https://scholar.korea.ac.kr/handle/2021.sw.korea/2940 Wed, 08 Apr 2026 17:29:56 GMT 2026-04-08T17:29:56Z https://scholar.korea.ac.kr/handle/2021.sw.korea/271405 Title: Integrating PVDF-based piezoelectric nanogenerators with highly conductive carbon nanofibers for energy-harvesting applications Authors: Khadka, Ashwin; Samuel, Edmund; Joshi, Bhavana; Aldalbahi, Ali; Periyasami, Govindasami; Lee, Hae-Seok; Yoon, Sam S. Abstract: Piezoelectric nanogenerators (PENGs) are gaining popularity in wearable electronics, self-powered devices, and pressure sensors for detecting acoustic, air, and water waves. In this study, electrospun polyacrylonitrile-derived carbon nanofibers (CNFs) were combined with polyvinylidene fluoride (PVDF) nanofibers for PENG applications. Incorporating highly conductive CNFs into the system and applying an electric field during electrospinning increased the electroactive beta-phase content of PVDF to 93.2 %, as confirmed by Fourier transform-infrared spectroscopy. CNF inclusion also caused 9.6- and 3.2-fold increments in the power density and piezopotential of PENG. The fabricated PENGs show stable performance over 12,000 cycles of continuous tapping with a force of 20 N at a frequency of 5 Hz. Besides showing promising potential in functional sensing and self-powered devices, the mechanically resilient systems reported in this study can harness energy from biomechanical movements and ultrasonic wave pressure, thereby exhibiting their applicability in healthcare monitoring devices and sensors. Sun, 15 Jun 2025 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/271405 2025-06-15T00:00:00Z https://scholar.korea.ac.kr/handle/2021.sw.korea/268533 Title: Transforming aid-funded renewable energy systems: A case study of policy-driven financial sustainability in rural Bangladesh Authors: Yi, Hyunah; Kim, Kyung Nam Abstract: Efforts to improve energy access in off-grid areas through donated photovoltaic (PV) systems often encounter sustainability challenges, particularly due to inadequate maintenance resulting from financial constraints. These challenges are compounded when national power grids extend to off-grid regions, leaving existing PV systems underutilized or abandoned. To enhance the sustainability of these systems, this study performs an economic analysis of connecting previously off-grid PV systems to the national power grid with the System Advisory Model (SAM). The analysis examines whether the existing PV systems can generate sufficient revenue to cover operational costs and ensure their long-term viability. Simulations evaluate two schemes -net metering and feed-in tariff- as potential solutions to integrating PV systems into the national power grid while maintaining economic benefits. Results demonstrate that donated PV systems can achieve economic viability under compensation rates lower than those currently supported by government policies. Such reduced compensation rates allow governments to procure electricity at a lower cost while enabling prosumers to meet operational expenses. These findings provide insights into enhancing the sustainability of equipment installed in off-grid areas as electrification expands and offer a framework for diversifying compensation rate policies in government initiatives. Sun, 15 Jun 2025 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/268533 2025-06-15T00:00:00Z https://scholar.korea.ac.kr/handle/2021.sw.korea/267639 Title: Pd nanoparticles fixed in zeolites promote low-temperature NO reduction via hydrogen spillover Authors: Lee, Eunwon; Lee, Jaeha; Park, Dong Chan; Moon, Sei; Song, Inhak; Jung, Hyeongdong; Kim, Do Heui Abstract: H2-selective catalytic reduction is a promising NOx control technology owing to its high intrinsic activity at low temperatures. We investigated catalysts composed of Pd NPs fixed in ZSM-5, which demonstrated enhanced activity for NO reduction by H2 at T <= 150 degrees C, achieving over 95 % NOx conversion and N2 selectivity at 100 degrees C. This system was particularly suited for studying the influence of hydrogen spillover on NO reduction activity because the fixed Pd NPs cannot interact with NO, while ZSM-5 can mediate hydrogen spillover and activate NO away from the Pd NPs on the Br & Oslash;nsted acid sites. Quantifying the kinetic isotope effect, and using catalytic measurements and in-situ infrared spectroscopy, we elucidate the reaction mechanism governing the catalytic activity. Under reaction conditions (NO + O2 flow at 100 degrees C), it was found that NO is activated as nitrosyl complexes on in-situ formed Pd cations as well as charge-compensating NO+ species at the cation exchange sites of ZSM-5, with the latter species serving as active intermediates. At this stage, the activated NO+ species on Br & Oslash;nsted acid sites undergo selective reduction to N2 by reacting with spillover hydrogen from Pd NPs. Furthermore, the fixed Pd structure reduces the susceptibility to O2 chemisorption, enabling the Pd NPs to preserve their metallic state against oxidative poisoning for efficient H2 dissociation. Our study provides insights into the characterization of zeolite-fixed metal NPs, which is distinct from conventional analyses that focus on exposed metal sites. Moreover, this study highlights the fixation of metal NPs on zeolites as an effective strategy for NO reduction by H2. Thu, 05 Jun 2025 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/267639 2025-06-05T00:00:00Z https://scholar.korea.ac.kr/handle/2021.sw.korea/270780 Title: PyPSA-Korea: An open-source energy system model for planning Korea's sustainable energy transition Authors: Kwak, Kyuil; Son, Woojin; Yang, YeHa; Woo, JongRoul Abstract: This study introduces PyPSA-Korea, an open-source energy system model with high temporal and spatial resolution designed to support Korea's sustainable energy transition. Developed using the Python for Power System Analysis (PyPSA) and PyPSA-Earth frameworks and incorporating public datasets, PyPSA-Korea facilitates both operational and investment planning. It enables regional siting and expansion of integrated power generation, transmission, and energy storage systems (ESS)—a critical requirement for renewable energy integration in Korea. The model was validated against historical data from 2023 and applied to a 2036 scenario aligned with the Nationally Determined Contribution and the Basic Plan for Long-Term Electricity Supply and Demand. PyPSA-Korea provides a flexible and robust framework for research and policy analysis on macro-level energy systems. The results emphasize the necessity of renewable energy deployment, transmission network reinforcement, and ESS expansion to mitigate intermittency and achieve carbon emission reduction targets. By offering an open and high-resolution modeling framework, PyPSA-Korea overcomes the accessibility barriers associated with closed-source models and is a valuable tool for evidence-based policy analysis and strategic decision-making for a sustainable energy transition in Korea. © 2025 The Authors Sun, 01 Jun 2025 00:00:00 GMT https://scholar.korea.ac.kr/handle/2021.sw.korea/270780 2025-06-01T00:00:00Z