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978-3-8439-2024-7, Reihe Ingenieurwissenschaften
Ufuk Alper Yusufoglu
Loss Reduction Methods for Crystalline Standard and Bifacial Photovoltaic Modules
163 Seiten, Dissertation Rheinisch-Westfälische Technische Hochschule Aachen (2014), Softcover, A5
Global photovoltaic (PV) module production is dominated by crystalline silicon based PV modules. The core element in PV modules are solar cells. Since the power of single solar cells is, however, not sufficient to supply electrical utilities several solar cells are connected in series. Additionally, this interconnection of solar cells alone cannot be deployed at outdoors forcing their encapsulation. These necessities, however, lead to cell-to-module losses. In this work a new software tool is developed to quantify these losses during the annual operation and it is used further to provide solutions to reduce them.
The Pmpp of a module is less than the sum of the Pmpp of individual solar cells. The common method to overcome these mismatch losses is to put solar cells with similar Pmpp at STC in the same module. Nevertheless, STC is not representative for the actual operating conditions. In this manner, analysing the annual operation of modules, two new sorting methods are introduced for solar cells. Implementing these new sorting methods, reduced mismatch losses and higher annual energy yields up to 0.44% are shown.
The encapsulation of solar cells constitutes another loss mechanism. Using the developed tool, AOI losses are analysed for the use of EVA and solar glass, and also considering the utilization of ARC on glass and the substitution of EVA with silicone. With the simulations, the impact of these materials on the annual energy yield of modules is investigated. The superiority of using ARC and silicone was shown for locations in higher latitudes under predominant diffuse light conditions and also for east/west facing modules providing gains of up to 1.1% in annual energy yield.
Bifacial modules provide an option for increased harvesting of solar radiation by utilizing both planes of the module. Hence, compared to monofacial modules, they are able to produce larger amounts of energy. Nevertheless, this advantage can only be achieved by a proper analysis of the parameters affecting their performance. Therefore, individual and combined effects of tilt angle of the module, reflective surface area, module elevation and reflectivity of the ground are analysed. Based on these analyses, this work presents for the first time how to maximize the annual energy generation of bifacial modules. Consequently, the superiority of bifacial modules against standard modules is shown by an up to 25% more energy generation during annual operation.