Conceptual engineering of a Power-to-Salt Carnot Battery Energy Storage System for a coal-fired combined heat and power plant, Netherlands

The challenge
 

A coal-fired combined heat and power plant in the Netherlands needed to assess whether its existing infrastructure could be repurposed to integrate a large-scale Carnot battery energy storage system, eliminating the coal boiler while preserving the turbines, buildings, pipes, and feedwater preheaters that represent significant remaining asset value. 

The old coal boiler building was identified as the location for the new Carnot battery. The engineering question was whether the molten salt system could be sized to fit that footprint, deliver the same steam parameters as the original coal boiler, and be built within a credible budget, giving the plant operator the technical and commercial basis needed to take an investment decision.

The approach

Aalborg CSP delivered a conceptual engineering package covering the complete Power-to-Salt Carnot Battery system, from charging the molten salt storage during periods of surplus electricity to discharging stored heat as high-pressure steam through the existing turbines.

The scope covered:

• Heat and mass balances for the complete system across charge and discharge cases
• Process flow diagram for the power island
• 2D and 3D arrangement of the Carnot battery within the existing plant footprint — sized to fit the old coal boiler building
• Molten salt tank dimensioning and design
• Pump requirements and sizing
• Instrumentation overview
• Electric heating elements and immersed electrical heaters in tanks
• Electrical heat tracing and heat loss estimation
• State-of-the-art component evaluation — tanks, pumps, heaters — based on current market conditions
• CAPEX estimation for the full system

The system was designed around a eutectic mixture of sodium nitrate and potassium nitrate as the storage medium, heated by electrical elements during periods of excess grid supply, stored in insulated tanks, and discharged through a steam generation system delivering steam at the same parameters as the original coal boiler. The Carnot battery operates in parallel with or as a replacement for the existing plant boiler, giving the operator flexibility to transition at a pace that suits the business case. The result was a complete technical basis the client could use directly in their project development and investment decision process.

Why it matters
 

Coal-fired power plants across Europe face the same structural challenge: assets built around continuous fossil fuel combustion that are becoming uneconomical to operate but contain significant infrastructure value in their turbines, grid connections, and buildings. 

The Power-to-Salt Carnot battery conversion model demonstrated here (charging from surplus renewable electricity, storing in molten salt, dispatching as dispatchable steam through existing turbines) offers a technically credible path to preserving that infrastructure value while eliminating fossil fuel dependency entirely. 

The engineering deliverables produced in this engagement gave the client the system design, equipment list, 3D layout, and cost basis needed to take the project to the next development phase.

Read more about our coal plant conversion work →