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Contract No. DE-AC36-08GO28308

Three-Prong Path to 

Comprehensive Technical 

Standards for Photovoltaic 

Reliability

Preprint

Sarah Kurtza, John Wohlgemutha, 

Tony Sampleb, Masaaki Yamamichic, 

Michio Kondoc, and George Kellyd

a National Renewable Energy Laboratory

b European Commission, JRC

c National Institute of Advanced Industrial Science and 

Technology (AIST)

d Sunset Technology, Inc.

Presented at the 40th IEEE Photovoltaic Specialists Conference

(PVSC-40)

Denver, Colorado

June 8-13, 2014

Conference Paper

NREL/CP-5J00-61208

July 2014
NOTICE

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Three-Prong Path to Comprehensive 

Technical Standards for Photovoltaic Reliability

Sarah Kurtz*a, John Wohlgemutha, Tony Sampleb, Masaaki Yamamichic, Michio Kondoc and George Kellyd

a

National Renewable Energy Laboratory, 15013 Denver West Parkway, Golden, CO, USA 80401;

b

European Commission,JRC, Via E. Fermi 2749, 1-21027 Ispra, Italy; cNational Institute of Advanced

Industrial Science and Technology (AIST), Central 2, 1-1-1, Umezono, Tsukuba, Japan; 

d

Sunset Technology Inc., Mount Airy, MD, USA 21771

Abstract — As the photovoltaic (PV) industry has grown, the 

long-term reliability of PV systems has become increasingly 

important. Many organizations are taking on the challenge of 

this multi-faceted issue. This paper describes three closely 

coordinated efforts that together will provide a comprehensive 

set of consensus standards and specifications for the technical 

aspects of verifying PV system quality and bankability. These 

three efforts are developing standards for 1) qualifying the design 

for the intended application (climate zone and mounting 

configuration), 2) quality management systems for PV module 

manufacturing, and 3) system-level inspections to ensure 

appropriate design, installation, commissioning, and operation of 

PV systems. A pathway has been identified for international 

implementation of these standards through the International 

Electrotechnical Commission.

Index Terms — reliability, photovoltaic systems, PV, quality 

management, accelerated testing.

I. INTRODUCTION

As financial incentives for photovoltaic (PV) deployment 

shrink, PV customers are becoming increasingly focused on

the long-term reliability of PV systems. Also, because PV 

prices dropped by more than a factor of four from early 2009 

to early 2013, module manufacturers were forced to reduce 

costs; concerns have been raised that some manufacturers 

have neglected reliability [1].

Confidence in the reliability of PV modules requires both 

that the module design is adequate for the use environment 

and that the design is consistently manufactured. In addition, 

reliability at the system level requires that all components 

have adequate quality, that all components are integrated 

correctly, and that the system is installed, maintained, and 

functioning properly.

Substantial work over the years has led to a widely accepted

set of standards to guide qualification testing of modules [2-8]

and balance-of-system components [9,10] and to guide the 

design and installation of PV systems [11-13]. Private test 

labs have developed a range of tests that go beyond the 

standard qualification testing for PV modules [8,14-25]. 

Additionally, multiple organizations are launching efforts to 

develop guidelines or standards for the design, installation, 

and operations and maintenance of PV systems. Each of these 

efforts is important for improving PV system reliability.

However, there is widespread sentiment that a more 

comprehensive and unified approach to PV reliability is 

needed.

This paper describes the three-prong effort that is being pursued by the International PV Quality Assurance Task Force

(PVQAT) to develop a comprehensive set of standards for 

ensuring the reliability of PV systems, including methods that 

are more comprehensive than IEC 61215 [3] for 1) qualification of the design for the intended application (climate zone 

and mounting configuration), 2) auditing quality management 

systems for PV module manufacturing, and 3) system-level 

inspections to ensure appropriate design, installation, commissioning, and operation of PV systems, as shown in Fig. 1. 

The paper starts with a historical overview of how the effort 

began, then describes the status and plans for each of the three 

coordinated efforts, building on the existing infrastructure of 

the International Electrotechnical Commission (IEC). This 

effort is unique among the many because a pathway has been 

identified to reach the goal of a unified and comprehensive 

solution. This description is intended to facilitate coordination 

with other relevant efforts.

Fig. 1. Conceptual diagram of how the three-prong standards 

effort provides a foundation for reliable, bankable PV systems.

