• Title/Summary/Keyword: Department of Energy

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Effect of Ag Alloying on Device Performance of Flexible CIGSe Thin-film Solar Cells Using Stainless Steel Substrates

  • Awet Mana Amare;Inchan Hwang;Inyoung Jeong;Joo Hyung Park;Jin Gi An;Soomin Song;Young-Joo Eo;Ara Cho;Jun-Sik Cho;Seung Kyu Ahn;Jinsu Yoo;SeJin Ahn;Jihye Gwak;Hyun-wook Park;Jae Ho Yun;Kihwan Kim;Donghyeop Shin
    • Current Photovoltaic Research
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    • v.11 no.1
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    • pp.8-12
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    • 2023
  • In this work, we investigated the thickness of Ag precursor layer to improve the performance of flexible CIGSe solar cells grown on stainless steel (STS) substrates through three-stage co-evaporation with Ga grading followed by alkali treatments. The small amount of incorporated Ag in CIGSe films showed enhancement in the grain size and device efficiency. With an optimal 6 nm-thick Ag layer, the best cell on the STS substrate yielded more than 16%, which is comparable to the soda-lime glass (SLG) substrate. Thus, the addition of controlled Ag combined with alkali post-deposition treatment (PDT) led to increased open-circuit voltage (VOC), accompanied by the increased built-in potential as confirmed by capacitance-voltage (C-V) measurements. It is related to a reduction of charge recombination at the depletion region. The results suggest that Ag alloying and alkali PDT are essential for producing highly efficient flexible CIGSe solar cells.

Model Development of Daily and Hourly Energy Load for Department Stores

  • Park Hwa-Choon;Lee Sung-Soo;Kim Dae-Jin
    • International Journal of Air-Conditioning and Refrigeration
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    • v.12 no.4
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    • pp.169-175
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    • 2004
  • Case study was performed to analyze energy load for department stores and develop energy load model to be applied to a cogeneration system. Energy loads of 14 depart­ments were analyzed based on energy load sheets written by operators and energy load of one department store was measured through modem communication for a year. Energy load of department stores showed various trends depending on when they were opened or closed, or by hour, day and month. In this paper, the measurement was compared with the data in energy load sheets and resolved, and energy load model for a department store was built. It is important to use an accurate energy load model for an accurate feasibility study applying a cogeneration system to buildings.

Parametric study on energy demands for steel special concentrically braced frames

  • Dogru, Selcuk;Aksar, Bora;Akbas, Bulent;Shen, Jay
    • Steel and Composite Structures
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    • v.24 no.2
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    • pp.265-276
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    • 2017
  • Structures are designed in such a way that they behave in a nonlinear manner when subject to strong ground motions. Energy concepts have been widely used to evaluate the structural performance for the last few decades. Energy based design can be expressed as the balance of energy input and the energy dissipation capacity of the structure. New research is needed for multi degree of freedom systems (MDOFs)-real structures- within the framework of the energy based design methodology. In this paper, energy parameters are evaluated for low-, medium- and high-rise steel special concentrically braced frames (SCBFs) in terms of total energy input and hysteretic energy. Nonlinear dynamic time history analyses are carried out to assess the variation of energy terms along the height of the frames. A seismic energy demand spectrum is developed and hysteretic energy distributions within the frames are presented.