Solar eclipse to cut Portugal’s solar output by 45%

Portugal’s near-total solar eclipse on August 12 is expected to cut solar power output during the event by 45%, according to a statement from grid operator REN. The system operator says extra backup generation will be needed to maintain supply.

REN said the eclipse will take place between 6:30 p.m. and 8:30 p.m., with expected magnitudes of 92% to 100% across mainland Portugal and the strongest effect in the north. It estimates a loss of 450 megawatts of solar generation, equal to about 7% of electricity consumption and 45% of the solar output expected for that period, based on average values. Compared with the forecast peak in solar generation, the impact is estimated at about 15%.

During the eclipse, the maximum loss is expected to reach 35 MW per minute. To offset the fall in generation, REN said it will need to mobilise additional reserves from hydro and/or thermal plants. The operator added that the impact is lower because the eclipse will happen late in the day, when solar production is already declining, although that will coincide with rising demand as Portugal moves into the evening consumption peak.

REN said its estimates cover only centralised solar generation and exclude some self-consumption units, which it said will also contribute to higher demand. The operator said that effect is being incorporated into its consumption forecasts for the day. Across Europe’s synchronous electricity area, the eclipse is expected to reduce generation by about 9,700 MW.

The warning comes after solar became Portugal’s largest electricity source in July, supplying 19% of consumption, ahead of hydropower at 16%, wind at 13% and biomass at 5%, according to the figures cited by REN.

Originally published at Eco.pt