A solar eclipse predicted by NASA on August 21 is unlikely to cause any reliability issues to the North American bulk power system, according to a white paper by the North American Electric Reliability Corp.

However, the white paper recommends preparation and increased coordination by system planners and operators to understand how the eclipse will impact power flows and resource commitment.

The white paper -- A Wide-Area Perspective on the August 21, 2017 Total Solar Eclipse -- also recommends that utilities in all states perform specific studies of the eclipse’s impact of solar photovoltaic power output on their systems and retain "necessary resources" to meet the increased electricity demand requirements.

Total solar capacity (distribution and transmission connected) in the United States has increased from 5 MW in 2000 to 42,619 MW in 2016 the paper says. It notes that a total solar eclipse occurred across Continental Europe, Nordic Countries, and Great Britain in 2015.

(Read "Solar Eclipse Leave European Electric Power Grid Largely Unaffected.")

That solar eclipse showed, “… a great deviation in the amount of solar generation that was available before, during, and post eclipse which caused the need for far more advanced coordination of primary, secondary, and tertiary reserves across Europe within a reduced time frame (faster than 10–15 minute intervals).”

NERC says this deviation in available solar generation indicates a need to study the potential effects that a solar eclipse would have on the North American bulk power system.

The eclipse will first be observable in Oregon at 10:15 a.m. (Pacific). The southern part of Illinois will observe the eclipse for the longest duration of time, a total of two minutes and forty seconds at approximately 1:19 p.m. (Central). The eclipse will be last observed in South Carolina at 2:49 p.m. (Eastern).

It will take roughly one hour and thirty-three minutes for the total eclipse to traverse the United States. NERC says that a large amount of photovoltaic resources during the eclipse will be removed as the moon obscures the sun. Utilities are expected to experience a sudden (less than 5 minutes) increase in load that was previously being supplied by behind-the-meter photovoltaic generators.

NERC says this increase in load may cause local ramping and balancing concerns.

Generation and system operators have more control of utility-scale solar resources, NERC says. However, operational planning and advanced power system studies must account for the impacts that may not be completely visible to the system operator, such as distributed and roof-top solar photovoltaic resources.

While solar generation levels are relatively low, states including California and North Carolina "are likely to experience the greatest impact" to solar photovoltaic resources and system operations during the August 21 total solar eclipse, according to the NERC paper. California has the nation's largest installed solar PV capacity. And the sun in North Carolina will be entirely obscured during the eclipse, eliminating entirely that state's distributed PV generating capacity.

Given the highly predictive nature of the upcoming eclipse, NERC says it has confidence that reliability can be maintained by system operators through comprehensive planning and awareness.

Seven years after the August eclipse, North America will again experience a total solar eclipse on April 8, 2024. NERC says that as 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.