However, half of Duke Energy’s 3.4 million customers were without power at some point during the storm. Actually, shortly after Florence had passed, both Duke’s and Strata’s solar farms went right back to generating electricity.
Before the storm hit, Duke Energy’s 40 solar power sites were “de-energized” and arranged horizontally to reduce wind damage to the panels, according to Quartz.
And rooftop solar installations did well, too. Just 8 out of 800 customers with Yes Solar Solutions reported any problems after the storm.
“What we’ve done this week just underscored what we’ve known for decades — generating assets are never the main vulnerability,” Chris Burgess, project director for the Rocky Mountain Institute tells Inside Climate News.
The most breakable parts are “the wires themselves, the overhead lines,” he said. That has certainly been the case in Puerto Rico, where power is still not fully restored after last year’s hurricane.
“I know sometimes we think, ‘Oh it’s the wind, it’s the panels flying around.’ But we haven’t found that to be the case,” said Randy Wheeless, a Duke spokesperson. “Our bigger worry usually is flooding.”
Flooding doesn’t impact the solar panels directly – and if the panels are deactivated and set in a horizontal mode, there is usually very little wind damage, either. Wheeless said his company only found wind damage at one installation, a 60 MW solar farm in Monroe, North Carolina, where 12 panels were damaged out of the more than 600,000 panels at the farm. The Monroe site is fully functioning today.
Strata Solar has more than 100 installations in the state, and they were particularly happy with how solar held up during the storm. “It’s fairly isolated damage,” said Brian O’Hara, senior vice president for strategy and government affairs for the company. “I think a lot of people were looking at Florence as a good test for solar generation’s resilience, and I think we’ve seen a really fantastic outcome.”
Thinking ahead was the key to success
It is no surprise that solar power did so well. It is all due to the careful planning and use of historical storm data in North Carolina that was incorporated into the projects before the solar farms were constructed. Not only did the companies who built them take all this into consideration, but they placed all critical electrical equipment on platforms where flooding was anticipated.
Most of the panels and rack systems are designed to withstand winds up to 140 mph range, according to RMI’s Burgess. And many of them have sun tracker systems that can be positioned remotely to minimize exposure to high winds.
Duke Energy has 3,000 MW (3 GW) of solar capacity connected to its energy system in North Carolina. At the peak of the solar outages, 1 GW of solar capacity was unavailable to the system. Of that 1 GW, 100 MW was Duke-owned solar capacity and the rest was either taken offline or tripped off during the storm (either grid or facility related).
Renewable energy proves itself over and over
With stronger and more frequent tropical cyclones and extreme weather hitting the U.S., renewable energy sources like solar and wind power have proven their resilience. Yet, even failures have proven to be a great teacher. Such was the case with Hurricane Maria’s devastation of Puerto Rico.
When Maria hit Puerto Rico one year ago on Sept. 20, it had sustained winds of 155 mph, well above Florence’s wind speeds after landfall, and some solar panel racks came loose. RMI’s Chris Burgess and his team studied the effects of that storm to learn how solar power designs and installations could be improved.
And in August 2017, when Hurricane Harvey hit Houston, Texas, the wind farms in Texas either continued operation during the storm or were up and running shortly after the storm had passed.
The case for microgrids
“From what we investigated on the ground in the Caribbean,” he says, “solar can be designed and can be installed to be extremely resilient to the most extreme storms.” But just because a solar power installation or rooftop installation survives high winds doesn’t mean the electricity it produces can be put to good use after a storm.
The one thing needed for electricity to get from a power source to the customer is a connection to the electrical grid. And if the grid is down, onsite management tools will shut the system down to protect utility workers from electrical shock while they are repairing broken wires.
This is where an “island mode” system would overcome widespread outages. With this type of system, some microgrids and home storage batteries are able to operate in “island mode,” which means they can still deliver electricity to local customers while being physically disconnected from the larger utility grid.
And just as the renewables revolution has taken hold, more and more businesses and corporations have become very influential in spurring innovation and new technologies that are making the country’s electrical grid “smarter,” and at the same time, helping to grow the public’s interest in microgrids.
