Night will fall on Europe’s power system a little early on Wednesday evening, as an eclipse is set to block solar generation across parts of the continent.
While the rare celestial event is expected to draw thousands of tourists eager to witness the eclipse from northern Spain, it will make for a more complicated afternoon than usual for technicians operating the region’s increasingly solar-reliant power grids.
There has been plenty of time to prepare, however. A solar eclipse, though rare, can be predicted centuries in advance. And this time, the impact on solar generation will be fairly muted. The sun will be nearing the horizon when the moon obscures it, meaning alternative sources of generation will already be stepping up to meet evening demand.
Still, the eclipse could knock out a meaningful amount of solar generation, leaving the shortfall to be covered by other sources such as natural gas, hydropower and nuclear plants. As a precaution, the UK’s grid operator issued a warning on tight margins for Wednesday evening, asking market participants to offer spare generation to help meet demand while the sun is blocked.
Britain’s National Energy System Operator forecasts a margin shortfall of nearly 1.8 gigawatts for Wednesday evening starting at 5pm local time. While such warnings are typically a winter phenomenon, they have become increasingly common this summer as extreme heat across Europe curbs output from traditional sources including nuclear and hydropower.
“The notice has been issued as a precautionary measure to the market due to the solar eclipse and there is no risk to customer electricity supplies,” a representative for Neso said in an emailed statement.
Britain’s biggest household energy supplier, Octopus Energy, has asked customers to not use electricity during the eclipse to avoid being forced to make up for the shortfall in solar energy power by turning on gas-fire power plants, which cause carbon emissions. To incentivise customers, Octopus has offered one hour of free energy on Sunday to those who alter their habits on Wednesday night.
“The effects are quite far-reaching geographically, all the way across Europe,” Ryan Carson from the energy forecasting team at the UK’s National Energy System Operator said in a presentation last week. “We have been analysing this since about one year ago.”
Varying impact
For the UK, the eclipse will hit around 8pm and is expected to reduce generation by slightly more than one gigawatt, with 95 per cent of the sun obscured, Mr Carson said. Across Europe, the impacts will vary, depending on the time of the eclipse, its extent and the size of the country’s solar fleet.
Overall in Europe, if the conditions are clear, solar output could decrease by about 9.7 gigawatts starting at about 7.15pm, according to a forecast from the Entso-e group of European power grid operators.
In Spain, where the eclipse will be total, solar farm operators say they are well prepared and co-ordinating closely with Red Electrica, the nation’s power system operator.
Acciona, which has some solar assets directly in the path of the eclipse, does not expect a major impact because the event coincides with sunset, when solar output is already declining. The company has nonetheless incorporated the eclipse into its generation forecasts.
“Everything is included in our models,” said Manuel Calleja, head of centres at Acciona Energia. “We include the eclipse in the forecast that we share with the TSO [transmission system operator], so they know in advance how photovoltaic production is going to reduce.”
He said flexible resources such as hydroelectric plants and combined-cycle gas turbines would be available to make up for any temporary loss of solar output, though those facilities would typically be running or preparing to meet Spain’s evening peak in electricity demand.
While this eclipse will have a relatively minor impact, another is headed for Europe next summer and that one will strike in the late morning, when solar can be the biggest source of electricity across much of the continent.
