A research team led by scientists from China’s Northeast Electric Power University has investigated the impact of frame perforation on reducing the temperature of PV panels using passive air cooling.

“Compared with previous studies, the main novelty of this study is the comprehensive effect evaluation of frame perforation on passive air cooling performance, thermal management, and electric performance of PV panels,” the group explained. “Detailed analysis of airflow field around PV panels and temperature field of PV panels is conducted, and effects of different frame perforation patterns and different hole shapes on the thermal and electric performances of PV panels are compared and discussed. The main objective of this paper is to provide a reference for passive air cooling technology research of solar PV panels.”

The research team investigated 17 different frame perforation designs using three-dimensional computational fluid dynamics (CFD) simulations.

The simulations were based on a monocrystalline silicon photovoltaic (PV) panel measuring 52.8 cm × 32 cm × 1.05 cm. The panel consisted of an aluminum alloy frame (2.5 mm thick), a glass layer (3.2 mm), an ethylene-vinyl acetate (EVA) layer (0.5 mm), a PV cell (0.6 mm), and a backboard (0.7 mm).

The computational domain was a cube measuring 0.8 m on each side, with an installation height of 0.4 m. The inlet wind speed was set at 6.0 m/s. The windward and leeward sides of the panel measured 52.8 cm, while the left and right sides were 32 cm. The incident solar irradiance was 900 W/m².

To validate their model, the researchers built an experimental setup using a smaller monocrystalline silicon PV panel with dimensions of 35 cm × 23.5 cm × 1.5 cm. The panel had a rated power of 10 W and was installed at a tilt angle of 50°. Experiments were conducted in Jilin City, central China, and the results were compared with a separate simulation model. Analysis showed an average temperature difference between simulated and measured values of just 0.2267 °C, with a maximum single-point deviation of 0.4 °C.

Once the CFD model was validated, the team optimized the tilt angle for passive cooling, identifying 11° as the most effective. All subsequent simulations of the perforation cases were conducted at this tilt. The 17 perforation designs were grouped into four categories based on the number of perforated frame sides: single-side, dual-side, tri-side, and four-side perforations.

Each case featured either circular or rectangular perforations. For panels with windward and leeward perforations, circular holes had a radius of 3 mm and were spaced 58.68 mm apart; on the left and right sides, the holes were also 3 mm in radius but spaced 64 mm apart. Rectangular perforations measured 4 mm × 100 mm with 107 mm spacing, and 5 mm × 70 mm with 60 mm spacing, depending on the side.

“Case 2 — with eight circular holes of 3.0 mm radius on the windward side — achieved the lowest average PV panel temperature (39.37 °C), the lowest maximum temperature (42.63 °C), the most uniform surface temperature distribution, the highest output power (24.18 W), and the greatest photoelectric conversion efficiency (15.9%),” the researchers reported.

“From the perspective of average PV panel temperature, 13 of the evaluated frame perforation designs outperformed the non-perforated frame (Case 1),” they added. Compared with the non-perforated panel, the Case 2 design reduced the panel’s temperature by 5.44 °C. Under no-wind conditions, the perforated frame decreased the average temperature by 37.8 °C and increased photoelectric conversion efficiency by 2.89%.

Only three perforation designs — Cases 3, 7, and 8 — underperformed relative to the non-perforated panel. Case 3 featured circular holes on the leeward side, Case 7 had rectangular holes on the leeward side, and Case 8 had rectangular holes on the left side. “Contrary to common assumptions, drilling more holes into the frame does not necessarily improve PV panel cooling performance,” the team concluded.

Their work was presented in “Effect evaluation of frame perforation on reducing photovoltaic panel temperature with passive air cooling,” published in Case Studies in Thermal Engineering. Researchers from China’s Northeast Electric Power University, Shengu Group, and University of Science and Technology of China took part in the study.