With utility-scale solar projects multiplying across the US, the quality assurance of solar panels has become a major subject of owners’ and investors’ focus. The success of multi-million dollar systems hangs in the balance and stakeholders have vested interests in the reliability of the products being installed.

Co-leading an international program, the Department of Energy’s National Renewable Energy Laboratory (NREL) has turned its attention to assessing and assuring the quality of solar panels.

Assessing the Reliability of Solar Panels

NREL’s Research Fellow Sarah Kurtz and Dirk Jordan analyzed data from 50,000 solar PV systems installed between 2009 and 2013. Kurtz and Jordan discovered that inverter failures and fuse failures were reported more often than failure of solar panels. They discovered only 0.1% of all PV systems were reported as being damaged or affected by underperforming solar panels per year, and less than 1% each year had hardware problems.

“But in the face of pressure to keep lowering prices,” said Kurtz, who is also manager of the PV Module Reliability Test and Evaluation Group, “it is essential that quality be maintained and assured.” NREL and its partners around the world are busy focusing on the critical needs of reliability and durability of solar panels, because as Sarah Kurtz notes, “reliability has become an even more central issue.”

The PV Quality Assurance Task Force Is Formed

Led by NREL in the United States, and the National Institute of Advanced Industrial Science and Technology in Japan, the International PV Quality Assurance Task Force (PVQAT) has been formed to develop a comprehensive set of standards for solar panels. Launched in 2011, the first PVQAT meeting addressed:

• Manufacturing consistency.
• Thermal and mechanical fatigue, including vibration.
• Durability to ultraviolet light, humidity, temperature, and voltage.
• Diodes, shading, and reverse bias.

Additionally, focus is being placed on appropriate means of communicating PV quality assurance ratings to the industry, stakeholders, and the public. PVQAT reports that its goals include implementing a quality assurance rating system “that will identify module designs suitable for deployment in different climates, provide a valid basis for manufacturers’ warranties, and provide investors with confidence in their investments.”

The PVQAT reports that it is also creating guidelines for inspecting solar panels during the manufacturing process at the factory, as well as post installation, “to ensure that the solar modules were installed properly, have the proper design, and are operating smoothly.”

The 3 Foundational Supports of PVQAT Standards

The standards that PVQAT are developing are to be implemented through the International Electrotechnical Commission (IEC). Aimed at helping customers easily determine the appropriate usage for specific solar panels, they will also provide quality assurance of the solar panels’ performance consistency. As provided in website statements, the three foundational supports of the PVQAT standards are as follows:

  • Qualification of the design for the conditions. This means that climate matters. If the solar modules are to be used in, say, climates with heavy snow, they may benefit from thicker glass. The rating system being developed seeks to define tests to differentiate among three climate zones—moderate, tropical, and desert—and two mounting configurations: open-rack and close roof.
  • Quality management of the manufacturing process. Rigorous quality management will help assure that solar panels manufactured on one day of the month will be the same quality as those manufactured on any other day of the month.
  • System quality. System-level inspections will confirm that the solar modules were installed properly, have the proper design, and are operating smoothly. Even if the solar panels are perfect, a system won’t function correctly if it’s not properly designed or installed, or if it’s not well-maintained.

NREL Notes Early Adoption of Manufacturing Standards

As the PVQAT notes, “The aim here is to award a certification based on international standards verifying that the system meets minimum safety and performance standards. Lenders and insurers want that kind of certification to know how to set rates or to determine whether they want to invest in the first place.” Owners of PV systems also require certification, ensuring that their system is operating effectively and safely.

The PVQAT’s proposal, “Guidelines for Increased Confidence in Module Design Qualification and Type Approval” was accepted early last year by the IEC. Although the technical specification is not expected to be published until later this year, NREL notes that some manufacturers have already adopted it to improve their solar panels. NREL anticipates that the new rating system will continue to be refined for several years. However, the first certificates for whole systems are expected to be issued through the IEC in 2016.