSN={["1359-4311"]}, DOI={10.1016/j.applthermaleng.2019.03.061}, abstractNote={Chillers and boilers based air handling unit (AHU) system is one of the most widely used heating and cooling systems in office buildings in Korea. However, in most conventional forced-air systems, the guidelines for the AHU discharge air temperature (DAT) are not fully established and thus AHU DAT are constantly fixed to a particular set-point, regardless of dynamic changes of operating variables. In this circumstance, this study aimed at developing a control algorithm that can operate a conventional VAV system with optimal set-points for the AHU DAT. Three-story office building was modeled using co-simulation technique between EnergyPlus and Matlab via BCVTB (Building Controls Virtual Test Bed). In addition, artificial neural network (ANN) model, which was designed to predict the cooling energy consumption for the upcoming next time-step, was embedded into the control algorithm using neural network toolbox within Matlab. By comparing the predicted energy for the different set-points of the AHU DAT, the control algorithm can determine the most energy-effective AHU DAT set-point to minimize the cooling energy. The results showed that the prediction accuracy between simulated and predicted outcomes turned out to have a low coefficient of variation root mean square error (CvRMSE) value of approximately 24%. In addition, the predictive control algorithm was able to significantly reduce cooling energy consumption by approximately 10%, compared to a conventional control strategy of fixing AHU DAT to 14 °C. These findings suggest that the ANN model and the control algorithm showed energy saving potential for various types of forced air systems by taking dynamic operating conditions into account in each time-step.}, journal={APPLIED THERMAL ENGINEERING}, author={Lee, Jong Man and Hong, Sung Hyup and Seo, Byeong Mo and Lee, Kwang Ho}, year={2019}, month={May}, pages={726–738} }
 @article{lee_seo_hong_choi_lee_2019, title={Part load ratio characteristics and energy saving performance of standing column well geothermal heat pump system assisted with storage tank in an apartment}, volume={174}, ISSN={["1873-6785"]}, DOI={10.1016/j.energy.2019.03.029}, abstractNote={A geothermal heat pump (GSHP) system has improved energy efficiency compared to conventional air-source heat pumps due to a more stable underground temperatures through the year. Among various types of GSHP systems, standing column well (SCW) system is a specialized type of open loop system, where water is drawn from the bottom of a deep rock well, passed through a heat pump, and returned to the top of the well, during which it exchanges heat with the surrounding bedrock. In this research a SCW system integrated with heat storage tank was assessed through dynamic energy simulation technique after comprehensive validation process of heat pump performance curves. For this purpose, the detailed analysis on the operational characteristics of SCW heat pump and its energy performance enhancement due to the connection with heat storage tank was performed, such as variations of part load ratios (PLRs), COP and the corresponding energy requirements, compared to window air-conditioner and boiler based conventional system. The results of this study showed that the SCW heat pump system connected with heat storage tank showed an annual energy saving of approximately 62% and 14% compared to the conventional system and the SCW system without heat storage tank, respectively. This indicates that energy efficiency can be significantly improved when SCW heat pump can be properly operated in combination with heat storage tank in residential buildings.}, journal={ENERGY}, author={Lee, Da Young and Seo, Byeong Mo and Hong, Sung Hyup and Choi, Jong Min and Lee, Kwang Ho}, year={2019}, month={May}, pages={1060–1078} }
 @article{yoon_seo_koh_cho_2019, title={Performance analysis of a double-skin facade system installed at different floor levels of high-rise apartment building}, volume={26}, ISSN={["2352-7102"]}, DOI={10.1016/j.jobe.2019.100900}, abstractNote={This paper introduces a Double Skin Façade (DSF) system that can be installed in existing apartments in South Korea as a replacement of poorly performing old balcony windows. The DSF system can bring thermal benefits, especially in heating dominant climate areas. The DSF system works as a thermal buffer area and passive heating system. The goal of this research is to evaluate the thermal performance of a DSF system installed in apartments at different floor levels. A typical 25-story apartment building is used as a case study to test the thermal performance of a DSF system in different floors. Heating energy savings are the focus since the location, Seoul, is a heating dominant climate area. The main parameters are temperature, wind speed, and pressure differences at different floor levels. A thermal simulation model for a Base-Case is developed and calibrated to measured data gathered from a real-scale DSF system physical model. Two other simulation models are developed on top of the Base-Case model to compare performances of the DSF system installed in apartments at different floor levels. Results show that the first floor apartment unit consumes the least heating energy and the 25th floor the most, as expected. The outside air temperature difference between the first floor and the 25th floor was about 0.4 °C. The results also show the largest heating energy savings of 30% in the 21st floor with the installation of the DSF system.