Standards are needed to show that 1) the durability of the design 

meets the intended use environment, 2) the tested design is 

manufactured consistently, and 3) the system is appropriately

designed, installed, commissioned, and operated.
2 

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II. HISTORY OF EFFORT

In December 2010, Hironori Nakanishi of the Ministry of 

Economy, Trade and Industry (METI) in Japan proposed to 

the U.S. Department of Energy the topic of PV module 

reliability testing as a collaborative effort between the United 

States and Japan as part of the Asia-Pacific Collaboration Program. METI proposed a joint workshop in spring 2011 to discuss PV module reliability testing at an international level. At 

the time, METI was contemplating a PV incentive program 

and wished to first have confidence in the quality of the hardware.

METI and the U.S. Department of Energy approached the 

National Institute of Advanced Industrial Science and 

Technology (AIST) and the National Renewable Energy 

Laboratory, respectively. Michio Kondo and Masaaki 

Yamamichi of AIST, and John Wohlgemuth and Sarah Kurtz 

of the National Renewable Energy Laboratory formed a steering committee to begin preparations for the workshop. Tony 

Sample of the Joint Research Centre of the European 

Commission joined the steering committee to represent Europe.

The March 2011 earthquake in Fukushima, Japan thwarted 

the original plan of a May 2011 workshop in Tokyo. The 

workshop was quickly rescheduled with help from SEMI; the 

International PV Module Quality Assurance Forum was held 

July 15-16, 2011 in San Francisco, CA. About 150 people 

representing module manufacturers, equipment suppliers, test 

labs, and a range of other organizations attended the Forum. 

Presentations and breakout sessions discussed the need for 

taking PV reliability standards to the next level and concluded 

by forming the International PV Module Quality Assurance 

Task Force [26] to address two primary goals (Fig. 2). Initially, five Task Groups were formed, as described in Table I. 

TABLE I

SUMMARY OF CURRENT TASK GROUPS

Groups for developing PV QA 

Testing

Date 

formed Prong

1. Guideline for manufacturing 

consistency July 2011 2 

2. Thermal and mechanical fatigue,

including vibration July 2011 1 

3. Humidity, temperature, and voltage July 2011 1

4. Diodes, shading, and reverse bias July 2011 1

5. UV, temperature, and humidity July 2011 1

6. Communication of PV QA ratings to 

the community Sept. 2011 1 

7. Snow and wind loading April 2012 1

8. Thin-film PV August 

2012 1 

9. Concentrator PV Sept. 2012 1

10. Connectors May 2013 1

11. PV Systems April 2014 3

Fig. 2. The 2011 Forum was a workshop that resulted in the 

formation of the International PV Module Quality Assurance Task 

Force to address these goals.

Task Group 1 was created to address the second of the goals 

in Fig. 2 (prong 2); Task Groups 2-5 were created to design 

stress tests for the rating system, specifically for crystalline

silicon modules, as in the first goal in Fig. 2 (prong 1). 

A few months after the forum, Task Group 6 was formed to 

help ensure that the rating system could be easily 

communicated to stakeholders. Although there was interest in 

immediately starting work on thin-film and concentrator PV 

module standards, the complexity of the project motivated a 

delay of a year and Task Groups 8 and 9 were formed in 

summer 2012. Task Group 7 was formed in response to 

concerns from Australia about the need to test for cyclonic 

winds, but Task Group 7 has so far focused more on snow 

loading. Task Group 10 was later formed to address issues 

with connectors. 

A key discussion topic for Task Group 1 was whether a 

guideline for PV module manufacturing should be developed 

and administered under IEC or ISO (International Organization for Standardization). The manufacturing process is commonly audited under ISO 9001, but there is a need to add 

technical aspects to the audit, implying benefit of involvement 

by IEC working groups. Discussions with the IEC uncovered 

a similar dilemma for the wind industry. In collaboration with 

representatives of the wind industry and the IEC, a solution 

was identified: IEC created IECRE [27], as discussed below. 

During the 2011 Forum and subsequently, multiple individuals suggested that PV systems should be included in the 

goals, but initially, the Task Force focused on only PV 

module issues. However, in spring 2014, in recognition of the 

need to address system-level issues and to better support 

IECRE, the leaders decided to broaden the scope of the Task 

Force, dropping the word “Module” from the name and using 

the abbreviated label PVQAT. To support the IECRE in 

developing all the standards needed to issue a system-level 

certificate, Task Group 11 was formed. Because IECRE PVsystem certificates will use multiple standards from IEC 

Technical Committee 82 (TC82) Working Groups 2, 3, and 6, 
3

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Task Group 11 will provide a forum for higher-level 

discussions and rapid identification of solutions when a need 

for a more comprehensive PV-system inspection is identified. 

The outputs of all the PVQAT Task Groups are submitted to 

IEC by the appropriate IEC working group for refinement and 

adoption through IEC’s international consensus-development 

process. Many individuals participate in both PVQAT and 

IEC, facilitating rapid adoption of the new standards. The 

coordination has been especially close between Task Group 5 

of PVQAT and the IEC TC82 materials group, which is 

investigating test methods for materials including durability to 

ultra violet light.

