Researchers in Iran have developed a computational model to predict hailstone trajectories and impact severity on PV modules under different wind conditions and panel tilt angles. The model accounts for wind speed, wind direction, and hailstone aerodynamics to assess potential mechanical damage to solar panels.
“We considered the combined effects of wind speed, wind direction, hailstone aerodynamic behavior, and photovoltaic panel tilt angle,” corresponding author Armin Hasanpour told pv magazine. “The trajectories were calculated by considering gravitational and aerodynamic forces and solving the governing equations using the fourth-order Runge–Kutta method.”
Hasanpour said the team aimed to develop mathematical relationships and numerical tools to predict potential hailstorm damage.
“Such quantitative approaches could eventually contribute to photovoltaic hail-risk databases used by insurance companies, support policymakers in assessing climate-related risks, and help designers determine more appropriate panel tilt angles based on local meteorological conditions,” he said.
The researchers used a 3 MW solar project in Takestan, Iran, as a case study, drawing on regional weather records from 2004 to 2024 to characterize local conditions. They developed a numerical model to simulate spherical hailstones with diameters ranging from 1 cm to 10 cm under wind speeds of 1 m/s to 50 m/s, assuming constant air and ice densities and an initial release height of 2,000 m.
The model incorporated gravitational forces and aerodynamic drag, with the governing equations solved using the fourth-order Runge–Kutta method. The researchers compared simulations using constant drag coefficients with those using Reynolds-number-dependent coefficients.
They projected the calculated impact velocities onto the direction normal to the panel surface to determine the perpendicular component of kinetic energy. The site-specific analysis compared panel tilt angles of 25° and 30° under four wind scenarios: 22.8 m/s from 350°, and 24 m/s from 200°, 350°, and 360°.
The researchers also developed a conceptual damage model using an assumed critical energy threshold of 2 J to classify impacts and illustrate potential cracking and indentation. They validated the simulation results against an angle-adjusted theoretical impact-energy calculation.
“One of the most interesting findings was the significant influence of wind direction on hailstone impact conditions,” Hasanpour said. “Wind speed alone cannot adequately describe the impact behavior; the interaction between wind direction, wind speed, and panel orientation can substantially change the angle and energy distribution of an impact.”
Hasanpour said another important finding concerned the drag coefficient. For relatively large hailstones, particularly those with diameters of 8 cm or more, assuming a constant drag coefficient could result in deviations of up to approximately 14% compared with calculations using a variable drag coefficient.
“This demonstrates why aerodynamic assumptions should be carefully considered when developing predictive models,” he said.
“We also found that changing the photovoltaic panel tilt angle from 25° to 30° alters the impact characteristics and the component of kinetic energy acting perpendicular to the panel surface,” Hasanpour concluded. “This suggests that panel orientation should not be selected based on energy production alone; local hailstorm conditions and potential damage risks should also be considered.”
The researchers presented their findings in “Numerical modeling and analysis of weather conditions effects on hail impact severity and damage to photovoltaic panels,” which was recently published in Sustainable Energy Technologies and Assessments. The research team included scientists from Iran’s Shahrood University of Technology, Radsun Energy Pars, and Asoo Vision Pardaz.
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