Michele Oliosi

@tecnum There are actually breaks in the slope every 5 years, only two of them are more extreme than the others. This is due to the mismatch values that are generated by Monte-Carlo (you see them given for every 5 years). This degradation is “random” in nature, so some erraticism is to be expected. The current code’s philosophy is that since this is a random model, that does not reflect “real values” for which we have good time series (unlike weather for which the statistics can be known over many years), there won't be much to gain in having a more fine-grained approach.

Sorry it's not possible at the moment to have different power factors between inverter and injection point. You should just use the grid injection point one.

Hi thanks for the suggestion, it makes sense. We will consider this as a possible improvement of the report. One worry might be users thinking that this new percentage IS the bifacial gain.. this is not what we want of course. But we can try to use a very clear denomination.

@vishnu Short answer: No, for system modellings it is best to stick with the simpler model used by PVsyst. Monofacial modules also receive irradiance on the backside, the only thing that changes is the PV conversion on the backside, which won't have a big impact. Longer answer: I understand that you want to include the backside irradiance as a contribution, but this contribution already exists in the case for monofacial modules. Therefore what you suggest is a new general model that should be be applied also for monofacial modules (they alse receive light on the backside). On top of the above, the model you suggest needs several tweaks. Most importantly the irradiance on the backside is not simply ???∗??????∗??????????? ??????. It is the result of the geometric model that takes into account both reflection on the ground and direct sunlight on the backside. This should be replaced by the PVsyst variable GlobBak. Also, the bifaciality factor modifies the efficiency ????. Finally, the absorption coefficient ? should affect also the backside part. So here is a new suggestion: Tc=??+((????∗?)∗(?−????)+(GlobBak∗?)∗(?−????∗??????????? ??????))/(?'?+(?'?∗??)) However, in this new formula U'c and U'v are not the ones used in the "monofacial" formula hence the primes. One should make one or rather several studies to find these values. Until this kind of model is not backed by a good corpus of literature and accurate measurements leading to the new U'c and U'v values, it is definitely best to stick with the simpler, partially validated, model. As mentioned above, even for non-bifacial modules, there will be irradiance on the backside, i.e. the original values Uc and Uv already took into account this contribution. There is no compelling reason to adapt it in PVsyst on ground of using bifacial models.

Hi bendesa1962, Your understanding and definitions are correct. However your example is incorrect. In the southern hemisphere it will be: Facing North is 0 Facing South is 180 Facing East is -90 Facing West is 90

Indeed this fix has been (long) forgotten, thank you for the reminder. It should be implemented in version 7.2.10.

The global fraction on ground, that you find in Bifacial system > Unlimited Trackers 2D model, is calculated for clear sky conditions. As such, it is not applicable to your simulation results (unless you have a clear sky meteo file). Your intuition about how the global incident on ground is calculated is correct. However, PVsyst does the calculation hour by hour and differentiates the beam and diffuse irradiance components. The beam and diffuse components have different "fractions on ground", that will generally vary every hour with the sun / tracker positions. Therefore it is difficult (probably even impossible) to calculate it from the current outputs of PVsyst, in particular from the monthly results.