Ground reflection on front side

[balajiicon]

HI,

There is a new parameter Ground reflection on front side shown in Loss diagram when simulated with Bifacial, this is giving a gain of 0.2% in GHI.Why this was not considered in conventional modules,please clarify.

Regards,

R.Balaji

[André Mermoud]

The “Ground reflection on front side” is a by-product of the Bi-facial model. It is not possible to calculate it with "normal" systems, without several additional parameters and a calculation model that we don't have at disposal at the moment (the bi-facial model is specific for unlimited sheds).

By the way its value is very low for usual tilts. To my knowing, this quantity is never calculated (nor taken into account) by any other PV system simulation tool.

[gpuy]

Hi,

I was wondering why with monofacial modules, although the Ground reflection on front side is neglected, the Global incident in coll. plane depends on the albedo coefficient. I've read what states here about the albedo Physical models used > Irradiation models > Transposition model (pvsyst.com) , but I don't get which is the difference between these 2 albedo contributions.

Regards,

Guillermo

[André Mermoud]

The irradiance incident on a tilted plane has basically 3 components: the beam, the diffuse, and a contribution of the reflexion of the sun's rays on the ground in front of (but far) from the collector plane.  These 3 contributions are taken into account in the transpostion models.

Now with bifacial systems, we work with the albedo of the ground just below the PV plant. This may be different from the albedo of the far terrain in front of the PV system.

 

 

[gpuy]

Thanks André.

I would like to know if:

• Do you have any model verification for the Ground reflection on front side?
• Is it possible to neglect the Ground reflection on front side during a simulation?

 

[André Mermoud]

No, we don't have any verification. This is a theoretical hypothesis, expecially for the coherency of vertical bifacial systems.

This contibution is low for other orientations (tilts around 10-20°) .

It is not taken into account in the simulations without Bifacial calculation.