The operator of North America’s largest power grid says it is prepared to ensure reliable electricity supplies during a total solar eclipse on Aug. 21, when solar power resources will fall temporarily. Although the eclipse will reduce solar power generation, PJM Interconnection expects no power grid reliability issues in its footprint, which includes 13 states and the District of Columbia and 65 million people.
PJM joins other U.S. grid operators and regulators, including those in solar-heavy California, that have also been working to mitigate the potential reliability issues from the upcoming eclipse.
“Certainly, this is an unusual solar event, but as far as potential impacts to the grid, PJM and its members are prepared,” says PJM President and CEO Andrew L. Ott. “While this is an anticipated event, we routinely plan and prepare for unpredictable events or things that can’t be forecast far in advance, such as severe storms and heat waves.”
When the moon blocks the sun on Aug. 21, PJM says solar power generators in its footprint will lose their fuel source in varying degrees from 1:30-3:40 p.m. ET. The grid operator expects a temporary reduction in solar power of up to 2,500 MW, and PJM says it will use its sufficient reserves for replacement generation.
The exact amount of solar power affected by the eclipse will depend on how sunny or cloudy it is that afternoon, PJM notes. Certain states in its footprint will experience a greater impact, including North Carolina, which will experience a complete solar eclipse, and New Jersey, which has more solar PV generation than most other states served by PJM.
PJM says it will ensure sufficient resources are ready to replace any solar generation loss and will refine its analysis prior to the eclipse to factor in the latest weather forecasts. The grid operator adds that its established planning, operations and markets functions have produced a reliable, diverse resource mix that includes natural gas, coal, nuclear, renewables and demand response.
About 500 MW of solar generation is connected to the PJM grid, and another 2,000 MW is generated by rooftop solar panels that serve individual consumers. A reduction in power from the rooftop panels results in an increase in electric demand on the grid. Although growing in the region, solar generation comprises less than 1% of PJM’s 185,000 MW of generation capacity.
For context, PJM notes, 1 MW can power up to 1,000 homes.
Because rooftop solar is not wholesale power and, therefore, not monitored by PJM, the grid operator says post-eclipse analysis will provide valuable information for future planning. PJM will also integrate lessons learned from the Aug. 21 event into preparing for the next solar eclipse, predicted to occur in 2024, when the grid is expected to have more solar generation.
According to PJM, Europe experienced a total eclipse in 2015, with no impact on electric reliability because of coordinated planning for the ramping up and down of electricity on the grid. PJM says the last total solar eclipse to occur in the continental U.S. was in 1979, before the rise of solar power. It was viewable only from the Pacific Northwest. Citing data from NASA, PJM says August’s planetary event will be the first total eclipse since the year 1257 to begin and end exclusively over the territory that now makes up the U.S.