A simple, semi-empirical performance modeling approach for partially transparent tracking-integrated concentrator photovoltaics

Abstract

While concentrator photovoltaics have long promised high power densities compared to standard photovoltaics, in practice, the requirement of sun tracking and the loss of the diffuse component of the solar resource have prevented this from being realized, especially in space-constrained settings such as building integration where it would have most value. Schemes for tracking integration, in which sun-tracking capability is incorporated into the CPV module, rather than being supplied by an external tracker, have thus far failed to change this state of affairs, due to the limited tracking range of practical integrated tracking systems, and the higher diffuse fraction on a fixed-tilt as opposed to a sun-oriented surface. Recently proposed systems promise to finally resolve this situation by combining tracking integration (TI) with partial transparency of the CPV module, which allows the module to simultaneously collect sunlight for illumination without degrading electricity production. This concept, which is currently undergoing commercialization, has substantial application potential in building-integrated and agricultural settings. In order to adequately evaluate the technical and economic potential of these technologies, a straightforward method for estimating their performance is required. Standard photovoltaic modeling tools are of limited value for this emerging and unique class of technologies, although significant development is ongoing. In this manuscript, we present a simple, semi- empirical method for performance modeling of semi-transparent tracking-integrated concentrator photovoltaics based on the outputs of a standard photovoltaic system model and experimental characterizations of actual modules. Optical and electrical and performances are considered in an easily-implemented performance model that avoids resorting to detailed module-level simulations. Based on the model, the economic viability of TI-CPVs is discussed. We have previously used this modeling approach to evaluate module performance in several target applications, which will be summarized, and we furthermore discuss ongoing work to increase the rigor and precision of the modeling approach while retaining simplicity of use.