International Energy Agency
Photovoltaic Power Systems Programme

In the last decade and longer, photovoltaic module manufacturers have experienced a rapidly growing market along with a dramatic decrease in module prices. Such cost pressures have resulted in a drive to develop and implement new module designs, which either increase performance and/or lifetime of the modules or decrease the cost to produce them. Many of these innovations include the use of new and novel materials in place of more conventional materials or designs. As a result, modules are being produced and sold without a long-term understanding about the performance and reliability of these new materials. This presents a technology risk for the industry. This report provides a global survey from IEA PVPS member countries of efforts being made to design new materials for photovoltaic cell and module applications. 

Bifacial photovoltaic cells, modules, and systems are rapidly overtaking the market share of monofacial PV technologies. This is happening due to new cell designs that have replaced opaque, monolithic back surface foil contacts with isolated contacts, which allow light to reach the cell from the rear side. Minor adjustments to cell processing steps have resulted in bifacial solar cells with rear side efficiencies from >60% to over 90% of the front side efficiency. Bifacial cells now come in many varieties (e.g., PERC+, n-PERT, HIT, etc.) and many cell lines have converted to producing bifacial cells.

This IEA PVPS Task 13, Subtask 2.5 reports on a benchmarking study of the various approaches for calculating the Performance Loss Rate (PLR) of commercial and research photovoltaic (PV) power plants in diverse climatic zones. PLRs are calculated with data from the PV systems’ power and weather data. The PLR is used by power plant owners, operators, and investors to determine the expected power output of a PV system over its installed life. Therefore, discrepancies in various calculation methods can greatly impact the financial around a PV installation. This benchmarking study is necessary due to the inconsistency in reported PLR results based on the many different approaches currently used to calculate PLR of PV systems. This study is focused on identifying which of the various approaches produce similar results and what causes inconsistencies between these different methods.

The goal of this document is to provide a compendium of new performance characterization methods for new photovoltaic (PV) system designs as a reference. New methods are described and explained by laboratory tests up to case studies. While performance characterization is more than evaluating efficiency of a component or a system in certain operating points, the results account for multidimensional usage and benefits. These assessments are intended to provide well-founded and comparable key figures in order to enable new PV system designs to move faster into new fields of application. This report gives a short introduction into current standards and definitions regarding performance characterization of PV systems as a starting point. New PV system components and complex new systems with PV are then described with their respective performance characterization methods. Where currently no performance characterization methods for complex PV systems particularly with multiple functions exist, their design and their performance, energetically and regarding multi-dimensional usage benefits, are presented and described by means of showcases. PV systems are not only PV modules and PV inverters in an optimally oriented system which produce as much electrical energy as possible. Current PV systems may provide a dual or even a triple use. However, as varied as the use of each system and each PV installation is, as different is the approach of performance evaluation.