By: Robert Walton

Warnings about fake viewing glasses and unusual pet behavior.  Advice on the proper gifts and kitsch for your watch party.  NASA will live stream it and bars will name drinks after it. The United States has gone crazy for next week’s eclipse.

On Monday morning, Aug. 21, a total eclipse will be observable at different times across the country. Beginning on the West Coast, the phenomenon will first be seen in Oregon at 10:15 a.m. PT, and then it will slice diagonally across the country, moving quickly east.

It will take just 93 minutes for the eclipse to move across the entire country, and it will appear only briefly. Southern Illinois will catch the longest glimpse, about two minutes and 40 seconds of total eclipse. It will last be seen in South Carolina, at 2:49 ET.

Less than three minutes of darkness, but preparations range from absurd to essential.

Source: U.S. Energy Information Administration

Columbia, S.C., has declared itself the “Total Eclipse Capital of the East Coast,” and there’s not a hotel room to be found for Sunday night, according to The State newspaper. The Oregon Museum of Science and Industry sold out a viewing party at the state fairgrounds, and small towns aren’t sure they have enough bathrooms to accommodate eclipse “chasers.”

But the electric utility industry may have the biggest stake of all. Solar generators provide a small but growing piece of the nation’s energy needs, and the eclipse will at least partially obscure the sun for approximately 1,900 utility-scale plants. According to the U.S. Energy Information Administration, more than 21 GW of solar capacity will be impacted.

On a broad scale, the impact is minor. Utility-scale solar provides less than 1% of the United States’ electricity use, and there are less than 20 utility-scale generators in the “band of totality,” where the sun will be wholly obscured.

But in specific regions, where utilities get a significant portion of peak load from solar, the impact is large enough that contingency plans were developed. And while the electric industry broadly agrees that customers are not likely to be impacted, the event will highlight the growing challenge of distributed resource integration — and prepare the industry for the next eclipse.

Three total eclipses in 45 years

There are actually several eclipses that can educate or stand as a benchmark for the utility sector. The last total eclipse visible from the United States was in 1979 and is notable because California had no grid-connected solar at the time.

Europe experienced a total eclipse in 2015 that impacted 90 GW of solar capacity — with 40 GW in Germany, supplying 40% of that country’s electricity demands. A report from the European Network of Transmission System Operators for Electricity called the eclipse “a true stress test, passed successfully.”

The California ISO says it consulted with the team that provided forecasting for the European total solar eclipse, which “has helped guide our forecasting and preparation.” Among the lessons learned was the need for specialized operator training, higher reserves, the strategic use of storage, and informed market participants.

Source:  North American Electric Reliability Corporation

Next week in the United States, largely in Georgia and North Carolina, hundreds of plants totaling 4 GW will be at least 90% obscured.  Another 2.2 GW and 3.9 GW of capacity are in areas that will be at least 80% and at least 70% obscured, respectively.

While California does not lie in the most-affected “path of totality,” the state has almost 9 GW of utility-scale solar and has done extensive planning for the event. Including rooftop solar, the ISO says it has more than 14,000 MW of solar generation capacity — double what it was just two years ago.

Considering that the state’s solar resources will continue to grow, utilities and ISO officials are closely watching this event to prepare for the next total eclipse in the United States, in 2024.

“As the industry continues to advance and modify the power system to meet customers’ needs by adding [distributed energy resources], the effect of eclipses on the bulk power system will become more relevant,” the North American Electric Reliability Corporation said in its own assessment of the eclipse’s possible impacts.

Biggest impacts in California and North Carolina

California, with 40% of the country’s solar capacity, will see the biggest impact, despite not lying in the band of totality. The eclipse will obscure solar plants about 75% in Northern California, and about 60% in Southern California.

For three hours, the eclipse will impact the California ISO Balancing Area and at peak will cause a loss of about 4,200 MW of utility-scale solar and 1,365 MW of rooftop solar. In total, the ISO will need to fill about a 6 GW gap.

An eclipse is a significant event, but it will not change grid operations, California ISO spokesperson Anne Gonzales told Utility Dive via email.

“We don’t expect any differences in how this is managed, as opposed to days when we have cloud cover or monsoons move in and reduce solar production, many times unexpectedly,” said Gonzales. While the eclipse will cover a wider geographic area than most weather events, on the other hand, it is more predictable.

“The eclipse certainly highlights the growing amounts of renewables on our grid,” Gonzales said. “Our operators have become increasingly adept at dealing with solar drops and quick ramps.”

Source: U.S. Energy Information Administration

While the exact resource mix that the ISO will draw on is unknown, Gonzales said the market “will be allowed to run as usual on that day, which means it will take the least-cost resource first.” Hydropower, gas-fired generation, and transfers in the Western Energy Imbalance Market EIM transfers are all options.

California has about 600% more solar than North Carolina, but because of plant location, the Tar Heel state will feel the impacts more than most. The state has about 2.8 GW of utility-scale installations, or about 13% of the national total, according to EIA.

Duke Energy is predicting solar energy production will drop from 2,500 MW to about 200 MW in an hour and a half. “Operators will have natural gas plants ready to step in during the eclipse,” the utility said in a recent post but noted it could also call on nuclear, hydro, coal or wind.

However, the difference in impact, between California and North Carolina, is significant. According to EIA, last August, utility-scale PV, utility-scale thermal solar and rooftop solar supplied about 14% of California’s generation compared with just over 3% in North Carolina.

The ramping challenge

The biggest issue is not finding sufficient energy, but in dealing with the rapid ramps that will occur. Utilities will need to be prepared for the jump in demand, as solar generation falls off; and likewise, they must be ready to manage the quick rise in power when the eclipse passes.

Flexible ramping energy from hydropower and gas plants will help the California ISO deal with rapid load changes. The state has access to about 6 GW of hydro resources, and high levels of supplies remain available.

According to the California ISO’s assessment, as the eclipse begins, the decrease in production will be about 70 MW/minute — and the ramp up is expected to be about 90 MW to 100 MW/minute as the sun reappears. For comparison, a typical average ramp-up rate is around 29 MW/minute during the same time period of the eclipse.

“There is plenty of capacity available to meet need,” the California Public Utilities Commission said in an eclipse-themed FAQ. “The California ISO has dealt with ramps of 13,000 MW in two hours in the evenings.”

NERC’s recommendations call for the addition of “controllable system resources that help to balance the electrical characteristics” for the bulk power system,” but also said its analysis showed no reliability impacts to bulk power system operations.

“Advanced coordination to address ramp issues and secure non-photovoltaic resources for August 21, 2017, can be readily obtained,” the reliability organization said. “Specific states (i.e., California and North Carolina) will experience the greatest impact…It is recommended that utilities in all states perform detailed studies and retain necessary resources to meet the increased and varying load.”



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