Bifacial Cell Temperature Model

[vishnu]

Hi,

I Would like to know if the following model would fit best for Bifacial Modules:

"Tc=??+(((????∗?)+(???∗??????∗??????????? ??????))∗(?−????))/(??+(??∗??))"

Thanks,

[Michele Oliosi]

@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.