Fielded PV Module Reliabilty and Durability

To the extent that industry stakeholders can optimize fielded module performance by minimizing hard losses due to failures and soft losses due to degradation, they can enhance the solar value proposition for customers and strengthen the position of companies throughout the value chain.

Fielded module performance is essential not only to PV project profitability, but also to the solar industry’s long-term viability. In a report for the Solar America Board for Codes and Standards (see Resources), Mani Tamizh-Mani and Joseph Kuitche note: “Technology risk—the concern that a technology will underperform (durability) or become obsolete prematurely (reliability)—is one of the major barriers to PV diffusion and project financing.” In effect, more than 95% of fielded PV modules need to meet or exceed manufacturers’ product and power warranty terms to satisfy investors.

Given that PV system service life is measured in decades, the acceptable performance standard for PV modules is a high bar to meet. The good news is that the industry literature summarized by TamizhMani and Kuitche suggests that failure rates (reliability losses) and degradation rates (durability losses) are on the order of 0.005% to 0.1% per year and 0.5% to 0.8% per year, respectively. The bad news is that module manufacturers are constantly adapting module construction and design to drive down product costs and the levelized cost of energy, so past performance is no guarantee of future results.

For this article, I reached out to seven subject matter experts—technical due diligence specialists, independent engineers, system risk assessors, researchers, O&M service providers and so forth—to find out what industry stakeholders can do to optimize module reliability and durability in the field and to identify and remedy unavoidable performance problems. Not surprisingly, this is a continuous process that starts with technical due diligence during product procurement, relies heavily on system design and installation best practices, and extends through plant operations.

What steps can industry stakeholders take to mitigate the impacts of PV module failures that originate directly from production, such as product design or manufacturing deficiencies?

PV module reliability is a cycle. New reliability issues develop whenever we introduce new technologies and manufacturing techniques into the industry. In addition, we will see new fault modes develop over time as our PV fleet ages. Since the entire industry relies on innovations to drive the cost reductions that allow solar to thrive, these issues are inevitable.

This does not mean that the industry is experiencing or will experience a crisis of reliability. Rather, industry stakeholders need to be diligent about identifying and correcting module reliability issues early. If we properly communicate field data, module manufacturers can proactively remediate reliability issues. Potential-induced degradation (PID) is a good example of this feedback loop. PID is a failure mode that emerged in PV modules as a consequence of material changes combined with new installation techniques. Because the industry identified and classified this defect, most module manufacturers know how to design products that will not experience this fault mode in the future.

Rob Andrews, chief executive officer, Heliolytics

PV system owners and installers should take two fundamental measures to significantly mitigate the risk of premature PV module failures. First, PV system designers should take a holistic approach to product selection and use only properly vetted products, installation methods and design principles. While innovation is obviously critical to cost reduction, it comes with risk, so due diligence is vital. Equipment manufacturers are increasingly designing products to integrate with other BOS components, and certification protocols are adapting, so coordination among vendors is more important today than ever before. Secondly, given the underlying nature of certain types of PV module defects, a robust supplier-quality program is critical to ensuring long-term quality assurance. This involves not only an initial qualification of the supplier, but also regular witnessing of production and validation testing of randomly sampled finished product at a third-party lab. I’ve seen a lot of variation in test results between initial samples provided by equipment suppliers and random samples selected from inventory by buyers or their representatives.

Brian Grenko, chief executive officer, Amplify Energy

Stakeholders should engage a due diligence firm to vet the supplier before committing large projects to a particular module manufacturer or model number. This could be as simple as selecting a prevetted module, on the one hand, or as involved as conducting third-party tests at the factory, on the other.

Paul Hernday, senior performance engineer, Vivint Solar


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