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Articles - PVDI

PV Module Reliability Scorecard

What is the risk of defective panels?

The cost of installing solar panels are still high. Replacing defective panels can be a pain. Defective panels can also cause fire.

How long are solar panels warrantied for?

Typically, solar panels are warrantied for 25 years. However, all solar panels degrade and gradually generate less electricity over time. But a review of 30,000 installations in Europe by the German solar monitoring firm Meteocontrol found 80 percent were underperforming. Testing of six manufacturers’ solar panels at two Spanish power plants by Enertis Solar in 2010 found defect rates as high as 34.5 percent.

What are the most reliable brands?

  • SunPower
  • Sanyo
  • Sharp
  • Kyocera
  • REC
  • Mitsubishi
  • Yingli
  • Trina
  • Suniva
  • First Solar: Although First Solar uses cadmium tellurium (Cd-Te) panels, which are less efficient than the crystalline panels, they have been able to consistently set world records for efficiency of the Cd-Te panels, first at 13.4% and now at 14.4%. The First Solar power systems are particularly attractive because they have the fastest energy payback time when compared to all other photovoltaic PV systems in the market.
  • Lumos

What are the quality standards?

  • Institute of Electrical and Electronic Engineers, P929: Recommended Practice for Utility Interface of Photovoltaic Systems. Institute of Electrical and Electronic Engineers, Inc., New York, NY (1998)
  • Underwriters Laboratories, UL Subject 1741: Standard for Static Inverters and Charge Controllers for Use in Photovoltaic Power Systems (First Edition). Underwriters Laboratories, Inc., Northbrook, IL (December 1997)

What are testing agencies?

What are the standards?

  • IEC 61853
  • IEC 61215 (crystalline silicon performance, describe the qualification tests, such as insulation tests, wet leakage, hail tests, breakage, etc)
  • IEC 61646 (thin film performance)
  • IEC 61730 (all modules, safety)
  • IEC 60904 - standard test conditions
  • International Organization for Standardization (ISO):
    • ISO 9488 Solar energy - Vocabulary
    • ISO 9000
    • ISO 9001
  • United Laboratory:
    • UL 1703
    • UL 1741
    • UL 2703
  • Electrical Safety Tester (EST):
    • EST-460
    • EST-22V
    • EST-22H
    • EST-110

What tests are offered by RETC?

Performance testing ensures that the panels a manufacturer ships perform according to their claims. An RETC report affirms that the product "will perform in the field the way it is expected to.".

RETC performance tests measures how much power the modules will deliver under different light and temperature conditions. We test at 15 degrees C, 25 degrees C, and 75 degrees C, and we measure at between 100 watts and 1,100 watts per square meter.

The last part of performance testing is for light-induced degradation (LID). “We take a set of panels, measure the power output at standard test conditions [STC] of 25 degrees C and 1,000 watts per square meter, and then light-soak them outdoors or in simulated light and keep measuring until the power output stabilizes.”

Knowing that initial degradation is important because it could be anywhere from 0.6 percent or 0.8 percent to as high as 5 percent or 6 percent. “Then they stabilize and the modules will degrade at maybe half a percent every year or so.”

RETC’s reliability protocol is called Thresher Test Flow. It is a model for a formal reliability testing protocol being designed by an NREL-led task force of which Kedir is a member. Thresher Test Flow includes extended chamber tests for thermal cycling, humidity freeze, damp heat, and biased damp heat.

“The standard IE certification requires 1,000 hours of damp heat chamber exposure. That’s 85 percent humidity at 85 degrees C. It is supposed to simulate 25 years of operation. But in reality, what we are finding is that under operation some panels have shown unexpectedly higher degradations,” Kedir said.

RETC’s reliability tests use established IEC test procedures for performance and safety, with extended exposure times.

RETC has found that some products that pass at 1,000 hours often fail at 1,100 hours or 1,200 hours. “If you add just 10 percent more stress, they may fail dramatically,” Kedir said. “A lot of our customers are opting to go beyond the 1,000 hours to 1,500 hours, 2,000 hours; some go as high as 3,000 hours. Once the product fails, we help them figure out what failed. The manufacturers then go and improve their products in those areas.”

