How albedo interacts with rooftop PV system patterns

Researchers have simulated 160 cases of PV rooftop installation in southern and northern Italy. Among changing parameters were size and type of the panels, as well as their roof cover rate. The considered albedos were 20%, 40%, 60%, and 80%, representing different types of roof materials.

July 1, 2025 Lior Kahana

Image: University of Calabria, Energy Reports, CC BY 4.0

A research group led by Italy’s University of Calabria has investigated the impact of albedo on rooftop PV power generation and has found that output radiation reflection from the solar panel surfaces to the rear of adjacent modules plays an important role in increasing solar electricity yield.

“The current study explores the performance of monofacial and bifacial solar panels on various roof typologies with variable installation patterns and albedos. In this regard, the comparison will aid in comprehending how roof albedo affects yearly energy production, the most suitable way to set up solar panels on the roof, and the distinction between monofacial and bifacial solar panels,” the scientists said. “The evaluation is specifically based on a set of 160 simulations.”

Using two case studies from Italy – one from the south and the other from the north of the country – the team focused its work on the different albedo impacts in various installation patterns.

All simulations were conducted on a 10 m x 10 m roof, with a total area of 100 m². Milan was chosen as the location of the north Italy simulations, with an annual average temperature of 13.5 C annual global irradiation of 1,317 kWh/m2 and a tilt of 39°, while Cosenza was taken as the south case study, with an annual average temperature of 17.7 C, annual global irradiation of 1,635 kWh/m2 and a tilt of 33°.

The experiments included two PV system sizes – 1 m x 1.5 m or 1 m x 2 m – covering either 10%, 20%, 30%, 40% or 50% of the roof. Two types of PV panels were considered: either a bifacial monocrystalline panel with 20% efficiency or a monofacial monocrystalline panel with 20% efficiency. The considered albedos were 20%, 40%, 60%, and 80%, representing different types of roof materials.

“On the limited area of a roof, by increasing the number of PV modules, the annual energy production can increase until a certain value, and then it might decrease due to the higher shadow frequency of solar panels on the surface of other solar panels,” the scientists stressed. “In this study, in south and north Italy, it happened after increasing the number of modules from 40–50% of the roof area coverage.”

According to the group, the enhanced bifacial output at this rate appears to be triggered by radiation reflection from the solar panel surfaces to the rear of adjacent modules, rather than the roof’s albedo. Also, the choice between monofacial and bifacial solar panels was found to depend on the coverage percentage of the solar panels on the roof.

“It can be concluded that with low coverage percentages of PV panels on the roof surface, installation of bifacial panels does not appear to be advantageous from the perspective of energy production,” the group said. “However, in a higher coverage percentage of around 50%, and due to the simultaneous impacts of roof albedo and reflection from solar panels, it is more beneficial to use bifacial solar panels, as in the case of Italy, the energy production has been increased up to 18%.”

The research work was presented in “Revealing the impact of albedo on solar panel power generation potential in various installation patterns: Case study of Italy,” published in Energy Reports. Scientists from Greece’s Aristotle University of Thessaloniki also participated in the study.

From pv magazine Global

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