Ki-Hyung Yu’s research while affiliated with Korea Institute of Civil Engineering and Building Technology and other places

In the Republic of Korea, the 2030 Nationally Determined Contributions aim for carbon neutrality by 2050, with the building sector targeting a 32.8% reduction in carbon emissions by 2030 compared with the 2018 baseline. To achieve these goals, significant efforts are underway to improve the energy efficiency of buildings. Building energy simulation is a standard method for evaluating energy performance as it assesses the current performance and predicts the potential contributions of energy retrofitting initiatives. However, industrial factories often lack specific energy simulation profiles, posing a challenge for accurate energy performance assessment. This case study aims to bridge this gap by investigating a detailed building profile for factory building based on the extended operational data and experimental measurements within a live factory setting. Energy simulations employing these factory-specific profiles yielded R 2 values (coefficient of determination) of 98.2% and 94.1% for cooling and heating energy accuracy, respectively, when compared with the actual monthly consumption data. Additionally, simulations with these profiles demonstrated a 2.81% improvement in R 2 accuracy compared to those using conventional office building profiles, particularly enhancing the precision during the cooling season. These findings highlight the effectiveness of customized profiles in building energy simulations, ensuring more precise and reliable energy efficiency assessments.

Indoor humidity control is increasingly important because indoor sensible heat ratio decreases to reduce building energy consumption. However, reference vapor compression cooling systems exhibit energy inefficiency and limitations in maintaining indoor thermal comfort. Therefore, this study proposes an alternative heat-pump- driven liquid-desiccant air-conditioning system, independently controlling air temperature and humidity. The reference and proposed systems are applied to a high-latent-load building to investigate their onsite indoor thermal comfort and energy performance empirically and simultaneously under various outdoor summer con- ditions. The reference system exhibits a thermal comfort satisfaction ratio of 97% only under limited hot and dry weather. Conversely, the thermal comfort satisfaction ratio sharply drops to 2% or less under humid weather. The proposed system consistently achieves a high thermal comfort satisfaction ratio exceeding 90% under various outdoor summer conditions. In empirical comparisons, the proposed system can maintain a thermally comfortable room for an hour while achieving energy savings exceeding 92.4% and 12.1% under warm and humid (rainy season) and hot and humid outdoor conditions, respectively. The proposed system is concluded to consistently maintain indoor thermal comfort while using energy efficiently, demonstrating its widespread applicability for general high-latent-load buildings characterized by low indoor sensible heat ratio values of 0.56 on average.

This paper aims to analyze optimal resolution for energy consumption data to improve data-driven building energy consumption diagnosis with the ASHRAE change point model. A 9-floor office building is selected as a target, and hourly data is measured throughout a year. Heating, cooling, and other types of energy consumption are measured separately, to find truth values of the heating change point and cooling change point, which refers to the temperature at which the building starts heating or cooling. After the truth change point is found, the total sum of the consumption is resampled along different time intervals, to reflect various levels of data resolution. Change point models are built with each differently resampled data, and their results including change point and RMSE were compared to find the optimal time interval of the data. The result showed 2-week interval is the optimal interval. However, an unordinary pattern, which may be due to individual heating or cooling appliances being counted as appliance consumption rather than cooling or heating consumption, is observed as well. The results of this study suggest that the resolution of public data needs to be improved for the energy consumption diagnosis based on public data, and the usage of individual heating and cooling devices needs to be considered additionally in the diagnosis process.

This study aims to institutionalize an evaluation methodology to assess water-source heat pumps (WSHPs) when designing a zero-energy building. Thus, regions where zero-energy buildings were designed were subdivided into 66 sub-regions, thereby standardizing the temperatures on the source side of WSHPs using river water and pipeline water. Based on these data, ground-source and water-source heat pump system-based simulation (new and renewable energy self-sufficiency rate compared to building energy consumption) values were derived for cases whose condition (region or heat source) was different among the buildings certified as zero-energy buildings. The application of the standard meteorological data and reference hydrothermal data to the ECO2 program and outcome evaluation led to the following findings: in all cases (reference: Seoul), ground-source heat pumps (GSHPs) showed a higher self-sufficiency rate than WSHPs (ground source > pipeline water > river water). The self-sufficiency rate of GSHPs was 11–33% higher than that of WSHPs. In a regional comparison among the cold (Jeongseon), central (Seoul), and southern (Jeju Island) regions, WSHPs exhibited higher energy self-sufficiency rates than GSHPs under the conditions of higher water temperatures in winter and lower water temperatures in summer, as in the southern region.

