Wind Pressure Testing Vital for Solar Trackers

Facing the challenges of climate conditions is becoming the new normal for solar developers and investors, requiring new measures to manage risks and ensure returns.
Understanding the importance of wind pressure testing and how different types of wind affect tracker design and production can help generators ensure suitable single-axis tracker technology for their plants and regions.
Various factors affect how wind impacts solar trackers on each plant, from local climate and terrain to the influence of nearby structures or objects. Since no two photovoltaic plants are identical, each site needs custom design, adding complexity to these projects.
Failure to properly consider wind profiles in tracker design can lead asset owners to face a range of issues, including remediation costs, downtime, lower power output, and ultimately failing to meet financial goals.
Examining the technical nuances involved in designing for different types of wind and understanding how appropriate tracker testing affects design features such as installation angles and damping can drive stable aerodynamic performance for long-term effectiveness.
Types of Wind Effects
Changes in wind speed, turbulence, and direction can have unexpected effects on solar trackers and their surroundings. Understanding wind effects helps developers and EPCs address uncertainties and optimize returns.
Wind effects can be categorized into three main types: static, dynamic, and aerodynamic elasticity.
Static winds exert stable and constant pressure on trackers, causing structural deflection or bending, thereby affecting tracker performance and accuracy.
Dynamic winds are unpredictable, fluctuating in speed and direction, which can result in significant vibrations and pressure on trackers, reducing tracking accuracy and causing misalignment, component wear, and tearing. Advanced aerodynamic models considering turbulence, gusts, and other variations are needed to interpret these dynamic wind loads.
Aerodynamic elasticity occurs when trackers interact with surrounding airflow, leading to effects like resonance, torsional flutter, and torsional oscillation, all of which can cause uncontrolled vibration or oscillation, leading to misalignment, reduced tracking accuracy, or component failure. Tracker designs must focus on countering these effects to achieve aerodynamic stability.
According to RWDI, a Canadian engineering company specializing in wind pressure testing, tracker designs must focus on countering these effects to achieve aerodynamic stability. Every component in the tracker structure must be assessed to ensure optimized resistance to wind loads. Many potential failures need to be considered, including:
Resonance, occurring when gust frequencies match the structure's natural frequencies, potentially leading to catastrophic failure.
Torsional flutter, a self-excited aeroelastic instability, causing significant oscillations in array twisting motion, leading to tracker failure.
Torsional oscillation, uniquely involving vertical motion. Trackers fail when high wind speeds exceed the structure's resistance.
Understanding wind effects is crucial not only for equipment design but also knowing how to mitigate gusts can optimize tracker performance. For example, knowing abnormal wind patterns at specific parts of a PV site means using wind barriers to reduce wind speed and turbulence, enhancing tracker stability and accuracy. Complex sensors can be deployed to detect wind changes and adjust tracker positions to optimize power output. Additionally, reducing tracker profile, increasing its rigidity, or designing with materials resistant to wind loads and aerodynamic elasticity effects can be employed.
Breaking the Constraints of Tracker Design through Testing
Wind tunnel testing plays a crucial role in the development of solar trackers. Small-scale models are used to assess how new trackers handle various wind conditions, revealing design limitations early in development. After adjustments to the design, full-scale, cost-effective trackers can be produced, minimizing risks.
Simulating adverse terrain is a key component of wind tunnel testing. This type of simulation replicates real-world obstacles that may influence winds, such as trees and buildings, or even other tracker arrays on-site.
Adverse behavior simulation includes different altitude profiles, adjustable surface roughness, movable barriers, and various types of wind activity, including phenomena like hurricanes and tornadoes.
Achieving Downwind with Tilt Angles
When designing wind-resistant solar trackers, careful consideration must be given to tilt angles and related static and dynamic wind loads. A useful mitigation strategy is damping, which dissipates or controls vibrational energy or oscillations within the system.
Dampers are a key part of formulating the optimal tilt strategy, especially for 0° tilt solar trackers susceptible to torsional forces, leading to twisting and rotational motion along torque tube axes. Testing different tilt angles in the wind tunnel during the development of wind-resistant 1P trackers helps formulate the optimal tilt strategy. Tests show that lower tilt angles provide less static loads on the structure and less overall force on the system. A 0° tilt angle offers the lowest coefficient values, as the lateral load approaches zero.
Higher tilt angles impose additional pressure on the structure, requiring more groundwork or increasing foundation and torque tube sizes to withstand additional lateral forces. Conversely, adopting a 0° tilt strategy with an appropriate level of overdamping and stiffness to resist deformation requires less groundwork.
The ideal design for 0° tilt balances stiffness, damping, and weight to control tracker costs, protect assets, and maintain efficiency. While storing at high tilt angles may be safe, it may increase wind loads on foundations and other structural parts, requiring a sturdier system or overdamped design to mitigate dynamic fluctuations leading to aerodynamic instability.
Addressing Challenges with Damping
Proper damping—suppressing vibration and oscillation—is crucial for ensuring stability in solar tracking systems. Determining the appropriate amount and type of damping depends on various factors such as the design's tilt angle, beam length, and structural quality.
Similarly, testing is crucial here. Under-damped systems become unstable, necessitating expensive mitigation measures such as auxiliary dampers to address torsional forces that could lead to tracker damage or failure.
For the 1P solar trackers discussed above, featuring a 0° tilt strategy and 30-40-meter-long beams, we found that installing two to four dampers per row is sufficient to build an adequately damped structure.
Since quality control is crucial for determining the right configuration, it's essential to select experienced tracker solution providers with expertise in dampers, capable of meeting project specifications, budget, and timelines.


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