Power outage: how to adapt the network with more renewables?

Network operators ensure a constant balance between electricity supply and demand. The indicator of this balance is the electrical frequency, calibrated at 50 Hz in Europe and 60 Hz in the United States. Too great a deviation from this standard can endanger the network.

Instability, not inevitable

Historically, the electrical system has relied on "conventional" power plants (gas, coal, nuclear, and hydroelectric): turbines coupled with "rotating machines" transforming mechanical energy into electricity. These machines are the keystones of the electrical system's stability.

With their gigantic rotors spinning at high speed, these machines provide inertia to the electrical system: if a power plant fails or if electricity demand increases too quickly, they help stabilize the network by releasing the motion (or kinetic) energy stored in the rotors.

But with the rise of solar and wind renewables - which use electronics to convert electricity on the grid, not rotating machines - this stabilization is becoming more difficult.

Producing electricity without fossil fuels will "make hydroelectric and nuclear power plants even more essential for stabilizing the system" thanks to their rotating machines, notes Marc Petit, professor of electrical systems at the CentraleSupélec school.

In the future, renewable energies will have to, in addition to providing carbon-free electricity, "help the system with additional controls to support the network, particularly in terms of inertia," emphasizes José Luis Domínguez-García, an expert in electrical systems at the Catalan Energy Research Institute (IREC).

Technical solutions already exist to compensate for the lack of inertia and thus support grid stability. In the midst of a transition away from coal, Great Britain is banking on flywheels, a very old concept: these systems use surplus renewable energy to turn a large wheel, which creates kinetic energy. And this stored energy can be transformed into electricity on the grid if necessary.

Compensate for variability

Just before the April 28 blackout, wind and solar power provided 70% of Spain's electricity. But these energies are intermittent and variable by nature: what happens when there's no wind or sun?

Depending on the country, security of supply is ensured by thermal power plants (gas or coal), nuclear power plants, or hydroelectric power plants. These resources must be available within minutes to take over.

Accelerating the rollout of renewables will require a significant effort in storage, using pumped storage in hydroelectric dams, the most widespread method, and increasingly, stationary batteries—large blocks similar to shipping containers—associated with wind farms or solar power plants. This is an area in which China dominates in terms of installed capacity.

According to the International Energy Agency (IEA), tripling global renewable energy capacity by 2030 while maintaining security of supply will require a sixfold increase in storage capacity, with batteries accounting for 90% of the effort.

Furthermore, demand will need to be made more flexible, in buildings, factories, and for charging electric cars. For example, by shifting consumption to when solar power is at its peak, in the middle of the day.

Resize the network

Giant outages of this type in the past have "almost always" been caused by transmission problems, not generation, said Mike Hogan, an advisor to the Regulatory Assistance Project (RAP).

The renovation of sometimes century-old power lines, the arrival of renewable energies and the connection of new consumption (data centers, electrification of factories) will require tens or even hundreds of billions of euros of investment to create new, more powerful lines or double existing lines.

Another project is strengthening interconnections between the countries, essential infrastructure that helped reconnect Spain via France during the blackout. By 2028, the exchange capacity between the two countries is expected to increase from 2,8 to 5 GW, reducing the peninsula's electrical isolation.