Weather patterns have always been considered when determining solar system lifetimes and performance. Safety is also considered when establishing installation guidelines and product standards. The recent intensity of natural disasters across the country—a direct result of climate change—brings the adequacy of safety and performance standards into question. Are solar installations prepared for the increased frequency and intensity of extreme weather events of the future?
For the most part, it seems like we’re faring OK. When bad weather hits, there are more solar success stories than major failures. Rooftop arrays are surviving multiple hurricane hits and panels barely feel hailstorms. But that doesn’t mean we shouldn’t be concerned as natural disasters get worse.
Global safety and testing organization UL is paying attention. A good baseline for product standards today may need to be adjusted in the future. UL factors the full lifespan of a project, including any potential climate changes in year 20 or 35, into how arrays should perform.
“We certainly look at safety margins and evaluate if they’re adequate for potential changes in weather events,” said Bruce Bailey, vice president of renewable energy for UL. “We don’t see any chinks in the armor or fatal flaws [right now], but there needs to be an industry awareness of these issues, and there’s clearly a willingness to respond to them.”
We’re seeing the greater impact of disastrous weather every day. Renewable insurance provider GCube found that 50% of solar claims (from 2011 to 2015) came from weather-related incidents, far outpacing the electrical failures we’ve come to expect most.
“Average solar claims severity in the last five years has increased by 87%, predominantly as a result of the greater impact of weather-related losses,” GCube said in its 2016 Cell, Interrupted report.
Clearly extreme weather is affecting the solar industry already. Here’s a look at how solar installations are coping with natural disasters today and how we’ll survive severe events of the future.
Huge sections of California felt the increased intensity of wildfires last year, and it feels unrealistic to expect a solar array to make it through the flames when entire homes are destroyed. But what is expected is that solar panels won’t contribute to a fire or be a danger to the surrounding area.
When traveling in the San Francisco Bay area, Solar Power World editors heard stories of residential solar panels exploding into pieces after the wildfires across Northern California in October 2017. Suddenly solar panels installed in fire-prone areas seemed like a dangerous decision.
If those exploding solar panel stories were true, they were probably freak accidents and not a result of poor solar panel standards, said UL principal engineer Ken Boyce.
“Fire is a living thing—it eats, it consumes fuel, it breathes, it needs to consume oxygen and it doesn’t want to die. When you bring that to bear on any piece of electrical equipment or building material, you can have a different range of responses,” he said. “That experience [of exploding panels] may have to do more with the intensity of the wildfire than the response of the PV panels to a particular condition.”
UL testing has done a good job making sure panels and mounting systems won’t encourage the spread of flames. It’s difficult to even find statistics on solar panels involved with fires, let alone starting or spreading them. Still, major fire events aren’t downplayed when building a safe and reliable industry.
“It’s the type of thing that we monitor,” said Boyce, who participates in SEIA’s Codes & Standards Working Group. “We talk about these types of things all the time to make sure we’re bringing the right thought to the building and fire codes and the electrical codes and that we’re managing that interface with product standards.”
Hurricanes and tornadoes
While Puerto Rico and other islands saw unbelievable destruction from the 2017 hurricane season, one piece of good news shined through the devastation—a 645-kW array on a medical center roof in San Juan survived and was functioning at 100%. Florida-based contractor Valor Construction installed the system at the VA Caribbean Healthcare System in 2015 using Sollega ballasted mounting systems supported by Anchor Products attachments.
The key to that installation’s success (and many others across the Caribbean) was its use of attachments, said Anchor Products president Joel Stanley.
“When you have an attached system, it’s just not going to move. It can’t; it’s attached,” he said. “Racking manufacturers are adapting racking systems that better accommodate attachments. When attachments are designed properly with the proper racking system, we can design wind load capacities to easily exceed 200 mph.”
Racking manufacturers becoming more comfortable with attachments is a result of experience in the industry and a commitment to tested and verified systems. The trend toward better testing and engineering of systems will continue to improve system success rates in hazardous weather areas.
“It comes down to engineering and designing systems properly,” Stanley said. “If structural engineers can maintain control, we’ll be able to design systems that withstand the forces that Mother Nature is going to have. We’ve done a lot of individual testing with Sollega; they have understood the results and that’s what’s allowed them to design systems like they did in Puerto Rico and St. Maarten and those jobs that have withstood so well.”
On the ground, solar arrays can still be at risk of wind damage. Trackers have gotten better at handling high-wind events because of improved designs and advanced sensors. Instead of depending on heavy steel to keep systems in place, control sensors can optimize stow angles in relation to wind strength to safely position tracking arrays during storms.
“It is always a challenge to face extreme climatic conditions,” said José Alfonso Teruel, R&D manager for tracker manufacturer Soltec. “Our R&D team has re-designed the control electronics, and a new high-speed motor design moves the tracker from the maximum tilt (60˚) to the horizontal position (0˚) in less than three minutes for rapid stowing.”
Residential solar installations in tornado zones are also surviving because of good product selection and common-sense engineering.
“We make a point to select quality equipment and install with good craftsmanship to resist the heavy weather we get in our area, but there will always be outlier events that cannot be planned for,” said Chris Rogge, director of solar services for Cromwell Solar in Lawrence, Kansas—an area known for its higher concentration of tornadoes. “We did have a system take a glancing blow from a tornado, and it stayed in place. A few panels were punctured by flying metal debris, but so was the metal roof of that building.”
Flying debris does seem to be the larger concern. Even when a solar mounting system does its job and keeps panels mounted to roofs and the ground, an airborne lawn chair or rock could be what pulls a system down. In those situations, homeowner’s insurance should take care of the damaged panels.
