The solar eclipse puts American photovoltaic to the test
Environment — di Cecilia Bergamasco
On 21 August, a solar eclipse will be visible across America — an important test for the country's electricity grid.
The solar eclipse puts American photovoltaic to the test
On 21 August, a solar eclipse will be visible across America — an important test for the country's electricity grid.
On 21 August, millions of people across America will turn their eyes (properly shielded) to the sky to observe the solar eclipse. On the same day, engineers will be busy analysing data to understand what happens to the electricity grid. Monday's eclipse will in fact be the first to put the country's electrical grid to the test in the era of solar energy.
#SolarEclipse2017 is just days away! See which #NationalLabs are in the path of totality ➟ energy.gov/articles/throw…
During the solar eclipse, 1,900 solar photovoltaic plants capable of generating up to 20 gigawatts (GW) of power will be blacked out — roughly fifty per cent of the installed solar capacity in America (43GW). Despite this, grid operators believe the situation is under control and that there are enough combined-cycle gas-fired power plants (the most flexible in terms of start-up and electricity generation) to prevent blackouts.
The eclipse will reveal a great deal about how Americans produce and consume electricity. John Moura of the North American Electric Reliability Corp (Nerc), an electricity grid regulatory body, underlines the scale of the challenge. "When Nerc tests the resilience of the system, it imagines shutting down two of the three 3.8 GW nuclear reactors at the Palo Verde plant in Arizona. If skies are clear, the solar eclipse could have twice the impact of the simulated tests carried out so far, even though the eclipse is a predictable and temporary phenomenon." The experience will help in dealing with the next two solar eclipses that will affect the United States in 2024, by which time the country will likely have three times more solar capacity than today. "If we're not ready for this, I have no confidence in our system," said Moura.
The solar eclipse will be a test for California's electricity grid
California, although not in the path of the total eclipse — which instead affects areas further to the north-east — will experience 62 per cent coverage. This is an important proving ground for the state, which with its 18.9 gigawatts of solar capacity is the leading photovoltaic electricity producer in the United States, followed by North Carolina with 3.3 GW.
At 10.20, when the eclipse casts its greatest shadow cone over California, the state's solar energy output will drop by approximately 5.6 GW before beginning to rise again and returning to normal levels.
Analysing the phenomena during the solar eclipse
The eclipse will put several factors as yet unknown to the test. One of these is the variation in winds, which change during an eclipse, and the effect this will have on wind farms.
Also to be analysed is the increase in electrical demand on the grid at the moment when the solar panels are blacked out; in this way it will be possible to measure how much residential solar generates. Operators are in any case attempting to curb electricity consumption during the eclipse by asking citizens not to use household appliances and to reduce air conditioning, so as to cut electrical demand by 3.5 GW.
The states affected by the solar eclipse
The total eclipse will cross the entire United States of America — an event that has not occurred on this side of the Atlantic for 47 years, specifically since 7 March 1970. It will be possible to see the total solar eclipse in America and in a small part of Europe and Africa. The event will affect in particular the United States, parts of Canada, Mexico, Cuba and the Caribbean. It will marginally affect some areas of northern Latin America, Greenland, Iceland, Scotland and Ireland, and the far north/west of Africa, especially Morocco.
The European solar eclipse of 2015
In managing the situation, American electricity system operators are also drawing on the European experience of 20 March 2015, when three hours of eclipse had to be handled with 90 GW of solar to manage.
In Italy, during the solar eclipse, Terna, responsible for managing the Italian electricity distribution grid, had — at the request of electricity distributors — scheduled a 7-hour disconnection of photovoltaic and wind plants connected at medium voltage, for a combined capacity of 4,400 MW of photovoltaic and 200 MW of wind. No disconnections took place in other European countries.
The 2015 solar eclipse had also served as a testing ground for electricity operators across the Old Continent, and Entsoe (European Network of Transmission System Operators for Electricity), the European association grouping all electricity transmission system operators, had warned that the eclipse should be treated as an important test, above all because of the repercussions that could potentially arise for the European electricity system.