SunShade: Enabling Soware-defined Solar-Powered Systems

Œe electric grid was not designed to support the large-scale penetration of intermiŠent solar generation. As a result, current policies place hard caps on the solar capacity that may connect to the grid. Unfortunately, users are increasingly hiŠing these caps, which is restricting the natural growth of solar power. To address the problem, we propose So‰ware-de€ned Solar-powered (SDS) systems that dynamically regulate the amount of solar power that ƒows into the grid. To enable SDS systems, this paper introduces fundamental mechanisms for programmatically controlling the size of solar ƒows, including mechanisms to both enforce an absolute limit on solar output and a new class of Weighted Power Point Tracking (WPPT) algorithms that enforce a relative limit on solar output as a fraction of its maximum power point (MPP). We implement an SDS prototype, called SunShade, and evaluate tradeo‚s in the accuracy and €delity of these mechanisms to enforce limits on solar ƒows. For example, we quantify the e‚ects of variable conditions, such as clouds, passersby, and other shading, on the €delity of a search-based WPPT algorithm, which must periodically deviate from its cap to discover changes in the MPP that a‚ect the cap’s accuracy.