Tracker Design for Series 4 Modules in High Wind Conditions – Part 2
April 26, 2018
Last week I discussed the first primary consideration when designing a Series 4 tracking solution for high wind conditions – the ability of the system to protect itself in response to real-time environmental conditions. This week, we’ll discuss the second design consideration – optimal module configuration for structural reliability.
Optimal Module Configuration
Optimal module configuration also factors into Series 4 tracker design. To address this, it’s important to first address the general form factor of Series 4. The module dimensions and landscape mounting requirements demand a non-standard mounting configuration compared to typical 72-cell modules. Based on dimensions, the one-high portrait 72-cell configuration of most tracker systems translates to two configuration options for Series 4: a three-high or a four-high landscape configuration.
In general, the goal with tracker design is to maximize generation capacity within the confines of structural limitations. So, theoretically, a four-high configuration for a given row would have one-and-a-third times the capacity of a three-high configuration, and therefore be a more optimal design. However, in wind speeds greater than 130 mph we see deflection in typical four-high rails that exceeds First Solar’s deflection limits established to ensure the modules avoid damage from high wind. Tracker companies have addressed these high wind conditions by configuring the system to three-high. A shorter rail, when exposed to the same environmental loads as a longer rail, experiences less deflection and is better able to meet First Solar’s design requirements.
Additional Benefits of a Three-High Configuration
When considering the transition from a four-high to a three-high configuration, there are additional benefits that come into play. The loads on the torque tube are proportional to the surface area of the modules, so in moving from a four-high to a three-high configuration, load per foot on the torque tube is reduced by one-third. The smaller surface area also reduces loading due to snow – which is beneficial particularly in the Northeast where you see high wind and snow loads coinciding.
A three-high configuration also has a shorter leading edge than a four-high. When combined with intelligent response to environmental conditions, the shorter leading edge can help protect the system from snow build-up in the Northeast or flooding in the Southeast. A longer leading edge, if required for a four-high configuration, would also require the system to be raised in respect to the ground and could potentially require an upsizing of posts, both of which increase the overall project costs.
And one last bonus benefit of a three-high design is that it leads to optimal stringing of 15 modules at 1500VDC. This multiple works well for optimizing site layouts and reducing field installation time.
With an appropriately designed system that combines intelligent real-time response with an optimized module configuration, your Series 4 tracker project will be able to withstand even Category 4 winds and reap the benefits of higher yield with CdTe technology. Happy tracking!
Emily Paris is a senior associate product manager at SunLink where she helps define SunLink’s next-generation of products and services.