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  • Mechanical Reliability of Fullerene/Tin Oxide Interfaces in Monolithic Perovskite/Silicon Tandem Cells

    de Bastiani, Michele; Armaroli, Giovanni; Jalmood, Rawan S.; Ferlauto, Laura; Li, Xiaole; Tao, Ran; Harrison, George T.; Eswaran, Mathan Kumar; Azmi, Randi; Babics, Maxime; Subbiah, Anand Selvin; Aydin, Erkan; Allen, Thomas; Combe, Craig; Cramer, Tobias; Baran, Derya; Schwingenschlögl, Udo; Lubineau, Gilles; Cavalcoli, Daniela; De Wolf, Stefaan (ACS Energy Letters, American Chemical Society (ACS), 2022-01-25) [Article]
    High-efficiency perovskite-based solar cells comprise sophisticated stacks of materials which, however, often feature different thermal expansion coefficients and are only weakly bonded at their interfaces. This may raise concerns over delamination in such devices, jeopardizing their long-term stability and commercial viability. Here, we investigate the root causes of catastrophic top-contact delamination we observed in state-of-the-art p-i-n perovskite/silicon tandem solar cells. By combining macroscopic and microscopic analyses, we identify the interface between the fullerene electron transport layer and the tin oxide buffer layer at the origin of such delamination. Specifically, we find that the perovskite morphology and its roughness play a significant role in the microscopic adhesion of the top layers, as well as the film processing conditions, particularly the deposition temperature and the sputtering power. Our findings mandate the search for new interfacial linking strategies to enable mechanically strong perovskite-based solar cells, as required for commercialization.
  • Streamlining the estimation of kinetic parameters using periodic reaction conditions: the methanol-to-hydrocarbon reaction as a case study

    Vicente, Hector; Gayubo, Ana G.; Aguayo, Andres T.; Castaño, Pedro (Chemical Engineering Journal, Elsevier BV, 2022-01-25) [Article]
    Reducing the experimental time required to obtain a robust kinetic model with reliable kinetic parameters has been a long-standing objective in reaction engineering. In the present study, we compare the kinetic modeling of two sets of data obtained using periodic reaction conditions (PRC) and stationary reaction conditions (SRC). As a case study, we use the well-known methanol-to-hydrocarbon reaction on HZSM-5 zeolite. The SRC experiments are conducted with a temperature of 425−475 °C, a total pressure of 2.5 bar, a partial pressure for methanol of 1.125 bar, a space time of 0.1−1.5 gcat h molC-1, a initial molar ratio water:methanol of 0–0.66 and 16 h on stream. The PRC experiments involve sinusoidal variation in the methanol and water flowrates of 135 ± 88 µL min-1 and 20 ± 20 µL min-1, respectively, with a period of 16 h or sinusoidal variation in the temperature of 450 ± 25 °C with periods of 8 and 16 h. Several strategies are then used in fitting the kinetic parameters of five models. We obtain relatively similar results in terms of model discrimination, the parameters, and confidence intervals with a cumulative experimental time of 64 h on stream under the PRC compared with 192 h on stream under the SRC, a reduction of 67% in the experimental time.
  • Colloidal silica fouling mechanism in direct-contact membrane distillation

    Jang, Yongsun; Lee, Jung-Gil; Fortunato, Luca; Lee, Jieun; Lee, Yejin; An, Alicia Kyoungjin; Ghaffour, NorEddine; Lee, Sangho; Jeong, Sanghyun (Desalination, Elsevier BV, 2022-01-24) [Article]
    Membrane fouling limits the performance of membrane distillation (MD) and its application to seawater brine treatment. Silica fouling is considered one of the most complex type of fouling. In this study, we evaluated the flux decline and fouling ratio due to colloidal silica fouling in direct-contact MD and characterized the fouled membranes. We also tested the efficacy of high flow-rate water flushing for the restoration of flux after fouling. The formation and removal of silica scaling were monitored in real-time with optical coherence tomography (OCT). Our work demonstrated that fouling formation is influenced by silica particle size, feed temperature, salinity, and flow rate. Notably, silica formed cake-layer fouling on the MD membranes. Smaller silica particle size resulted in a higher flux decline and a denser cake layer. A higher feed temperature resulted in a higher flux, but more severe fouling. We also found that fouling was minimized at an optimal flow rate and salinity did not significantly affect fouling formation. OCT monitoring showed that silica fouling deposited on the membrane surface and evaluated the effect of each cleaning strategies on the cake layer. This comprehensive investigation provides valuable insights for the development of silica fouling control strategies in MD.
  • A variable fractional-order inductor design

    Zhang, Li; Kartci, Aslihan; Bagci, Hakan; Salama, Khaled N. (International Journal of Circuit Theory and Applications, Wiley, 2022-01-24) [Article]
    Recently, interest in fractional-order inductors (FOIs) has increased since theyallow for accurate and robust models of dynamical systems to be designed.However, practical implementation of these models has not been possible dueto the lack of single FOI realizations. To address this challenge, in this work,we propose a simple-to-realize fractional-order inductor design with variableconstant phase angle (CPA). The design relies on characteristics of transverseelectromagnetic (TEM) mode propagating on a coaxial structure filled withconductive material, more specifically NaCl-water solution and flour-basedmixtures. The CPA of the resulting FOI can be tuned by changing the conduc-tivity of the dough mixture. Analysis of the proposed FOI design show that theCPA can vary in a range from 0 to 90 . Two of these CPA values are verifiedagainst experiments in the frequency band changing from 1 to 10 MHz
  • Forecasting high-frequency spatio-temporal wind power with dimensionally reduced echo state networks

    Huang, Huang; Castruccio, Stefano; Genton, Marc G. (Journal of the Royal Statistical Society: Series C (Applied Statistics), Wiley, 2022-01-23) [Article]
    Fast and accurate hourly forecasts of wind speed and power are crucial in quantifying and planning the energy budget in the electric grid. Modelling wind at a high resolution brings forth considerable challenges given its turbulent and highly nonlinear dynamics. In developing countries, where wind farms over a large domain are currently under construction or consideration, this is even more challenging given the necessity of modelling wind over space as well. In this work, we propose a machine learning approach to model the nonlinear hourly wind dynamics in Saudi Arabia with a domain-specific choice of knots to reduce spatial dimensionality. Our results show that for locations highlighted as wind abundant by a previous work, our approach results in an 11% improvement in the 2-h-ahead forecasted power against operational standards in the wind energy sector, yielding a saving of nearly one million US dollars over a year under current market prices in Saudi Arabia.

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