Eclipse reduces solar power generation by 45%

REN – Redes Energéticas Nacionais, in close collaboration with other European electricity transmission system operators, has been preparing the National Electric System (SEN) for the effects of the nearly total solar eclipse, with expected magnitudes ranging from 92% to 100% in mainland Portugal.

The phenomenon, which will be most pronounced in the north of the country, will occur between 6:30 p.m. and 8:30 p.m. on August 12 and will cause an estimated loss of solar generation of 450 MW, representing about 7% of consumption and 45% of the National Electric System’s solar production forecast for this time period (average figures). Given the projected peak in solar production, the impact of the eclipse is estimated at approximately 15%.

The estimated figures represent only centralized solar generation as recorded/measured by REN and do not take into account other solar generation associated with certain Self-Consumption Generation Units, which will also have an effect on increased consumption. This effect is also being estimated by REN and duly incorporated into the consumption forecasts for that day, in order to reduce and mitigate unexpected effects in real time.

During the eclipse, a maximum loss of 35 MW per minute is expected. To mitigate the impacts of the generation loss associated with this eclipse on the balance between generation and consumption in the National Electricity System (SEN) and on the control of deviations in the interconnection with Spain, it will be necessary to mobilize additional reserves from hydroelectric and/or thermal generation.

Preparations for this event have been carried out in coordination with other European transmission system operators, particularly through the Short-Term Adequacy (STA) service, which ensures the balance between electricity generation and consumption over a seven-day horizon. Across the European synchronous area, an estimated production loss of approximately 9,700 MW is projected.

The effect of this nearly total solar eclipse in Portugal will be less significant given the time of day it will occur (late afternoon), when solar generation is already declining; consequently, its main effect will be a sharper-than-usual reduction in solar generation, combined with increased consumption as the day approaches its peak consumption period (late afternoon/early evening).

In July, solar generation supplied 19% of consumption—the first month in which solar technology dominated the national grid compared to other renewable sources, with hydropower accounting for 16%, wind power for 13%, and biomass for 5% of national consumption.

In recent months, Portugal has maintained a sustainable trajectory in the progressive integration of domestic renewable sources, supported by successive records in renewable energy production, while upholding the primary objectives of security of supply and quality of service in the National Electricity System (SEN), even under the most challenging conditions.

*image generated using AI