The current status of the eleven task groups is briefly 

summarized in Table I. An analysis of the standards needed 

for IECRE to complete a PV-system inspection is reviewed by 

Kelly, et al. [27]. A technical description of the rating system 

that is being developed is described by Wohlgemuth, et al.

[28]. The current status of the guideline for PV manufacturing 

consistency is described by Eguchi, et al. [29].

Most of the PVQAT work has been executed by telephone 

and web-facilitated meetings, but about two face-to-face 

meetings have been held each year [26].

III. THREE-PRONG APPROACH

Although PV system reliability is more frequently 

compromised by inverter failures than by other component 

failures [30], the PV modules represent the greatest single 

component risk because of the high cost associated with 

module replacement. Also, the modules are more directly 

subjected to the weather than are some other components, 

which may be housed in enclosures. Thus, two prongs of the 

three-prong approach focus specifically on the design and 

manufacture of the modules; the third focuses on the function 

of the entire system.

A. Durable design: Qualifying the design for the intended 

application

Qualification tests seek to identify design flaws that could 

lead to early failures, but PV manufacturers and customers 

would like to also understand the wear-out mechanisms that 

are likely to limit the service life of PV modules. These wearout mechanisms usually strongly depend on the climate and 

mounting configuration in which the module is deployed. 

Most module manufacturers provide a single warranty 

regardless of deployment location or configuration. Some 

manufacturers void the warranty if the module is deployed in 

a marine or corrosive environment, but typically do not

differentiate between hot and cold or wet and dry climates. 

Historically, manufacturers have preferred to manufacture a 

single module design. But as the industry has grown, 

companies have sought to differentiate their products, 

sometimes within their own product line and, often, from their 

competitors’ products. It is advantageous for manufacturers to 

create multiple module designs if the cost of the module can 

be reduced for limited markets. For example, a module 

deployed in a location with high snow loads may require 

thicker glass, frame, or support rails increasing upfront cost 

but decreasing levelized cost of electricity (LCOE) over 

modules with thinner glass that might fail in the first year

[31]. As the industry matures and seeks to reduce cost, PV 

customers will benefit from a simple way to identify modules 

that meet their needs at the lowest price. Ultimately, the PV 

industry will reduce LCOE further if reduction in module cost 

is quantitatively linked to service life as a function of the use 

environment. The rating system that is being designed by 

PVQAT and implemented through IEC seeks to do exactly 

this by defining tests to differentiate use environments 

involving three climate zones (nominally, moderate, tropical, 

and desert climates) and two mounting configurations (openrack and close-roof mounting) [28]. If manufacturers find that 

they can achieve the lowest LCOE with the same module 

design for multiple use environments, then fewer than six use 

environments may be needed.

The implementation of this rating system will be managed 

alongside the current international standards. This strategy 

was chosen over creating a new standards organization to 

hasten the standards creation process and minimize the need 

for new community education efforts.

The details of the tests that are being proposed are based on 

observations of the most commonly observed field failures

[25,28,32-36].

B. Consistent manufacturing: Quality management systems 

for PV module manufacturing

Consistent manufacturing is needed to ensure that all 

modules replicate the intended design. Confirming that every 

module functions correctly at the beginning of life is 

straightforward; however, controlling the long-term reliability 

is much more challenging. Even with highly accelerated tests, 

it could take months to determine whether the manufacturing 

process has drifted out of specification.

IEC TC82 accepted “Guideline for increased confidence in 

module design qualification and type approval” as a new work 

item in January 2014. This technical specification will add 

PV-specific details to ISO 9001 and will be implemented

through IEC TC82 and IECRE after it is published in 2015. 

Even before the IEC technical specification is published, the 

concept of a requirement for a PV-specific quality 

management system is being embraced in multiple locations. 

More than a dozen companies are already certified to the

Japanese version, JIS Q8901 [37], which was used as a 

starting point for the international version. TÜV Rheinland, 

acting as a Standards Development Organization, has begun 

creation of a U.S. standard [38] and China has been 

developing guidelines for differentiating quality management 

systems. Eguchi, et al. [29] has summarized the history and 

status of the IEC guideline in more detail.
4

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C. System verification: System-level inspections

Ultimately, even if the modules are perfect, a PV system 

may not function correctly if the system is not correctly 

designed, installed, and operated. Just as a restaurant or an 

elevator displays a certificate showing a successful inspection, 

each PV system can have a certification (based on an 

international standard) verifying that the system meets 

minimal safety and performance standards. This certification

would be useful to:

• an insurance company determining rates

• a PV customer or the lender for a customer who wishes 

independent confirmation of the state of a system before

investing in a plant

• an owner of a PV plant who wishes to ensure that the asset 

is being operated safely and effectively. 

