One of the most critical stages of CPV module safety investigations is the construction review, which directly impacts and sets the tone for the entire investigation. Kenny Villegas from Solar Compliance describes the ins and outs of the construction review, and why it’s important to understand both end product and internal component requirements.
by Kenny Villegas, Solar Compliance LLC
February 2, 2010 – In the US, when a concentrating photovoltaic (CPV) manufacturer completes a design and assembly of a solar product, it must successfully certify its CPV module for safety according to the regulatory requirements set by the installation site. The Standard for Concentrator Photovoltaic Modules and Assemblies, UL 8703, is the foundation for the safety investigation of a CPV module.
One of the most critical stages of CPV module safety investigations is the construction review, because it sets the tone for the entire investigation by directly impacting every phase of the investigation. During the construction review, consideration is given to not only the applicable end product requirements, but also how the internal component requirements relate to the end product. Understanding the internal component/end product relationship is one of the key concepts that will maximize the chances of success, as well as avoiding any unwanted last minute surprises during the investigation.
A certification laboratory’s CPV module construction review can be summarized into the following stages: overall requirement compliance, component traceability, descriptive report, test program design, and construction review report.
Overall requirement compliance. The module’s (end product) construction is assessed for compliance to UL 8703. The application class of the module is applied as one of four classes (Class A, B, C, or X), each of which vary in the module’s degree of accessibility and level of voltage and energy. The module enclosure is defined into three types: electrical, mechanical, and fire enclosures. In some cases, the same enclosure may serve as one, two, or all three enclosure types. Each module enclosure type is evaluated for its degree of protection against safety hazards of the user and service personnel. All internal components (i.e., polymeric materials, optics, connectors, electrical wiring, over-current protection, light shield means, PV cell, control circuits, etc.) are evaluated for suitability to their respective applications.
Each internal component is subject to its corresponding component standard and consideration is given to compliance with its standard, and how the internal component has been evaluated previously for its use in the module end product. In particular, an internal component that is intended for use only under limited conditions (e.g., certain temperatures not exceeding specified limits, prescribed electrical ratings, suitability for outdoor use, etc.) shall be used only under those specific conditions within the module end product.
Overall compliance with the National Electric Code, including bonding, grounding, and minimum electrical spacing throughout the module, is also determined during the overall requirements compliance stage. Although this review covers the key construction requirement considerations for the module and internal components, there are other detailed requirements that must be addressed accordingly. Overall requirement compliance is considered to be the most involved and painstaking part of the construction review process since it is also the most critical.
Component traceability. A construction review will require all module parts and internal components be validated for component traceability. Component traceability refers to the ability to establish a paper trail for all components and materials in the build of a product in order to document where all components come from. Component traceability serves to insure the construction of the product does not change in a manner different from that of the originally tested construction. This will become the basis for the descriptive report, noted below.
Descriptive report. A descriptive report describes every part of the overall module that is considered to affect its safety properties. Each part is described by its applicable overall dimensions, thickness, material manufacturer and model number, ratings (electrical, mechanical, flammability, etc.), and specific conditions of use. The means by which each part is secured — and to what it is secured — are listed in the descriptive report. This report ensures the module’s construction does not change from what was originally tested, and serves as the basis for all subsequent manufacturing inspections of the module.
Test program design. The test program consists of a battery of tests that must be successfully executed for the module construction. Anticipated testing includes environmental chamber, outdoor, mechanical, electrical, and abnormal condition testing. The module test program depends on the conclusions reached in the overall requirement compliance section mentioned above. Testing is conducted on a module end product, receiver, and internal component level, as applicable. When internal component testing is required, it is done with the intent of determining the suitability of its application within the module construction. The design of the test program will greatly impact the duration and severity of the investigation.
Construction review report. A construction review report provides a comprehensive list of all noncompliant findings and concerns for both the end product and internal components of the module. This report includes the anticipated test program, as well as issues related to component traceability. The construction review report serves as midpoint of the investigation of the module in that it provides corrective actions and areas of risk for the construction of the module.
Solar manufacturers have placed an increasing premium on successfully navigating regulatory requirements in order to get their products to market. Such requirements have placed an increased burden on CPV manufacturers because of the relative immaturity of module safety standards. The construction review of a CPV module is a time consuming and detailed process, but with diligent and proactive preparation, it can accelerate navigation through a safety certification investigation for a CPV module.
Kenny Villegas received his bachelor’s degree in electrical engineering at UC San Diego, and is president of Solar Compliance, LLC, P.O. Box 1761, Chino Hills, CA 91709 USA; ph.: 909-851-4141; e-mail Kenny@solar-compliance.com; www.solar-compliance.com.