Solid Oxide Fuel Cell Stack Heat Treatment with Eductor Recycling

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Solution Overview

Problem

Fuel cell stack fabrication processes face challenges with thermal gradients causing cracks or warping, leading to failed stacks and inefficient quality control, with previous process controls being slow, expensive, and ineffective in improving stack quality.

Innovation Solution

The use of an eductor to recycle air and fuel streams within the furnace, along with a hydrogen separator, to maintain consistent temperatures and reduce thermal gradients, enabling tighter performance specifications and identifying failure modes in fuel cell stacks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional process control methods are used with external gas supplies and exhaust systems, then the fuel cell stacks can be processed, but thermal gradients cause cracks or warping leading to failed stacks

Engineering Contradiction:

Improvestack qualityVSAvoidthermal gradients

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The patent recovers heat from exhaust gases and reused process gases, redirecting them back into the furnace to maintain uniform temperature distribution. This heat recovery system eliminates thermal gradients that cause cracking and warping, thereby improving stack reliability without sacrificing processing capability

Inventive Principle:

Principle #34Discarding and recovering

Solution Approach 2:

The patent implements a feedback control system that monitors temperature distribution within the furnace and adjusts gas flow and heating accordingly. This ensures uniform temperature maintenance throughout the fuel cell stack during processing, preventing thermal gradient-induced defects

Inventive Principle:

Principle #23Feedback

2Measurement precision

If previous process controls were implemented at end user level, then defective stacks could be identified, but the control was slow to respond and expensive

Engineering Contradiction:

Improvedefect detectionVSAvoidresponse time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent incorporates real-time monitoring and control systems that detect potential defects during the fabrication process itself, rather than waiting for end-user inspection. This preliminary detection allows immediate corrective action, reducing response time and preventing defective stacks from completing processing

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent implements continuous feedback monitoring of process parameters including temperature, gas flow, and stack performance during fabrication. This real-time feedback enables immediate detection and correction of issues, eliminating the delay inherent in post-manufacturing inspection systems

Inventive Principle:

Principle #23Feedback

3Ease of operation

If blowers and mass flow controllers regulate process gas flows with external supplies, then gas flow control is achieved, but energy consumption increases and furnace components experience wear

Engineering Contradiction:

Improvegas flow controlVSAvoidenergy consumption

Core Design Contradiction:

Ease of operationVSUse of energy by moving object

Solution Approach 1:

Inventive Principle:

Principle #34Discarding and recovering

Solution Approach 2:

The system recycles its own exhaust gases and process gases back into the furnace, creating a self-sustaining thermal environment. This reduces the need for continuous external energy input and minimizes wear on heating components while maintaining precise gas flow control

Inventive Principle:

Principle #25Self-service

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 approach improves the sensitivity to failure modes, reduces the likelihood of defective stacks being produced, and enhances the overall quality and performance of fuel cell stacks by maintaining consistent temperatures and recycling heated air and fuel, thus reducing energy consumption and wear on furnace components.

Implementation Method 1

an eductor is used to recycle air into the air inlet stream

Methodology Applied

Scientific EffectThermal convection: Convection

Implementation Method 2

maintain consistent temperatures and reduce thermal gradients

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 3

a hydrogen separator is used to recycle hydrogen to the fuel inlet stream

Methodology Applied

Scientific EffectGas separation:

Implementation Method 4

The fuel cell, operating at a typical temperature between 750° C. and 950° C.

Methodology Applied

Scientific EffectThermal heating: Heating

Implementation Method 5

Fuel cell stack fabrication may require sintering of the fuel cells and separate conditioning of the fuel cells

Methodology Applied

Scientific EffectSintering: Sintering

Data Source

PatentUS9142845B2Solid oxide fuel cell stack heat treatment methods and apparatus

Publication Date: 2015.09.22 BLOOM ENERGY CORP

AI summary

Systems and methods are provided for fuel cell stack heat treatment. An eductor may be used to recycle air into the air inlet stream or to recycle fuel into the fuel inlet stream. An eductor may also be used to exhaust air away from the furnace. The stack heat treatment may include stack sintering or conditioning. The conditioning may be conducted without using externally supplied hydrogen.