Materials & Fabrication

Materials & Fabrication 2020-07-29T16:45:22+00:00

Sandia researcher Greg Nielson, team leader on the Microsystems-Enabled Photovoltaic cell project, holds up a sample of the cells that won a regional Excellence in Technology Transfer Award from the Federal Laboratory Consortium (FLC). (Photo by Randy Montoya)

Today’s energy world requires dynamic, innovative thinking and the flexibility to rapidly accommodate changing market demands. The solar photovoltaics (PV) industry has advanced significantly in recent years, yet the PV world of tomorrow has only been imagined. Sandia National Laboratories contributes to the advancement of PV technology through research in advanced PV technologies, such as III-V thin cells, and advanced small and thin c-Si. The lab also offers extensive experience and expertise in systems integration, micro-fabrication, MEMS and microsystem technologies, semiconductor device technology, and advanced PV systems analysis.

SNL’s advanced research and development (R&D) supports the U.S. Department of Energy’s (DOE’s) goals to reduce PV system costs and facilitate high penetration of PV technologies into the nation’s energy mix.

We are collaboratively working with the U.S. photovoltaic industry, the DOE, the National Renewable Energy Laboratory, other government agencies, and international organizations to increase the world-wide use of photovoltaic power systems by reducing cost, improving reliability, increasing performance, removing barriers, and growing markets.

The Durable Module Materials (DuraMat) National Laboratory Consortium is designed to accelerate the development and deployment of durable, high-performance materials for photovoltaic (PV) modules to lower the cost of electricity generated by solar power, while increasing field lifetime.

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Sandia National Laboratories and Lawrence Berkeley National Laboratory will collaborate to develop an alternative climate classification system based on existing meteorological data sets tailored to PV degradation, rather than trying to re-work the Koppen-Geiger classification. We expect this work to be used to improve our understanding of how climate affects PV degradation, and eventually, to make more precise economic estimates for installed solar plants.

The goals of the collaboration are to:

  • Identify relevant environmental stressors
  • Calculate stressors using meteorological data
  • Analyze geographical stressors in the United States
  • Classify geographical zones

Contact:
C. Birk Jones, Principal Investigator
Phone: (505) 844-9261
Email: cbjones@sandia.gov

Project Partner:
Lawrence Berkeley National Laboratory

Publications:
Jones, C. B., T. Karin, A. Jain, W. B. Hobbs and C. Libby. “Geographic Assessment of Photovoltaic Module Environmental Degradation Stressors.” 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC), Chicago, IL, USA, 2019, pp. 1346-1351, doi: 10.1109/PVSC40753.2019.8980741.

Karin, T., C. B. Jones and A. Jain. “Photovoltaic Degradation Climate Zones.” 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC), Chicago, IL, USA, 2019, pp. 0687-0694, doi: 10.1109/PVSC40753.2019.8980831.

Accelerated stress testing is required to validate expected lifetimes of PV modules. However, accelerated tests that focus on a single stressor often fail to identify degradation modes that are activated by multiple combined environmental factors. This project seeks to define naturally occurring stressors (such as UV radiation) and develop concepts around enhancing or concentrating these stressors in combination with other naturally occurring stressors (such as temperature and humidity) to accelerate degradation and predict lifetime.

Contact:
Bruce King, Principal Investigator
Phone: (505) 284-6571
Email: bhking@sandia.gov

Project Partners:
National Renewable Energy Lab (NREL) – Lead Lab

Currently, multiple new approaches to accelerated stress testing (AST) of PV modules and materials are being proposed and tested, including sequential stress testing and combined stress testing. This project leverages state-of-the-art accelerated testing, materials characterization, simulation and data analytics to drive the establishment of best practices and validation of AST protocols by characterizing changes in backsheets subjected to ASTs and outdoor exposure. This work will demonstrate a set of capabilities to assess new AST protocols, starting with the combined accelerated stress testing (C-AST) from the National Renewable Energy Laboratory (NREL) and the Module Accelerated Stress Testing (M-AST) at DuPont.

Contact:
Ashely Maes
Phone: (505) 844-0771
Email: amaes@sandia.gov

Project Partners:
National Renewable Energy Laboratory
Name: Michael Owen-Bellini, Principal Investigator
Email: Michael.OwenBellini@nrel.gov
SLAC National Accelerator Laboratory
Lawrence Berkeley National Laboratory

Publications:
M. Owen-Bellini, D. C. Miller, L. T. Schelhas, S. L. Moffit, D. R. Jenket, A. M. Maes, J. Y. Hartley, T. Karin, P. Hacke, “Correlation of advanced accelerated stress testing with polyamide-based photovoltaic backsheet field-failures.” (2019 IEEE 46th Photovoltaic Specialists Conference (PVSC), Chicago, IL, USA, 2019, pp. 1995-1999), doi: 10.1109/PVSC40753.2019.8980750.

