FLEXIBLE GENERATION

In Belgium, ENGIE is developing flexibility to support the evolving power mix

By ENGIE - 15 December 2025 - 15:33

ENGIE’s decarbonization strategy in Belgium has reached a major milestone with the Flémalle gas-fired power plant and the Vilvoorde battery park. These flagship projects strengthen the stability of the power grid and help integrate renewables into Belgium’s electricity mix.

 

Since the first power plants began operating in 1885, ENGIE has been a major energy player in Belgium. The planned shutdown of five of the country’s seven nuclear reactors, and above all the 2022 energy crisis, has brought security of supply back to the top of national energy priorities.

To rise to this challenge, ENGIE is rolling out so-called “flexibility” solutions. These make it possible to generate electricity quickly when needed, but also to store power when consumption is lower than production and release it during peak hours. Such assets are essential to ensure the smooth integration of renewable energy sources (RES) and to maintain real-time grid balance.

Indeed, renewables are expanding rapidly. In Belgium, the Group is pursuing an ambitious investment program in this area, with a target of 1,000 MW of onshore wind and 300 MW of solar capacity by 2030.


Complementary flexibility solutions

ENGIE is targeting 5 to 6 GW of flexible capacity in Belgium by 2030, based on a portfolio of complementary technologies.
 

  • Hydraulic reservoirs: the Coo pumped-storage power station, near Liège, is a strategic asset whose capacity was increased to 1,160 MW in 2025. This pumped-storage facility moves large volumes of water between two reservoirs to generate electricity when demand is high. It can be activated within just a few minutes, making it a key tool for absorbing rapid fluctuations in renewable generation.
  • Flexible thermal generation: the imminent commissioning of the Flémalle combined-cycle gas turbine (see below) will provide dispatchable, highly responsive capacity—essential for meeting demand peaks and securing the grid during periods of stress.
  • Battery storage: the Vilvoorde battery park, one of the largest in continental Europe (200 MW), was commissioned in mid-November 2025 (see below). It will be complemented in 2026 by the Kallo (100 MW) and Drogenbos (80 MW) projects.

Yasmine, an ENGIE employee in Belgium, takes us behind the scenes of the Coo pumped-storage power plant.


 

ENGIE also promotes demand-side flexibility through tools that encourage consumers to shift their consumption to off-peak hours. On the Smart App, an Energy Score helps guide customers in managing their usage. The Empower Flextime solution, meanwhile, optimizes the charging of electric vehicles.

 

Did you know?

ENGIE is the leading energy player in Belgium. The Group accounts for nearly 40% of electricity generation and more than 40% of electricity supply. In 2025, ENGIE supplied electricity to 2.8 million of Belgium’s 5.2 million households.

ENGIE is also the operator of Belgium’s nuclear power fleet.

 

The five strengths of the Flémalle power plant

The Flémalle combined-cycle gas turbine (CCGT) power plant plays a key role in the resilience of Belgium’s power grid—and more besides. It stands out for several major technological advantages.
 

  1. High ramp-up capability: it can increase output by 50 MW per minute, allowing it to correct grid imbalances in record time.
  2. High capacity: with an output of 875 MW, it is the most powerful gas-fired plant in the country. It is designed to generate between 4.4 and 5.3 TWh per year—equivalent to the annual consumption of more than one million households (Belgium has 5.2 million households).
  3. Outstanding efficiency: with an efficiency rate of 63%, it is among the most efficient CCGTs in the world, outperforming current plants by 5 to 10% thanks to an exceptionally large heat recovery steam generator.
  4. Lower fuel use: it uses 20% less gas to produce the same amount of electricity, resulting in lower costs and reduced CO₂ emissions compared with a conventional plant.
  5. Future-ready: it will be able in the future to integrate CO₂ capture or burn green gases such as hydrogen, biogas, or synthetic methane.

 

Vilvoorde, one of Europe's largest battery parks

In Vilvoorde, on the outskirts of Brussels, ENGIE operates two giant batteries, each rated at 100 MW / 400 MWh. This is one of the largest battery parks in continental Europe. Managed by an algorithm, they optimize charging and discharging in real time to stabilize the grid and enable greater integration of renewable energy. Recently selected through a competitive auction, the new Drogenbos battery project—also near Brussels—will further strengthen daily flexibility. This future storage system (80 MW / 320 MWh), made up of 88 modules, will be able to inject electricity for four hours, equivalent to the daily consumption of nearly 38,400 households. Construction will start in March 2026, with commissioning scheduled for September 2027.

Following Vilvoorde (200 MW / 800 MWh) and Kallo (100 MW / 400 MWh), Drogenbos will bring ENGIE’s total battery storage capacity in Belgium to nearly 400 MW.

 

How Belgium’s “CRM” system supports the development of flexible assets

To ensure grid resilience, the Belgian regulator has introduced the Capacity Remuneration Mechanism (CRM). This scheme guarantees revenues to players capable of supplying electricity during peak periods.

The capacities concerned are backed by contracts of up to 15 years with Belgium’s transmission system operator, Elia, which remunerates their availability and provides producers with predictable revenues. The aim is to encourage the development of ultra-responsive capacities that can be mobilized at any time to ensure the stability of the power grid.

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