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Simulating Multiple Orientations (Azimuth +90/-90) with Bifacial modules

Janani Krishna

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Dear PVsyst Team,

We were in the process of simulating Est-West oriented system with bifacial modules for one of our projects. We found a way to do so, irrespective of shading scene with mutiple orientation with bifacial modules is not possible currently with the software.

we defined "Plane Orientation" with Azimuth 0 deg and in the shading scene, we turned the scene such that the modules face east &west. With this definition, we were able to run the simulation and obtain below yield with bifacial gain as well. Please validate if this methodology is correct to predict the energy yield from the system.

the proposed site location is at 8 deg N/78deg E (close to equator)




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52 minutes ago, Janani Krishna said:

Please validate if this methodology is correct to predict the energy yield from the system.

As with any trick, you should expect a tradeoff in terms of precision. With this methodology, you are relying on two approximations:

  • Using a single orientation instead of two. In terms of backside irradiance, it is ok if the tilt is not that large, e.g., your 5°. However, the tradeoff is that the transposition and IAM losses are not modeled using the true orientations. This means that the front side irradiance may have some error !
    • Please compare the front side irradiance values carefully between the variant using two orientations and the variant with the approximation.
    • You are gaining about 1% bifacial gain, as expected for such a system with a high GCR. This is almost equivalent to a monofacial system, because there is almost no light on the backside. This may be well below the increased uncertainty in the front side irradiance, so please be very careful when interpreting these results, especially the final energy yield.
  • Aligning the system with E-W, strictly. This is unnecessary. You can switch to a single orientation by using the 3D scene > Tools > Orientation management. There you can increase the tolerance and identify the orientations anew. This will apply even if the modules are not strictly aligned with the E-W axis.
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