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  1. Home
  2. Browse by Author

Browsing by Author "S. A. Rahman"

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    Publication
    Advancing Ohl Rating Calculations: Modeling Mixed-convective Cooling And Conductor Geometry
    (IEEE, 2022)
    K. Kopsidas
    ;
    S. A. Rahman
    ;
    M. A. AlAqil
    ;
    Stefano Rolfo
    The existing standard current-temperature calculations for overhead line (OHL) conductors have been adequate for conventional conductors and their operating temperatures. However, these calculations make assumptions and include simplifications about conductor geometry and aero-thermal-dynamics, introducing an error in the High-Temperature Low-Sag conductors operating temperatures. To quantify the error introduced by the shape of strands, the paper employs a Multi-Physics Finite Element Modeling approach that calculates the conjugate heat transfer for trapezoidal stranded OHL conductors. Furthermore, it proposes corrective equations to improve the accuracy of existing methods. The equations incorporate a new Nusselt number correlation for mixed convection and capture the surface area ignored by current calculations. The outer conductor geometry assumptions and the combined natural and forced convective cooling omission in the IEEE and CIGRE methods introduce an error at low (below 0.12 m/s) cross-flow wind speeds suggesting an underestimation of conductor temperature by up to 4%. In medium wind speeds, typically at 0.5 m/s–0.61 m/s, the standard methods overestimate the conductor temperature limiting its current-carrying capability. A 5% uprating for existing OHLs is potentially feasible, particularly for the trapezoidal stranded conductors, when removing the assumptions made in existing methods.
      4
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    Publication
    Impact Of Ideality Factor And Semiconductiong Material On PV Module Performances
    (Universiti Sains Islam Malaysia, 2020-10-15)
    Mahasniza Ibrahim
    ;
    S. A. Rahman
    ;
    Marinah Othman 
    ;
    K. N. Zainul Ariffin
    conventional power resources since it is clean and renewable. The PV system allows the Sun’s energy to be converted to electricity using solar cells which currently is made by silicon. This project aims to evaluate the impact of ideality factor and semiconducting material variations on the I-V and P-V characteristics of the PV cell. For the purpose, five mathematical equations used to replicate the operations of PV module are modelled in MATLAB/SIMULINK and the electrical performances of the PV modules are analyzed. The results indicated that the electrical performances of a PV cell are highly dependent on the types of semiconducting material used and the ideality factor. From the tested material, it is found that at a temperature below the standard temperature condition (STC) of 25°C, Gallium Phosphide, GaP with a bandgap of 2.26eV would be the better option. An improved of 9.52% in maximum power is observed at 10°C when compared to silicon. However, at a temperature above the STC of 25°C, the use of Germanium with a bandgap of 0.67eV would be the better option than silicon as an increased of the maximum power of 4.97% is found at 40°C. Besides, the improper fabrication process (e.g. n= 2.0) would reduce the Pmax of the PV modules by 12%.
      1  10
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