Reading the Sun from the Ground: A Mixed-Methods Voltage-Signature Framework for Season-Aware Micro-Siting of Small-Scale Solar Photovoltaics in District Jamshoro, Sindh, Pakistan

Abstract

Pakistan's distributed solar market has grown faster than its resource data. Rooftop and off-grid systems are now sized and placed mostly on satellite-derived estimates that rarely capture the micro-environment of a particular roof or field. This study proposes a new way to read ground evidence from inexpensive hardware. Using the archived field record of a portable, self-tracking polycrystalline photovoltaic logger deployed at four sites in District Jamshoro, Sindh (Looni Kot, Kotri, the University of Sindh campus and Aliabad) during winter and summer, we treat the logged panel voltage not as a stand-in for irradiance but as a site-specific "voltage signature". A convergent mixed-methods design was adopted. The quantitative strand recovered one-minute series from archived charts and computed level, stability, responsiveness, plateau occupancy, morning readiness and change-point structure. These were tested with Kruskal–Wallis, Dunn–Holm, Cliff's delta and block-bootstrap procedures and combined into a Ground-truth Micro-Siting Index (GMSI), stress-tested against 20,000 random weightings. The qualitative strand applied the framework method to 29 documentary evidence units across six themes. Sites differed strongly in both seasons (winter H = 66.3, ε² = 0.62; summer H = 29.1, ε² = 0.27). Crucially, the ranking reversed with season. Arid, open sites led in winter (GMSI ≈ 0.99) but fell to the bottom in summer, whereas the riverine-industrial Kotri site rose from third to first (GMSI = 1.00). These ranks held in 85–100% of weightings. Qualitative coding explained the reversal through three micro-environmental regimes, linking thermal–moisture buffering to the summer advantage and obstruction to the winter penalty at the campus. The study contributes a framework, an index and an open protocol for season-aware micro-siting, and argues that low-cost ground signatures should complement, not replace, calibrated reference stations.