IEEE Power & Energy Magazine - November/December 2016 - 77

There are four keys to dealing successfully with the
events of the 21 August 2017 solar eclipse: preparedness,
prudence, coordination, and controllability.
✔ Preparedness really needs no explanation. Being
prepared is fundamental to success in anything. In
this respect, we're in an enviable situation. We face
a new challenge, but it involves a familiar if infrequent astronomical phenomenon, and we know exactly when it will occur and how it will proceed. We
have a recent European experience, and we can learn
from that. We have well-planned and well-managed
synchronous interconnections, with operators who
are trained and experienced.
✔ Prudence is called for as this is still new ground. In
the 20 May 2015 total eclipse, Germany, which had
the highest percentage of solar installations, made no
attempt to reduce solar output prior to the event, but
the path of totality was well to the north. Although
the United States has a smaller percentage of solar
capacity than the Continent, the path of totality will
pass right over us. We haven't experienced a solar
eclipse of this magnitude since solar generation has
become a measurable part of our capacity mix; the
last eclipse across the lower 48 states was in 1979.
In such a case, prudence is the best policy. Simply
stated, solar generation that is controllable could be
reduced, and conventional generation increased proportionally, prior to the start of an eclipse. Prudence
is also indicated in scheduling power transfers. Operators often reduce long-distance flows across the
grid when an ice storm, solar magnetic disturbance,
or similar event is imminent.
✔ As in any situation, coordination among system operators will be essential. The Eastern and Western
Interconnections in particular are truly vast, encompassing most of North America from coast to coast.
Failure to effectively coordinate long-distance power
transfers, scheduled generation and transmission
outages, and information on unplanned outages has
played a role in most blackouts over the last half-century, most recently in 2003. Given their numerous
control areas (balancing authorities), close coordination among the various system operators, both before
and during the event, would greatly improve reliable
operation during the event.
✔ Controllability is perhaps the most difficult of these
requirements. The current political climate encourages production by renewable resources. However, the
reliability and integrity of the system demands that
it be protected from the sudden large reductions that
will accompany a solar eclipse. Several hours of controlled reductions is a small price to pay to protect the
grid for an event that will happen only five more times
during the entire 21st century (in 2024, 2045, 2078,
and 2099).
november/december 2016

We also need to consider the case of distributed generation, sometimes called DERs, or behind-the-meter generation. At present, these are only sometimes under the
control of the system operator, but increased control may
be happen in the future. The North American Electric Reliability Corporation (NERC), which has a long history in
developing criteria and other regulations to maintain reliability, has specifically made this recommendation: "The
ability to observe, control and dispatch DERs will be
important considerations when planning and operating
a reliable BPS [Bulk Power System] with large amounts
of DER-particularly because the majority of DERs are
variable and outside the control of the System Operator"
(NERC 2015 Long-Term Reliability Assessment, December 2015, p. 22).
NERC is considering a project to assess preparations for
the 2017 solar eclipse. The analysis could include examinations of potential operational and planning challenges
throughout the United States, including reserve, frequency,
and ramping issues. In addition to the effects the eclipse
has on PVs, its effects on loads would need to be considered. And wind generation output remains a factor in any
system assessment.
So much for 2017. The next total solar eclipse in the continental United States will occur 8 April 2024. It's never too
early to start planning!

For Further Reading
NASA Scientific Visualization Studio. (2015, Sept. 9). 2017
total solar eclipse in the U.S. [Online]. Available: http://svs.
gsfc.nasa.gov/cgi-bin/details.cgi?aid=4314
Solar Industries Association. (2016, Feb. 22). U.S. solar market sets new record, installing 7.3 GW of solar PV
in 2015. [Online]. Available: http://www.seia.org/news/
us-solar-market-sets-new-record-installing-73-gw-solarpv-2015
European Network of Transmission System Operators
for Electricity. (2015, Feb. 19). Solar eclipse 2015-Impact
analysis: Report by Regional Group Continental Europe and
Synchronous Area Great Britain. [Online]. Available: https://
www.entsoe.eu/Documents/Publications/SOC/150219_
Solar_Eclipse_Impact_Analysis_Final.pdf
European Network of Transmission System Operators for
Electricity. (2015, July 15). Solar eclipse March 2015: The
successful stress test of Europe's power grid-More ahead,
policy brief. [Online]. Available: https://www.entsoe.eu/
Documents/Publications/ENTSO-E%20general%20publications/
entsoe_spe_pp_solar_eclipse_2015_web.pdf
North American Electric Reliability Corporation. [Online]. Available: http://www.nerc.com/Pages/default.aspx

Biography
George C. Loehr is an independent consultant and novelist
in Albuquerque, New Mexico.
p&e

ieee power & energy magazine

http://svs http://gsfc.nasa.gov/cgi-bin/details.cgi?aid=4314 http://www.seia.org/news/ http://https:// http://www.entsoe.eu/Documents/Publications/SOC/150219_ https://www.entsoe.eu/ http://www.nerc.com/Pages/default.aspx

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