Browsing by Department "Polytechnic University of Catalonia"

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    Development of a reduced order model of solar heat gains prediction
    (MDPI AG, 2020-12) Tamm, Meril; Macia Cid, Jordi; Capdevila Paramio, Roser; Farnos Baulenas, Joan; Thalfeldt, Martin; Kurnitski, Jarek; Tallinn University of Technology; Centre Tecnològic de Catalunya; Polytechnic University of Catalonia; Department of Civil Engineering
    The aim of this study was to elaborate and validate a reduced order model able to forecast solar heat gains as a function of the architectural parameters that determine the solar heat gains. The study focused on office buildings in Catalonia and Spain and their physical values were taken from the Spanish Building Technical Code and European Union Directive 2018/844. A reduced order model with three direct variables (solar heat gain coefficient, shade factor, window to wall ratio) and one indirect design variable (building orientation) was obtained and validated in respect to the International Performance Measurement and Verification Protocol. Building envelope properties were fixed and the values were taken from the national standards of Spain. This work validates solar heat gain coefficient as a primary variable in determining the annual solar heat gains in a building. Further work of developed model could result in building energy need quick evaluation tool in terms of solar heat gains for architects in building early stage as it has an advantage over detailed building simulation programs in terms of instant calculation and the limited need for predefined input data.
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    Recombination processes in passivated boron-implanted black silicon emitters
    (2017-05-14) von Gastrow, Guillaume; Ortega, Pablo; Alcubilla, Ramon; Husein, Sebastian; Nietzold, Tara; Bertoni, Mariana; Savin, Hele; Department of Electronics and Nanoengineering; Polytechnic University of Catalonia; Arizona State University
    In this paper, we study the recombination mechanisms in ion-implanted black silicon (bSi) emitters and discuss their advantages over diffused emitters. In the case of diffusion, the large bSi surface area increases emitter doping and consequently Auger recombination compared to a planar surface. The total doping dose is on the contrary independent of the surface area in implanted emitters, and as a result, we show that ion implantation allows control of emitter doping without compromise in the surface aspect ratio. The possibility to control surface doping via implantation anneal becomes highly advantageous in bSi emitters, where surface passivation becomes critical due to the increased surface area. We extract fundamental surface recombination velocities Sn through numerical simulations and obtain the lowest values at the highest anneal temperatures. With these conditions, an excellent emitter saturation current (J0e) is obtained in implanted bSi emitters, reaching 20 fA/cm2 ± 5 fA/cm2 at a sheet resistance of 170 Ω/sq. Finally, we identify the different regimes of recombination in planar and bSi emitters as a function of implantation anneal temperature. Based on experimental data and numerical simulations, we show that surface recombination can be reduced to a negligible contribution in implanted bSi emitters, which explains the low J0e obtained.