Solar power output set to fall by 45% during eclipse in Portugal

Solar power generation in Portugal is expected to drop by around 45% during the eclipse on August 12, prompting the country’s grid operator to prepare additional energy reserves to maintain the balance between electricity supply and demand, Redes Energéticas Nacionais (REN) has said.

The Portuguese energy company made clear that it expects to mobilise additional hydroelectric and/or thermal generation to compensate for the decline in solar output and manage fluctuations in electricity exchanges between the Portuguese and Spanish grids, Caliber.Az reports, citing Euronews.

The eclipse will occur between 18:30 and 20:30 on August 12. It will be total across large parts of Spain, while in Portugal it will be almost total, ranging from 92% in the Algarve to 100% in the municipality of Bragança. The village of Guardamil is considered the best location in Portugal to observe the eclipse in full.

REN estimates that the eclipse will reduce solar generation by around 450 MW. That would equal approximately 7% of electricity consumption and 45% of the solar generation expected during that period based on average values.

Compared with the forecast peak in solar production, the impact is expected to be around 15%.

The estimates cover centralised solar generation and production measured by REN but exclude electricity generated by households for their own consumption. However, the expected reduction in household solar generation has been incorporated into the day's electricity demand forecasts.

REN said preparations for the eclipse had been coordinated with other European transmission system operators, including through the Short Term Adequacy (STA) load-coverage assessment service, which helps maintain the balance between electricity generation and consumption over seven days.

Across the European synchronous electricity area, the overall loss of generation is estimated at approximately 9,700 MW.

REN noted that the eclipse will take place in the late afternoon and early evening, when solar generation is already declining, meaning its impact on the electricity system is expected to be more limited.

Portugal’s solar sector reached a major milestone in July, when solar power became the country’s largest source of electricity for the first time, accounting for 19% of total consumption. Renewable sources collectively covered 53% of the country’s energy consumption during the month.

By Bakhtiyar Abbasov