Ag Seal Protection in Solid Oxide Fuel Cells
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Solution Overview
Problem
The use of silver (Ag) seal materials in solid oxide fuel cells (SOFCs) degrades due to water vapor, leading to porosity and cracks, causing fuel gas and oxidant gas leaks and reducing power generation efficiency.
Innovation Solution
A dense body, preferably made of glass or lanthanum chromite, is formed over the Ag seal portion to prevent hydrogen, oxygen, and water vapor from entering, thereby preventing degradation and contact between fuel and oxidant gases, maintaining high sealing performance and power generation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Ag seal material is used to separate fuel gas and oxidant gas, then high compactness and gas impermeability are achieved, but degradation occurs due to water vapor causing porosity and cracks
Solution Approach 1:
A dense body coating is introduced as an intermediary layer between the Ag seal material and the corrosive environment (water vapor, hydrogen, oxygen). This coating acts as a protective barrier that prevents direct contact between the aggressive gases and the Ag material, thereby maintaining the sealing performance while protecting the Ag from degradation
Solution Approach 2:
The seal structure is transformed from a single-material Ag seal into a composite structure consisting of Ag seal material combined with a dense body coating layer. This composite structure leverages the high compactness of Ag while adding the protective properties of the dense body coating to resist water vapor and gas-induced degradation
2Reliability
If Ag seal material is used, then excellent gas seal properties are achieved, but fuel gas and oxidant gas leak due to pore formation
Solution Approach 1:
The dense body coating is applied in advance to the Ag seal material before the fuel cell operates. This pre-formed protective layer prevents water vapor and gases from penetrating into the Ag material and causing pore formation and cracks, thereby cushioning against future gas leak problems
Solution Approach 2:
The dense body coating serves as an intermediary barrier that blocks the pathway for gas molecules to reach the Ag seal material. By preventing direct interaction between the gases and Ag, the coating eliminates the mechanism that leads to pore formation and subsequent gas leaks
3Productivity
If Ag seal material is used, then high power generation efficiency is achieved, but efficiency deteriorates due to gas contact and water production
Solution Approach 1:
The dense body coating acts as a mediator that ensures fuel gas and oxidant gas remain separated throughout operation. By preventing unintended contact between these gases, the coating eliminates parasitic reactions that produce water and consume energy, thereby maintaining high power generation efficiency
Solution Approach 2:
The harmful effect of gas interaction is extracted and isolated by introducing the dense body coating as a separate functional layer. This coating specifically addresses and removes the degradation mechanism (gas contact leading to water production) while preserving the beneficial sealing function of the Ag material
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 dense body effectively prevents degradation of the Ag seal material, reducing gas leaks and maintaining high power generation efficiency by preventing contact between fuel and oxidant gases, thus enhancing the sealing performance and output of the SOFC.
Implementation Method 1
A dense body at least partially formed over at least either a fuel gas side surface of the Ag seal portion or a oxidant gas side surface of the Ag seal portion
Implementation Method 2
high compactness (gas impermeability) of the Ag seal portion to suppress degradation due to oxidation or the like
Implementation Method 3
Fuel gas is supplied to one electrode, and oxidant gas (air, oxygen, or the like) is supplied to the other electrode, and a power generation reaction is caused at a relatively high temperature to thereby generate power
Implementation Method 4
The unreformed gas is introduced into a reformer containing a reforming catalyst and reformed into fuel gas rich with hydrogen
Data Source
AI summary
In a fuel cell unit 16 that constitutes a fuel cell module 2 of an SOFC device 1, a collector cap 86a is connected to an inner electrode layer 90 via a seal material 96 as an Ag seal portion. A glass coating 30 (dense body) is filled up between the inner electrode layer 90 and an electrolyte layer 94 and the collector cap 86a to cover an upper end surface 96a of the seal material 96. As such, the fuel cell unit 16 includes the seal material 96 constituting as an Ag seal portion that separates a fuel gas from an oxidant gas, and a glass coating 30 at least partially formed to over at least either the fuel gas side surface of the seal material 96 or an the oxidant gas side surface of the seal material 96.