This report, authored by Gerald T. Robinson of Lawrence Berkeley National Laboratory (LBNL) and prepared for the U.S. DOE Solar Energy Technologies Office (SETO), argues that the solar PV industry’s fastener and joint failures are not primarily a product-quality problem — they are a standards problem. The industry lacks the engineering consensus standards that allow other industries to design, procure, assemble, inspect, and arbitrate structural connections with predictable outcomes. Until those standards exist, the failures will continue regardless of what individual manufacturers do.
Jon Ness, PE of Matrix Engineering Consultants, contributed to this research. The report draws on three independent evidence streams — expert interviews, structured failure case analysis, and field surveys of racking products at RE+ trade shows from 2022 through 2024 — that consistently point to the same conclusion: solar PV mounting structures are being designed and built without an adequate rational engineering foundation, and the consequences are showing up in field failures at wind speeds well below design thresholds.
What the report covers:
- Why solar structures need their own standards — Engineers currently apply building codes designed for high-mass, static structures to solar PV arrays, which are lightweight, flexible, and dynamically loaded systems with fundamentally different behavior. Solar racking exhibits low natural frequencies, large deflections, and aeroelastic phenomena such as vortex shedding and self-excited vibration. These characteristics amplify the demands placed on fastened joints in ways that static building standards do not account for. An LBNL study of 83 fastener failure cases found that only 22% were clearly linked to severe wind events such as hurricanes or tornadoes — meaning the majority of failures occurred at or below ASCE design wind speeds.
- Six core standards gaps — The report identifies six specific gaps where the absence of rational design methodology and consensus standards is directly contributing to failures: understanding of critical structural connections under dynamic and cyclical loading; lack of design specifications; absence of strength standards paired with relevant testing; inadequate coverage of alternative fasteners (clips, clamps, cam-based hardware); self-evident code gaps such as nonstructural hardware appearing in structural roles; and electrical bonding through critical structural joints. The first three gaps are deeply interdependent — testing must capture systems-level dynamics before it can support rational design, and rational design must exist before standards committees can codify it.
- Evidence from expert interviews and failure cases — Seven industry experts were interviewed, drawn from rack manufacturers, standards developing organizations, industry associations, and nationally recognized testing laboratories. All seven identified the first four gaps independently. Separately, structured interviews with 28 industry respondents covering 84 documented failure cases found that failures occurred across all U.S. geographies and were reported at frequencies that respondents described as “too many to count” or affecting “all systems.” The failure breakdown showed top-down clamps (33%) and through-bolted fasteners (30%) as the most common failure types — both categories that fall outside RCSC structural joint standards and should be treated as alternative connections requiring independent engineering justification.
- The CAPEX problem — Without a minimum practice floor established by mature standards, cost dominates design decisions. The report documents how CAPEX-driven value engineering has produced lightweight structures with minimized structural sections that fail under moderate wind loading. Periodic re-tightening of solar PV joints has become routine industry practice — something not accepted in any other structural industry — and the associated OPEX costs are driving substantially higher lifecycle costs (LCOE) than asset owners anticipated at project finance.
- Self-evident hardware misapplications — Field surveys at RE+ from 2022 through 2024 found no meaningful year-over-year improvement in practice. Examples documented include hose clamps used as torque tube connections, stamped license plate clip-on nuts used in structural roles, and a variety of alternative fastener hardware that would have insufficient strength capacity to resist even mild wind loading. The Fastener Quality Act (FQA), which requires fasteners to be marked with manufacturer identification and a reference to a consensus standard, is routinely not followed in solar PV — meaning there is no traceability or enforcement mechanism when failures occur.
- Stainless fastener marking gaps — A significant portion of stainless steel fasteners in solar PV installations are marked only with material designations such as “304,” “316,” or “S30400” — none of which reference a fastener consensus standard, define yield or tensile strength, or comply with the FQA. Without a consensus standard reference and manufacturer mark, counterfeiting cannot be enforced, characteristics cannot be verified without expensive lab testing, and fasteners cannot be properly arbitrated in a failure investigation.
- Current standards progress and remaining gaps — Three active efforts are addressing these gaps: the ASCE Solar Structures Committee Manual of Practice, which introduces rational design methodology requirements including controlled pretension for critical connections; updated UL 2703 revisions approved in May 2025, which add critical property disclosure requirements, separating load and shear load calculations, and provisions for alternative fastener testing; and a pending IEC TC 82 working group focused on module-to-mounting-structure interfaces. The report maps each gap against each standard’s effort, concluding that some gaps are seeing substantial improvement while others — particularly systems-level dynamic loading characterization and product-level testing standards — remain largely unaddressed and require dedicated research investment to resolve.
- First-generation systems-level testing — A DOE-SETO-funded test rack has been developed at LBNL to replicate how PV system components interact under realistic wind loading. Test cycles were developed using CFD modeling and FEA to simulate deflection and frequency profiles representative of moderate wind conditions. This represents the starting point for the kind of research-grade dynamic testing the industry needs, and the report outlines a roadmap from current research-level testing through rational design development to eventual product-level test standards available to independent commercial test labs.
The report is part of a larger Guidance Document on Critical Structural Joints in solar PV racking systems, comprising ten chapters covering topics from bolted joint loosening fundamentals to electrical bonding, clearance hole specifications, and failure case analysis. Engineers, asset owners, investors, and standards professionals working in the solar PV industry will find this chapter essential context for understanding why the structural reliability problem is systemic rather than incidental — and what a path to resolution requires.
Jon Ness
PE, PMP, NPDPJon is a Managing Governor and Principal Engineer at Matrix Engineering and has over 34 years of experience in business and engineering team leadership. His career has been focused on the development of off-highway equipment and powertrains. He has unique technical expertise in designing and validating dynamically loaded bolted joints. In his consulting role, Jon has led numerous joint failure investigations, including re-design efforts to mitigate risks to the system owners. He actively participates in ongoing research projects and has taught many classes related to Failure Modes and Effects Analysis and Bolted Joint Design and Validation. He received a Bachelor of Science in mechanical engineering from South Dakota State University. A licensed engineer in Minnesota, Jon is an active member of the UL2703 Standards Technical Panel, a contributor to the ASCE Manual of Practice for Solar PV Structures, and a Certified Fastener Specialist through the Fastener Training Institute.