Molten Carbonate Eutectic for High-Temperature Thermal Energy Storage
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Solution Overview
Problem
Previous thermochemical energy storage materials, particularly carbonate eutectic materials, face issues such as agglomeration, sintering, slow gas diffusion, reactivity, and low energy density due to limited reacting surface area, leading to inefficient and unsustainable energy storage reactions at high temperatures.
Innovation Solution
A thermochemical energy system utilizing a molten metal carbonate eutectic formed by reacting metals with carbon dioxide, which can reversibly reform metal oxides, maintaining carbon dioxide partial pressure below equilibrium to prevent agglomeration and sintering, and utilizing high enthalpy carbonate-based materials for efficient heat storage and release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If powdered carbonate materials are used for thermochemical heat storage, then the reacting surface area is increased, but the particles undergo agglomeration and sintering during cycling, reducing volumetric density and reaction efficiency
Solution Approach 1:
The patent changes the physical state parameter of the carbonate material from solid powder to molten liquid state. By operating above the melting point of the carbonate eutectic mixture, the system transforms the material into a liquid phase that maintains high reacting surface area without particle agglomeration or sintering, thereby resolving the contradiction between surface area and cycling stability
Solution Approach 2:
The patent uses a eutectic mixture of multiple carbonate salts (e.g., Li2CO3, Na2CO3, K2CO3) that creates a composite material system with a depressed melting point. This composite approach allows the material to remain molten at lower temperatures, maintaining liquid-state advantages while using readily available carbonate materials
2Productivity
If smaller particles are used to increase reacting surface area, then the energy conversion efficiency is improved, but the volumetric density is reduced to 10% of theoretical and particle sintering occurs
Solution Approach 1:
The patent changes the aggregation state from solid particles to liquid molten state, eliminating the need for small particles. The liquid molten carbonate maintains high surface area for reaction while preserving 100% volumetric density, as the material forms a continuous liquid phase rather than discrete particles that would require size reduction
3Quantity of substance
If molten carbonate eutectic materials are used for heat storage, then the energy density is improved, but the materials suffer from agglomeration and sintering that prevents sustained cycling
Solution Approach 1:
The patent maintains the material in a molten liquid state above its melting point throughout the cycling process. This parameter change prevents agglomeration and sintering that occur in solid materials, while the liquid state preserves high energy density. The system achieves both high energy density and material stability by operating in the liquid phase
4Area of moving object
If powdered materials are used, then the reacting surface area is increased, but gas diffusion and reactivity are slowed
Solution Approach 1:
The patent changes the material state from solid powder to liquid molten carbonate. In the liquid state, gas diffusion occurs through the bulk liquid phase rather than being limited to surface reactions in powders. This parameter change dramatically increases gas diffusion rates and reactivity while maintaining high effective surface area throughout the liquid volume
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves high thermal energy density, efficient heat storage and release, and long-term storage capabilities, with high exergetic efficiency and cost-effectiveness, suitable for applications like concentrated solar power systems, overcoming previous limitations of energy density and cycling stability.
Implementation Method 1
At high energy input, an endothermic reaction takes place, effectively storing energy in the chemical bonds formed during the reaction
Implementation Method 2
The reaction products are stored separately and later recombined in an exothermic reaction to release the stored energy
Implementation Method 3
Molten carbonate eutectic technology has previously been utilized for heat storage primarily using phase transformation of the molten salts
Data Source
AI summary
Disclosed are thermal energy storage systems and methods that utilize metal carbonate eutectics that can undergo high temperature reversible reactions to form mixtures of metal oxides. The metal oxides undergo an exothermic reaction with carbon dioxide to form the molten metal carbonate eutectics, and the molten metal carbonate eutectics undergo an endothermic decarbonization reaction to form the metal oxides and carbon dioxide. By carrying out the reversible reactions at a temperature above the melting point of the carbonate eutectic, the systems provide high thermal conductivity and reversible stability for thermal energy storage.