Solar Plant Gets Int'l Certification for 1st Time in Japan

Third-party German verification/test firm inspects system

2014/05/07 21:15
Kenji Kaneko, Nikkei BP CleanTech Institute

A pastoral view spreads across Aio district in Yamaguchi City by the coast of the Seto Inland Sea. "Yamaguchi City Aio Mega-Solar (MS) Power Plant" with an output of 1.4MW, which West Holdings Corp constructed and completed in August 2013, is located in the plain that faces the sea (Fig. 1). It appears to be an average power generation facility with an output of around 2MW in Yamaguchi Prefecture, where a number of mega (large-scale) solar power plants have been constructed one after another. However, this plant features "Japan's first" something.

That "something" is the international standard certification that this plant obtained from a third party for the first time among mega-solar power plants in Japan. Starting in November 2013, TUV SUD Japan Ltd (Shinjuku-ku, Tokyo), the Japanese unit of German TUV SUD AG, engaged in verification and inspection, examined the plant and granted the third-party authorization Feb 14, 2014 (Fig. 2) in compliance with the International Electrotechnical Commission's (IEC) "IEC62446."

IEC62446 is an international standard that describes the minimum requirements for inspection, commissioning tests and system documentation that have to be fulfilled when the grid connected PV system is completed. Unlike a standard for each item such as a solar panel, this standard is characterized by evaluating the eligibility and reliability of the whole photovoltaic (PV) power generation system.

Executive Officer Kenji Araki of West Holdings cited two factors behind the authorization of the international standard certification by a third party. The company has constructed PV power generation systems for more than 30 years since its foundation.

"Compared with the projects for home use based on systems of up to several kilowatts, a mega-solar power plant's output is by far larger," he said, explaining one of the two factors. "Partly because the market has expanded rapidly, we have been accumulating technology while studying and moving forward at the same time. We wanted to confirm that our design and construction methods are not incorrect by having a third party evaluate them in compliance with international standards."

"We aim to differentiate itself by obtaining an international verification/test company's authorization that our mega-solar power plant design and construction are of high quality and reliable, partly to boost our bankability (loan qualification) in view of future development," Araki said, describing the other factor.

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Assessment through 'documentation screening,' 'plant inspection'

The reason why West Holdings chose "Yamaguchi City Aio MS Power Plant" as the site to acquire the first authorization in Japan largely stemmed from the fact that the power producer was affiliated with West Holdings, along with the optimum timing of completion. As the on-site inspection needs the operation to temporarily stop, it is said to be difficult to implement the inspection without the power producer's permission.

The reason why it requested Germany's TUV SUD to test its system for verification was "The firm had the richest experience in the world in terms of third-party authorization of IEC62446," West Holdings said. TUV SUD has reportedly inspected and certified hundreds of solar power generation systems across the world, primarily in Europe and China thus far. Yet it was TUV SUD's first inspection of a mega-solar power plant in Japan.

"We are trying to conduct a cross-areal inspection combining the solar power generation, electrical and structural technologies from the perspective of long-term reliability of a PV power plant, rather than specializing in solar panel, PV inverter and other product areas that are specific to solar power generation," said Kiyotake Sugita, senior manager, Product Safety Group, TUV SUD Japan.

IEC62446 primarily consists of "documentation screening" and "plant inspection." The documents required for the documentation screening total 14 major items including contract documents, design documents, calculation sheets, construction plans, major components' specifications/warranties and the O&M (operation and management) manual, according to the contents of the IEC62446 documentation.

The plant inspection includes (1) electric and functional tests on an array (a circuit connecting multiple solar panels) and PV inverters, (2) electric safety tests against earth faults (leaks) and electrification, (3) checks of the completed construction, etc (Fig. 3). According to the contents of the IEC62446 documentation, five are visual examination items and seven are electric test items (Fig. 4).

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Concern about solar panel wiring pointed out

To issue a certification, TUV SUD first examines the documentation, evaluates whether the system design is appropriate or not, and verifies if the construction is carried out in accordance with the design through visual and electric tests by actually visiting the power generation facility's site. After that, TUV SUD issues a certification if there are no problems.

In the case of "Yamaguchi City Aio MS Power Plant," West Holdings had prepared the required documents in November to December 2013 before the examination started. The plant inspection took place for about three days in January 2014, and the third-party certification was issued on February 14. In this case, the verification started after the plant's completion; however, in some cases, the assessment is carried out in parallel from the design phase (Fig. 5).

Should anything not meet the criteria after the plant inspection, TUV SUD would point it out in three grades of "critical," "major" and "minor" in accordance with the degree of seriousness. Compared with "critical," which is a serious failure that directly affects the qualification for the certification, "major" requires improvement, whereas "minor" only demands careful observation. The power producer would have to consider correcting or improving its system in accordance with each grade. In the case of "Yamaguchi City Aio MS Power Plant," there were no "critical" issues, but there were more than ten "minor" and "major" issues.

Among the indicated issues was an item concerning crossover cables that connect panels (Fig. 6). The cables were pushed above the panel at some points, and TUV SUD pointed out that the cables could shade the panels and affect their output depending on the hours of the day. Upon hearing this, West Holdings corrected the position of the cables so they would not shade the panels.

TUV SUD also suggested the wiring diagram and the emergency contact information should always be kept in the connecting and collecting boxes. This is for the purpose of enabling quick response if, for example, the PV system malfunctions. Partly because the deployment of a chief electric engineer in every site is mandated for mega-solar power plants in Japan, such considerations for third parties were barely given in some aspects. West Holdings improved all these issues pointed out by TUV SUD.

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Toughest task was to prepare 'required documents'

West Holdings' Araki confessed, "What troubled us the most in the effort to acquire the certification was the preparation of the required documents for screening rather than the plant inspection." Above all, it was particularly hard to prepare documents that indicate based on what standards and specifications the major components such as the solar panel and PV inverter were designed.

Yamaguchi City Aio MS Power Plant adopted Toshiba Mitsubishi-Electric Industrial Systems Corp's (TMEIC) PV inverter (Fig. 7). Some TMEIC products for export have acquired third-party certification of international standards, etc., but none for domestic use has acquired such certification. Accordingly, West Holdings requested TMEIC to issue a "self-declaration of conformity" on international standards and was authorized in documentation screening with this document.

At present, there is no standard for large PV inverters in Japan.

"People consider products of leading manufacturers to be good in Japan, but they cannot be trusted internationally without specifying what standard the products are based on in a written form," Araki said. "We wondered if this much was really necessary when we started approaching the third-party verification but can now understand it is necessary in the long run."

Behind the IEC62446's requirement for specifying the standards and specifications of major components lies the doubt that, should the existing specification and standard be changed in a proprietary way, a potential failure could exist even though the system were generating power as expected at the time of handover. The requirements of the documentation are aimed at making it easy to understand the design specifications even if the plant owner changes in the future.

West Holdings said it is planning to acquire IEC62446 certification at multiple mega-solar power plants and boost its employees' test skills from now. The company had constructed 87 mega-solar power plants as of the end of February 2014, and will continue to build more in the future.

"It would become difficult to maintain quality without specific rules if we aim for further expansion of the mega-solar power plant business," Araki said. "On the other hand, it would be a great advantage if we make the international standard a rule together with international certification/test companies."