As floodwaters recede from one of the largest and most damaging hurricanes to ever hit the East Coast, power crews are bringing electricity service back for residents. As of Thursday afternoon, Duke Energy estimated that 98% of its customers in North Carolina had power.
North Carolina, where Hurricane Florence made landfall last Friday, also hosts the 2nd-largest capacity of solar of any U.S. state after California, at 4.5 GW according to the Solar Energy Industries Association (SEIA).
More than 2/3 of that is in the service area of utilities owned by Duke Energy, and today Duke gave an update on the status of solar projects, both the ones that it owns and those owned and operated by other parties.
Duke estimates that up to 1 GW-AC of the roughly 3 GW-AC of solar in its service area was offline at the peak of the storm, and that 700 MW is still not available. The company notes that much of the solar that is offline is in areas of extreme flooding. “There is a lot of solar near the coastal counties of North Carolina,” explains Duke spokesperson Randy Wheeless.
Duke itself owns 35 PV plants, and notes that three are still offline, totaling 101 MW-AC. All three are in counties that are either on the coast or very near it. Additionally, the 60 MW Monroe plant in Union County had a dozen panels damaged due to strong winds, but is currently online.
Lines down, components up
As is the case with other forms of centralized generation during storms, the problem appears to be largely one of the power lines connecting these large-scale solar plants to the grid. While Duke estimates that it has restored power to 1.6 million out of the 1.7 million customers who lost power in its service area, there are still a large number of downed power lines.
“There could be solar facilities that are ready to reconnect, but the grid isn’t there to do that,” notes Wheeless. This includes solar facilities where the power was turned off beforehand. “I’m sure there are solar facilities that you can’t even get to.”
For NEXTracker, which supplies select operations and maintenance (O&M) services for the plants that it supplies trackers for, the track record is better. The company says that of the 18 plants it services in North Carolina, 17 are back online, and that the final one is inaccessible.
NEXTracker notes that one of the key features that has allowed plants using its tracking system to get back online is the design of its trackers, where all of the key components including controllers are located high on piers. This is particularly important in floods like those which are still happening in North Carolina.
“They all think about the wind and the damage from the wind, but they don’t think about the water,” notes NEXTracker VP of Global Services Marty Rogers told pv magazine. He also notes that his company has online communications to 60% of its sites, which helps when they are cannot be reached by technicians.
There is far less behind-the-meter solar in North Carolina, whose deployed solar is dominated by large plants. And while no kind of solar is going to be at full production during a hurricane or other storm event, it has repeatedly been demonstrated that distributed generation can create more stable and resilient grids, as rooftop and other small-scale PV systems are typically located near demand are not as dependent upon large power lines.
The legacy of coal ash
It is important to note that solar plants are not the only large power plants to be affected, and that all large generators are only as good as the power lines that serve them. As of Tuesday EIA reported that the 1.9 GW Brunswick Nuclear Generating Station was still offline, and that the 2.3 GW McGuire Nuclear Station was running at 50% power while it undergoes maintenance.
Additionally a cooling reservoir at the gas-fired Sutton Plant is also overflowing, but there are not expected to be any long-term affects from this. The same can not necessarily be said of the state’s deposits of coal ash, a legacy of the state’s coal-fired fleet.
On Saturday night Duke Energy revealed that heavy rains from Hurricane Florence caused a slope to collapse at a coal-ash landfill, releasing 2,000 cubic meters of soil and the heavy metal-laden ash. Duke reports that water samples from multiple locations show that coal ash has not impacted water quality at nearby Sutton Lake.
This is only one of several instances when coal ash has been discharged from dumps in recent years, which has led to fines for Duke Energy. These piles of toxic residue, containing arsenic, lead and mercury are still growing, as coal represented more than 1/4 of in-state generation in North Carolina during the first half of 2018.