It’s also difficult to hide from hail. An April 2016 hailstorm in Texas damaged 4,000 panels at a 4.4-MW site. Baseball-sized hail hit Alamo 2 solar farm near San Antonio, and some panels saw multiple points of impact. The tracking system stowed horizontally when high winds came through, but that left the panels more exposed to falling hail. It was ultimately decided to replace all 18,000 panels in case there were undetected micro-cracks.
Texas Green Energy was hired to replace the panels, and president Adam Burke said he wanted to prove to solar naysayers that damaged panels only have to be a slight inconvenience.
“I wanted to prove a point that these things happen and there are mechanisms in place to repair this just like anything else,” he said. “It’s minor downtime and the whole plant is renewed and restored.”
Freak accidents aside, hail damage is not a huge concern. NREL analyzed 50,000 solar systems installed between 2009 and 2012 and found the probability of damage from hail was below 0.05%. Solar panels are tested and certified to withstand 25-mm (1-in.) in diameter hailstones flying at 23 m/s (51 mph). And for the most part, hail doesn’t often fall larger or faster than that.
“We do get our fair share [of hail] around here. We’ve probably seen less than five panels with visible hail damage, though. We have seen great coverage from these customers by homeowner’s insurance,” said Cromwell Solar’s Rogge. “We had a good amount of hail this past spring, but it just led to a lot of removal and reinstallations for roof replacements. The arrays have been fine.”
Earlier this winter, Erie, Pennsylvania, received an astounding 65 in. of snow in 60 hours—34 in. came on Christmas Day alone. While communities in the Great Lakes’ snowbelt are used to heavy snow, this was still a record-breaking event. No one wants 5 ft of snow sitting on top of solar panels.
The weight of that snow will probably not harm a solar array, especially since tilted solar panels help to shed snow blankets (just watch your head below). Buffalo, New York’s CIR Electrical Construction always includes partial snow cover in customer solar production plans, and the installation company tells its customers to just let nature do its thing.
“We do not recommend our customers to clear snow off their panels,” said Ashley Regan, director of business development for CIR. “Using a shovel, brush or similar item could damage your panels and system. Your system warranties do not cover any cracked glass or disturbed electrical wiring that may result from a homeowner trying to remove snow, so it’s best to let them be.”
CIR installs solar year-round and can often be found shoveling snow off roofs and using leaf blowers to warm roofing shingles before beginning work. That’s where snow affects solar most: installation speed.
“Winter and other intensive weather conditions may slow down installation time due to additional steps and safety precautions,” Regan said. “If it’s too cold we don’t force our staff to stay out, especially on the roof. In severely bitter cold, we try to do inside work, including mounting the balance of system, mounting inverters, interior conduit runs and structural attic work if necessary.”
CIR uses power optimizers so each panel can produce independently, which helps with shading from snow coverage. The company also prefers elevated flashing to increase water mitigation from penetrations in case of heavy snowfall.
Snow is just as common as rain, and building codes and product tests account for that. While no one wants great amounts of snow to fall in a short period of time, the good news is that it’s not a permanent weight solar panels have to carry. Snow melts eventually.
Rising sea level maps show southern sections of Florida swallowed by the effects of global warming by as soon as 2100. New buildings in Miami are preparing for increased water and storm surge. The plaza level of the new Frost Museum of Science sits 21 ft, 8 in. above sea level, and the 66-kW solar system on its roof should never experience flood waters.
For those unplanned, temporary floods, solar developers are adapting. Mauricio Añón, brand ambassador at utility-scale contractor Inovateus Solar, said civil engineers will suggest raising array heights or redirecting flooding channels to allow for ground-mounts to work in floodplains, but it really comes down to costs.
“We get an audit when there is land with potential problems,” he said. “Sometimes [the solution] is just finding different land or a different place and moving the project. If the outcome is not promising, you don’t want to do all that work and not have the warranties [for system protection].”
Executives with Soltec claim that its SF7 tracker has the highest mounting height for the tracking motor and electronics in the industry at a minimum of 5.9 ft, which should keep equipment high enough even in floodplain applications. Soltec also uses torque tubes to protect wires from external threats. Flood-level sensors will activate a tracker to adjust to safe angles in case water levels start to rise.
“The standard height of the tracker, together with additional sensors and an improved tracker control algorithm, allow the tracker rotation to adjust to the flood stage and prevent the tracker from the harmful action of water runoffs while the plant keeps functioning,” said Soltec’s Teruel.
For residential installations, flood waters affect the inverter more than the panels.
“The flooding that we normally see is a few feet and typically will not reach the solar inverter that is wall-mounted on our homes,” said David Dixon, business development manager for Texas installer NATiVE. “Because homeowners are not typically building in flood plains, this has not been a major issue for us, yet.
“I do see this becoming more problematic with coastal installations and the more and more frequent occurrence of extreme weather that we see,” Dixon continued. “Because our equipment is up on walls and roofs, it is usually out of harm’s way. I am beginning to think about battery systems though, which are typically heavy and mounted on grade. They will be vulnerable to even minor flooding events.”
Richard Sherwood with Houston-based installer Adaptive Solar said the region’s four days of heavy rain (peak accumulations reached 60.58 in.) from Hurricane Harvey in late August 2017 really opened up the conversation of battery backup.
“I was bracing for the worst; I didn’t think anyone would be looking at solar for the next three months. [The hurricane] has piqued interest, and we’re seeing a lot more leads but almost exclusively with the battery backup right now,” he said.
Where to house these energy storage technologies may be the next big concern when considering disastrous weather.
As extreme weather events continue to plague the United States, solar installers will have to keep innovating to ensure systems last through hurricanes, hail and tornadoes. Perhaps an increase in solar panel installations will mean a decrease in climate change and wild weather, but only time will tell.
source: Solar Power World