A Spot-Area Method to Evaluate the Incidence Angle Modifier of Photovoltaic Devices—Part 1: Cells

The angle of incidence of solar irradiation on photovoltaic modules varies throughout the day. At larger angles of incidence, the modules are subject to higher reflection losses, resulting in lower light transmission and energy yield. The impact of the relative angular transmittance on the energy yield is often evaluated with a correction factor, commonly referred to as incidence angle modifier (IAM). In this article, a new method to quantify the IAM of photovoltaic devices is presented, which is different from the methods proposed in IEC 61853-2: It encompasses a spot-area irradiation, a customized angle probe holder, and a current-to-voltage converter. This first part focuses on single-cell minimodules and validates the new method on two different cell architectures—an interdigitated back-contact solar cell and a four-busbar solar cell, with an analysis of the measurement bias due to busbars. A second part will follow on the implementation of the same method to commercial-size silicon modules. The study is intended to contribute to the IEC 61853-2 standard. A detailed uncertainty analysis is presented and the method is validated versus IEC 61853-2. Our proposed method shows great potential as it is less expensive and more adaptable than existing standard methods.