Engineering Insight: Inside Solar FlexRack’s second generation tracker

Amid the solar market’s mad dash to offer tracker solutions, Solar FlexRack has been taking its time. The company launched its first offering, the TDP Turnkey Tracker in early 2016, with the focus on a total solution. In contrast to competitors that were providing stand-alone solutions, Solar FlexRack offered a full services package coupled with its tracker to ensure project execution. The TDP carried a low total project cost by including full design, geotechnical analysis, installation, commissioning and support services bundled in one contract.

By the end of this year Solar FlexRack will have 2 GW installed and has built a reputation of taking care of its clients with a robust service offering. Solar FlexRack handles the installation on nearly 40 percent of the trackers it sells. All 50 installations of the first product are standing up and running, causing none of the wild tracker system failures that you may have seen captured on video around the world. On the contrary, Solar FlexRack has often been invited to those sites to fix prior mistakes.

“We’ve seen a lot of things out there,” says Steve Daniel, EVP of Sales and Marketing at Solar FlexRack says. “We’ve seen other trackers completely twisted in the wind and lying on the ground. We’ve seen a lot go wrong with bearing assemblies — a crucial component that attaches the posts to the torque tube. We’ve seen people undersize the torque tube, which leads to the torque tubes twisting when there is too much wind. We’ve seen modules completely blown off the tracker in wind events due to under design.”

The diligent and methodical philosophy continues with Solar FlexRack ready to debut its first self-powered tracker, TDP 2.0. Like a basketball player that makes a living off the fundamentals more so than risking highlight plays, the TDP 2.0 isn’t a flashy new concept, but one that rounds out the company’s offering for developers and EPCs in the utility-scale space in need of a reliable, full service solution. After building one as crooked as they could, to literally try and break it, and seeing it hold up, the fastidious engineering team felt confident in the offering.

“We’ve invested a lot in the engineering side and made a conscious decision to have that service offering. We’re extremely cautious on our tracker design and feel our approach has resulted in a solid offering which will last the required life cycle of the project specifications,” Daniel says.

What’s new about 2.0?

Solar tracking exists in order to harvest as much power from the sun on a site as possible, which means you shouldn’t lose sight of module density when selecting a tracking solution. This is top among the advantages of the Solar FlexRack TDP 2.0, which is only forfeiting 18 in. of space in a span of 90 modules for the module over the motor.

The first version of the TDP maxed out with 60 modules and a rotation of 90 degrees. The TDP 2.0 is a 90-module table with a 110 degree rotation. The TDP 2.0 achieves a balanced system similar to NEXTracker by having the slew drive higher than the axis of the actual torque tube.

The tracker control unit (TCU) is a proven solution that has been deployed in over 1 GW of its unit around the world. The self-powering starts with a small, 30-watt panel mounted above the motor to provide power to a lithium-iron battery.

Efficiencies in design cascade from there.

“Most trackers you run AC power coming into the field and don’t usually use parasitic power off the modules, so you run AC wire to every drive post in the array,” Daniel says. “With self-powered, you eliminate all of that and the switch gear you need to have come into the field. This decreases installation and BOS costs significantly. It does increase O&M costs a bit, but there’s more efficiency in installation and much less wiring.

Before the TCU on the TDP 2.0, you’d have one tracker control unit that serviced 4 tables, which meant you’d be running DC wiring from one TCU to the motors on the other three tables. Added together, that’s a decent chunk of DC wiring. The TDP 2.0 has one TCU per table mounted directly onto the torque tube under panels and next to the motor. This limits DC wiring to a 3 -ft whip cord from the TCU to the motor.

The next tweak was bumping the rotation up to +/- 55 degrees, which analysis shows is the optimal angle for capturing that morning and late day production and generating as much revenue as possible. Producing more power late in the afternoon is becoming more important, especially in California with the changing rate structure.

“We tried 60 degrees but realized it was such a sharp angle, we weren’t going to get much more energy yield out of that design. The 55 degrees is the most efficient,” Daniel says.

Still a market for version 1?

While the expectation is the TDP 2.0 product will be in demand, there is still a market for the original 60-panel version. The TDP 2.0 is more of a utility-scale space solution, so the original TDP might still be the better route for projects in the 1- to 5-MW range where the economics of a 90-panel array might not pencil out.

“For some, 60 works well,” Daniel explains. “Lot of farmers in Central Valley understand actuator motors and are comfortable with that design. It’s a nice solution in the small C&I DG space, and we don’t want to mess with that. We’re providing choices.”

“With a 1,000 volt system, the table sizes tend to be 18, 19, 20 and the math doesn’t work as well,” Daniel says. “The closer you get to 90 panels, the more efficient the design is because you’re amortizing the cost of the controller and motor over more panels. But if you have say 20 modules in a string, you can put four of those strings on the TDP 2.0, and only get to 80 modules. So you don’t get the efficiency of getting close to 90.”

The move to 1,500 volt business makes this step up to 2.0 imperative because the string sizes will be 27, 28, 29 or 30 usually, which translates to three strings of 81, 84, 87 or 90.

“I don’t think we lost deals by not having this, but it certainly opens up more of the market for us,” says Steve Daniel, EVP of Sales and Marketing for Solar FlexRack. “People are moving toward self-powered trackers in certain areas, mostly where the sun is reliable and it doesn’t get too cold.”

— Solar Builder magazine

[source: https://solarbuildermag.com/featured/solar-flexrack-tracker/]