In this study, the long-term operational performance of building-integrated photovoltaic (BIPV) systems was analyzed in the Carbon Zero Building of the National Institute of Environmental Research (NIER) of South Korea, with a total area of 2449 m². Three types of BIPV modules (glass to glass, glass to Tedlar/crystal, and amorphous) were installed in the building envelopes (roofs, walls, windows, atrium, and pergola) with a total capacity of 116.2 kWp. Over a five-year period, the average annual energy production was 855.6 kWh/kWp, the system loss ranged from 0.14 to 0.31 h/d, and the capture loss ranged from 0.21 to 1.81 h/d. The causes of capture losses were degradation of the power generation efficiency of the horizontal installation module due to the accumulation of dust and reduced energy production due to application of the same inverter for the crystal system module and amorphous module. As a result, the BIPV systems with an installation angle of 30° exhibited approximately 57% higher energy production than vertically (90°) installed systems under the same solar radiation. Moreover, horizontal (0°) BIPV systems exhibited up to 14% higher energy production than vertical BIPV systems.

In this study, the energy consumption and generation characteristics, the operation status of a photovoltaic (PV) system, and the energy balance of a net-zero energy building (nZEB) in South Korea were analyzed based on the data collected over a 10-year period (2012–2021). The average annual power consumption of the nZEB was 101.3 MWh, 6.2% higher than the estimated power consumption. The PV system of the nZEB had an annual power generation capacity of 105.8 MWh, indicating an increase of 10.6% compared to the estimated value. The failure of PV systems such as module cracks, inverter failures, and performance degradation led to a decrease of 21.5% in the power generation. Energy balance analysis was conducted by comparing the energy consumption and generation data based on yearly, monthly, daily, and hourly time intervals. In addition, load coverage factor (LCF) and supply coverage factor (SCF) were used to evaluate the load matching rate. The nZEB achieved a net-zero energy status for 5 out of the 7 years of normal operation (2012–2018) based on average annual data. However, the energy balance analysis using hourly measured data showed that there was both a surplus and a shortage of power every year, and that the average annual power surplus and shortage were 56.4 MWh and 54.3 MWh, respectively. In addition, the load matching analysis showed that the annual LCF and SCF were approximately 0.36 and 0.32, respectively. Thus, the advanced nZEB design, hourly data-based energy analysis, fault diagnosis and maintenance, and the strategies enhancing the self-consumption rate should be considered to expand nZEB dissemination.

In this study, a basic study was performed to analyze the seasonal temperature status of a research room in the Global Environment Research Building, where ceiling-embedded indoor units are installed to study the room temperature status of the building, as well as to improve its thermal environment. In addition, a direction for improvement of the indoor thermal environment in the winter was proposed through a CFD (computational fluid dynamics) simulation and was proven by an additional experiment. Through the results of this study, it appeared that if the ceiling-embedded indoor unit was installed in the small indoor space without considering the thermal vulnerability of its perimeter boundary, the air temperature of the upper part was greatly different from that of the bottom part in the winter. Based on the PMV measurement result, the case that used both FCUs and convectors showed 1.33, the biggest maximum and minimum difference, and the case that used all FCUs, convectors and circulating fans showed 0.68, the smallest maximum and minimum difference. Therefore, it was considered that the operating method suggested in the room used in this study would improve not only the temperature stratification but also the thermal comfort. Hence, in this study, as a means to improve the stratification, convectors were installed to minimize the effect of the external thermal environment, and angle-controllable air flowing fans were installed to mitigate the stratification distribution. With such a result, it was intended to present essential data for the improvement of the thermal environment, as well as the conservation of heating energy in the winter, by reviewing the use of the ceiling-embedded indoor units in the future.

In this study, a basic study was performed to analyze the seasonal temperature status of a research room in the Global Environment Research Building where ceiling-embedded indoor units are installed to study the room temperature status of the building as well as to improve its thermal environment. In addition, a direction for improvement of the indoor thermal environment in the winter was proposed through a CFD (computational fluid dynamics) simulation and was proven by an additional experiment. Through the results of this study, it appeared that if the ceiling-embedded indoor unit was installed in the small indoor space without considering the thermal vulnerability of its perimeter boundary, the air temperature of the upper part was greatly different from that of the bottom part in the winter. Hence, in this study, as a means to improve it, convectors were installed to minimize the effect of the external thermal environment and angle-controllable air flowing fans were installed to mitigate the stratification distribution. With such result, it was intended to present the essential data for improvement of the thermal environment as well as conservation of heating energy in the winter for buildings by reviewing the use of the ceiling-embedded indoor unit in the future.