Uncertainties in irradiance measurements of sensors to POArear of bifacial solar panels

In recent decades, photovoltaic (PV) panels have emerged as one of the leading renewable energy technologies. A new development is the advent of bifacial modules which enhance the energy production by conversion of rear side irradiance. To accurately know the performance ratio of PV parks with bifacial modules, it is necessary to also measure the backside irradiance. It is still not well known what factors influence the backside irradiance measurement uncertainty and to what extent. In this work, the back of array (POA(rear)) irradiance was measured with sensors and panels at different tilt angles and albedos, providing representative conditions for various locations. Kipp & Zonen pyranometers, working class reference cells and an experimental pyranometer were used to collect irradiance data. By means of measurements and calculations, the uncertainty of different measurement technologies and their installation position with respect to panel height are quantified.