SOFC Stack Assembly with Decoupled Compression for Gas Tightness
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Solution Overview
Problem
Existing technologies fail to adequately address mechanical stress in multiple stack assemblies of planar electrochemical cells, particularly in compact enclosures, while maintaining mechanical compression and gas tightness, which can lead to irreversible deformation and failure.
Innovation Solution
A stack assembly with a decoupled load-applying mechanism using independent tightening units for the stack and manifold sections, incorporating compliant and dielectric materials to prevent short-circuiting and gas leaks, and a spring-loaded assembly in a cold section to manage thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If materials are used to exert compression on the stack in close vicinity, then mechanical compression is maintained, but cost increases due to prohibitive material requirements
Solution Approach 1:
The compression system is segmented into two independent parts: a first compression system using tie rods with springs/washers located in cold sections, and a second compression system using a compression frame in the hot section. This segmentation allows each system to be optimized for its specific location and function, reducing overall cost.
Solution Approach 2:
A load-applying mechanism acts as an intermediary between the tie rods (in cold section) and the stack (in hot section). This mechanism transfers and distributes the compression force from the tie rods to the stack through a compression frame, enabling cost-effective materials to be used in the cold section while still providing necessary compression to the stack.
2Ease of manufacture
If tie rods extend to cold section with springs/washers, then compression is achieved with lower cost materials, but device complexity increases
Solution Approach 1:
The tie rods serve multiple functions: they provide mechanical compression, allow for thermal expansion compensation through springs/washers in the cold section, and can be adjusted to maintain proper compression force. This multi-functionality reduces the need for separate components, simplifying the overall design despite the extended structure.
3Power
If multiple cells are integrated in each repeating element, then power density increases, but thermomechanical stress increases leading to deformation and failure
Solution Approach 1:
Different parts of the stack receive different compression forces tailored to their specific needs. The load-applying mechanism distributes compression force through the compression frame to specific areas of the stack, allowing optimized stress distribution that accounts for local variations in thermomechanical stress, thereby preventing deformation and failure while maintaining high power density.
4Temperature
If stacks are placed in same hot enclosure, then thermal gradients are reduced, but mechanical stress between stack and surroundings increases
Solution Approach 1:
The system changes the thermal parameter by extending tie rods from the cold section into the hot section, creating a temperature gradient along the tie rod length. This allows the stack to be thermally isolated in the hot section while the tie rods in the cold section provide compression, thereby reducing thermal gradients across the stack while managing mechanical stress through the temperature-dependent properties of the compression elements.
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 solution effectively reduces mechanical stress, prevents deformation, and maintains gas tightness, ensuring long-term operational reliability and efficiency of the electrochemical device.
Implementation Method 1
Alleviation of mechanical stress between the stack and its surrounding, which is basically caused by the same phenomena as those present within the stack (thermal expansion coefficient (TEC) mismatch, physico-chemical alterations, thermal gradients)
Implementation Method 2
mechanical compression of the stack needs to be maintained
Implementation Method 3
Mechanical stress can manifest itself on different levels, i.e. within the stack, or between the stack and its surroundings to which it is mechanically connected
Implementation Method 4
incorporating compliant and dielectric materials to prevent short-circuiting and gas leaks
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention refers to a stack assembly (27) for a solid oxide fuel cell (SOFC) or solid oxide electrolyser (SOE)device. The assembly (27) comprises: - a housing, - at least one stack arrangement (1) mounted within said housing, the at least one stack arrangement (1) comprising: - a base plate (3), - a top plate (2), - a stack (S) mounted between said base plate (3) and said top plate (2), - at least one sealing element disposed in the at least one stack arrangement (1) to provide a fluid-tight stack assembly (27), - a load applying mechanism with a first tightening unit (5) adapted to apply a tightening load to the at least one stack arrangement (1) in stacking direction. The load applying mechanism comprises a second tightening unit (4) adapted to apply a tightening load to said manifold section of the stack (S). The first tightening unit (5) and the second tightening unit (4) are independent of each other.