Solar Eclipse August 21, 2017
Craig Williams, Specialist
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Trivia Question
• What were you doing on February 26th, 1979.
– Jimmy Carter was President.
– Do Ya Think I’m Sexy by Rod Stewart and Heart of
Glass by Blondie played on the radio.
– The Warriors was in movie houses.
(Can you dig it?)
– Two weeks earlier, 43 million Americans watched
Elvis, an ABC movie starring Kurt Russell as Elvis
Presley.
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Trivia Question
The last total solar
eclipse to darken the
American mainland
occurred on February
29, 1979.
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History
• August 21, 2017 will mark the first time in 99
years that such an event is readily visible in
the US from coast to coast.
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Europe Eclipse March 20, 2015
• It had been anticipated that, under clear skies,
around 35,000 MW of solar energy would
decrease from Europe’s electrical system over the
course of just over two hours.
• This power loss would be the same as losing
nearly 80 medium size conventional energy
generation units.
• Managing such an event offered an
unprecedented challenge to European
Transmission System Operators (TSOs).
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The Downs and Ups
• TSOs had to balance the speedy loss of solar
energy from the power grid as shadow
overtook the sun, beginning at 9:00 am
Brussels time.
• The loss of around 17 GW was then followed
by an even speedier (three times the normal
maximum) reintegration of 25 GW of solar
generation as the shadow completed its
course.
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European Solar Eclipse
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Preparations for the Eclipse
• In Italy, power grid operator Terna decided to
reduce its risks by turning off all of its largescale (>100 kW) PV plants for the day in order
to prevent severe energy fluctuations on the
grid.
• Approximately 5 GW PV were taken off the
system between 7:00 am and 2:00 pm. After
2:00 pm, Italian TSOs began reconnecting the
PV.
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Good Preparations Paid Off
• Ulrike Hoerchens, spokeswoman for TenneT, a
high-voltage energy grid firm, told Reuters,
“Good preparations paid off, we were able to
handle all swings in production.”
• TenneT operates in the region with the highest
share of photovoltaic units.
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Lessons From Europe
• Transmission System Operators
Higher Reserves
Keep ACE near zero
Strategic use of large loads
Limited generator outages
Reduced HVDC line capacities
Operated emergency telecommunications and back
ups
– Training for operators
– Awareness at all levels
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Expected MW Effects on the CAISO
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Effects of Rooftop Solar in EIM Areas
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Questions
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