Linking lacunarity to inertial particle clustering: Applications in solar photovoltaics

Abstract

The presence of wind-flung debris is inevitable in solar photovoltaic (PV) systems, negatively altering production and lifespan by way of adhesion (i.e. soiling) and forceful particle impacts. The propensity and magnitude of particle-to-panel interactions is largely dependent on environmental and panel-invoked turbulence, ultimately dictating local debris concentration and trajectories. This study confronts the mechanisms leading to PV panel soiling by developing a lacunarity-based framework for particle heterogeneity quantifying preferential concentration within asymmetric panel wakes due to inertial coupling. Drawing from established studies in multi-phase homogeneous isotropic turbulence (HIT), presented analysis demonstrates lacunarity as a comparable measure to Voronoï distributions for understanding particle clustering. Considering benchmark data obtained in experimental particle-laden HIT flow, global particle heterogeneity is shown to correlate with $R{e}_{\lambda }$ and ${\varphi }_v$ dependencies observed through Voronoï tessellations. Further expanding to consider PV panel wakes, Voronoï analysis and lacunarity uncover location-dependent variations in local particle clustering relating to asymmetric turbulent wake features. In total, this work represents a novel perspective of characterizing particle-laden turbulent flow by way of lacunarity-based heterogeneity and motivates preferential concentration as a complex feature impacting particle trajectories in PV systems.