Energy loss through windows can be high relatively compared to other opaque surfaces because insulation performance of fenestration parts is lower in the building envelope. Electrically heated window systems are used to improve the indoor environment, prevent condensation, and increase building energy efficiency. The purpose of this study is to analyze the thermal behaviors of a heated window under a field experiment condition. Experiments were conducted during the winter season (i.e., January and February) with the energy-efficient house that residents occupy. To collect measured data from the experimental house, temperature and heat flux meter sensors were used for the analysis of heat flow patterns. Such measured data were used to calculate heat gain ratios and compare temperature and dew point distribution profiles of heated windows with input power values under the changed condition in the operating temperature of the heated glazing. Results from this study indicated that the input average heat gain ratio was analyzed to be 75.2% in the south-facing and 83.8% in the north-facing at nighttime. Additionally, compared to January, reducing the operating temperature of the heated glazing by 3 °C decreased the input energy in February by 44% and 41% for the south-facing and north-facing windows, respectively. Through such field measurement study, various interesting results that could not be found in controlled laboratory chamber conditions were captured, indicating that the necessity of establishing various control strategies should be considered for the development and commercialization of heated windows.

As a major driver to achieve feasible long‐term goals of the Korean Green New Deal policy, a renewable system application in a building, such as the building‐integrated photovoltaics (BIPV) system, has been expedited by raising a BIPV installation subsidy to 70%. Among the technology of BIPV modules, the CuInGaSe₂ (CIGS) type module has been drawing attention and considered as one of the effective alternatives because of its benefits, including its flexibility, lightweights, and relative ease to use as a building material. However, the lack of information understanding of its real application to buildings has still existed under various outdoor experimental conditions. In response to this gap, this study analyzed the power generation performance of flexible CIGS modules under outdoor exposure conditions to evaluate their applicability to BIPV buildings. To conduct the test, the CIGS module was installed on an inclined plane (30°) and vertical plane (90°) using a mock‐up installed facing the south. In particular, this study assessed performance ratio (PR) values to analyze the power generation performance behaviors under direct/diffuse irradiance conditions along with diverse cloud cover conditions. Results from this experimental case study indicated that the power generation performance of the vertical CIGS module decreased compared with that of the inclined CIGS module during all analysis periods, except for the February period. This phenomenon became more distinct as the solar altitude angle increased, and the power generation performance of the vertical module became similar to that of the inclined module as the altitude angle decreased. By experimenting with the diffuse irradiance condition depending on the change in cloud cover, the PR decreased by approximately 12%.

Crack issues afflicting a building integrated photovoltaics (BIPV) system are major concerns in terms of the system’s maintenance and power degradation. Although there may be many circumstances that bring about cracks in BIPV modules during the installation process, identifying the degradation of PV module efficiency resulting from the effects of cracks tends to be a very difficult task unless actual indoor or outdoor tests or detailed electroluminescence imaging tests are conducted. Many current studies have demonstrated that cracks may or may not impact the output performance of PV modules depending on the damage levels or where the damage is located. For BIPV applications such as replacement for building materials, there is still a lack of information and case studies addressing crack issues in a quantitative manner for evaluating BIPV output performance. Therefore, the objectives of this study are to investigate the effects of cracks in BIPV modules on power outputs and to identify detailed relationships between the cracks and power output based on experimental and simulated analysis. An experimental facility located in Daejeon, South Korea, was used to gather data from cracked and non-cracked BIPV modules. By using the field-measured data and facility’ information, a simulation model was developed using SolarPro software, and a simulated-based analysis was conducted to evaluate the impact of cracks in BIPV modules on output values after proper validation of the model. The results from this study reveal that cracks in BIPV modules exhibit significant degradation in BIPV modules’ outputs of up to 43% reduction during the experimental period. From the annual comparative results, output degradations of 34.6–35.4% were estimated when the BIPV modules included cracks. As a result, the cracks in the BIPV modules could be carefully addressed as issues occurring in the BIPV installation process.