A 66-year assessment of photovoltaic solar resource trends across Yemen

Abstract

Yemen’s rapidly warming climate poses critical challenges to solar energy efficiency despite abundant irradiance. We observe pronounced warming across all thermal indices, with mean surface air temperatures rising by +0.25 °C per decade (p < 0.001), accompanied by increases in maximum (+0.21 °C/decade) and minimum (+0.28 °C/decade) temperatures for the period 1958 to 2024. Photovoltaic (PV) cell operating temperatures mirror this trend, climbing by +0.26 °C/decade. We further found cumulative efficiency losses of 0.4 - 0.5 % per °C for crystalline silicon PV modules, compounding Yemen’s energy vulnerabilities. Counterintuitively, downwelling surface solar radiation (SRAD) remains stable with a near-zero trend (slope ≈ -0.00 W/m² yr^-1), while declining wind speeds of -0.002 ms yr^-1 reduce natural cooling of PV modules. Our spatiotemporal analysis reveals stark regional contrasts whereby coastal zones exhibit stable or increasing PV resource potential (PVres; +0.10 W/m²/year), while inland deserts like the Rub’ al Khali margins show declines of up to -0.10 W/m²/year, likely driven by intensifying dust aerosols and land degradation. Nationally, PVres shows no significant long-term trend (-0.043 W/m²/year, p = 0.070), obscuring these critical regional vulnerabilities. Seasonal extremes ranging from April peaks of 264 W/m² to December troughs of 201 W/m² highlight the necessity for adaptive energy storage systems. We identify a critical paradox wherein nationally stable solar resources mask spatially divergent risks requiring high-resolution energy planning. Coastal regions emerge as optimal for PV deployment, whereas inland areas necessitate dust-resilient technologies and hybrid systems. We recommend that policymakers and development partners implement region-specific strategies combining coastal PV expansion with inland adaptive measures to mitigate efficiency losses.