Nextpower developed a steel frame that shows lower module deflection than a standard aluminum frame under a 2,000 Pa downforce test
The NX CoreFrame uses Zn-Al-Mg coating and has been tested under C5 corrosion conditions
Steel framing can also diversify the frame supply chain and contribute to domestic content requirements in markets such as the US
The pursuit of power over the last few years has led to bigger modules and smaller-profile frames, which help reduce balance of system (BOS) costs. These changes, however, took a toll on module rigidity, with glass breakage becoming the most common issue among other mechanical failures.
A pioneer in modern smart solar tracking, Nextpower developed a module frame based on high-strength steel to address some of the common module reliability issues faced by PV project stakeholders. In a technical white paper, Nextpower outlined the challenges with the mainstream aluminum frames and how steel can be a better alternative, with its advantages of high strength, supply resilience, and sustainability.
Kiwa PVEL reliability scorecard highlights that about 61% of module failures under hail impact occurred on modules with 2 mm glass on both sides, and the breakage rate doubled when frame thickness fell below 35 mm (see: PV Module Failures Increase Under Mechanical And Environmental Stress Tests).
Nextpower’s steel frame offers superior strength compared with the mainstream aluminum-based frame. Marketed as NX CoreFrame, it reduces module deflection and, in turn, the stress induced on the glass, improving resistance to wind and snow loads. With steel, the module itself gains additional stiffness instead of relying on the module substructure or tracker reinforcement. These advantages are demonstrated through mechanical testing. For the tests, Nextpower used 30 mm and 35 mm of its NX CoreFrame on dual-glass laminates, and also tested standard aluminum-framed modules for comparison. All the modules were mounted on Nextpower’s 400 mm NX Horizon tracker. A downforce test at 2,000 Pa showed deflection of 100 mm for aluminum-frame modules, while only 35 mm with Nextpower’s steel frame.
Steel, however, has a disadvantage of corroding, which is mitigated using coatings, particularly zinc-aluminum-magnesium (Zn-Al-Mg), which Nextpower already implemented in its tracker systems. These are roll-formed steel frames, and the cut edges are coating-free regions that can act as potential corrosion ingress points. However, the nature of Zn-Al-Mg coating is that of a self-healing one, in which the coating near the exposed regions corrodes, and cations migrate to the exposed steel regions to form a corrosion barrier by itself. Nextpower’s frames were also tested for corrosion under the environment classification of C5 (severe coastal and industrial conditions) and passed IEC 61701 standards. The product comes with a 12-year structural and corrosion warranty, which is less than half of the product and performance warranties offered by current mainstream modules.
Another advantage of a steel frame is that its supply chain is not concentrated in one country; rather, it is distributed and can also help meet any region's domestic content requirements for its final PV module. According to Nextpower, sourcing steel within the US qualifies for a 6% domestic content bonus. Additionally, CO2 emissions associated with steel are about 90% lower for US-made steel than for imported aluminum manufactured via the electric-arc furnace process, as validated by a third-party agency.
