A general illumination method to predict bifacial photovoltaic system performance

TL;DR

This paper introduces a general bifacial illumination method called the scaled rear irradiance (SRI) method, which accounts for spectral albedo effects and extends standard testing protocols to better predict bifacial photovoltaic system performance.

Contribution

The paper develops the SRI method that enhances existing standards by incorporating spectral albedo effects, enabling more accurate indoor testing and comparison of bifacial PV modules.

Findings

SRI method accounts for spectral albedo effects.

Enables standardized indoor testing of bifacial modules.

Improves accuracy of bifacial PV performance predictions.

Abstract

Bifacial photovoltaic technologies are estimated to supply >16% of global energy demand by 2050 to achieve net-zero greenhouse gas emissions. However, the current IEC bifacial measurement standard (IEC 60904-1-2) does not provide a pathway to account for the critical effects of spectral or broadband albedo on the rear-side irradiance, with in-lab characterization of bifacial devices limited by overestimation of rear incident irradiance, neglecting spectral albedo effects on the rear, or both. As a result, prior reports have limited applicability to the diverse landscapes of bifacial photovoltaic deployments. In this paper, we identify a general bifacial illumination method which accounts for spectral albedo while representing realistic system operating conditions, referred to as the scaled rear irradiance (SRI) method. We describe how the SRI method extends the IEC standard, facilitating indoor testing of cell or module performance under varied albedo with standard solar simulator set-ups. This enables improved comparisons of bifacial technologies, application-specific optimization, and the standardization of bifacial module power ratings.