Sandia National Laboratories researcher Joshua S. Stein recently co-led activities resulting in two new International Energy Agency (IEA) Photovoltaic Power Systems Programme (PVPS) reports focusing on bifacial modules and systems, and the design of new photovoltaic materials. Stein is a member of the IEA PVPS Task 13, which focuses on photovoltaics performance and reliability, and aims to “provide support to market actors working to improve the operation, the reliability, and the quality of PV components and systems,” according to IEA.
The reports, which were released earlier this spring, act as technical references on the state of the photovoltaics field and address the issues that are important to industry stakeholders, Stein said.
“The bifacial report is the culmination of several years’ work with an outstanding group of researchers from around the world,” Stein said.
“Bifacial Photovoltaic Modules and Systems: Experience and Results from International Research and Pilot Applications,” examines the growing popularity of bifacial photovoltaic cells, modules, and systems. Within the last couple of years, bifacial PV on single axis trackers has become the solar technology with the lowest levelized cost of energy (LCOE) in most parts of the world. New cell designs that have replaced opaque, monolithic back surface foil contacts with isolated contacts, allow light to reach the cell from the rear side, and result in bifacial solar cells with rear side efficiencies from >60% to over 90% of the front side. These cells now come in many varieties (e.g., PERC+, n-PERT, HIT, etc.) and many cell lines have converted to producing bifacial cells.
Newly discovered bifacial-specific degradation issues, such as light and elevated temperature induced degradation (LeTID), and rear side potential induced degradation (PID), are examined, as well as new optimized bifacial systems and models. For instance, a bifacial PV modelling comparison was organized to evaluate the state of the art of bifacial PV performance models. Four hypothetical system designs and two designs based on field measurements were defined and the necessary input parameters and weather files were provided to volunteers from 13 different research and commercial entities, each with their own bifacial PV performance model. These models are described in detail, showing that the current bifacial models result in a range of results, with some models being unable to simulate all of the scenarios. The resulting predicted bifacial gains varied by as much as a factor of two, demonstrating the value of defining standard test cases to verify and validate bifacial performance models.
The last section of this report provides a summary of eleven bifacial field test sites around the world, along with examples of field results. Many of these sites include a variety of bifacial test arrays with different orientations, designs, and site conditions.
Christian Reise, of Fraunhofer ISE, Freiburg, Germany, and Stein were the report’s lead co-authors. In total, 49 international scientists contributed to the publication, including Sandia researchers, Cameron Stark and Dan Riley.
“Designing New Materials for Photovoltaics: Opportunities for Lowering Cost and Increasing Performance through Advanced Material Innovations,” examines the rapidly growing photovoltaic market, including the dramatic decrease in module prices.
“There is concern in the PV industry that falling module prices may result in lower quality and reliability issues,” says Stein. “This report helps stakeholders better understand the opportunities for higher performance and lower cost that new materials can offer, and also reviews current efforts to ensure long module lifetimes.”
The report provides a global survey from IEA PVPS member countries of efforts being made to design new materials for photovoltaic cell and module applications, and is organized by module component, including reviews of material innovations being made in: (1) front-sheets, (2) encapsulants, (3) backsheets, (4) cell metallization, and (5) cell interconnects. Section 1 is an introduction; Section 2 presents the state of the art in PV module materials, including the functional requirements of each component and the common materials typically used to meet these requirements; Section 3 discusses the motivations for applying new material solutions to PV modules; and Section 4 presents the global survey of novel material solutions being developed and tested for the next generation of PV modules.
Gernot Oreski, of the Polymer Competence Center Leoben (PCCL), in Austria, led the report, with Stein as second author. A total of 24 researchers and scientists from around the world contributed to the publication.
Contact Joshua S. Stein and/or visit the PV Performance and Modeling Collaborative (PVPMC) to learn more about the IEA Photovoltaic Power Systems Programme’s (IEA PVPS) TASK 13 reports. Read more about the International Energy Agency (IEA) programs.
Be sure to Save the Date for the 15th Photovoltaic Performance Modeling Collaborative Workshop to be held in Salt Lake City, Utah, Oct. 19-20th, 2021. The two-day workshop, which is co-sponsored by Sandia National Laboratories, CFV Labs and GroundWork Renewables, will examine the technical challenges and opportunities related to PV Systems.