Most solar project developers and equipment buyers require two key certifications for solar PV modules – IEC 61215 and IEC 61730 or UL 1703. They demonstrate that PV modules are safe. None of these test standards address long-term PV module reliability and performance in the field.
• IEC 61730 and UL 1703 only certify that PV modules are not hazardous to operate.
• IEC 61215 only screens for defects that would appear in the first few years of operation.
• Manufacturers select the specific modules that are used in certification tests. It is possible to send “golden samples” that are constructed more carefully than commercially produced modules.
• Manufacturers can change some component combinations of their module BOM without recertifying the module model.
Additionally, updating IEC and UL standards is a multi-year process that cannot keep pace with the rate of innovation in solar PV module technology. Both standards fail to identify major field performance issues associated with technical advances, such as Light and elevated Temperature Induced Degradation (LeTID) and Potential-induced Degradation (PID). An LeTID test will be included in the next version of the PVEL PQP, which will be released in summer 2019.
Testing for Reliability and Performance While IEC and UL certifications are important indicators of module safety, long-term reliability and performance are also important to PV buyers. Since its founding in 2010, PVEL has consulted with developers and financial institutions to continually develop test programs that address specific issues observed in the field and with emerging and even proven technologies. By extending IEC 61215 sequences and incorporating additional tests, PVEL’s PQP approximates the impact that decades of exposure in the field has on PV modules.
What are the limitations of PV module warranties?
Nameplate and Solvency
Some module power degradation is expected, so a degradation factor is usually built into solar assets’ energy yield and financial models as well as manufacturers’ warranty terms. Warranties typically guarantee approximately 97% of the nameplate rating during the first year followed by an annual 0.6 to 0.7% reduction in the subsequent 24 years. However, warranties only protect buyers when manufacturers are solvent and responsive to claims.
Measuring power degradation that could be a warranty claim is extremely difficult – if not impossible – in the field. Measurement tools and sensors simply lack sufficient precision. A 3% allowance for uncertainty is usually applied for warranty enforcement, which effectively reduces guaranteed power output by 3%. Most successful warranty claims are therefore limited to excessive underperformance or total failure.
Even when claims are accepted, most warranties only cover the cost of replacement modules, not costs associated with labor or lost energy production. Advances in the manufacturing process can also jeopardize future module replacement. For example, the product roadmaps of many major manufacturers today call for increasing wafer size and thus module size. This will result in modules that are not compatible with the modules they sell today. Asset owners may be unable to replace defective modules in operating systems, which makes procuring reliable PV modules even more important.
Certifications and warranties cannot fully protect PV module buyers from field failures and subsequent financial consequences.
PV module PQP methodology
PVEL launched the PV Module Product Qualification Program (PQP) in 2012 with two goals:
1. To provide PV equipment buyers and power plant investors with independent, consistent reliability and performance data that supports effective supplier management.
2. To independently recognize manufacturers who outpace their competitors in product quality and durability.
Today the PVEL PQP is a common requirement for PV modules installed in systems around the world.
Wet leakage test
PQP test development
Throughout the year and on a global scale, PVEL investigates field failures and monitors developments in the PV standards community. We work with research institutes, conduct experiments, and receive feedback from the upstream module manufacturers and downstream module purchasers (i.e. EPCs, developers, investors and insurance companies). These inputs guide annual updates to the PQP and ensure that PVEL’s reports deliver the data that equipment buyers need.
The Key principles of the PVEL PQP
The PQP replaces performance assumptions with empirical metrics that help PVEL’s Downstream Partners optimize revenue and energy yield models. Each PVEL PQP provides nine detailed test reports that PVEL’s partners freely access to support their purchasing decisions.
No hand-picked samples
All Bills of Materials (BOMs) of products submitted to PQP testing are witnessed in production - from opening of raw materials packages through every step of the production process - to wrapping the completed pallet in tamper-proof tape.
All BOMs are tested in the same way, using consistently calibrated equipment and in consistent laboratory environments. This enables a leveled comparison across all manufacturers.
The rapid pace of technology development requires a test program that stays current in order to properly assess and qualify new products. PVEL updates the PQP annually to provide buyers with consistently relevant data to evaluate PV products.
The PQP results presented in the 2019 Scorecard were factory witnessed within 18 months of 2019. Results presented in the bar charts on the subsequent pages show average values for the different test samples and BOMs which together represent a single module model. Each test sequence had a varying number of manufacturers and model types participating. The Top Performers in each test category are listed in alphabetical order. Top Performers are model types that degraded less than 2% for the entirety of the test sequence. Reading the Results Each test sequence is detailed over two pages and includes:
• An overview of the stress testing and real-world context of the specific failure mechanism
• An example of high levels of degradation, including electroluminescence (EL) images and electrical parameters
• The 2019 results graphically presented showing the average power loss by model type
• An alphabetical list of Top Performers
• A results summary for that specific test
PVEL cautions that not all products/model types are represented in every test. For example, some model types are not subjected to all tests, or some results may not have been available at the time of publication. Buyers should contact PVEL to obtain the full reports that comprise these results. The full reports contain BOM-level results whereas the results herein are reported at the model level.
New for this Scorecard edition is the inclusion of PVEL’s historical data from nearly ten years of testing. The bar charts that follow indicate how the 2019 Scorecard results compare to PVEL’s historical dataset.
The presented data indicates a general trend of improved performance in thermal cycling and potential-induced degradation; however, a wider range of performance can be observed for damp heat and the dynamic mechanical load sequence.
PQP participants tend to place a higher value on the quality of their products than non-participants. As such, the median results may be better than those of the broader industry, especially for modules one might source on the open market. See Procurement Best Practices on page 30 for PVEL’s module purchasing recommendations.
Consistent top performance in the PV Module Reliability Scorecard demonstrates a manufacturer’s commitment to product quality. As new products are introduced and older models are retired, manufacturers must adhere to strict quality control standards to maintain high levels of reliability and performance of their products. The Historical Scorecard below shows the 2019 Top Performers and their history of top performance in previous editions. Manufacturers are listed by the number of years they have been designated a Top Performer, in alphabetical order.
This article is excerpted from the PV Module Reliability Scorecard, published by PV Evolution Labs, June 2019.
Written by Tara Doyle, Chief Commercial Officer, Ryan Desharnais, Chief Technology Officer, and Tristan Erion-Lorico, Head of PV Module Business, PV Evolution Labs