Solar Lattice

Symptom

Inter-row shading

ID
symptom:inter-row-shading
IRI
https://solarlattice.org/kb/symptom/inter-row-shading
Status
active
Also known as
row-to-row shading, self-shading, row shading

Inter-row shading happens when one row of modules casts a shadow on the row behind it. The shadow changes with the time of day and the season. You can see it during a visual inspection. In monitoring data, it shows up when you compare shaded strings with unshaded strings or with a shading simulation. In IR images, the cells shaded by the row in front can appear overheated. Prolonged shading can lead to hot spots, which can cause follow-up damage such as burn marks or bypass diode failures. On tracker sites, the extra shading can come from rolling terrain, which upsets the backtracking geometry. It can also come from tracker twist, where one section of a row sits at the wrong tilt. Terrain-related losses repeat with sun position and cluster at grade breaks and motor block boundaries. Twist shows up as rows whose shadow lines and measured angles differ from their neighbours under the same command. Start by comparing normalized row or inverter output across morning, noon and afternoon windows, since losses tend to peak at low sun angles. A tracker that follows its commanded angle can still lose energy if the terrain model or motor block layout is too coarse. Check the backtracking settings as well as the hardware.

<!-- review notes

Claims

observed_as

c1 drafted · lead Hot cell in IR image

IR imaging has shown cells overheating where a neighbouring module row shades them.

c2 drafted · lead String current below average

Found by comparing monitoring data from shaded strings against unshaded ones. The shaded strings produce less, and the gap moves with the time of day and the season.

review note: support check: partial - Passages say shading is seen by comparing monitoring data of shaded vs unshaded strings and varies with day/season, but do not mention string current specifically or that shaded strings fall below.

c3 drafted · lead PR drop at low profile angle

Average PR is computed separately for times when the solar profile angle is above the shading angle and times when it is below. The difference between the two, called PRdrop, estimates row shading loss but also contains low-light and inverter part-load effects.

c4 drafted · lead Loss aligned with grade breaks

On rolling terrain, losses tend to cluster at grade breaks, swales and rolling sections that differ from the slope assumed in the model. They are strongest at low sun angles.

review note: support check: partial - Passage describes clustering at grade breaks, swales, rolling sections and strongest at low sun, but attributes it to terrain undulation losses; the link to inter-row shading is implied only by 'locally excessive shading'.

c5 drafted · lead Loss aligned with motor blocks

A single command angle across a large motor block that spans different terrain can cause extra shading of some rows.

c6 drafted · lead Row shadow line offset

In drone orthomosaic or oblique images, the row-end shadow lines of a twisted tracker row differ from those of neighbouring rows.

review note: support check: partial - Drone imagery to compare row-end shadow lines against neighbours is stated for a twisted row, but the passage doesn't explicitly say they differ or tie it to inter-row shading.

c7 drafted · lead Low normalized row current

Rows affected by tracker twist can show lower normalized current than the rows next to them, mainly at low sun angles and during backtracking transitions.

review note: support check: partial - Passage says affected twisted rows show lower normalized current than adjacent rows, mainly at low sun angles/backtracking; it ties this to twist and doesn't mention inter-row shading explicitly.

typical_power_loss

c8 drafted · lead 1–5 PERCENT

Conditions: Typical cumulative annual shading loss of PV systems, all shading causes including row-to-row self-shading

review note: possible conflict with c9 (same source; check the conditions)

c9 drafted · lead 20–30 PERCENT

Conditions: Energy loss from shading that can be observed on rooftop or facade systems, reported as 'up to 20-30%'

review note: support check: partial - The 20-30% is stated as 'up to' for rooftop/facade systems, not a typical value, and not specific to inter-row shading.; possible conflict with c8 (same source; check the conditions)

Referenced by

Data