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Öğe Evaluation of residential stand alone photovoltaic systems in mega cities of the world(Taylor & Francis Inc, 2024) Akgayev, Berkeli; Unsur, VeyselGrowing concerns about the climate change accompanied with energy crisis due to the unrest in the world have pushed the energy market to utilize sustainable and secure alternatives such as solar photovoltaics (PV). However, for residential consumers, the primary concerns are the reliability of the supply and the cost of PV-generated electricity. This study reports on the economic feasibility and technical analysis of PV systems in megacities worldwide. Nine mega cities, Beijing, Berlin, Istanbul, London, New Delhi, New York, Paris, Seoul, and Tokyo, have been selected based on their significant population sizes and the pronounced demand for electricity independence among residents. The annual production, load matching, and PV-electricity and battery dispatch are discussed, with Lazard's levelized cost of electricity (LCOE) and net present value (NPV) employed as economic indicators. While calculated LCOEs ranged from $0.084/kWh to $0.27/kWh across different cities, the NPVs were predominantly negative, varying approximately between -$2,000 and -$20,000, with Berlin as an exception. Finally, a sensitivity analysis was conducted, revealing that the LCOE is more sensitive to financial parameters than to module efficiency and irradiation.Öğe A mathematical investigation of the impact of gridline and busbar patterns on commercial silicon solar cell performance(Springer, 2020) Unsur, Veysel; Chen, Nian; Ebong, AbaThe cost and efficiency of solar generation are two parameters that must be optimized if it is to replace fossil-fuel sources in the electricity production market. Since the single-junction cell structure still holds the promise of cost-effectiveness and simple production, it is imperative to find ways to increase the efficiency above 20% in production. A comprehensive empirical grid model is first established herein to investigate front grid designs with three, four, and five busbars, the results of which are compared with numerical analysis using Griddler 2-D modeling software. It is found that a combination of segmented tapered metal grids (SG) and uneven busbars (UEB) leads to an increased short-circuit current density (J(SC)) and open-circuit voltage (V-OC) without sacrificing the fill factor. The five-busbar SG-UEB combination results in efficiency above 20% for industrial-sized solar cell without an additional step or layer. The improvement in the cell efficiency obtained using the uneven busbar design is attributed not only to the decreased shading but also to reduced contact recombination underneath the busbars. In addition to increasing the efficiency, the results show that the cost of the front Ag metallization for each cell can be reduced by 1.4 & xa2; per cell by using the presented segmentation method.Öğe Rapid thermal processing of cost-effective contacts for silicon solar cells(Wiley, 2019) Unsur, Veysel; Klein, Talysa; van Hest, Maikel F. A. M.; Al Jassim, Mowafak; Ebong, AbaThis paper reports on the investigation of rapid thermal processing (RTP) of contacting the Al-BSF solar cell with Ag, Cu, and Ni in conjunction with aerosol printing technique. The study showed a liftoff and delamination, respectively, for the bi and tri stack layers of Ag frit/Ni and Ag frit/Ni/Cu fired above 790 degrees C peak firing temperature. The 770 degrees C peak firing temperature gave excellent electrical performance for both bi and tri stack layer contacts, which is not favorable to forming thick back surface field (BSF) required for high open circuit voltage (V-OC). This suggests that the bilayer and trilayer contacts involving Ag frit are limited to low peak firing temperature, but Ni frit, on the other hand, showed a wider firing temperature range. This is supported by low reverse saturation current density (J(02)) of 1.1 x 10(-11) A/cm(2) and high shunt resistance (R-SH) of 5750 omega center dot cm(2) for the Ni frit fired at 800 degrees C peak firing temperature. More so, the adhesion of Ni Frit to silicon is better than Ag counterpart as evidenced in the SEM micrograph. Thus, by adopting RTP Ni/Cu contacts, the cost of metallization of solar cell can be dropped from 35% of total processing cost to only 5% to 6%, which is approximately 30% drop in the total cost of processing.Öğe Screen printable fire through nickel contacts for silicon solar cells(Elsevier, 2023) Akgayev, Berkeli; Sezgin, Aysegul; Yilmaz, Mucahit; Unsur, VeyselMetallization of crystalline silicon (Si) solar cells is indispensable for reducing the cost while increasing the overall efficiency. Developing alternative materials to the most commonly used screen printed silver (Ag) contacts is a critical factor. Here, in this study, a nickel (Ni) metal paste consisting of Ni metal particles, glass frit and an organic vehicle is fabricated for screen printed Ni contacts. To prevent possible Schottky barrier formation, a graphene layer is placed on the front surface of the Si solar cell between Ni and Si forming a metal-2Dsemiconductor structure ensuring the ohmic (or ohmic-like) contacts. It is demonstrated here that the graphene is transferred successfully onto the textured front surface of the cells and G/2D peaks are observed clearly, indicating the good quality of the graphene layer. Constituents of Ni metal paste, glass frit and organic vehicle, are fabricated in concordance with nickel metal powder and mixed to achieve optimal electrical output parameters. The findings suggest that the transition temperature of the glass frit is between 270 degrees C and 300 degrees C resulting in around 475 degrees C softening temperature, which gives excellent etching behavior to the paste. The average contact resistance of the screen printed Ni contacts governed by etching process is measured around 6.9 m & omega; cm2. The SEM images of the contacts show a uniform distribution and sintering behavior similar to that of silver counterparts. The light current-voltage measurements read the open circuit voltage of 660 mV, the short circuit density of 39.11 mA/cm2 and the fill factor of 81.4% resulting in around 21% efficiency.