More investment needed in quality and reliability of solar energy

Although quality assurance test programs are available for solar energy and innovative testing technologies are being developed on an ongoing basis, losses of earnings and installation and safety defects are still widely observed in solar systems.

TÜV Rheinland made this observation in its Quality Monitor – Solar 2014 at the Intersolar specialist trade fair.

“We are at a crossroads: In the long term, the acceptance of photovoltaics as a way of generating solar energy hinges on the reliability of the technology and its profitability. Companies that skimp on quality assurance and confuse something that is cheap with good value are hurting themselves in the long run as well as the industry,” explains Willi Vaassen, who has followed the development of technology in the industry for more than thirty years in his role as Head of the Solar Energy division at TÜV Rheinland.

New data from a research project led by TÜV Rheinland looking into fire prevention in photovoltaic systems recently showed that although the risk of fire is very low, almost all fires experienced would have been preventable before the system was even connected to the grid without any costly additional expense.

It has been established with certainty in around 210 cases in Germany to date (of over 1.4 million systems in operation) that fires were caused by photovoltaic systems. The most frequent causes of fire are installation faults followed by product and planning defects. In addition, most fires take place in the first year of operation and then in the first five subsequent years.

Systematically expanding testing of specialist companies

According to the assessment of experts from the world’s leading testing service provider in the industry, there is still a lack of awareness when it comes to quality as well as the necessary qualifications.

Back in 2013, TÜV Rheinland discovered based on defect statistics for large-scale power plants that around 30% of all large-scale power plants inspected by the testing company in recent years had serious defects. These were either safety-relevant problems that required immediate action or significant accumulations of problems that strongly impaired the plants’ functionality. Half of all defects identified were installation errors. For this reason, TÜV Rheinland launched a new testing standard for specialist installation companies in recent months. “We are pursuing out aim of promoting specialist qualifications and always conforming to the highest technological standards,” explains Vaassen.

Certified specialist installation companies are monitored on an annual basis. The same applies to maintenance companies that wish to receive certification from TÜV Rheinland. Since spring 2014, TÜV Rheinland has been testing companies specializing in the maintenance of photovoltaic systems using another newly developed standard.

The experts from TÜV Rheinland use a wide-ranging catalog of criteria in order to test companies specializing in the maintenance of photovoltaic systems. This focuses on the qualification of maintenance personnel and the quality of the technical maintenance services that the specialist company must perform on systems once a year. This must ensure that the system operates safely and with no faults.

The maintenance of older systems will also become increasingly relevant very quickly especially in Germany, which has a large number of installed systems. Vaassen: “System operators should not hold off from having their systems maintained.” The experts in fact recommend getting small systems, such as those installed on the roofs of residential houses, inspected once a year, ideally after winter. The extent of the checks performed can vary widely. A major inspection is not always necessary.

New test procedures for comprehensive quality assurance

TÜV Rheinland is continuing in its concerted effort to optimize test procedures at individual stages of the value chain in the solar industry in order to be able to offer comprehensive quality assurance programs throughout the implementation of photovoltaic projects in the future. In 2014, TÜV Rheinland and the logistics service provider DB Schenker introduced a world first – a jointly developed and implemented monitoring system for the transportation of photovoltaic modules.

Industry experts estimate that transport has an unnecessary and detrimental effect on between 5% and 10% of all modules and that it impairs their performance.

The aim of the new monitoring and control system is to systematically increase transparency, data validity and safety along the solar modules’ global transport route, from the outgoing inspection at the manufacturer’s plant to delivery to the building site, as well as to identify risks for the modules.

The project’s development and test phase took more than one year to complete. The procedure helps to establish a reliable goods issue system based on valid measurements as well as to identify transport damage before the performance of a solar power plant or solar system is impaired.

An important component in the development of the new service is the analysis and evaluation of loads to which the individual modules are exposed. As analysis technology is progressing constantly, TÜV Rheinland also believes that the measurement of aspects such as micro-cracks and snail tracks are becoming more significant. After all, a crack is by no means just a crack.

