Nextpower deployed its automated hail stow system at DESRI-operated PV sites in the US Midwest, enabling trackers to move into protective positions ahead of storm arrival
The system combined third-party weather forecasts with automated controls to trigger high-tilt stow positions of around 60°
The case study reports no recorded hail damage, with monitoring used to confirm that stow actions were carried out as planned
Hail risk is increasingly becoming a design and operational consideration for utility-scale solar assets in several parts of the United States. A case study from leading solar tracker manufacturer Nextpower (previously Nextracker) details the deployment of its NX Horizon trackers integrated with the Hail Pro automated stow functionality. Projects operated by US-based renewable energy developer and owner DESRI (D. E. Shaw Renewable Investments) illustrate how automated tracker responses are being used as a mitigation strategy. DESRI has deployed NX Horizon trackers across more than 6 GW of its solar portfolio, with over 2.4 GW equipped with automated hail stow functionality.
The ideal locations for solar are increasingly becoming scarce. Thus, expanding solar deployment into regions with severe weather conditions is gaining attention. Hail is one of the concerns of cause. The case study highlights that projects in the US Midwest encountered severe hailstorms in 2024 and 2025. The reported hail sizes exceeded the typical module certification threshold of 25 mm, with stones in some areas reaching approximately 40-50 mm. Such conditions increase the risk to solar assets, particularly the risk of glass breakage. To mitigate this, the case study describes the implementation of automated high-angle stow functionality.
In this instance, the mitigation approach relied on integrating meteorological alerts with tracker controls. Nextpower used third-party meteorological forecasts from DTN, a US-based weather intelligence and data analytics provider, to trigger predefined protection sequences. Based on site-specific parameters configured in NX Navigator, the system automatically initiated the stow response. Once triggered, the trackers rotated to a high-tilt configuration, typically around 60° (with a capability up to 75°), prior to storm arrival. The control system is supported by redundant communication pathways to help ensure that the stow command is executed when required. Real-time stow monitoring and automated post-event reporting are integrated into the platform, allowing operators to review system performance after each event.
The objective of this strategy is straightforward: reduce the probability that hail strikes the glass surface at perpendicular impact angles and limit the energy transferred to the module laminate. Higher stow angles can also help smaller stones slide off the surface rather than accumulate.
According to the case study, the affected site reported no hail-related damage following the 2024 and 2025 storm events. Automated stowing also reduces dependence on manual intervention, which can be constrained during fast-moving convective storm conditions.