Case Review: Why a Shenyang Rooftop PV Plant Chose UAV Daytime EL for Its Module Survey

ⓘ This article is currently published in Chinese. An English version is being prepared — read the Chinese original.

A field review of a real C&I rooftop PV project in Shenyang where the owner needed an internal-quality survey of modules laid flat across a large factory roof. This article walks through the reasoning behind the survey design rather than the procedure itself: why module-by-module ground EL was ruled out on a working rooftop, why daytime UAV EL fit the factory's production schedule where night work could not, how flight routes were planned against string-level power injection so every image landed on an energized array, and why the team kept a handheld EL unit on the ground to re-check suspect modules instead of trusting aerial images alone. It also states the limits honestly: which rooftops are poor candidates for UAV EL survey - cluttered roofs with dense obstacles, small arrays where mobilizing a drone crew costs more than it saves, and sites where airspace rules block flight. The takeaway for rooftop owners: the aerial-survey-plus-ground-recheck combination is not about replacing ground EL, it is about spending detailed inspection effort only where the wide-area scan says it is worth spending.