Experimental and analytical study of light uniformity in the double-incidence powersphere based on ellipsoidal reflection within a cavity

Abstract

The powersphere is an enclosed spherical photovoltaic receiver designed to achieve light uniformity through multiple reflections. However, in practical applications, the high absorption rate of the laser cells causes a significant difference in irradiance between direct and reflected light, preventing optimal light uniformity. This results in power loss and reduces both the conversion efficiency and output power in laser wireless power transmission. To address this, we propose a method that uses dual laser incidence and employs an ellipsoid for light reflection within the powersphere. A mathematical model of the powersphere, based on elliptical reflections inside the cavity, was developed and theoretically validated. Using this model, this study designed a system with symmetrical laser incidence from both ends of the powersphere and elliptical reflection within its cavity. Simulation analysis demonstrated improved light uniformity and intensity on the inner surface. An experimental platform based on dual-beam incidence and ellipsoid reflection was constructed, with results showing improved voltage uniformity from 0.09 to 0.86, current uniformity from 0.25 to 0.96, and a 26% increase in output power. These theoretical, simulation, and experimental findings confirm that dual-beam incidence and ellipsoid reflection effectively enhance both uniformity and output power in the powersphere.