Coloring photovoltaic modules using printed textiles: Fabrication, validation and the prediction of appearance & energy yield

Abstract

The targets set by many nations to increase renewable energy production lead to a greater demand for photovoltaic modules (PV). In order to reduce the additional area required, it is advisable to first utilize existing areas that were previously unused for energy generation. As a result, building-integrated PV modules, especially those integrated into façades, are gaining in importance. However, such PV modules not only provide energy, they also have to meet aesthetic requirements. For a cost-benefit analysis and the calculation of the payback period, an accurate yield prediction is essential. However, a yield prediction for PV modules modified in appearance and mounted vertically onto a façade is less accurate than a yield prognosis for standard and roof-mounted modules. In this work, I present the Colored Textile (CoTex) method, which alters the appearance of PV modules by using imprinted textiles, such as nonwovens. I validate this method by various laboratory and long-term measurements in terms of durability, energy yield and appearance of such CoTex modules. Depending on the selection of the textile used and the printed color, the energy yield varies. For example, a PV module in light gray design achieves an energy yield of 89% compared to a standard module. The CoTex method allows endless possibilities for the appearance of the manufactured modules by using printed materials. Depending on the textiles and printing parameters used, a different appearance is created. To ensure that the appearance and energy output of specific CoTex modules are known before they are manufactured, I perform the simulation of a digital prototype. After calibration based on eight different colored sample modules, a digital prototype can be simulated for any combination of the three printing inks cyan, magenta and yellow. The deviation between the simulated and the measured color are hardly perceptible for an observer, the deviation of the simulated from the measured energy yield is below 2 %. Using the energy yield determined by the digital prototype, a total yield prediction can be performed for a CoTex module. By applying the ground view factor for vertically mounted PV modules and including ground shading from objects in the surrounding area, I reduce the deviation between measured and simulated energy yield by up to 10.5 % over a 12-month period compared to using the standard model to calculate ground reflectance. By adding an angular correction of the transmission of the CoTex layer depending on the position of the sun, the yield prediction for CoTex modules can be performed with an accuracy comparable to that of standard PV modules.