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The performance of the Operable Building Integrated Photovoltaic (OBIPV) system applied to the building envelope to reduce the building energy consumption varies significantly depending on the operation method and influence of the surrounding environment. Therefore, optimization through performance monitoring is necessary to maximize power generation of the system. This study used temperature-corrected normalized efficiency (NE*) to evaluate the power generation performance of the operation methods and predict that of the OBIPV system based upon the measured data. It was confirmed that power generation performance decreased when the photovoltaic (PV) operation angle changed, the system remaining the same. A decrease in power generation performance due to partial shading from an overhang was also observed. As a result of the power generation prediction for two months using NE*, the error of the measured values was found to be less than 3%. In addition, with or without any partial shading of the OBIPV system, its performance degradation was predicted with an annual electricity generation decrease by 36 kWh/yr (6.5%). Therefore, NE* can be used as an indicator for evaluating the power generation performance of PV systems, and to predict generation performance considering partial shading.

Photovoltaic (PV) systems are commonly used as on-site electric power generators for ZEBs in the Republic of Korea. To enhance the performance of PV systems, considering efficient installation conditions, such as the optimal azimuth and tilt angles, is critical. Under domestic PV application guidelines, the azimuth of installation for building-applied PV systems is stipulated within a maximum of ±90° based on the south-facing direction. In general, the northfacing direction is known as a weak position for PV systems. However, several studies have shown that the north-facing direction can be a good option for building PV installations, typically when the installation areas are limited within a building site. Even if the PV panel faces north, the system can operate effectively with proper performance when installed at a suitable inclination angle. In existing studies, system behavior has been verified based on simulationbased analysis, but actual operational data analysis remains insufficient. This study aims to evaluate the feasibility of north-facing PV systems based on a performance evaluation of the measured data of a roof PV system. The roof PV system analyzed in this study was composed of modules, module-level power electronics (MLPE), and one inverter. The PV modules and MLPEs were installed on both the southern (SIR) and northern (NIR) inclined roofs. Based on the annual cumulative DC power, the energy yields of the MLPE connected to modules of the SIR and NIR are 1,445.0 and 1,068.7 kWh/kWp, respectively. Our study found that the ratio of the performance of MLPE on the NIR to MLPE on the SIR was 74.0%. This ratio was similar to the energy yield of the PV system on the south vertical plane as compared to that on the south slope plane. The analyzed results revealed that an acceptable performance of the PV system installed on a northern slope at a suitable inclination angle could be expected as compared with other PV installations such as the southern vertical.

Building-integrated photovoltaic (BIPV) systems are gaining global popularity as a means to reduce carbon emissions. The optimal implementation of BIPV requires consideration of various physical factors. One such factor is the temperature rise of the photovoltaic module, which can have detrimental effects, such as decreased power generation and thermal damage. The temperature rise is influenced not only by weather conditions, but also by the finishing characteristics of the building envelope, including the surrounding finishing conditions and bonding materials. In this study, the thermal conditions of BIPV systems were assessed by analyzing the rear air and back surface temperatures under different rear natural ventilation conditions. Experiments were conducted using steel-plate-integrated solar modules and steel plates, and back surface and air temperature data were collected from these simulated systems. The experimental conditions were categorized based on whether the ventilation control vents located at the upper and lower ends of the system were open or closed. The experimental results showed that the average back-surface temperature of the solar module was approximately 11°C higher during high solar irradiance conditions (800 W/m 2 ) in summer, when both the upper and lower ventilation control vents were shut off, compared to the conditions in which both vents were open. These findings confirm the need for back-ventilation adjustments when implementing BIPV systems.Keywords: 신•재생 에너지(New and renewable energy), 건물일체형 태양광 시스템(Building integrated photovoltaic), 강판 일체형 태양광 모듈(Steel plate integrated photovoltaic module), 후면 조건(Rear air channel condition)한국태양에너지학회 논문집