Sandia is building an outdoor bifacial PV performance test bed in Albuquerque, NM to collect data to be analyzed and shared with the community. This data will be used to develop predictive performance models that can eventually be included in commercial applications. Based on a review of literature on this topic, we designed our test facilities to be able to vary design parameters that are known to affect bifacial PV performance.

The amount of additional energy generated from the backside of a bifacial module can be analyzed by calculating the bifacial gain. Bifacial gain is measured using two modules, one bifacial and another monofacial reference module at the same orientation. Both modules should ideally have the same front-side power rating, but corrections can be made for differences in the ratings. Bifacial gain is then defined as:

$BG_{i}=&space;100\times&space;\left&space;(&space;\frac{P_{bifacial}/Pmp_{bifacial}}{P_{monofacial}/Pmp_{monofacial}}-1&space;\right&space;)$,

where $P_{bifacial}$ and $P_{monofacial}$ are the energy measured from the bifacial and monofacial arrays, respectively.  $Pmp_{bifacial&space;}$ and $Pmp_{monofacial}$ are the STC power ratings from the modules measured on the front side only (with backside of bifacial module covered).

An integrated bifacial gain in energy, $BG_{E}$ (for example, one month) can be calculated as:

$BG_{E}=&space;100\times&space;\left&space;(&space;\frac{\sum&space;P_{bifacial}/Pmp_{bifacial}}{\sum&space;P_{monofacial}/Pmp_{monofacial}}-1&space;\right&space;)$.