"We take a lot of the basic tests and we apply [the conditions for] two times or three times longer," Kedir said.

For damp heat, the module is tested at 85 degrees C and 85 percent humidity for 1,000 or more hours. “Then we do another test, the PID [potential induced degradation], which is very stringent," Kedir said. “It is the same test conditions, but with a system voltage bias added.” It is performed for between 100 hours and 2,000 hours.

With more rigorous testing, Kedir said, “we are finding issues with encapsulation, back sheets, and components such as junction boxes and connectors and cables. We are finding issues with diodes. A lot of things are showing up that before didn’t register when everybody was passing, but performance in the field was not up to par.”

What is PV+ Test?

If a module manufacturer wishes to be listed on the PV+ list, they must have their modules tested by an accredited TÜV Rheinland test lab (at significant cost). Once the results are released, the manufacturer can decide if they want their brand name listed beside their score i.e. if their modules did not perform well they wouldn't list their name - the scores would be listed as 'anonymous'. By default, the PV+ Test list is a 'best of' list.

A critical difference in this test, compared with Australian Standard tests for example, is that PV+ purchase the modules for testing from the marketplace. The manufacturer cannot control what modules are tested.

The analysis conducted by PV+ Test reveal what they think makes up a good module. A crucial aspect is whether the product lives up to the manufacturer's claims. A module receives top marks if it performs the way the experts would like it to in a particular property – in other words, the way the latest technology should work today. The total number of points and the total score are given at the end. A module is expected to get at least half of the possible assessment points, otherwise it fails the test.

What is the standard test condition (STC)?

PV performance quoted by manufacturers are based on the performance with "standard" 1000W per sq. meter light, at standard cell temperature (which I am not sure of the value). When deployed, the light that reached the panels are not the same as this 'standard" light - mostly lower and the light causes an increase in the surface temperature of the PV cells. These 2 parameters will reduce the output.

What is VDE Quality Tested?

A 'VDE Quality Tested' certificate also indicates a module exceeds existing standards. The VDE test procedure has been developed to prove increased reliability and durability as well as to validate lower degradation rates in modules. Along with the laboratory testing of the modules to a range of requirements, it also requires manufacturing in-line quality tests controlled and audited by the VDE. Some of the defined in-line tests are required for 100 per cent of the modules produced.

The novel VDE test approach goes well beyond existing standards. It requires regular laboratory controls of modules with increased test time and sample rates that exceed international test standards.

What is TÜV Thresher Tested?

The TÜV Sud Thresher Test certification provides information on the long-term safety and power-output performance of PV modules. Panels are independently tested by TÜV Sud for extended durability and performance, exceeding the requirements of existing standards.

The TÜV Sud Thresher Test extends standard IEC testing by two times to four times the accelerated test durations and helps identify those modules with truly differentiated long-term reliability and performance. In the tests, environmental stresses are simulated and repeated sequentially. The Thresher Test gathers and reports degradation through the course of the test sequences, and the module passes if this degradation remains within a prescribed window of the initial power rating data. Power drop, leakage current and visual observations are important factors in the final result.

The TÜV Sud Thresher Test was developed by a group of leading manufacturers along with the US DOE and NREL to establish a test that measured long term performance beyond the requirements of the minimum standards.

TUV Rheinland PTL provides PV design qualification and type certification services to many standards including: IEC 61215, IEC 61646 and IEC 62108 standards; PV safety testing services per ANSI/UL 1703 and IEC 61730 standards; and other working group standards for concentrated PV modules and systems (CPV).

What is Atlas 25+® certification?

Atlas 25+ is a certification that also focuses on the long-term performance of panels. It consists of a series of tests that are designed to subject photovoltaic modules to the environmental degradation stresses which can be expected over long-term service. Like the above schemes, the Atlas 25+® mark serves as a product differentiator providing customers with the proof of independent third-party testing that exceeds the current standards. There are two versions of the program – a six-month streamlined 'basic' program and an expanded 12-month 'premium' offering that includes additional climate factors and performance measurements.

What is Fraunhofer PVDI testing?

