On April 28th, 2025, a major power outage struck the Spanish and Portuguese power grids, leaving over 50 million people without electricity for at least six hours, and in some cases, considerably longer. Fortunately, the daytime occurrence in Spring mitigated potential impacts and fatalities.
The changing renewable landscape
The blackout affecting the Iberian Peninsula underscores the evolving operational dynamics of its power grids. Although the definitive causes remain under investigation, the incident highlights the increasing influence of renewable energy sources, particularly wind and solar power, on Spain and Portugal’s electricity infrastructure.
These nations have made substantial strides in integrating variable renewable energy into their grid mix. Notably, during periods of favorable weather conditions and lower energy demand, especially in the spring, the combined output from wind and solar farms has, at times, been sufficient to meet the entirety of their electricity needs. This achievement signifies a major shift towards a more sustainable energy future. Growth in these technologies is expected to accelerate further with Spain planning to phase out Nuclear power by 2035.
This has a fundamental impact on the way the power grid operates. The complexities associated with managing a power system with such a high penetration of intermittent renewable generation are becoming increasingly apparent. Factors such as the inherent variability of wind and solar resources, the need for grid management, and the importance of robust energy storage solutions are critical considerations for maintaining grid stability and preventing widespread outages.
The Iberian blackout will likely prompt a thorough analysis of current grid management practices, the adequacy of existing infrastructure to handle high levels of renewable energy, and the potential need for further investments in grid modernization and energy storage technologies to ensure a reliable and resilient power supply in the future.
Grid balancing
While the cause of the black out remains unknown, the blackout served as a reminder of the inherent fragility of interconnected power grids. These complex systems necessitate a continuous and precise equilibrium between the total electricity being generated and the aggregate consumer demand to uphold the critical target alternating current (AC) oscillation frequency, typically 50 Hertz.
Maintaining this delicate balance is the paramount responsibility of grid operators. They must meticulously coordinate the output of a diverse array of connected power sources, ranging from large-scale power plants to distributed renewable energy installations, ensuring that all operate at precisely the same synchronized frequency. Any significant deviation from this target frequency can cascade into instability, potentially leading to widespread outages and severe disruptions.
To maintain the grid’s 50 Hertz synchronization, a stable power supply is essential. This stability is typically ensured by rotational energy in large-scale facilities like nuclear, gas, and hydroelectric plants. Their rotating machinery provides inertia, acting as a crucial buffer against disruptions such as abrupt shifts in power generation or consumption.
However, variable renewable sources, such as solar photovoltaic, do not have this capability. They generate direct current which is converted to alternating current at 50 Hertz, but they cannot react automatically to frequency variations.
On April 28th, with solar providing more than half of all generation, there was little by way of spinning inertia in the Iberian grids. This left it vulnerable to sudden changes in supply and demand. At 12:33, an imbalance occurred, causing protective shutdowns of plants to protect equipment from damage. Interconnectivity with France was lost, to protect the French grid, and a cascade of further shutdowns occurred meaning that many GW of power generation switched off in a matter of seconds.
Ancillary service and hydropower
Maintaining grid stability amidst fluctuations in electricity supply and demand is crucial for preventing blackouts. One effective method for achieving this balance involves utilizing spinning machines that possess inertia. These machines act as a buffer, their rotational energy helping to smooth out inconsistencies in the grid frequency.
Hydropower stands out as a renewable energy source capable of providing this essential functionality. Unlike some other renewable sources that are intermittent, hydropower offers a unique combination of characteristics that make it ideal for grid balancing. Its fast response time allows for rapid adjustments to power output in response to changing demand or sudden supply drops. The flexibility of hydropower plants, with their ability to quickly ramp up or down electricity generation, further enhances their value in maintaining grid stability. Moreover, hydropower is a reliable source of energy.
The dispatchability of hydropower is a key differentiator. Unlike wind or solar power, which are dependent on weather conditions, hydropower can be dispatched on demand, meaning it can be called upon to generate electricity whenever it is needed. This dispatchability, coupled with its renewable nature, positions hydropower as a resource for a sustainable and stable energy future as the proportion of renewables increases. Its ability to provide both clean energy and grid balancing services makes it a key component of a modern, resilient power system.
Currently, across the Spanish and Portuguese grids there is more than 25GW of hydropower capacity. At the time of the outage, less than 10% of this was operating. Maintaining a higher level of hydropower in the grid could have benefited the grid by providing stabilization through helping to maintain AC frequency as well as providing reserve power (though facilities not operating at their peak capacity). Load following, where output is matched to demand is another key capability of hydroelectric power.
Another advantage of hydropower is its ability to ‘black start’. Most other forms of electricity generation including wind require a supply of electricity to start generation. This is not the case with most hydropower facilities. It was not surprising to see Hydropower providing a much higher proportion of energy to the grid in the aftermath of the outage.Hydropower offers a significant advantage through its “black start” capability.
Predictable hydropower generation through AI
Hydropower offers a significant advantage over other renewable energy sources through the ability to store water, predict inflows, and therefore provide flexible generation. This capability relies on hydrologic forecasts. These forecasts predict future water conditions within a watershed, encompassing river flows, reservoir inflows, snowmelt, and rainfall-runoff. They utilize data from weather forecasts, snowpack measurements, soil moisture levels, and historical trends to estimate future water availability at specific locations and times.
A hydrological forecast helps hydropower operators anticipate water inflows, enabling them to optimize reservoir management and schedule power generation more effectively. This improves their ability to reliably provide electricity and ancillary services like frequency regulation or spinning reserve. It also helps reduce spill risk and maximize revenue from both energy and grid support markets.
Employing advanced AI hydrology forecasts, such as Upstream Tech’s Hydroforecast, offers a substantial advantage in water resource management. These sophisticated models surpass the limitations of traditional forecasting methods by providing extended prediction horizons and enhanced accuracy. This improved forecasting capability is particularly beneficial for hydropower generators, enabling them to more precisely anticipate water inflow into their reservoirs.
Consequently, generators can optimize the scheduling of electricity generation, including the crucial allocation of frequency regulation and spinning reserve resources. This proactive and data-driven approach leads to greater operational efficiency, reduced risks associated with water availability fluctuations, and ultimately, a more reliable and sustainable power supply. The detailed insights provided by AI-powered hydrology forecasts empower hydropower operators to make informed decisions, maximizing energy output while ensuring grid stability and environmental stewardship.
