Spatially uneven loss means some zones, rows or strings of a plant lose more energy than others under the same irradiance. With granular dust soiling the loss is usually spread over a zone, but roads, exposed soil, farming, construction, prevailing wind and row edges can make some areas much dirtier than others. Uneven dust gives strings or substrings different effective irradiance, so look for mismatch in string currents and check whether the loss slowly builds in dry weather and then recovers after rain or washing. With terrain undulation yield losses the loss repeats with sun position, is worst at low sun angles, and clusters at motor block boundaries, grade breaks, swales and rolling ground. A tracker that follows its commanded angle can still lose energy on undulating ground, because the command itself may come from a terrain model or block layout that is too coarse. First map the underperformance against block IDs, row locations and time of day, and compare it with topographic survey data and as-builts. Then separate out curtailment, clipping, outages and inverter limits, and use drone imagery, row-end angle surveys, tracker command logs and normalized string or inverter output to see whether the loss follows terrain or points to equipment failure. Do not measure dust soiling from one dirty irradiance sensor alone, because drift, poor cleaning or a local obstruction can look like soiling.
<!-- review notes
observed_asc1 drafted · lead Loss aligned with grade breaks
Terrain undulation losses can cluster at grade breaks, swales and rolling sections that differ from the modeled representative slope; strongest at low sun angles.
sec=h4 h=7ebb164fa9e1sec=h6 h=c071b96206e3c2 drafted · lead Loss aligned with motor blocks
Recoverable energy losses concentrated in specific tracker motor blocks or clustered at motor block boundaries.
sec=front h=52c6d93eccc6sec=h4 h=7ebb164fa9e1sec=h2 h=0eaaad46eb44sec=h6 h=c071b96206e3c3 drafted · lead Spread in normalized inverter yield
Uneven power reduction across a large plant; compare normalized row or inverter production across zones and across morning and afternoon windows.
sec=front h=52c6d93eccc6sec=h2 h=0eaaad46eb44tbl=4 h=29ce7be13dc7review note: support check: partial - Passages say to compare normalized row/inverter production across zones and morning/afternoon and cite a figure of uneven power reduction, but do not state irradiance is uniform or POA normalization.
c4 drafted · lead String current below average
Nonuniform dust deposition gives strings or substrings different effective irradiance, causing mismatch.
sec=h5 h=43575746a7d7review note: support check: partial - Nonuniform deposition causing mismatch between strings/substrings is stated, but not that some string currents are lower on the same inverter where dust is heavier (though module current falls with deposition).
presents_as c12presents_as c6