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Production & Inspection

First Testing Standards for Solar Module Materials

In most manufacturing industries, companies can count on a basic level of material quality when they’ve been certified by organizations such as Underwriters Laboratories. There are no such assurances in the solar industry. With no standards bodies to reconcile the differences in testing and quality assurance from one material supplier to the next, solar module manufacturers are left to vet their vendors themselves at considerable time and expense. The variation in quality and performance standards in solar module manufacturing is a growing issue in the industry. As the market for solar modules increases, manufacturers are offering longer warranty periods to appeal to a broader range of customers. With those longer warranties comes the risk of losses from premature module failures caused by low-quality materials─backsheets that de-laminate, for example, eroding production and raising the prospect of early replacement. This article examines how industry groups are reconciling the differences between manufacturers to arrive at trustworthy safety and performance standards. It will use development of solar backsheet standards as an example of the broader efforts.

By Robin Kobren



New industries have growing pains, and solar has had more than its share. Most of them stem from the economics of selling solar energy at market rates when higher costs drive prices higher. Solar module manufacturers are doing everything they can to bring manufacturing costs down to help reduce the cost of energy, and that includes looking for the lowest-cost providers of key materials like backsheets, frontsheets, glass and adhesives.

In most manufacturing industries, switching suppliers is a routine process. Companies can count on predictable performance and safety either because their supplies are raw commodities that vary little in quality, or because a certification body such as Underwriters Laboratories sets out and enforces standards for performance testing that must be achieved before they will certify a product.

Solar module manufacturing requires finished materials that can vary widely in quality. Owing to the industry’s relative immaturity, there has been no industry-wide alignment of testing methods to ensure manufacturers are using comparable tests that enable buyers to make meaningful comparisons between competing products. Manufacturers are using different testing methods to make the same representations. For example, a backsheet manufacturer uses the Society of Automotive Engineer’s test methodology to conclude that its backsheet’s layers will stay adhered for at least 20 years. A second manufacturer uses a less stringent test to determine that its layers will also adhere for 20 years. Both manufacturers make the same claim to prospective customers. Right now, customers lack a frame of reference for weighing the two vendors’ claims. Often, their only option is to have the competing products tested at their own expense.

This variation in quality and performance standards in solar module manufacturing is a growing issue in the solar industry. Solar module manufacturers are offering longer warranty periods to appeal to a broader range of customers. With those longer warranties comes the risk of losses from premature module failures caused by low-quality materials backsheets that de-laminate, for example, eroding performance and raising the prospect of early replacement.

The International Electrotechnical Commission (IEC) and Underwriters Laboratories have teamed up to reconcile or ‘harmonize’ differences in test procedures in the solar industry. Their goal is to mitigate solar module manufacturers’ risk and save them from incurring additional cost by certifying standard test processes. Standard test processes will help ensure that key solar module components meet quality and performance guidelines.

The IEC’s Photovoltaics Material Project Team consists of 88 international members representing all major stakeholders in solar module component production and testing:

-module, adhesive, backsheet, frontsheet and encapsulant manufacturers;

-industry experts;

-certification bodies; and

-national laboratories.

The Photovoltaics Material Project Team is halfway through a 36-month process for creating a matrix of testing standards. Its initial focus is on developing testing standards for backsheet testing. Then it plans to move on to encapsulants and frontsheets. When the group’s work is complete, solar module manufacturers will be able to shift suppliers to secure better prices with confidence, knowing that they won’t be compromising quality standards.


Matching Test Methods


The project team is developing testing standards to ensure that solar module components comply with IEC standards 61730, 61215 and 61646, which all pertain to photovoltaic material safety and performance, as its baseline. It will apply those standards to tasks that range from characterizing material safety and performance to writing pre-selection guidelines for solar modules. Employing hazard-based analysis, it has begun listing characterization and related tests, and assigning authors to write the guidelines. The team has also started reviewing and prioritizing tests lists based on safety and performance. It will move on to creating retest variation guidelines, and compliance criteria based on design and application.



The initial backsheet safety and performance standards are concentrating on four areas: partial discharge, bond strength, volume resistivity and ‘creep’. The regimen will evaluate backsheet testing for hazards such as electrical shock protection, mechanical strength and flammability. Backsheets will be tested when they are new and after environmental aging, both at normal operating temperatures. The process will define environmental conditioning and aging.

Tests will address the causes of hazards including optical degradation, shunting, increased series resistance, moisture ingress, corrosion and de-lamination. It will break each hazard down by its potential causes and match them up with tests and test methods. The result will be a matrix of conforming tests for the major causes of every hazard.

Take electrical shock as an example. Ten causes of failure are associated with the hazard of electrical shock. They cover physical breakdowns, such as degraded insulation and water ingress, and operational problems such as tearing and punctures during installation. Each breakdown has a test and a test method associated with it. The test methods are from established engineering organizations such as IEC, SAE (Society of Automotive Engineers) International, ISO (International Organization for Standardization) and ASTM International (formerly American Society for Testing and Materials). To be able to say they met the IEC standard for electrical strength testing, a supplier must certify that they have used either IEC test method 60243 or 60216-5. For mechanical protection from tearing, they must have tested for tensile strength and tear resistance using ISO 527-3, ASTM D1004, or IEC 61730-2. For some tests, such as water ingress from de-lamination, they will have only one approved method, ISO 62. Manufacturers will be subject to Underwriters Laboratory audits to confirm they are complying with testing requirements.


Long-Term Cost Reduction


The solar energy industry is under constant pressure to lower the cost of solar-produced electricity to make it market competitive with fossil fuels. On average, U.S. consumers pay about 12 cents per kilowatt hour for conventionally generated electricity. Averaging out a wide range of estimates, solar costs about 25 cents per kilowatt hour, roughly double the cost of conventional electricity.

Lowering solar’s cost will come from increasing solar module efficiency and reducing production costs. Efficiency is the attention grabber. The industry and the federal government are pouring research money into raising solar module efficiency. There are dozens of startup and early-stage companies developing new technology to get efficiency into the twenty, thirty, even forty percent range.



The IEC’s Photovoltaics Material Project is a major initiative to address the other part of the equation. It is among the changes that have to take place to change the solar industry’s cost dynamics. Solar module manufacturers must have the agility to switch suppliers to take advantage of low prices the same way their counterparts in other industries can. If solar module efficiency improves three or four percent every year but production costs go up with them, we aren’t reducing the price of solar energy. We’re eating our own success.

At the same time, price is not the only issue. Manufacturers cannot sacrifice safety and performance. Worker injuries and premature module failures from faulty materials will curb the solar energy industry’s growth at just the time when the political, economic and social conditions exist for it to take root. If we dont make the price per kilowatt hour of solar-generated electricity grid-competitivewhich is to say in the same range as fossil fuels, nuclear or other renewable energy sourceswithin the next few years, solar will be a fringe technology. We will lose the best opportunity in a generation to make solar energy a credible, widely implemented energy source.


Robin Kobren is a member of the Electroctechnical Commission’s Photovoltaics Material Project Team.



For more information, please send your e-mails to pved@infothe.com.

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