TPP AES Galabovo, Bulgaria: feasibility study and pre-engineering for coal-to-molten salt conversion

The challenge
 

TPP AES Galabovo is Bulgaria's most modern coal-fired power plant, built in 2010. As European decarbonisation targets accelerate, AES Bulgaria needed to find a transition path that preserved the value of a significant asset, protected local employment, and contributed to grid stability in a Bulgarian energy system increasingly dependent on intermittent renewables.

The question was not simply how to decommission, it was whether the existing infrastructure could be repurposed into something more valuable than scrap.

The approach
 

Since 2023, Aalborg CSP has been collaborating with AES Bulgaria on a feasibility study and subsequent pre-engineering work, assessing the conversion of TPP AES Galabovo into a large-scale molten salt energy storage facility. 

The work evaluated a Power-to-Salt approach: replacing the coal-fired boiler with a molten salt Carnot battery, while retaining the existing steam turbines, generators, and high-voltage transmission infrastructure.

The proposed solution converts surplus electricity from wind and solar into heat, stores it in molten salt at temperatures up to 565°C, and generates high-pressure steam on demand to drive the existing turbines, producing electricity without fossil fuel combustion.

The project
 

AES Bulgaria has publicly confirmed the technical feasibility of the conversion. Preliminary figures for the project indicate a storage capacity of 1,725 GWh (345 MW dispatchable for five hours) and a preliminary investment estimate of approximately €400 million.

The economics are driven by the reuse of existing infrastructure. Replacing only the boiler rather than building a greenfield storage facility eliminates a significant share of capital expenditure and avoids the cost of decommissioning.

Why it matters beyond Bulgaria
 

There are more than 250 coal-fired power plants across Europe facing decommissioning in the coming years. TPP AES Galabovo represents a template: a modern, well-maintained asset that becomes a liability under decarbonisation regulation, but which contains turbines, generators, and grid connection infrastructure that would cost hundreds of millions to replicate from scratch.

The Power-to-Salt conversion model turns that liability into a long-duration storage asset, exactly what grids with high renewable penetration need most.

"Our state-of-the-art coal-fired power plant represents valuable infrastructure for the country and we are actively working on a solution that aligns with European and Bulgarian energy transition goals. This transformation would enable more renewable energy to be integrated into the market by storing surplus production and releasing it when demand is high." — Ivan Tzankov, President, AES Bulgaria