California-based independent engineering and certification test laboratory for renewable energy products Renewable Energy Test Center (RETC) spent 2018 testing more than 2,500 solar modules from 46 crystalline silicon and thin-film suppliers and has released its first PV Module Index with the results. The modules were tested for reliability, performance and quality across 18 different indicators. Through this data collection, RETC determined only two manufacturers demonstrated high achievement across the indicators in all three core categories: LONGi Solar and Panasonic.

LONGi Solar excelled in every individual test described below while Panasonic hit multiple high points in each category. Other module suppliers excelled in specific areas but not across the board. For example, JinkoSolar is a high-performer in the reliability category and JA Solar showed success in the performance category, but neither had excellence consistently across all categories.

More than 150 different module families were tested from the 46 suppliers. While RETC evaluated modules on 18 different criteria, the report focuses on eight important criteria (described below) that best represent the three categories of reliability, performance and quality.

“RETC is releasing this index to help the entire solar industry better evaluate modules based on important attributes beyond efficiency and cost,” said Cherif Kedir, RETC president and CEO. “It’s worth noting that high-achieving quality module manufacturers put their products through an exhaustive set of accelerated reliability tests, while other manufacturers choose to select only a few of the tests to characterize their products. We congratulate the high achievers in each of the categories, and look forward to working with all manufacturers to continue to demonstrate their product excellence.”

For reliability, the PV Module Index reviews the results of module tests such as damp heat, dynamic mechanical load and potential induced degradation (PID). High-achieving modules withstood abuse from these tests and saw minimal degradation in power output, versus their peers.

High-achieving module brands in damp heat tests: JinkoSolar, LONGi Solar

High-achieving module brands in dynamic mechanical load tests: Canadian Solar, CertainTeed, Hanwha Q CELLS, JinkoSolar, LONGi Solar, Mission Solar, Panasonic, Trina Solar

High-achieving module brands in PID tests: JinkoSolar, LONGi Solar, Merlin Solar, Panasonic, Solar Frontier

Performance tests measure a module’s efficiency in power generation and see how they do in actual real-world conditions, such as high temperatures, and early morning and afternoon sun conditions. Tests conducted include I-V characterization of module efficiencies, conditions at elevated temperatures such as PVUSA Test Conditions (PTC) and pan file testing, which evaluates modules in various light and temperature conditions. Seven high achievers demonstrated greater than 19% module efficiency. Four high achievers received performance ratios above 85% by demonstrating simulated performance, via PVsyst software, which was 85% of their nameplate rating.

High-achieving module brands in efficiency tests: Hanwha Q CELLS, JA Solar, LONGi Solar, Panasonic, Solaria, Sunpreme, Yingli

High-achieving module brands in elevated PTC testing conditions: Bangkok Solar, Eterbright Solar, LONGi Solar, SolarTech Universal, Sunpreme

High-achieving module brands in pan file tests: JA Solar, JinkoSolar, LG, LONGi Solar

High-achieving module brands in light-induced degradation (LID) tests: JA Solar, LONGi Solar, Mission Solar, Panasonic, Solar Frontier

RETC measured a manufacturer’s commitment to quality through its adherence to high-quality standards in its R&D process, engineering changes, manufacturing and vendor management. Quality products should be well manufactured with repeatable processes, materials, production equipment, and labor techniques. To demonstrate quality, the PV Module Index provides an exhaustive characterization of a module family across a multitude of tests to develop its “Product Qualification Program/Thresher Performance Matrix.” Degradation of less than 2% for a given test demonstrates high achievement and four manufacturers reached this level of performance.

High-achieving module brands in RETC’s product qualification program/Thresher performance matrix: JinkoSolar, LONGi Solar, Panasonic, Solar Frontier

The entire report can be found on RETC’s website. The paper also shares data on new technologies, such as bifacial and PERC, and the differences between laboratory testing and real-world field performance and reliability testing.

“As the industry has matured, solar professionals may want to focus on the cost per watt, but modules with the lowest price are not always top values in performance, quality or reliability,” said Chris Beitel, Head of Business Development at RETC. “By focusing on all three categories, module manufacturers can have confidence their products are well-equipped to perform across the board, while downstream players can feel assured the products they are selecting are engineered to deliver as expected.”

Additional tests discussed in the report include humidity freeze, thermal cycling and ultraviolet exposure. In performance, other tests include incidence angle modifiers and light and elevated temperature degradation. Finally, in the area of quality, additional tests in the report cover engineering changes, bill of material changes, randomized sampling, factory audits and factory inspections.

The tests were completed at sites in Fremont, California; Pahrump, Nevada; Los Andes, Chile; and in Cagayan de Oro City, in the Philippines.