Reducing extreme weather damage risk for solar trackers

As the global temperature continues to rise, so does the severity of weather events occurring annually. Hail, high winds, snow and floods are all risks to ground-mounted solar projects, and companies producing solar trackers are actively addressing how these kinetic racking systems can avoid damage from adverse weather conditions.

“We can’t move [our foundations]. We are where we are, so we’re experiencing the conditions that are at that site,” said Aaron Gabelnick, chief strategy and technology officer for Array Technologies. “We have to be actively pursuing ways in which to mitigate the potential damage that can occur from severe weather.”

Automated weather response and atmospheric sensors may come standard on solar tracker operating systems, but advances in other solar products — like solar panels growing in size — make predicting how arrays react to weather events a trickier exercise. Luckily, the solution to preventing weather damage on solar tracking systems is mostly about finding the right angles.

De-risking severe weather

Weather damage mitigation starts with understanding the environment in which a solar project will be built. Northern climates will likely have annual snowfall, Southeast states may experience hurricanes and there’s not a single site immune from wind issues. These factors determine a solar tracker project’s design, down to the thickness of the steel used for racking and foundational posts.

“[Solar trackers] are novel structures to major infrastructure,” said Colin Caufield, VP of sales at Soltec, a single-axis solar tracker manufacturer. “Having a moving post and beam structure is not something that was really thought of when these design codes were made however many decades or even centuries ago in some cases.”

Wind is the most common weather exposure for trackers. Strategies for curbing damage from oncoming wind on single-axis trackers have shifted from stowing solar module rows at a flat, 0° angle to pointing them at an angle closer to 45°. Studies and field testing have shown that modules stowed flat on these trackers were at risk of torsional damage. Tilting the modules instead of stowing flat so the leading edge is lower than the farther edge can reduce that oncoming pressure, causing wind to fly above or below the module with less movement in the tracker itself. Dual-axis trackers can still stow flat to mitigate wind pressure, because they are typically installed atop poles, which have lower wind resistance than single axis foundations.

Solar trackers manufactured for projects in snowy regions should account for the weight of snow resting on solar modules. The common solution for dealing with snow is tilting panel rows down to one side to shed snow accumulation.

However, snow shed isn’t the only risk snow presents to trackers. On sites with windy conditions, snow drift can pile beneath a solar tracker row and affect its tilt clearance. And with a freeze-thaw cycle, piled snow can harden enough to be detrimental to tracker arrays. Overcurrent protections can keep trackers from crashing into obstructions, functioning like a garage door that won’t close if it detects something underneath it.

“If a tracker is tracking into that hard surface and it doesn’t have some type of overcurrent protection, motors can be damaged, modules can be damaged, because the tracker just keeps tracking down into an obstruction,” Caufield said. “It’s much like having a truck parked underneath a tracker.”

Additionally, in northern geographies, solar trackers should have tolerances built in for physical expansion and contraction in warm and frigid temperatures. Low temperatures can affect system movement and how electronic components perform.

Heavy rainfall isn’t an issue for a solar tracker until it begins to pool beneath the system. Arrays can be outfitted with flood sensors to direct trackers to stow panel rows above the water surface if flooding levels climb too high. In flood-prone areas, trackers can be produced with elevated post heights to anticipate rising water levels.

“Modules can be submerged, according to manufacturers, but by and large, we’re asked to design our system such that the clearance is above floodplain,” Caufield said. “So, the leading-edge height is still above floodplain even at a wind-stow tilt.”

Then there’s the danger posed by hail. In the last few years alone, hail has been the cause of hundreds of millions of dollars in damage to solar projects. These balls of ice hurtling from the sky are the greatest risk to the panes of glass encasing solar cells.

“The relatively recent issues around hail that have been catastrophic for some projects out there have put pressure on all manufacturers to come up with mitigation strategies,” Caufield said.

To anticipate hailstorms, it’s advised that operators use atmospheric sensors and subscribe to weather services to predict weather conditions. The common method to reduce damage to modules from falling hail is to create as steep an angle as possible so the pellets just graze the surface of the solar panel. Pointing the front of a module perpendicular to the fall path of hail makes it more susceptible to damage.

Soltec has experimented with directing modules so their backsides are exposed to hail, but that requires more structural reinforcement with additional components like dampers, since solar trackers are typically built to take wind head on. Array Technologies developed a proprietary Hail Alert Response system to help its solar trackers preempt and reduce damage from hailstorms.

“All this stuff has been designed to satisfy insurance agents and financial institutions to protect the asset,” Caufield said. “But I venture to say that it’s impossible to achieve 0% risk on any of these jobs, especially the ones that are in the ‘Hailstorm Alley’ of West Texas to Mexico and going north into the Colorado Plains, where it’s so common.”

All weather events that could be detrimental to solar systems are accompanied by high winds too, so it often comes down to operators to determine what to prioritize protecting against. Each weather event poses a specific risk to trackers.

“When it’s hailing, if there is wind, you prioritize wind against hail,” said Hadi Hajimiri, CEO of Stracker Solar, a dual-axis tracker manufacturer. “With hail, you may have damaged solar panels, but with wind, you may have entire system damage and potentially harm for your surroundings, because you don’t want the tracker to be bending and falling off.”

Although extreme weather is on the rise, technology can ensure trackers keep projects online and spared from damage. Using the latest operating systems driven by safety algorithms and atmospheric sensors can better predict and defend projects against the elements. These are automated systems controlling miles of tracker rows following the sun throughout the day, capable of reacting to the slightest change in wind speeds.

Companies making solar trackers plan to keep preparing these moving PV projects for a changing climate and hope to one day be the solution for solving it.

“It’s incredibly important that we continually advance our capabilities in severe weather control, because your insurance premiums go up, the likelihood of damage increases, the levelized cost of energy goes up,” Array’s Gabelnick said. “Everything goes up, and solar becomes less competitive against some of the other renewable energies that are out there.”