In this study, a comparative economic analysis was conducted for typical greenhouses, plant factories with natural and artificial light, and those with only artificial light, based on the insulation, artificial light, and photovoltaic (PV) installation costs. In addition, the results of research on primary energy consumption and greenhouse gas (GHG) emissions from the use of fossil fuels were presented. By comparing the case-wise annual energy consumption, when all energy sources were converted into primary energy consumption based on the applied coefficients for collection, transport, and processing, to unify calculations for different fossil fuel energy sources, the case of the installed PV systems exhibited large reductions, of 424% and 340%, in terms of primary energy consumption and GHG emissions, respectively. Furthermore, electric heating resulted in higher primary energy consumption and GHG emissions than oil. When the economic analysis included the plant factory installation cost used to maintain the temperature required for plant growth in winter, the PV installation exhibited the highest cost; additionally, all plant factories showed an investment payback period of seven to nine years, which is comparable to typical greenhouses. Based on these results, we aim to reduce the use of fossil fuels for sustainable energy by combining architectural technology for improved energy performance in the agricultural environment.

This study presents a methodology and process to establish a mandatory policy of zero-energy buildings (ZEBs) in Korea. To determine the mandatory level to acquire the rating of a ZEB in Korea, this study was conducted under the assumption that the criteria of ZEB was a top 5% building considering the building’s energy-efficiency rating, which was certified through a quantitative building energy analysis. A self-sufficiency rate was also proposed to strengthen the passive standard of the buildings as well as to encourage new and renewable energy production. Accordingly, zero-energy buildings (ZEBs) in Korea are defined as having 60 kWh/(m2·yr) of non-renewable primary energy (NRPE) consumption in residential buildings and 80 kWh/(m2·yr) in non-residential buildings, and the self-reliance rate should be more than 20% of the renewable energy consumption as compared to the total energy consumption of the buildings. In addition, the mandatory installation of building energy management systems (BEMS) was promoted to investigate the energy behavior in buildings to be certified as zero-energy in the future. This study also investigated the number of ZEB certificates during the demonstration period from 2017 to 2019 to analyze the energy demand, non-renewable primary energy, renewable primary energy, and self-sufficiency rate as compared to those under the previous standards. For ZEB Grade 1 as compared to the existing building energy-efficiency rating, the sum of the NRPE decreased more than 50%, and renewable energy consumption increased more than four times.

This study presented a methodology and process to establish a passive level for policy making of building energy in South Korea. A passive level in Korea specified in the 2017 Roadmap for non-residential buildings, which was 15 kWh/m2·year, was defined as the heating energy requirement to strengthen the building energy saving design standards, which were typical building energy regulations in Korea. This study also presented insulation standards of roofs, floors, outer walls, and windows in Pyeongchang, Seoul, Gwangju, and Jeju, which were represented cities of four zones in Korea (Middle 1, Middle 2, Southern, and Jeju). Furthermore, the study results were extended to 66 cities around the nation to calculate the heating energy requirements and a severely cold region was added to existing three regions (Middle, Southern, and Jeju) to extend this to four regions (Middle 1, Middle 2, Southern, and Jeju). Afterwards, insulation standards for four represented regions were presented to derive a measure that minimized an energy loss through outer walls or windows in buildings. Finally, this study derived that a return of investment can be achieved in 10 years, which was determined through the comprehensive economic feasibility analysis due to strengthening insulation performances, proving the rationalization of the legal strengthening.

Accurate standard meteorological data sets for each city are essential elements to assess and analyze high-performance buildings quantitatively in order to ensure that they comply with energy saving policies of the nation. ECO2, which is an assessment program of building energy in Korea, has employed meteorological data of the closest city to the target location from 13 urban meteorological data references; the employment of this program has demonstrated the ability to reflect climatic differences between cities. The present study expanded urban meteorological data to ISO TRY (International Organization for Standard Test Reference Year), an international standard methodology that can calculate the data in a relatively simple manner using observed data in Korea, as much as possible in order to reflect meteorological data, including the air temperature relevant for heating and cooling energy as well as solar radiation (cooling/heating energy) for each city, that affected the assessment of building energy the most. In the present study, existing data is expanded to a show the standard meteorological data of 66 cities that can be put into the Korean assessment program (ECO2). This data considered valid meteorological data (minimum statistical period, air temperature, relative humidity, wind, and solar radiation, etc.) among manned and unmanned observational data obtained from 479 locations from 2001 to 2010. For cities other than the 66 aforementioned cities, zoning was conducted to separate cities that had and did not have the standard meteorological data using a cumulative temperature density graph. In this way, meteorological data can be available in all cities, which will enable more accurate simulation assessments on building energy.