Ground-mounted PV reduces overall soil loss but intensifies erosion beneath panel edges

A research group in China has investigated how PV installations reshape soil erosion patterns and hydrodynamic processes on hillslopes. Using simulated rainfall experiments, the researchers examined the effects of PV panel installation height, tilt angle, and array configuration on runoff and erosion dynamics.

“PV panels disrupt the natural rainfall-surface interaction through two concurrent mechanisms,” the researchers said. “They intercept rainfall over a substantial portion of the slope, reducing splash detachment and surface sealing, while simultaneously concentrating intercepted water along panel lower edges as high-energy drip flow. This redistribution creates a distinctive spatial pattern in which covered zones receive no direct rainfall while drip lines receive concentrated flow with substantially enhanced erosive energy.”

The researchers conducted rainfall simulation experiments using a 2.0 m × 1.0 m × 0.4 m adjustable soil flume. They filled the flume with clay-loam agricultural soil collected from the southern Loess Plateau in China and set it at a fixed 10-degree slope. Four custom-made PV modules, each measuring 57 cm × 48 cm, were installed above the soil in either a linear (1 × 4) or block (2 × 2) configuration.

The team tested combinations of three installation heights – 0.4 m, 0.6 m, and 0.8 m – and three tilt angles – 30 degrees, 35 degrees, and 40 degrees. The researchers subjected each configuration to simulated rainfall at an intensity of 80 mm/h for 60 minutes. They also tested equivalent bare-slope controls and repeated each scenario twice.

During each trial, the researchers collected runoff and sediment samples and measured flow velocity and depth across covered and uncovered sections of the slope. After each experiment, they recorded the initiation time, length, width, and depth of erosion channels that formed beneath the panel drip lines. They also conducted eight mitigation trials using either 20-cm-wide turf mats or gravel strips.

“Slope-scale sediment export fell by up to 56.6%, with the strongest mean reduction at 0.4 m installation height (46.3%) and 35° tilt (36.3%),” the researchers said.

Transverse rills, or small erosion channels running across the slope, developed beneath the drip lines in every PV configuration, while none formed on the bare slopes.

“Erosive energy accumulated longitudinally, with flow velocity rising by 148% from the uppermost to the lowermost covered zone under laminar (Re <500) and subcritical (Fr <1.0) conditions, so the downslope-most panel row constitutes the critical location for foundation scour,” the researchers said. “Rill location and spacing (48–57 cm) were dictated by panel layout, with rill width and depth increasing with installation height to 3.44 cm and 1.84 cm at 0.8 m, evidencing an externally imposed erosion geometry absent on natural slopes.”

The researchers said the findings show that PV arrays can reduce overall sediment loss while concentrating erosion at specific locations beneath panel drip lines, particularly around the lowest panel rows.

The results were presented in “Photovoltaic panel arrays reshape soil erosion patterns and hydrodynamic processes on hillslopes,” published in the Journal of Hydrology. Researchers from China’s Northwest A&F University collaborated on the study with scientists from the Chinese Academy of Sciences (CAS).