}, journal={JOURNAL OF BUILDING ENGINEERING}, author={Yoon, Yeo Beom and Seo, Byeongmo and Koh, Brian Baewon and Cho, Soolyeon}, year={2019}, month={Nov} }
 @article{yu_seo_hong_yeon_lee_2018, title={Influences of different operational configurations on combined effects of room air stratification and thermal decay in UFAD system}, volume={176}, ISSN={["1872-6178"]}, DOI={10.1016/j.enbuild.2018.07.015}, abstractNote={The non-insulated underfloor supply plenum and the heat gain of the cool supply air into supply plenum results in significant magnitude of thermal decay defined as the supply air temperature rise. Eventually, these changes have influence on the room air stratification, causing negative effects throughout whole system. Therefore, for the optimization of UFAD system, it is important to understand these fundamentals and relevant effects on the overall system operation. In this study, comparative analysis was conducted during cooling period using validated EnergyPlus model, after employing different operational configurations related to room air stratification and thermal decay. The thermal behavior and cooling energy performance were analyzed by observing the convective heat transfer, thermal decay, airflow, stratification among different operational configurations. As a result, it was observed that the existence of non-insulated supply plenum have influences on the thermal behavior in occupied zone, and the corresponding heat transfer has load reduction effect of the space by about 40%. However, there were still significant amounts of cooling energy consumption in the form of thermal decay despite the reduced cooling load, indicating that unintended and additional energy consumption was occurred in supply plenum. In addition, return air temperature rise by the room air stratification increased the cooling coil load. Eventually, these effects canceled each other out. As a result, compared to CBAD system, standard UFAD system consumed more electric energy by approximately 30%, and for fully-insulated UFAD system, 6% energy saving could be achieved.}, journal={ENERGY AND BUILDINGS}, author={Yu, Byeong Ho and Seo, Byeong-Mo and Hong, Sung Hyup and Yeon, Sanghun and Lee, Kwang Ho}, year={2018}, month={Oct}, pages={262–274} }
 @article{kim_seo_lee_choi_lee_2018, title={Operational behavior characteristics and energy saving potential of vertical closed loop ground source heat pump system combined with storage tank in an office building}, volume={179}, ISSN={["1872-6178"]}, DOI={10.1016/j.enbuild.2018.09.025}, abstractNote={A ground source heat pump (GSHP) system utilizes a relatively stable underground temperature to achieve energy-saving for heating and cooling in buildings. Among various types of GSHP systems, Vertical Closed Loop Ground Source Heat Pump (VGSHP) has received increasing attention due to a variety of advantages such as the potential to be installed in a relatively small space and improved energy efficiency. In this research, in order to improve the system performance of a VGSHP, a VGSHP system coupled with heat storage tank was evaluated. For this purpose, the detailed analysis on the operational behavior of heat storage tank and the variations of heat pump energy performance due to the connection with heat storage tank was performed, and characteristics of heat pump part load ratios (PLRs) and the corresponding energy requirements, compared to chiller and boiler based conventional system, were analyzed in detail, using dynamic energy simulation after comprehensive validation process of heat pump performance curves. The results of this study showed that the VGSHP system coupled with heat storage tank showed an energy saving effect of about 20% for cooling and about 77% for heating compared to the conventional air conditioning system, and an energy saving effect of about 2% for cooling and about 15% for heating compared to the VGSHP system without heat storage tank, mainly due to the fact that the operational pattern of heat pump such as PLR and COP characteristics was changed by the operation of heat storage tank.}, journal={ENERGY AND BUILDINGS}, author={Kim, Min Ji and Seo, Byeong Mo and Lee, Jong Man and Choi, Jong Min and Lee, Kwang Ho}, year={2018}, month={Nov}, pages={239–252} }