Mothballed CCGT plants

Added Values, in collaboration with Dansk Fjernvarme, is exploring whether decommissioned and nearly scrapped power plants can be “revived” and help strengthen the security of the electricity system.

Date

Feb. 11. 2025

Author

Added Values

Mothballed CCGT plants can alleviate Dunkelflaute in Denmark.

Added Values, in collaboration with Dansk Fjernvarme, is investigating whether decommissioned and nearly scrapped power plants can be “brought back to life” and help strengthen the security of the electricity system.

The background: Risk of capacity shortfalls

As an increasing share of Northern Europe’s electricity production shifts to wind and solar power, we are inevitably facing longer periods from hours to days, and sometimes even weeks where serious capacity shortfalls may occur across parts of the region. These periods are referred to as Dunkelflaute.

One such example occurred in September 2023, when Northern Europe experienced a weather phenomenon known as an Omega block a meteorological pattern that unfortunately brings very stable weather conditions with little or no wind across large areas of the continent.

The consequence is that our domestic wind power production can drop to near zero. At the same time, we risk losing the electricity supply guarantee provided by international transmission connections, as typically wind-rich countries like Germany and the UK also experience calm conditions.

Top graphic: A period of approximately 12 days with little to no wind production in Denmark. Source: Added Values

Bottom graphic: Ω – Omega block with stable weather across Northern Europe. Source: DMI

Power capacity inadequacy

If such a situation occurs during winter, solar power production is also at a minimum just as it is every night of the year. This creates a critical scenario with a real risk of Dunkelflaute or power capacity inadequacy the term used by Energinet.

In the worst-case scenario, power inadequacy can lead to a brownout (the disconnection of certain consumers or regions) or, even worse, a blackout (the collapse of parts of the power system).

In the coming years, this risk will only increase as large CHP plants in both Denmark and neighboring countries are decommissioned (mothballed or scrapped) and replaced by district heating facilities without associated electricity generation.

We are exploring whether powerplants can be brought back to life

Dansk Fjernvarme is one of the stakeholders highlighting this risk, and they have tasked us at Added Values with investigating whether these decommissioned and nearly scrapped but not yet dismantled power plants can be reactivated and contribute to securing the electricity system. The project focuses primarily on CCGT (combined-cycle gas turbine plants) and gas engines.

We are approaching this project by engaging in dialogue with operational staff at selected CHP plants to gain an overview of both the technical challenges that must be overcome to make the plants grid-ready again and the associated costs.

Two common technical issues found at CCGT plants are:

Bottlenecks that prevent rapid and controlled acceleration of the gas turbine plant from the moment the “start” button is pressed
Outdated control systems that may need to be replaced so that newer staff can operate them safely and effectively

Once these issues are addressed, a CCGT plant on the verge of being scrapped could potentially be brought back online and in doing so, play a meaningful role in maintaining supply security.