Located in Lostant, Illinois, in LaSalle County, Solitude II is a 3-MW community solar project brought to life by Nexamp, a solar developer that works with communities, businesses, and municipalities to democratize clean energy via community solar.
For Nexamp, determining the best-fit racking solution for Solitude II started with understanding the dirt. The site has a 10% grade and flat topography, but it was critical to learn more about subsurface conditions, risk of frost heave, and weather challenges.
Project planning process: During the planning stage, tools such as a geotechnical report and pull test can help you better understand subsurface conditions. In addition to this, Nexamp has a long history of working hand in hand with Terrasmart to kickstart new solar opportunities. So, they utilized a proprietary engineering tool from Terrasmart that helps to determine site-specific wind and snow loads, ensuring an optimized design.
“Over 10,000 wind coefficient values are processed for a single project, in conjunction with an average of 63 different load combinations,” Terrasmart notes. “This allows our engineers to accurately calculate the peak load combinations for each unique site based on the project’s terrain, topography, and location. With real-time feedback, this automated tool helps to determine design elements, such as optimal foundation positions and torque tube size. Essential design elements are processed through this system and analyzed to determine the best configuration for a project’s needs.”
Outcome: The outcome of this analysis is that the Solitude II site would be a good fit for the TerraTrak 1P tracker, due to its wind-resilient design and ease of installation. In the end, both teams combined to install 5,616 modules and 2,016 ground screws on time and on budget. Here are some of the deciding factors that led to the TerraTrak 1P.
12 key questions to ask your tracker provider
- Has the tracker manufacturer conducted comprehensive multi-row static, dynamic, and aeroelastic wind tunnel tests within the past few years?
- Can the tracker manufacturer demonstrate that their tracker design adheres to the tolerances specified in their wind tunnel studies (e.g. array height, chord length, tracker length, GCR, natural frequency, damping, tracker length)?
- Can the tracker manufacturer provide evidence that their design accounts for all specified pressures and wind tunnel-specific load combinations beyond standard building code requirements?
- If dampers are required for the tracker manufacturer’s design, can they confirm that dampers were included in the aeroelastic wind tunnel tests and that the tested dampers accurately represent the final damper design?
- Has the full-scale tracker undergone thorough pluck testing?
- Has the tracker manufacturer performed component-level testing on each individual connection and system-level testing on full sub-assemblies and the entire tracker, and can they supply reports?
- Has the tracker manufacturer tested module-specific compatibility with their tracker design, and can they supply reports?
- Has the tracker manufacturer conducted full-scale lifecycle testing, and can they supply reports?
- Does the system exhibit slight twisting under extremely low loads (e.g. a person pushing on it), giving it a “loose” feel?
- Can the tracker be customized to meet project-specific requirements?
- Is the system capable of remote upgrades, enabling continuous improvements over time?
- Can you access sites remotely for easy troubleshooting?
TerraTrak 1P vs. 2P
Nexamp has already installed over 150 MWs of TerraTrak 2P – so why TerraTrak 1P? It is more than just optimizing for the site. Developers continue to face challenges such as rising costs, installation speed, reliability, ease of O&M, and hitting energy goals.
Since Terrasmart offers both 1P vs 2P tracker configurations, with both ground screw and driven pile foundations, its engineers were able to advise Nexamp on the best-fit solution for the Solitude II site. Keys here included reducing project costs through fewer parts and efficient installation.
- Fewer foundations. For this project, the two-string rows required seven foundations, while the one-string rows required only four foundations. This is because TerraTrak 1P’s zero-degree stow reduces static and dynamic wind loads, resulting in fewer foundations per MW. This, in turn, results in fewer materials needed and faster installation, saving time and money for Nexamp.
- Fewer components (30% less overall). TerraTrak 1P’s spherical bushings result in a 73% reduction in bushing assembly parts. The spherical shape allows for more tolerances and efficient torque tube alignment, making it easier to install. The tracker’s easy wire management design also helps to facilitate faster wire installation and save on skilled labor. Additionally, the efficient wire layout requires fewer materials and ensures long-term safety and reliability by routing the wiring along the torque tube.
These other TerraTrak 1P benefits factored in as well:
Aerodynamic stability. TerraTrak 1P can easily withstand the 105 mph wind load incurred at Lostant, Illinois. Terrasmart’s engineering team spent over 500 hours conducting wind tunnel testing in collaboration with RWDI to determine the optimal balance of wing length, stiffness, and damping. You can read more about that analysis in this white paper.
Terrasmart’s PeakYield software works in tandem with the TerraTrak 1P as well to protect assets in inclement weather, and minimize downtime. The Terrasmart system includes a weather station, network controller, and one row box per tracker row. The on-site weather stations come equipped with sensors that send data to the network controller, which commands sites to stow when wind and snow thresholds are crossed.
Meanwhile, advanced weather API predicts when bad weather is coming and stows sites, preventing damage. TerraTrak 1P comes with a snow shed feature to avoid a heavy snow build-up in winter when the tracker is in a stowed position.
The PeakYield backtracking algorithm determine how a row should be positioned based on angle of the sun to avoid shading the next row, while also considering the terrain of the row directly to its east and west. Machine learning and historical data build a projection of where the sun will be at different times of the day to optimize module positions to gain maximum energy yield.
Foundation versatility. The TerraTrak 1P can be paired with both driven pile or ground screw foundations. For the Solitude II site, the decision was made to pair the tracker with Terrasmart’s patented ground screws to eliminate the risk of refusal.
“Our trackers are designed with screw extensions that allow for up to 36 inches of vertical adjustability,” Terrasmart’s team notes. “This allows our ground screws to have varying heights based on the site’s topography—particularly on undulating terrain. This adaptability allows the field team to adjust in real time and speed up the installation process.”
— Solar Builder magazine
Leave a Reply
You must be logged in to post a comment.