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Currently, perovskites/silicon tandem solar cells and bifacial solar cells are amongst the most-discussed trends within the photovoltaic community.
Accurate numerical simulations of large PV systems consisting of bifacial solar modules are vital their optimization. In this work we present a detailed illumination model for solar modules in a big PV field. This model takes direct and diffuse illumination from the sky and from the ground into account, accounts for shadowing of the modules onto each other and the ground, and allows to calculate the annual energy yield as a function of distance and tilt of the modules.
Using realistic spectral weather data and the spectral reflectivity of the ground, we can perform detailed optimizations for the different tandem solar cell configurations. In general, four-terminal cells yield a higher electricity generation because in contrast to two-terminal (2T) cells no performance losses caused by current mismatch occur, but the balance-of-system costs for 2T cells are lower. By increasing the perovskite thickness and/or decreasing the perovskite bandgap, the top-cell current density can be increased leading to a higher overall current density under bifacial operation. We will compare the optimized energy yield for 2T cells with the energy yield of comparable 4T cells. For these simulations, we use a detailed-balance model with realistic absorption data of perovskite and silicon layers.
Finally, we present minimizations of the LCOE for mono- and bifacial modules as a function of the land cost. We see that increasing the land cost leads to a lower optimal module distance, where the optimal tilt is lower than for larger module distance in order to compensate for more shadowing. With respect to the LCOE corresponding to a module distance determined by a rule-of-thumb, the minimized LCOE can differ significantly especially for higher land cost.
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