Fuel Cell Stack Seal Paste Thermal Setting

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Solution Overview

Problem

Fuel cell stacks, particularly those with planar geometry, face challenges in maintaining effective seals at high operating temperatures and during thermal cycling, which can lead to seal failure and potential fuel gas leakage or ignition.

Innovation Solution

A method involving the application of a seal paste, such as one containing glass ceramic or glass powder in an organic binder, to fuel cell components like interconnects, followed by thermal treatment to set the seal, using techniques like screen printing or stencil printing, ensuring the seal can withstand high temperatures and thermal expansion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional sealing methods are used, then seals can prevent fuel gas leakage at start-up temperatures, but seals fail to maintain integrity at high operating temperatures between 750°C and 950°C

Engineering Contradiction:

Improveseal integrityVSAvoidoperating temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The seal paste composition is specifically formulated with glass ceramic or glass powder materials that undergo controlled thermal transformation at high temperatures. The binder burns off and the glass ceramic matrix softens and sets between 750-950°C, creating a seal that is flexible at low temperatures but rigid and stable at operating temperatures, thus resolving the contradiction between low-temperature sealing and high-temperature integrity

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The seal paste comprises a composite formulation combining organic binder with inorganic glass ceramic or glass powder materials. This composite structure provides dual functionality: the organic binder ensures adhesion and flexibility at room temperature for proper sealing, while the inorganic glass ceramic phase provides thermal stability and structural integrity at high operating temperatures up to 1000°C

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If seals are made rigid to withstand high temperatures, then thermal stability is improved, but mechanical stresses from thermal cycling cause damage to components

Engineering Contradiction:

Improvethermal stabilityVSAvoidmechanical strength

Core Design Contradiction:

Stability of the object's compositionVSStrength

Solution Approach 1:

The glass ceramic material in the seal paste undergoes a controlled phase transition during thermal cycling. The glassy phase allows for gradual deformation and stress relaxation during heating and cooling cycles, preventing catastrophic failure. This phase transition capability enables the seal to maintain both thermal stability and mechanical strength under repeated thermal stress

Inventive Principle:

Principle #36Phase transitions

Solution Approach 2:

The seal paste formulation is designed to match the thermal expansion characteristics of adjacent fuel cell components. By controlling the coefficient of thermal expansion through material composition, the seal expands and contracts harmoniously with surrounding components during thermal cycling, minimizing differential stress and preventing mechanical damage while maintaining seal integrity

Inventive Principle:

Principle #37Thermal expansion

3Ease of operation

If seal paste is applied manually, then application flexibility is improved, but manufacturing precision and consistency of seal quality deteriorate

Engineering Contradiction:

Improveapplication flexibilityVSAvoidseal application precision

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The seal paste application process is segmented into controlled stages: screen printing or stencil printing creates a precise pattern, followed by controlled drying and thermal treatment stages. This segmentation allows each step to be optimized independently, achieving both precision in seal placement and flexibility in the overall manufacturing process

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Manual application methods are replaced with screen printing or stencil printing techniques that use controlled material deposition through screens or stencils. This substitution maintains ease of operation and adaptability while dramatically improving manufacturing precision, consistency, and repeatability of seal application across production batches

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 method provides durable seals that maintain integrity at temperatures up to 1000°C, preventing fuel and air leakage and minimizing mechanical stresses, thus enhancing the reliability and longevity of fuel cell stacks.

Implementation Method 1

thermally treating the fuel cell stack to set the seal paste into a seal

Methodology Applied

Scientific EffectThermal treatment: Heat Treatment

Implementation Method 2

Expansion and contraction of fuel cell stack components (including seals) due to thermal cycling

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS8968509B2Methods and devices for printing seals for fuel cell stacks

Publication Date: 2015.03.03 BLOOM ENERGY CORP

AI summary

Various embodiments include a fuel cell stack seal application method including the step of applying a seal paste to a fuel cell, placing the fuel cell in a fuel cell stack, and thermally treating the fuel cell stack to set the seal paste into a seal. Further embodiments include applying the seal paste to an interconnect using stencil printing.