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Terrain-following solar tracker with
a pneumatic twist
By
Anne Fischer
June 1, 2023
Sunfolding’s new TopoTrack rows are reportedly 10 times shorter than
traditional trackers, and they can provide 20 degrees of variation
between trackers, thus improving slope tolerance between rows.
![](images/images_06_05_2023/Sunfolding_TopoTrack-600x442-1.jpg)
Sunfolding TopoTrack with posts in the ground,
actuators on posts, and purlins connected to actuators and solar
modules.
Image: Sunfolding
What sets Sunfolding’s terrain-following tracker apart from other
designs is pneumatics, a 360-year old technology that converts power
into movement.
Traditional trackers are mechanically more complex, which can make
installation and maintenance costly. Sunfolding developers discovered
that pneumatics offered a simpler approach with advantages in certain
solar designs. Some of those advantages include a reservoir (or
bladder) for air storage so they can continue operating through loss
of power.
They can also operate through loss of air and can run continuously
without the threat of overheating. Read more about solar and
pneumatics in Sunfolding’s white
paper. Without batteries or metal drive components, the pneumatic
technology is also able to withstand extremely low temperatures where
traditional trackers have had issues.
As noted by Chip McDaniel in Industrial
Equipment News, pneumatics offer the advantage of simplicity, low
cost and reliability, providing “a quick path to motion,” providing
significant force in a small space.
The patented AirDrive technology used by Sunfolding was invented by
Leila Madrone, company founder and chief technology officer. Madrone
is a roboticist, having received both her bachelors and masters in
electrical engineering and computer science from MIT, with a focus on
robotics and mechatronics. Early in her career she worked on
automation for the genomics industry and the commercialization of NASA
robotics hardware. Founded in 2012, Sunfolding was spun out of MIT’s
Otherlab. In 2016, the company won a $4.2 million ARPA award for its
“pneumatically-actuated PV tracking system.”
The AirDrive
system
At the heart of its tracking system is the AirDrive. Based on
Madrone’s invention, it consists of flexible bladders (shown above)
enclosed in a metal housing with a bladder to the east and one to the
west. When the bladders are pressurized to different levels, one side
expands and tilts the solar structure in the opposite direction.
AirDrive X actuators in the Sunfolding system reportedly weigh less
than 50 pounds. Wes Fuller, vice president of sales and strategic
partnerships, told pv
magazine USA that two people can lift them and attach them to
posts anchored in the ground. The automotive-grade pneumatic harnesses
connect with the supply air system—one for each 5 MW. These systems
come pre-assembled and can be dropped into place on site.
The pneumatic system has fewer critical points of failure than
traditional mechanical systems, dramatically reducing maintenance
costs, according to Sunfolding. The AirDrive X actuator uses advanced
polymers supplied by DuPont, helping them weather exposure to wind,
heat, rain and snow.
Sunfolding’s first product was the T29 tracker, which reportedly
changed the tracker landscape with its use of pneumatics, is installed
in 39 projects in 12 states including sites in California, Colorado,
Georgia, Pennsylvania and Texas.
The TopoTrack, introduced in September 2022, is designed for varied
terrain. Like the T29, it uses the AirDrive technology, but has
mechanically independent, scaled down tracker rows.
The company reports that TopoTrack’s rows are 10 times shorter than
traditional trackers, and that they can provide 20 degrees of
variation between trackers, thus improving slope tolerance between the
rows and allowing for articulation in terrain, including complete
directional change in terrain if needed.
![](images/images_06_05_2023/spacebetweenrows.png)
The design uses two posts, two actuators and two purlins. As a result
of the tracker’s flexibility and simplicity, Sunfolding says that the
tracker’s footprint across a project site can be increased when
tracker-to-tracker spacing is reduced. Fuller noted that TopoTrack can
reduce the need for grading by an estimated 97%, thus resulting in
further cost savings.
Headquartered in Alameda, Calif., Sunfolding’s posts, actuators and
purlins are made in the U.S. The company partners with auto industry
component suppliers to manufacture the AirDrive, and reports that 90%
of its bill of materials are sourced from a 250-mile radius of its
manufacturing facility in the Midwest, enabling short lead times and
reducing procurement risks.
TopoTrack was recently deployed on a site with strict environmental
protections in place. This site featured complex terrain in a high
snow load location. TopoTrack technology reportedly enabled the
customer to perform zero grading on this site, greatly minimizing the
cost of handling complex terrain and permitting risk.
Green Play Ammonia™, Yielder® NFuel Energy.
Spokane, Washington. 99212
www.exactrix.com
509 995 1879 cell, Pacific.
exactrix@exactrix.com
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