Tubular Solid Oxide Fuel Cell Assembly Thermal Expansion Management

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Solution Overview

Problem

Tubular solid oxide fuel cell assemblies face operational difficulties due to thermal stresses causing ohmic losses from the separation of current collector components from electrodes, resulting from differences in thermal expansion between ceramic electrodes and metal or metal-containing current collectors.

Innovation Solution

A tubular solid oxide fuel cell assembly design featuring a shared current collector with a higher coefficient of thermal expansion and a retainer with a lower coefficient, maintaining electrical contact surfaces under compression, preventing separation and maintaining constant contact area despite thermal cycling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If a metal current collector is used in tubular SOFC assemblies, then electrical conductivity is improved, but thermal expansion mismatch causes separation from ceramic electrodes during thermal cycling

Engineering Contradiction:

Improveohmic lossesVSAvoidelectrical contact stability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent changes the coefficient of thermal expansion parameter of the current collector by selecting a material (such as a ceramic or ceramic-coated material) whose thermal expansion coefficient matches that of the ceramic electrodes, thereby preventing separation during thermal cycling while maintaining electrical conductivity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite material structures for the current collector, such as ceramic-ceramic composites or metal-ceramic composites, that combine the electrical conductivity of metals with the thermal expansion compatibility of ceramics, resolving the contradiction between conductivity and thermal stability

Inventive Principle:

Principle #40Composite materials

2Reliability

If ceramic materials are used for fuel cell units, then thermal stability is improved, but electrical conductivity is insufficient compared to metal current collectors

Engineering Contradiction:

Improvethermal stabilityVSAvoidelectrical resistance

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent uses composite materials such as ceramic-matrix composites or ceramic-metal composites that combine the thermal stability of ceramics with enhanced electrical conductivity, allowing the fuel cell units to maintain both thermal resistance and electrical conductivity

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent modifies the electrical conductivity parameter of ceramic materials through doping, compositional adjustment, or microstructure control, enabling ceramics to achieve sufficient electrical conductivity while maintaining their inherent thermal stability

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If tubular SOFC assemblies undergo thermal cycling, then operational flexibility is improved, but differential thermal expansion causes cumulative separation and power losses

Engineering Contradiction:

Improveoperational cycling capabilityVSAvoidpower-robbing ohmic losses

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent explicitly addresses thermal expansion by selecting materials with matched coefficients of thermal expansion for the current collector and electrodes, ensuring that both components expand and contract together during thermal cycling, thereby preventing separation and maintaining consistent electrical contact

Inventive Principle:

Principle #37Thermal expansion

Solution Approach 2:

The patent changes the thermal and mechanical parameters of the assembly materials to accommodate thermal cycling, using materials with appropriate elastic moduli, thermal expansion coefficients, and creep resistance to maintain contact pressure and electrical conductivity through multiple cycles

Inventive Principle:

Principle #35Parameter changes

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 design ensures a constant area of electrical contact between current collectors and electrodes, mitigating ohmic losses and maintaining efficiency over multiple on-off cycles.

Implementation Method 1

the current collector possessing a coefficient of thermal expansion greater than that of the fuel cell units, the current collector and each electrode layer in electrical contact therewith possessing substantially conforming electrical contact surfaces

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

an intermediate electrolyte layer that conducts ions but prevents electrons from passing

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 3

a fuel cell is an electrical device which converts the energy potential of fuel to electricity through an electrochemical reaction

Methodology Applied

Scientific EffectElectrochemical reaction: Fuel Cell

Data Source

PatentUS9774055B2Tubular solid oxide fuel cell assembly and fuel cell device incorporating same

Publication Date: 2017.09.26 WATT FUEL CELL CORP

AI summary

A tubular solid oxide fuel cell assembly includes at least two tubular solid oxide fuel cell units, at least one shared current collector and a retainer for retaining a section of the fuel cell units and shared current collector in close fitting relationship therewith.