As the Earth’s temperature continues to rise, so does the severity of weather conditions occurs annually. Hail, high winds, snow and flooding are all risks to ground-mounted solar projects, and solar tracker companies are actively investigating how these kinetic racking systems can prevent damage from adverse weather conditions.
‘We can’t move [our foundations]. We are where we are, so we experience the conditions in that location,” said Aaron Gabelnick, Chief Strategy and Technology Officer of Array Technologies. “We must actively look for ways to limit the potential damage that can occur as a result of severe weather.”
Automated weather responses and atmospheric sensors may be standard on solar tracker operating systems, but advances in other solar products – such as solar panels that are increasing in size – make predicting how arrays respond to weather conditions a trickier exercise. Fortunately, the solution to preventing weather damage on solar tracking systems lies mainly in finding the right angles.
Reduce the risk of severe weather
Mitigating weather damage starts with understanding the environment in which a solar project will be built. Northern climates are likely to experience annual snowfall, southeastern states may experience hurricanes, and no place is immune to wind problems. These factors determine the design of a solar tracker project, down to the thickness of the steel used for the scaffolding and foundation piles.
Credit: Soltec
“[Solar trackers] are new structures for large infrastructure,” says Colin Caufield, VP of Sales at Soltec, a manufacturer of single-axis solar trackers. “Having a moving post and beam structure is not something that was really considered when these design codes were created, however many decades or even centuries ago in some cases.”
Wind is the most common weather exposure for trackers. Strategies for mitigating damage from oncoming winds on single-axis trackers have shifted from storing rows of solar panels at a flat 0° angle to placing them at an angle closer to 45°. Studies and field tests have shown that modules stored flat on these trackers were at risk of torsional damage. By tilting the modules rather than storing them flat so that the leading edge is lower than the more distant edge, oncoming pressure can be reduced, allowing wind to fly above or below the module with less movement in the tracker itself. Dual-axis trackers can still be stored flat to reduce wind pressure because they are typically installed on top of piles, which have lower wind resistance than single-axis foundations.
Solar trackers manufactured for projects in snowy areas must take into account the weight of snow resting on solar panels. The usual solution for dealing with snow is to tilt the panel rows to one side to prevent snow accumulation.
However, snow shed is not the only risk that snow poses to trackers. In locations with windy conditions, snow drift can accumulate under a solar tracker row, which can affect tilt clearance. And with a freeze-thaw cycle, accumulated snow can harden enough to be harmful to tracker arrays. Overcurrent protection devices can keep trackers from bumping into obstacles and function like a garage door that won’t close when it detects something underneath.
“If a tracker is following that hard surface and doesn’t have some form of overcurrent protection, motors can get damaged, modules can get damaged, because the tracker just keeps tracking an obstacle,” Caufield said. “It’s a lot like parking a truck under a tracker.”
In addition, solar trackers in northern areas should have built-in tolerances for physical expansion and contraction in warm and cold temperatures. Low temperatures can affect system movement and affect the performance of electronic components.
Heavy rainfall is not a problem for a solar tracker until it begins to collect under the system. Arrays can be equipped with flood sensors to direct trackers to place panel rows above the water surface if flood levels rise too high. In flood-prone areas, trackers can be produced with increased pole heights to anticipate rising water levels.
“According to manufacturers, modules can be flooded, but generally we are asked to design our system so that the headspace is above the floodplain,” Caufield said. “So the height of the leading edge is still above the floodplain, even in gusty winds.”
Then there is the danger of hail. In the past few years alone, hail has been the cause of hundreds of millions of dollars in damage to solar projects. These ice balls that come from the air pose the greatest risk to the glass plates in which solar cells are encased.
“The relatively recent issues surrounding hail, which have been catastrophic for some projects, have put pressure on all manufacturers to come up with mitigation strategies,” Caufield said.
To anticipate hailstorms, operators are advised to 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 that the pellets just brush the surface of the solar panel. Orienting the front of a module perpendicular to the fall path of the hail makes it more susceptible to damage.
Soltec has experimented with orienting modules so that their backs are exposed to hail, but this requires more structural reinforcement with additional components such as dampers, since solar trackers are typically built to block wind. Array Technologies has developed a proprietary Hail Alert Response system to help its solar trackers prevent and reduce damage from hailstorms.
“All this stuff is designed to please insurance agents and financial institutions and protect the assets,” Caufield said. “But I dare say it’s impossible to achieve zero percent risk on all of these courses, especially those that are in ‘Hailstorm Alley’ from West Texas to Mexico and north to the Colorado Plains, where it is so common.”
Any weather conditions that can be harmful to solar energy systems also involve high winds, so it often comes down to operators determining what they prefer to protect themselves against. Each weather event poses a specific risk to trackers.
Credit: Stracker Solar
“If it’s hailing and there’s wind, you prioritize wind over hail,” says Hadi Hajimiri, CEO of Stracker Solar, a manufacturer of dual-axis trackers. “In hail you may have damaged solar panels, but in wind you may have damage to the entire system and possibly damage to your surroundings because you don’t want the tracker to bend and fall off.”
Although extreme weather events are on the rise, technology can ensure trackers keep projects online and spared from damage. By using the latest operating systems, powered by safety algorithms and atmospheric sensors, projects can be better predicted and protected from the elements. These are automated systems that control miles of tracker arrays that follow the sun throughout the day and can respond to the slightest change in wind speeds.
Companies that make solar trackers plan to continue preparing these moving PV projects for a changing climate and hope to one day be the answer to solving this problem.
“It is incredibly important that we continue to expand our capabilities in severe weather management as your insurance premiums increase, the potential for damage increases and energy costs increase,” said Array’s Gabelnick. “Everything is going up and solar is becoming less competitive versus some of the other renewables out there.”