How a white foil increases the performance of your PV system

The field test was carried out on the PV system on Rhodes, Greece. (Source: Solar Capital)

Solar energy has been on everyone’s lips since this year at the latest: more and more balcony power plants are being thrown onto the market, with which a lot of energy – and therefore money – can be saved.

One of the options for such solar systems is a Bifacial Modul.

These are literally two-sided PV modules that capture solar radiation on both the top and back and convert it into electricity.

As a comparatively young product field, balcony power plants still have a lot of potential for improvement.

An option for this has now been proposed on a large scale by the company Solar Kapital 2,500 square meter area tested in Lagkadas (Greece).

Geotextiles for more performance

For the field test, below the solar system white geotextile appropriate. Such films can be found for home use in well-stocked hardware stores.

The PV modules themselves were connected via two 100-kilowatt inverters each, at a fixed angle of inclination of 25 degrees, and were located 1.5 meters above the ground.

For a year the Albedo Effect measured. This describes the reflectivity of a non-reflective surface; i.e. the ratio between reflected and absorbed radiation.

For this reason, a white foil should also be used – darker surfaces tend to absorb the light instead of reflecting it, which contradicts the basic idea of ​​the bifacial modules.

More performance, shorter payback period – with a catch

According to the report in PV-Magazine, the results were measured between June 2022 and May 2023. The result:

The weighted average power increase of the two inverters is enclosed 6.4 percent.

The measurement results were subject to slight fluctuations, since there were different insolation levels due to the weather. The values ​​were compared with identical inverters measured between May 2021 and April 2022.

According to Solar Capital, the payback period for laying out the geotextile at around two and a half years, which is based on a feed-in tariff of 7.3 cents per kilowatt hour.

However, it should be noted that the period should be understood as a rough estimate – after all, the installation costs can increase depending on the surface. In addition, the geotextile loses its degree of reflection over time as it is constantly exposed to weather and dust.

In parallel, since April 2023 another test projectt performed where the modules used were not specifically configured for bifacial alignment.

Here, too, around 200 square meters of white geotextile were placed under the respective modules. In the two months since then, an increase in performance of 2.5 percent has been observed compared to the device without a foil.

According to Solar Kapital, the amortization period with a feed-in tariff of 33.5 cents per kilowatt hour should be somewhat less than a year lie and thus quickly pay for themselves.

Do you already use a balcony power plant? What is your experience with your models? Will you also test the experiment with the white foil at home? Let us know in the comments!