Fuel Cell Interconnect Assembly CTE Matching
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Solution Overview
Problem
Solid oxide fuel cells (SOFCs) face challenges with thermal expansion mismatch between components, leading to mechanical stress, leakage, and reduced efficiency, especially under pressurized conditions, where existing sealing methods either crack or allow excessive gas leakage.
Innovation Solution
A fuel cell stack design with a hermetic seal and interconnect assembly where the coefficient of thermal expansion (CTE) of the interconnect and fuel cell elements satisfy a predetermined matching condition, using braze joints and hermetic seals to maintain integrity and prevent gas leakage, allowing for the use of cheaper, lighter metallic interconnects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional sealing methods are used between interconnect and fuel cell element, then assembly is easier to manufacture, but thermal expansion mismatch causes mechanical stress and leakage
Solution Approach 1:
The patent changes the CTE parameter of the interconnect assembly by selecting specific materials (e.g., metallic interconnect with CTE of 10-20 × 10^-6/K) and designing the composite structure to achieve CTE matching with the fuel cell element (e.g., 8-15 × 10^-6/K). This parameter matching eliminates thermal expansion mismatch while maintaining manufacturing feasibility through standardized assembly procedures.
Solution Approach 2:
The interconnect assembly is designed as a composite structure comprising a metallic interconnect and ceramic interfaces, where each material contributes its favorable properties. The metallic interconnect provides ductility and CTE adjustability, while the ceramic interfaces provide chemical stability and electrical insulation, together achieving both sealing integrity and ease of manufacture.
2Stability of the object's composition
If CTE-matched materials are used for interconnect assembly, then thermal expansion mismatch is reduced, but material selection and manufacturing become more complex
Solution Approach 1:
The patent applies local quality by providing CTE matching specifically at the critical interface between the interconnect assembly and fuel cell element, while other parts of the system can use different materials. The ceramic interfaces are specifically engineered with CTE values between 5-25 × 10^-6/K to match the fuel cell element, while the metallic interconnect provides structural support with its own CTE characteristics.
3Reliability
If hermetic seal is implemented with CTE-matched components, then gas leakage is prevented, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs a flexible sealing approach where the ceramic interfaces and braze joints provide compliance to accommodate minor dimensional variations. The sealing structure can flex and deform elastically during thermal cycling, compensating for manufacturing tolerances and maintaining hermetic sealing without requiring extremely tight manufacturing precision.
4Weight of moving object
If metallic interconnects are used instead of traditional materials, then weight is reduced, but thermal expansion matching becomes more challenging
Solution Approach 1:
The patent utilizes the advantage of metallic materials having higher and more adjustable CTE values (10-20 × 10^-6/K) compared to traditional ceramic interconnects. By carefully selecting the metallic alloy composition and thickness, the overall CTE of the interconnect assembly can be tuned to match the fuel cell element, achieving both weight reduction and thermal expansion stability.
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
This design maintains hermetic sealing and increases fuel cell efficiency and economy by matching thermal expansion rates, preventing leakage and enabling pressurized operation without weight or conductivity penalties.
Implementation Method 1
a fuel cell element coupled to the interconnect assembly at the interface side via a hermetic seal
Implementation Method 2
a cathode-side interface coupled to an interconnect via a first braze joint, and an anode-side interface coupled to the interconnect via a second braze joint
Implementation Method 3
the interconnect assembly having a first coefficient of thermal expansion (CTE) at an interface side of the interconnect assembly... the fuel cell element having a second CTE at the interface side, the first CTE and the second CTE satisfying a predetermined CTE matching condition
Data Source
AI summary
A fuel cell stack is described. The fuel cell stack comprises an interconnect assembly comprising a cathode-side interface coupled to an interconnect via a first joint, and an anode-side interface coupled to the interconnect via a second joint, the interconnect assembly having a first coefficient of thermal expansion (CTE) at an interface side of the interconnect assembly. The fuel cell stack further comprises a fuel cell element coupled to the interconnect assembly at the interface side via a hermetic seal, the fuel cell element having a second CTE at the interface side, the first CTE and the second CTE satisfying a predetermined CTE matching condition.