Just as an elevator is rated for the number of people it can 

transport, some aspects of PV system design and performance 

may need to be documented by the inspection. For example, 

some PV systems are knowingly designed to underperform 

because of shading or inverter clipping. It is useful to a potential customer of a system to be able to quickly quantify these.

As described above, responding to a similar need in the 

wind industry, in recent years IEC Technical Committee 88 

began an effort to develop system-level certification of wind 

systems. However, conformity assessment is considered outside the scope of IEC Technical Committees and it was 

unclear who might have authority over a system-level 

certification. To fill this void, the IEC Conformity Assessment 

Board created IECRE in June 2013 to guide system-level 

inspections for all types of renewable energy systems

including wind, PV, solar thermal, and marine energy. Many 

of the needed detailed standards for a PV-system inspection 

already exist. So although this organization is just starting, 

IECRE plans to issue the first certificates by the end of 2015.

Kelly, et al. [27] have provided a more detailed description of 

the work of IECRE and the standards that will be included in 

the system-level inspection.

IV. ACCOMPLISHMENTS AND PLANS

Since the Forum in 2011, the Task Groups have been 

discussing the scientific basis for the desired standards, 

designing experiments to answer pivotal questions, collecting 

the best ideas, and submitting these to the IEC TC82 

consensus standards process. Some of the primary 

accomplishments to date (notably drafts in progress with IEC)

are summarized in Table II.

Plans for implementing the three-prong effort are 

summarized in Table III. IECRE plans to begin issuing 

certificates for large PV plants in 2015. As noted above, the 

PV-specific reviews of quality management systems are 

already being done in Japan, and are expected to begin in 

other parts of the world in 2015. Completion of the rating 

system to assess durability as a function of use conditions is 

expected in 2016, but refinement will continue for years to 

come.

TABLE II

SUMMARY OF PVQAT-SUPPORTED ACCOMPLISHMENTS AND STATUS

IEC 

Designation

Title Stage Forecast 

Publication Date

Task 

Group

IEC 62892-1 Ed. 

1.0

Comparative testing of PV modules to differentiate performance in 

multiple climates and applications – Part 1: Overall test sequence an 

method of communication

Approved 

work item 2015-12 2-6, 8

IEC/TS 62916 

Ed. 1.0 Bypass diode electrostatic discharge susceptibility testing Approved work item 2015-02 4

PNW/TS 82-800 

Ed. 1.0

Guideline for Increased Confidence in PV Module Design Qualification 

and Type Approval

Approved 

work item 2015-10 1

IEC 62925 Ed. 

1.0

Thermal cycling test for CPV modules to differentiate increased thermal 

fatigue durability

Approved 

work item 2015-8 10

PNW 82-791 Ed. 

1.0 Non-uniform snow load testing for photovoltaic (PV) modules Proposed work item 2015-12 7

Not assigned Bypass diode thermal runaway test Proposed 

work item 2016 4

Comparative testing of PV modules to differentiate performance in 

multiple climates and applications – Part 2: Mechanical and Thermal 

Cycling Stress Testing

Draft 2016 2

Comparative testing of PV modules to differentiate performance in 

multiple climates and applications – Part 3: UV and Humidity Testing Concept 2016 3,5
5

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TABLE III

SUMMARY OF HIGH-LEVEL PLANS FOR THREE-PRONG EFFORT

Current Status 2014 goal 2015 goal 2016 goal

Durable Design (Comparative 

test) Proposed as concept Enumerate tests; establish framework

Submit all test procedures to 

IEC

Approve IEC 

rating system

Consistent Manufacturing 

(Quality Management 

Systems)

Revision of original 

proposal is resubmitted

Publish technical 

specification

Start use of TS in factory 

inspection and as part of

IECRE

Revise QMS TS 

to reflect feed

System Verification (Systemlevel inspection) IECRE is being formed Identify needed standards 

and create drafts as needed Issue first certificates Refine approach

V. SUMMARY

This three-prong path to a unified and comprehensive set of 

technical standards for PV-system reliability is one of many 

efforts underway to help PV customers, investors, and 

insurers easily assess PV modules and systems. It is 

distinguished from most other efforts underway because a 

pathway has been identified for how the standards will be 

created and implemented. Mainstream standards organizations 

and test laboratories will implement the new standards, 

providing a rapid path to unified implementation of a 

comprehensive treatment of PV-system reliability and quality.

VI. ACKNOWLEDGMENT

This work was supported by the U.S. Department of Energy 

under Contract No. DE-AC36-08-GO28308 with the National 

Renewable Energy Laboratory. We thank T. Earnest for 

useful conversations.

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