Hyung-Jun Song

With the enlargement of underground parking lots, the risk of massive smoke and toxic gases generated during a fire will be increased, resulting in significant casualties, property damage, and difficulties in firefighting operations. To address these issues, installation of ventilation fans and inducer fans together has been proposed to extract smoke and hazardous gases more efficiently to the outside. However, the disturbance of ventilation caused by simultaneous operation of inducer fans and ventilation fans limits smoke extraction efficiency. In some worst cases, smoke disturbance may even lead to further smoke spread. Therefore, this study aims to suggest an efficient smoke extraction strategy for underground parking lots equipped with ventilation and inducer fans by optimizing the orientation of ventilation fans in the event of vehicle fires. Computational fluid dynamics-based simulation results showed that installing ventilation fan intakes and exhausts perpendicularly (PE, 90° apart) was more effective in controlling smoke than installing them in parallel (PA, horizontally facing each other). In the case of PE, the smoke stagnation area around the intakes decreased markedly from 38.18% to 3.68%. Although the smoke area near the exhausts increased in the PE configuration (53.66%) compared with the PA configuration (26.13%), this indicates that smoke was being effectively transported from the intakes to the exhausts. Furthermore, the overall smoke distribution across the entire space decreased by 4.5% under the PE setup compared with the PA setup. As the intake and exhaust flow rates of the fans increased, the efficiency of smoke removal was enhanced under the PE configuration. Consequently, in environments equipped with both ventilation and inducer fans with given conditions, perpendicular installation of fan intakes and exhausts is more efficient. These results are expected to provide practical design guidelines for ensuring effective smoke extraction in underground parking facilities.

Perovskite solar cells (PSCs) have emerged as a promising photovoltaic technology due to their high efficiency and low-temperature processing. However, scaling PSCs into perovskite solar modules (PSMs) faces significant challenges, particularly performance inconsistencies among individual cells, such as short-circuit current (I_SC) mismatches. These mismatches can result in localized heating and reduced power output. In this study, we systematically investigated the impact of current mismatch on the performance and reliability of PSMs operated by a central inverter, focusing on variations in I_SC across PSCs. Experimental results revealed that even minor I_SC mismatches (as low as 2%) can increase the temperature of underperforming cells by up to 8 °C. Theoretical analysis of a PSM with 200 series-connected PSCs showed that power losses correlate with the standard deviation of I_SC (σ I_SC ). The losses caused by current-mismatch are negligible for a σ I_SC of below 2%, but increase to 12–17% at a σ I_SC of 10%. While bypass diodes can mitigate power losses by maintaining a higher operating current, they cannot fully prevent local heating arising from reverse bias. Alternatively, employing multiple inverters to optimize operating currents for non-uniform cells shows potential, but its economic feasibility remains unresolved. These findings highlight the importance of minimizing σ I_SC to enhance PSM performance and reliability for its commercialization.

Building integrated photovoltaics (BIPVs) combine building materials and PV cells to support net zero energy buildings and maintain aesthetics. Quantum dot‐luminescent downshifting (QD‐LDS) technology can improve BIPV performance by converting barely harvested ultraviolet light into wavelengths that correspond to the high‐efficiency range of the device, using environmentally benign materials such as indium phosphide (InP) QDs. Despite their potential, InP QDs face photochemical instability against outdoor environments. To address this issue, an approach is demonstrated to formulate polymer composites with InP QDs using thiol–ene bonds, forming a crosslinked network with a transparent acrylate resin. The polymer composite shields the QDs from environmental factors, enhancing stability without deteriorating transmittance. The formulation of QD‐polymer composite enables to integrate the QD‐LDS layer into various dimensions with high degree of freedom for efficient and pleasant applying BIPV. Colored PV utilizing QD‐LDS layer demonstrates potential for developing highly efficient and stable BIPV modules, paving the way for innovative and sustainable energy solutions.

Recent advances in quantum dot light emitting diode (QLED) technology have enhanced their stability and efficiency. Studies have demonstrated that QLEDs are robust against oxygen, moisture, and low‐voltage stress. However, the impact of instantaneous high‐voltage exposure on QLEDs, which can occur during manufacturing due to electrostatic discharge (ESD) from friction between non‐conductive components, remains unclear. This study systematically investigates the degradation mechanisms of QLEDs caused by ESD at the level of individual layers, pixels, and the overall display panel. When subjected to ESD pulses of several thousand volts for a few nanoseconds, QLEDs exhibit increased leakage current, reduced electroluminescence intensity, and the formation of dark spots within pixels due to the degradation of electrodes rather than the degradation of QDs. Under severe ESD stress (over 10 kV), the electrodes migrate within the device and are finally disconnected. Microstructural analysis confirms that the decreased physical distance between the two electrodes intensified the electric field, potentially converting a diode into a short circuit. The directly exposed pixels are affected by ESD, and those positioned between the ESD source and the ground may also be damaged. These findings underscore the necessity of managing electrostatic accumulation during QLED fabrication to mitigate ESD‐related degradation.

The aviation industry is adopting renewable energy sources to reduce greenhouse gas emissions. One of the strong candidates to meet the energy demand of airports with a sustainable way is photovoltaic (PV) systems. This paper systematically assesses the potential risk and energy generation capabilities of installing PV at nine Korean airports. It was found that the risk of PV, particularly concerns about glare and severity of collision accident, is lower than other renewable energy sources. These remaining safety issues of PVs can be mitigated to acceptable levels by maintaining a safe distance from aircraft routes (105 m) and rotating them to face opposite possible routes. The safety management of airport PV ensures to utilize glare‐free solar energy harvesting systems throughout the year. Under this safe scenario, the estimated energy generation would be 1.78 ± 0.17 times higher than the energy demand of the airports. Notably, the surplus energy generation by PVs located at smaller airports can offset energy demand of larger international airports. The estimated levelized cost of energy for PVs with acceptable risk is 64.7 ± 0.1 $/MWh, lower than the cost of energy supplied by an external source (103.4 ± 32.7 $/MWh). These findings suggest that PV installations with acceptable risk can significantly contribute to the energy self‐sufficiency and sustainability of airports in South Korea.

Bifacial photovoltaic (PV) modules can capture both front and rear incident light simultaneously, thereby enhancing their power output. Achieving uniformity in rear incident light is crucial for an efficient and a stable operation. In this study, we present a simple, yet effective textured rear reflector, designed to optimize the performance and stability of bifacial PV modules. The three-dimensional textured surface was created using an ethylene vinyl acetate sheet (EVA) through a hot-press method at 150 °C. Subsequently, the textured EVA surface was coated with solution-processed silver ink, increasing the reflectance of the textured reflector through a low-temperature process. The integration of the developed textured rear reflector into bifacial crystalline silicon (c-Si) PV modules resulted in an additional 6.9% improvement in power conversion efficiency compared to bifacial PV modules without a rear reflector, particularly when the rear reflector is close to the PV module. Furthermore, the textured rear reflector may mitigate current mismatch among cells by randomizing incident light and uniformly redistributing the reflected light to the PV cells. Consequently, the proposed textured reflector contributes to the enhanced performance and stability of bifacial PV modules.