Simulation framework shows performance of bifacial solar modules
The framework, developed as part of the EnrgyVille collaboration, has a higher accuracy compared to previous approaches by computing the energy yield of the individual cells and modules based on local and varying meteorological conditions and the way it is influenced by module frames, system components’ geometry, and varying albedo.
To enable implementation of advanced optical simulations (using ray-tracing) at system level, special care was also taken to optimize the computational flow and still operate quickly.
“An important achievement is that our tool will be capable of calculating the energy yield of an entire system, while maintaining a low error margin of < 5% (daily RMSE) even in complex scenarios and at high speed of calculation,” said said Eszter Voroshazi, R&D manager of PV modules and systems at imec/EnergyVille. “The impact of technological and system configuration details on the non-uniformity at the rear side of the modules has a surprisingly important effect and can trigger major losses up to 40% due to mismatch between modules, hence we pursue the further development of our simulations combining a physics-based approach with high performance computing techniques.”
“Our final goal is to calculate with high precision the bifacial gain at module, string and system level and enable a multi-objective and automated PV power plant design tool on
the longer-term,” he added.
Bifacial PV systems can annually generate 5 to 20 % more electricity than their traditional monofacial counterparts on little or no extra cost. Because of this benefit, bifacial PV installations are gaining market share. However, the limitations of the current simulation tools to precisely determine their expected energy yield could hinder further deployment as the data is not accurate enough for investors.
While the existing commercial energy yield simulation tools and approaches used for the design of PV power plants have become more and more precise for standard monofacial silicon solar modules, their estimations for bifacial systems still include high error margins. Calculating the energy yield of bifacial solar modules is more challenging because energy generation from light received at the rear side depends on many variables that are hard to determine and may vary during the day, e.g. self-shading, plant geometry, mounting structure, ground albedo (= the percentage of sunlight reflected by the ground to the PV module’s rear side).
The rear illumination also causes differing total energy generation at module level and consequently electrical mismatch losses at string level. This means that the string configuration also plays a role in the global solar power plant energy yield.
“The fact that we are working on a solution that can accurately predict the energy yield of both individual bifacial panels and entire systems is not only important from an R&D point of view, but we expect it will stimulate implementation of bifacial modules in the field, further reducing the price of green energy. Since current energy yield prediction tools for bifacial technology are not so precise, investors do not have a good view of their return on investment, making them hesitant to take the step. We are currently in the final validation phase of our simulation framework. Once it will be fully available it will give PV plant developers more confidence of the achievable bifacial gain, hence allowing easier funding of bifacial power plants,” said Philip Pieters, business development director at imec/EnergyVille.
The simulation framework has already been validated at module level at EnergyVille, a collaboration between the Flemish research institutes KU Leuven, VITO, imec and UHasselt in the field of
sustainable energy and intelligent energy systems, and in collaboration with Kuwait University. Now the framework is ready to be validated on large scale installations in real-life conditions and in different climates across the world.
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