Scientists have analyzed how forced convection PV, free convection with finned plate PV, and forced convection with finned plate PV can reduce solar module temperatures under the climate conditions of Lebanon.

An international research team has evaluated three air-based cooling methods for photovoltaic panels.

They investigated, in particular, forced convection PV (forced-PV), free convection with finned plate PV (free-finned-PV), and forced convection with finned plate PV (forced-finned-PV). They conducted parametric analysis for the three techniques based on energy gains, economic savings, and CO2 reductions.

“These systems utilize air as the heat transfer fluid but differ in the mechanism of air flow,” explained the academics. “The forced-PV system employs active airflow through fans to increase convective heat removal. The free-finned PV uses passive air flow as free convection heat transfer while utilizing fins to extend the area of heat transfer between the plate and the atmosphere. Finally, the forced-finned-PV combines both extending the surface area through fins and the active air flow through fans for enhanced heat transfer.”

The parametric study was done on monocrystalline panels with a maximum power of 470 W and 2,182 mm × 1,029 mm dimensions. Two cases were considered – one of a household with 10 panels and another one of a power station with 2,127 PV panels. Both were under the climate conditions of Lebanon. All results were considered with R as a multiplier.

The median efficiency increase for each solution was calculated based on previous literature. The median efficiency increase was 18.31% for forced-finned-PV, 14.4% for free-finned-PV, and 11.48% for forced-PV.

“The parameter R scales the theoretical maximum output power from the photovoltaic system to match energy consumption by application in the real world, hence allowing a more realistic quantification of values and gains due to cooling,” said the team. “Thus, the enhanced energy, CO2 reduction, and savings values represented in the presence of R, gives insights on relative efficiency enhancement gains with respect to the consumption ratio of application.”

The analysis showed that forced-finned PV had the best energy results for both the household and power plant scenarios. “In the case of a domestic house, the system of forced-finned-PV panels showed a total energy production of 6,829.10 × R kWh, the system of free-finned-PV panels showed a total energy production of 6,603.40 × R kWh, while the system of forced-PV panels showed a total energy production of 6,434.85 × R kWh,” noted the scientists.

As for the ground-mounted power plant, the system of forced-finned-PV panels showed a total energy production of 1,452,549.7 × R kWh, the system of free-finned-PV panels showed a total energy production of 1,404,544.8 × R kWh, while the system of forced-PV panels showed a total energy production of 1,368,694.5 × R kWh.

As for the economic analysis in the case of the household, the systems of forced-finned-PV, free-finned-PV, and forced-PV panels had a total annual savings of $2,936.51× R, $2,839.46× R, $2,766.98× R, respectively. In the case of the power station, the savings were $624,596× R, $603,954× R, and $588,538 × R, respectively. The payback period was 1.41 years for the forced-finned-PV, 1.32 years for the free-finned-PV, and 1.18 years for the forced-PV.

“The environmental analysis in the domestic house case showed that the systems of forced-finned-PV, free-finned-PV, and forced-PV panels had a total CO2 reduction of 3,960.87× R kg, 3,829.97× R kg, and 3,732.21× R kg respectively,” concluded the team. “While the environmental analysis in the power plant case showed that the systems of forced-finned-PV, free-finned-PV, and forced-PV panels had a total CO2 reduction of 842,478× R kg, 814,636× R kg, and 793,843× R kg respectively.”

The three techniques were presented in “Cooling photovoltaic panels with air convection – Parametric environmental and economic analysis with case studies,” published in e-Prime – Advances in Electrical Engineering, Electronics and Energy. The study was conducted by researchers from Lebanon’s Lebanese International University LIU, the International University of Beirut BIU, Kuwait’s Gulf University for Science and Technology, and China’s Tianjin University of Commerce.