The PV Durability Initiative (PVDI) is a program of Fraunhofer Institute for Sustainable Energy Systems in Germany. Modules are subjected to accelerated stress testing such as damp heat and thermal cycling, beyond that required by the international standards, as well as Potential-Induced Degradation (PID) testing, and dynamic mechanical load testing to see susceptibility to transport damage. Modules are rated on a scale of 0 to 5. -

What is ISO?

It can be somewhat difficult to quantify a product’s overall quality numerically, which is one of the reasons that the International Organization for Standardization (ISO) developed its ISO 9000 series of quality assurance standards for the manufacturing industry. Among the ISO 9000 series, ISO 9001 details the requirements that product manufacturers must meet in order to be certified ISO 9000-compliant. Solar panel manufacturers that have undertaken the rigor to become ISO 9001-compliant may be viewed more favorably than those who haven’t, although lack of ISO 9001 certification doesn’t necessarily imply an inferior product from a quality perspective.

How can manufacturer improve quality?

Developers, EPC firms, banks, and insurance companies are instituting sophisticated supplier qualification and ongoing quality monitoring programs to mitigate the risk of underperforming panels. Effective diligence can include reliability testing, evaluation of energy yield, third-party .pan files, and factory audits. Unfortunately, few PV module buyers have the resources to properly keep up with qualifying suppliers, especially with the fast evolution of the products they're buying. Whether its Taiwanese cells or cast mono, lower cost encapsulants or backsheets, or "PID-free" modules, products are changing fast to keep up with costs and to differentiate in a crowded field.

What are the top 10 panels?

#1. Kyocera KD315GX-LPB. The Kyocera KD315GX-LPB solar panel gets top marks for its high solar efficiency, which is the amount of energy converted from sunlight per unit of surface area in the panel. At 16 percent, this solar panel is not the most efficient on the market, but it ranks high. (Silicon-based solar cells like this one usually operate at an efficiency of 18 percent or lower, according to the University of Pennsylvania.) The Kyocera KD315GX-LPB panels are also durable and come with a complete five-year warranty. The company guarantees that the panels' power output will remain at 80 percent of the minimum power promised by manufacturers for at least 20 years.

The panels meet industry standards for withstanding loads (it can hold up under 113 pounds per square foot of pressure from snow or ice on the roof) and can handle a beating by hailstones with a 1-inch diameter in winds of up to 51 mph.

#2. Canadian Solar CS6X-305M. Founded in 2001, Canadian solar offers its panels in 50 countries around the globe. The company's Canadian Solar CS6X-305M model took second place in the Top Ten Reviews rankings for power, durability and visual appeal. The panels' shape is more rectangular than Kyocera's offering, which may appeal to some homeowners. The efficiency of these panels is rated at 15.9 percent, barely behind the No. 1 Kyocera model. The Canadian panels also meet industry standards for durability and are able to handle up to 113 pounds of snow per square foot. The warranty guarantees 95 percent output for one year, and 80 percent output for 25 years.

#3 Grape Solar 390W. Grape Solar is a Eugene, Oregon-based company founded in 2009. It makes solar panels, largely manufactured in Asia but assembled in the United States. The Grape Solar 390W panel has an efficiency percentage of 15.21, a solid number, and can handle 50 pounds of snow per square foot. The warranty promises 90-percent power output for 10 years and 80-percent output for 25 years. Grape works with Costco and Home Depot and has a network of installers throughout the United States.

What are some statistics?

Eventually, all solar panels degrade and produce increasingly less electricity, but recent evidence suggests that the panels are not performing as they should. According to a review of 30,000 installations in Europe by Meteocontrol, a German solar monitoring firm, 80 percent of the installations were underperforming. In 2010, Enertis Solar tested the solar panels of six manufacturers and found defect rates were as high as 34.5 percent. -

The rate of defects in an audit of 50 Chinese factories was 5.5 percent to 22 percent over 18 months, according to Ian Gregory, the senior marketing director of SolarBuyer.

What does CEC abbreviate for?

CEC abbreviate for a number of different things / entities:

  1. California Energy Commission
  2. Clean Energy Collective - Clean Energy Collective develops community-owned solar gardens … CEC is your trusted partner whether you need a turnkey solution or just a little help.
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