Portugal’s electricity transmission system operator REN – Redes Energéticas Nacionais is preparing the National Electric System (SEN) for the impact of the nearly total solar eclipse expected on August 12, which is forecast to reduce solar generation by around 450 MW.

REN has been working closely with other European transmission system operators to prepare for the event. In mainland Portugal, the eclipse is expected to reach between 92% and 100% magnitude, with the strongest effects forecast in the north of the country.

The phenomenon will take place between 6:30 p.m. and 8:30 p.m. local time. According to REN’s estimates, the resulting loss of solar generation will represent around 7% of electricity consumption and approximately 45% of the National Electric System’s forecast solar production during this period, based on average figures.

Given the projected peak in solar generation, REN estimates that the impact of the eclipse could reach approximately 15%.

Up to 35 MW of solar generation lost per minute

The eclipse is expected to cause a maximum reduction in generation of 35 MW per minute. REN says additional reserves from hydroelectric and/or thermal generation will therefore need to be mobilised to mitigate the impact on the balance between electricity generation and consumption.

Additional measures will also be required to help control deviations in the interconnection between Portugal and Spain.

REN’s estimates cover only centralised solar generation that it records and measures. They do not include other solar generation associated with certain Self-Consumption Generation Units.

However, the transmission system operator is also estimating the impact of this generation on electricity consumption and has incorporated it into its consumption forecasts for August 12. According to REN, this is intended to reduce and mitigate unexpected effects in real time.

European power systems prepare for 9.7 GW loss

Preparations for the eclipse have been coordinated with other European transmission system operators, particularly through the Short-Term Adequacy (STA) service.

The service provides a seven-day outlook to help ensure the balance between electricity generation and consumption. Across the European synchronous area, the expected production loss associated with the eclipse is estimated at approximately 9,700 MW.

The impact in Portugal is expected to be less significant than it could be at other times of day because the eclipse will occur in the late afternoon, when solar generation is already declining.

As a result, REN expects the main effect to be a sharper-than-usual reduction in solar generation combined with increasing electricity consumption as the country approaches its peak consumption period in the late afternoon and early evening.

Solar supplied 19% of Portugal’s consumption in July

The eclipse comes as solar power has strengthened its role in Portugal’s electricity system.

In July, solar generation supplied 19% of national electricity consumption, marking the first month in which solar technology became the leading renewable source in the national grid. Hydropower accounted for 16% of consumption, followed by wind power at 13% and biomass at 5%.

REN said Portugal has maintained a sustainable trajectory in the progressive integration of domestic renewable energy sources in recent months, supported by successive records in renewable electricity production.

The transmission system operator also highlighted that this expansion has taken place while maintaining the National Electric System’s primary objectives of security of supply and quality of service, including under challenging operating conditions.