Analysis of PV performance data to determine degradation requires careful and reliable filtering of the performance data. Filtering should remove data suspected to be erroneous,but also should isolate times when the PV system is operating without external constraints, for example, when portions of the array are shaded or when DC output is limited due to inverter curtailment.

Data filtering is currently a manual, time-intensive task which often does not account for non-time series data such as O&M records. We will significantly enhance data preparation capabilities by providing open-source libraries that can automatically filter time-series irradiance and PV power data, and by creating methods to automatically translate textual O&M records to time series indicators of PV system availability.

Contact:
Clifford Hansen, Principal Investigator
Phone: 505-284-1643
Email: cwhanse@sandia.gov

Project Partner:
NREL

Publications:
python library for PV data analytics: www.github.com/pvlib/pvanalytics

This capability area utilizes computational simulation to examine the effects of mechanical, thermal, and electrical environments on module packaging integrity at various scales, from tabbed cells to minimodules to full modules. Our models enable insights into how difficult-to-measure damage mechanisms are driven by environmental conditions and help to quantify sensitivities to module design parameters.

Project areas include development of material and physics models to enable higher fidelity finite element model predictions, and development of computational failure criteria to enable models to predict where and under what conditions to expect module damage. To validate simulation predictions, computational models of the mini-modules undergoing the Combined Accelerated Stress Testing (C-AST) protocol will be developed and compared against observations from their experimental counterparts when exercising relevant physics.

Contact:
James Y. Hartley, Principal Investigator
Phone: (505) 284-8267
Email: jkyuan@sandia.gov

Project Partner:
National Renewable Energy Laboratory (NREL)

Publications:

Hartley, M. Owen-Bellini, T. Truman, et. Al. “Effects of Photovoltaic Module Materials and Design on Module Deformation Under Load”. IEEE Journal of Photovoltaics, vol. 10, pp. 838-843, May 2020.

Meert, M. Owen-Bellini, P. Hacke., J. Hartley. “Computational Modeling of Photovoltaic Mini-Modules Undergoing Accelerated Stress Testing”. Proceedings of the 47th IEEE Photovoltaics Specialists Conference. Virtual Conference. June 15-August 21, 2020.

Bosco, J. Hartley, M. Springer. “Multi-Scale Modeling of Photovoltaic Module Electrically Conductive Adhesive Interconnects for Reliability Testing”. Proceedings of the 47th IEEE Photovoltaics Specialists Conference. Virtual Conference. June 15-August 21, 2020.

The DuraMAT Field-Aged Module Library has established a collection of modern PV modules – selected for technological interest and commercial relevancy – to study material degradation and to develop and validate non-destructive field forensics methodologies. Modules from seven manufacturers are represented in the library. Five of these were included in the US domestic Top 10 for 2019. Modules were procured from third party sources to avoid concerns of confidentiality. Field modules are installed at fixed latitude tilt with module-scale power optimizers. One module from each manufacturer is permanently removed from field deployment annually for destructive characterization. Characterization prior to deployment and retention of pristine samples of each module minimize uncertainty as to initial state of the modules, a common limitation of contemporary fielded module degradation studies.

Contact:
Bruce King, Principal Investigator
Phone: (505) 284-6571
Email: bhking@sandia.gov

The backsheet is a significant component of a PV module. It provides critical protection from the environment but also represents a significant fraction of the cost of a module. In this project, we are studying a variety of backsheet materials to assess the role of structure, layer materials and coatings on durability. This effort focuses on natural outdoor aging, while other project partners address accelerated aging. In order to link accelerated testing observations to field observations, both mini-modules and bare backsheet materials are being subjected to outdoor exposure. Outdoor exposure is carried out at PSEL and FSEC and is planned to last for 24 months.

