Architectural integration of photovoltaics: Performance evaluation of curved modules
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BiPV (Building integrated photovoltaics) stands on the bridge between architecture and energy production, some photovoltaic companies in the last decade are engaging in the design and production of non conventional PV technologies (Cerón, Caamaño-Martín, and Neila 2013). BiPV industry aims to transform PV from power plant to building material, thus is coming up the need for features such as freedom of color and dimensions, and flexibility. In this paper a method is presented for the estimation of power production on curved active surfaces, the performance of two samples of flexible thin film photovoltaic modules are evaluated as a validation. Because of its curved application, the performance of the modules under study is affected by electrical layout and non-uniform temperature issue. The work shows a method to simulate the performance of curved photovoltaic modules subject to uneven irradiation. For the experimental set-up, a curved shelter was built (of those typically used to shield market carts outside of supermarkets). Two different flexible photovoltaic modules are glued onto the curved roof of the structure, each module is equipped with an MPPT tracker connected to a data logger, there are then 2 thermocouples to measure temperatures in the two different modules. Because of the curved shape of the photovoltaic surface the incoming irradiation cannot be measured with a pyranometer, and should therefore be accessed by geometry based computer simulation. The irradiation is simulated using ray-tracing computations (Ward 1996). The simulation uses weather data retrieved from the weather station located at the ABD airport in Bozen (less then 1 Km away). The main result is the comparison between the simulated power production and the measured one. Both simulated and measured power, points to a better performance linked to one electrical layout over the other. More values are of interest such as Ross coefficient on the module for this particular type of shape and integration. The study shows an acceptable level of agreement between the simulated power production and the measured one provided that some parameters are calibrated. The possibility of simulating this technology opens the path for economic analysis and feasibility studies to access the real potential of this technology in non-flat application cases.