One of the most important parameters to consider for the energy yield assessment (EYA) of PV plants equipped with bi-facial modules is the albedo

“Albedo” is a measure of the amount of light that is reflected from a surface, without being absorbed (expressed as a number between 0 and 1). The closer it is to 1, the more diffused light will be reflected.

There are no international standards to measure albedo, which until now, was not considered an important parameter for the EYA of monofacial PV plants. It is thus advised to use two pyranometers. One, facing the sky, to measure the global horizontal irradiance, and the other facing the ground to measure diffuse, reflected irradiance. The ratio of the values given by the two devices will provide an accurate value of the albedo. This parameter changes depending on the time of year, therefore it is recommended to undertake seasonal assessments.

The modelling of bifacial technology in EYAs is limited in both PVSyst and other yield modelling software. The limitations can be explained by:
insufficient data to validate the models
the complexity of accurately modelling albedo, which can significantly affect the models’ performance
the reliance on data provided by manufacturers to incorporate into models.

Several studies found an increase in energy production of between 5% and 10% for PV plants located in Europe [1, 3].

[1] WSP, Technical Briefing Note – Bifacial PV Technology —January 2019
[3] Solar Power World, Kelly PICKEREL, What are bifacial solar modules?, 02/04/2018

By : David Roisse – Asset Manager

Find out how Greensolver can help you with your solar PV needs on our services page.