Contact:
Bruce King, Principal Investigator
Phone: (505) 284-6571
Email: bhking@sandia.gov

Project Partners:
DSM (Project Lead)
National Renewable Energy Lab (NREL)
SLAC National Accelerator Laboratory
Florida Solar Energy Center (FSEC)

DuraMAT is a 5-year consortium funded by DOE-SETO. The overarching goal of DuraMAT is to discover, develop, de-risk, and enable the rapid commercialization of new materials and designs for photovoltaic (PV) modules with the potential to improve performance and lifetime, while achieving a levelized cost of electricity (LCOE) < $0.03/kWh. As part of the Energy Materials Network, DuraMAT brings together the best of the national lab and university research infrastructure in collaboration with the PV and supply-chain industries to achieve this goal. DuraMAT management, through a leadership team with members from SNL, NREL, and SLAC, solicits and funds proposals, interfaces with our 15 member Industry Advisory Board, and holds workshops and webinars to disseminate results.

Contact:
Margaret Gordon, Deputy Director and Principal Investigator at SNL
Phone: 505-284-9630
Email: megord@sandia.gov

Project Partners:
Teresa Barnes, NREL DuraMAT Director
Members across National Laboratories, Industry and Universities.

Publications:
DuraMAT Annual Report 2019. https://www.nrel.gov/docs/fy20osti/77076.pdf

This project seeks to design and fabricate photovoltaic (PV) modules with built-in instrumentation, to enable direct measurement of the internal stresses and strains created by deployment environments. If successful, the instrumented module concept could be used to validate computational model predictions by providing comparison data at otherwise inaccessible locations or be deployed to the field to record real-time mechanical effects within the module.

Three modules containing strain gauges were built successfully without causing module damage or instrumentation failure, and preliminary results have demonstrated that mechanical environments are detectable by the internal instrumentation. Additional study is needed to better correlate gauge output with module deformations and to reduce sensor noise and drift.

Contact:
James Y. Hartley, Principal Investigator
Phone: (505) 284-8267
Email: jkyuan@sandia.gov

Publications:

Maes, A., J. Hartley, M. Rowell, et. Al. “Instrumented Modules for Mechanical Environment Characterization and Simulation Model Validation.” Proceedings of the 47th IEEE Photovoltaics Specialists Conference, Virtual Conference, June 15-August 21, 2020.

While much effort has been made to identify the presence and length of PV cell cracks in laminated modules using EL and UVF imaging techniques, little is known about the distribution of crack apertures or gaps and how they change with changing temperature, mechanical stress, and age. The major reason for this lack of understanding is that it is very difficult to accurately measure crack apertures in full sized modules with most existing optical methods (e.g., microscopy, optical profilometry, light transflection, etc.). In this proposed work, we will apply a relatively new application of Digital Image Correlation (DIC) to this problem. DIC has recently been shown to be able to measure cell crack apertures in laminated, full-sized modules down to a few microns (Haase et al., 2018). This method characterizes spatial displacements in 3D by analysis of paired, stereoscopic photos of PV modules before, during, and after the stress was applied. The method works best when a random dot pattern is applied to the surface of the cells prior to lamination.

Contact:
Joshua S. Stein PhD, Principal Investigator
Phone: 505-845-0936
Email: jsstein@sandia.gov

Publications:

Haase, F., J. Käsewieter, S. R. Nabavi, R. R. Eelco Jansen and M. Köntges (2018). “Fracture Probability, Crack Patterns, and Crack Widths of Multicrystalline Silicon Solar Cells in PV Modules During Mechanical Loading.” Journal of Photovoltaics 8(6): 1510-1524.

This project will combine a polymer and tunable negative thermal expansion ceramic into a new composite with a reduced coefficient of thermal expansion (CTE) to be used as a photovoltaic panel backsheet. We will tailor the ceramic/polymer composite’s CTE to match that of a solar cell. Matching the CTE of the backsheet and the cell will eliminate daily thermal cycling stresses to the backsheet that cause cracking and delamination, a primary photovoltaic panel failure mode over a 30-year lifetime. Addressing this major degradation mode in photovoltaic panels will increase reliability and lifetime; and further a secure and reliable US energy future.

Contact:
Margaret Gordon, Principal Investigator:
Phone: 505-284-9630
Email: megord@sandia.gov

Project Partner:
Ashley Maes, PhD

Publications:

Weck, P. F., E. Kim, M. E. Gordon, J. A. Greathouse, S. P. Meserole, C. R. Bryan. “Elucidating Structure-Spectral Property Relationships of Negative Thermal Expansion Zr2(WO4)(PO4)2: a First Principles Study with Experimental Validation,” J. Phys. Chem. C., 123 no. 35, (2019): 21607.