Quantification of the spectral coupling of atmosphere and photovoltaic system performance: Indexes, methods and impact on energy harvesting

Abstract

Photovoltaic system performance is affected by changes in the input sunlight spectrum. Moreover, the different photovoltaic materials employed show different spectral responses, having different spectral behaviour as a result. Many authors have developed methods and proposed indexes for quantifying the spectral influences in photovoltaic systems under the time-varying weather variables. These methods use different equipment, different procedures and assumptions, present different levels of complexity and accuracy, and have advantages and disadvantages in each specific context and application. In this paper, for the first time, a systematic review of the available methods and photovoltaic spectral indexes is presented. Each alternative is analysed in detail and a comparative study is done. In addition, as several authors have measured and/or calculated the spectral impact on the energy yield of the different photovoltaic technologies at particular locations and climates, the existing results are summarized and discussed in order to elucidate the spectral behaviour of each technology as a function of the relevant atmospheric parameters, i.e. air mass, aerosol optical depth and precipitable water. The presented study covers non-concentrating and high-concentrating photovoltaic technologies and is intended for clarifying the methods available for the spectral analysis and the spectral impact on energy harvesting of the photovoltaic technologies.