Mounting solar panels on tracking systems instead of fixed-tilt racking increases the energy yield of a project. But more moving parts means different O&M considerations must be made for these advanced arrays. Here’s how to keep tracking systems running smoothly.
Monitoring single-axis trackers
Distributed and centralized trackers come with different requirements for O&M operators. Distributed trackers (also known as decentralized or independent) use one driving mechanism per row of panels. Centralized trackers move many rows of panels with a single, centralized motor. More moving parts may lend to more required maintenance.
Solar mounting solutions manufacturer RBI Solar entered the tracking market in 2017 with its distributed-row, single-axis tracker Sunflower. The tracker can use either AC or DC power controls and is built to also function in northern climates, a territory that’s been a difficult proposition for solar tracker projects in the past, said Eric Oetjen, senior project manager at RBI Solar.
The company assists its tracker customers and system operators with remote and on-site training, provides O&M guidelines and offers to send in-house technicians to replace failing components.
“We’ve had a long-standing relationship with our customers by providing our expertise throughout our projects’ cycles — design, engineering, manufacturing, installation, maintenance services — the last of which is often underrated,” Oetjen said. “Trackers do require maintenance and service to sustain production output that, in our opinion, can be overlooked.”
Control units on each tracker can give operators an idea of what maintenance is required immediately, like which rows are tracking or not, and in some cases, what upkeep will be needed shortly, remotely via system controls.
A major cause of tracker downtime in single-axis systems is the driveline. The tracker is put in motion by a driveline powered by a motor, which are the components of the tracker that do the most work, Oetjen said.
“So, just like your car, if your engine or brakes were to go out, your car wouldn’t serve its purpose,” he said. “That’s a more serious example, but these issues often show signs prior to occurring and can be prevented. That’s where a prevention plan and periodic check-in to the site can justify its own cost — in preventing these more critical issues.”
An important step in preventing tracker downtime is performing general maintenance where operators perform physical assessments to check for things like loose bolts and dangling wires.
“Most of your issues seem to occur near startup and end of life of the system,” Oetjen said. “You probably need some oversight within the first few months of the job and then periodic checkups from there. There’s always startup troubleshooting and it’s critical.”
He recommends carrying spare parts on or near a project site to limit downtime.
NEXTracker produces independent-row single-axis trackers that are commonly deployed on utility-scale projects that require a different approach to O&M practices than smaller solar systems. Projects can potentially be tens of megawatts in size in utility applications, with rows of solar panels installed across acres of land.
“They’re vast, so trying to [inspect] them by visual cues is just gone,” said Marty Rogers, VP of asset management and global support for NEXTracker. “You can’t see across 8,000 trackers and try to figure out what’s going on.”
NEXTracker has an in-house team monitoring minute-by-minute system analytics across its portfolio of solar projects. Those analysts correspond with technicians, providing recommendations for predictive maintenance on their solar systems.
The motors powering trackers are also used in more demanding applications outside of solar — sometimes requiring hundreds of rotations every second, compared to the slow tick of movement that’s needed for a single day of sun-tracking — so the motors themselves are rarely the cause for downtime, Rogers said.
He and Rue Phillips, CEO of solar technician dispatcher 365 Pronto, authored a white paper titled, “Tracking Your Solar Investment: Best Practices for Solar Tracker O&M.” Working at a utility-scale on tracking solar projects means O&M takes on different financials as well. NEXTracker’s focus is on predictive analytics to save project owners money and keep truck rolls minimal.
“Keeping everything productive and on target is critical, but also knowing that if a certain piece of the plant is not producing today, it’s not the end of the world and the cost variation needs to be balanced into the equation of the analytics,” he said.
Solar contractor LightWave Solar’s O&M technicians handle upkeep for about 2.5 MW of tracking solar arrays, composed of both single- and dual-axis trackers. LightWave’s techs have found that malfunctioning trackers are often fixed through system resets, but downtime can also be caused by loose drive shafts, dead sensors and rusted motors from moisture intrusion through broken gaskets.
“Keeping water out of them is the most important thing and it’s worth the money replacing those gaskets and those plastic pieces,” said Silas McRae, O&M technician with LightWave. “The manufacturers probably told you that those pieces would last two years, but they won’t when they’re baking in the sun.”
Too much exposure to the sun can make gaskets crack and break, letting water into vital driving components on trackers. Periodically replacing a gasket is marginally cheaper than ripping a rusted motor off a tracker, he said. If a tracker isn’t working, check the sensors and power supply; see if a breaker tripped or if the motor burned out.
Monitoring dual-axis trackers
Dual-axis trackers promise even more energy yield per-panel than their single-axis counterparts, by tracking the sun more accurately by moving on two axes. The systems are built atop posts or elevated supports to allow this movement while bearing the load of up to 100 modules.
“In a case where you’ve got 10 or 20 motors and systems to move a hundred panels, the likelihood of failure by one unit is much higher,” said Michael Fakukakis, CEO of Mechatron Solar.
Mechatron manufactures both single- and dual-axis trackers and trains solar EPCs to install these systems. Its new M18kD Gearless Dual-Axis Tracker is mounted on an extended post, leaving enough space for vehicles to pass underneath.
“I have seen other dual-axis trackers where a cleaning vehicle or truck has actually hit a panel,” Fakukakis said. “In terms of maintenance, that has to be observed.”
A less dramatic issue that affects tracker production is dust buildup on the optics that determine a tracker’s path throughout the day. If operators notice a discrepancy in projected and actual yield, there could be a problem mechanically but could also just be dust on the optics affecting the computer system.
Dual-axis trackers are elevated sometimes quite high, so reaching the panels requires a ladder or a longer pole for a cleaning tool.
Before starting any type of O&M on a tracking solar array, LightWave’s McRae recommended contacting the system’s manufacturer.
“Talk to the manufacturer about the problems they see a lot,” he said. “They can tell you what’s going to fail, what to look for and what to get ahead on. Whenever you let them know you’re interested in getting ahead of things, they know what to do.”