Long-term observation and measurement of damage by TÜV Rheinland is playing an increasingly important role in practice. A consortium of renowned companies and scientific institutes is currently working with TÜV Rheinland to investigate the long-term effects that typical damage to photovoltaic modules has on the function and performance of the modules. The aim is to determine in step with actual practice which typical faults and damage are actually relevant to the module’s performance or functionality and which are most likely tolerable.

Optimizing module testing further

TÜV Rheinland tests photovoltaic modules in laboratories worldwide on the basis of underlying IEC design certification requirements. It is still noted here that new module types are well designed to meet these design certification requirements. For example, the number of faults identified in certification tests in 2013 stood at approximately 10%, around the same level as 2012. The long-term trend is clear: Ten years ago, over 30% of all modules failed the IEC design certification tests at TÜV Rheinland.

Jörg Althaus, also Head of Solar Energy at TÜV Rheinland, states: “What is even more important than this consideration is ensuring uniform quality in production. Special, more in-depth tests for modules based on their respective application are also much more important.” He explains that the key words here are the development of modules for specific applications and performance changes that often only become apparent in practice.

Examples of these tests include real yield measurements in different climate zones and tests relating to potential-induced degradation (PID), where the output of a module is reduced if it is exposed to a high voltage between the cells and ground during operation and favorable climate conditions exist for this effect to take place. TÜV Rheinland works in accordance with a standardized procedure when determining PID in order to ascertain the susceptibility of modules.

TÜV Rheinland is currently investigating the energy yield of solar modules around the world based on the climate. These measurements should answer the fundamental question regarding the extent to which climatic factors have an impact on the yield of photovoltaic modules. Besides temperature and the spectrum of the sunlight, climatic factors also include humidity and precipitation as well as the potential detrimental effects of sand and salty air.

Based on experience and analyses performed to date, the experts at TÜV Rheinland believe that the yields of different modules and module technologies may differ by more than 10% depending on the respective climate. TÜV Rheinland constructed five test facilities in different climate zones in order to take comparable measurements of the energy yield.

Climatic conditions also play an important role in the ongoing development of existing load tests for solar modules. For example, since this year, TÜV Rheinland has provided an intensified hailstorm test, which is available not only to solar collectors and photovoltaic modules. Test objects can be bombarded with up to 50-millimeter hailstones at speeds of up to 30.8 meters per second.

The background to this new test is the fact that insurance firms and project developers are increasingly insisting on the more rigorous tests as hailstorm damage to solar systems has risen significantly in the past few years. Althaus: “With these tests, our aim is to help ensure that projects can still be insured. After all, this may become a vital component for the industry.”

Other extreme climatic loads can arise in desert regions where more and more solar projects are being established around the world just recently. Significantly higher ambient temperatures and therefore module temperatures, as well as sand and dust, play a role here, but these are not included in existing standards. TÜV Rheinland is collaborating with a test laboratory experienced in the measurement of sand abrasion. Higher UV radiation and temperature loads will also be included in future test sequences.

The ongoing development of quality and safety tests at TÜV Rheinland is still driven by technical innovations and product changes. For example, TÜV Rheinland is working with partners from the industry on a research project investigating the safe disconnection of solar systems in situations such as emergencies. When the AC grid is switched off by the energy company during an emergency, the DC lines and connection points between the photovoltaic modules and the inverter in solar systems remain live as long as light hits the cells.

This can pose an additional risk for people. The research project, which will run until summer 2015, is focusing on the development of a technical basis for the measurement, testing and construction of technical switches.

Another area of innovation concerns storage systems for solar energy, which are also playing an increasingly important role at Intersolar. TÜV Rheinland has developed a test program for solar power systems with stationary storage facilities similar to those used in single-family detached homes, for example. The method takes into account existing test standards for batteries and electric components, inverters and modules as well as regulations that form a basis for funding the German Reconstruction Credit Institute (KfW).

The key word here is “KfW-ready.” Prerequisites for funding include certain criteria relating to the safety and commissioning of the storage system. TÜV Rheinland’s tests relate to individual components of the overall system and the reliable interaction of all components. The tests include an overcharge test, vibration and shock tests and climate tests involving extreme temperature changes and cover the aspects of self-discharge and cycle stability in particular as performance tests.

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