# Production from bifacial model

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Dear Support (or users)

i have a project that i did using bifacial moduls.

1.in the energy report i would like to know what is the % of total energy coming from the rear side? where i can see this ?(i see just the gain in irradiance)

2.and how the -0.66% (bificiality 70%) is calculated

Thanks

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Dear timgreen13,

1. This is correct, there is no entry listing the total energy gain. You could state "The rear side of the module areas provides additional 24.85kWh of usable radiation (2.25% of the radiation after the previous gains and losses were added) per square meter being available for energy conversion". You could use this to estimate the total energy gain for the system.

2. The bifaciality factor is given by the modules and typically ranges between 0.7...0.8 (70...80%) https://help.valentin-software.com/pvsol/2021/en/calculation/pv-modules/bifacial-modules/

I hope this clarifies your question.

Best regards!
Frederik

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Dear Frederik

if i would like to estimante the % of total energy coming from the rear side ,is my cacluation ok ?

so

(24.8524.85kWh/m2 *4355m2)-32466kWh(bifacialty loss)=75755

75755/816889=~9% gain in energy from the rear side

is this correct ?

Thanks

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Dear timgreen13,

no. The fact that the radiation gains are at 2.25%, there must not be a higher system gain! Have a look at this table:

Gain/Loss are the values from your results. On the right side you can see the percentaged change of the accumulated values illustrated by the yellow bar charts (as shown in the table). The gain of 2.25% is based on the last accumulated value (1104.97kWh/m²) which means the bifacial gain part results in 2.20% of the global irradiation onto the module (1129.82kWh/m²).

The weighting of this additional irradiation to the rear side is 70% for the modules you have chosen. This 70% bifaciality factor means another 30% reduction of the rear side radiation, which results in another -0.66% losses.

In total this means 1.54% more energy compared to an analogue one-sided module which seems reasonable.

Best regards,
Frederik

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While answering your question and after some tinkering with some bifacial modules: Here are three projects with the same location and inverters and reasonably comparable modules (I attached the projects too):

1. South orientation, non bifacial

2. South orientation (same as first), bifacial

3. East-west orientation (90° inclination), bifacial

Where bifacial modules clearly shine is the third project, bifacial east-west 90 degree inclination. Naturally this is one of the most interesting of applications: Agricultural PV systems, perfect due to the doubled area usage plus the flattening effect for system operators.

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