Fuel Cell Molar Ratio Control During Stoppage
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Solution Overview
Problem
Fuel cell systems experience power generation performance degradation due to oxidation of carbon in the cathode-side catalyst when unused, leading to excessive hydrogen consumption.
Innovation Solution
A fuel cell system with calculation and control means to maintain a molar ratio of hydrogen to oxygen at 2 or more during stoppage, preventing electrochemical reactions and maintaining a hydrogen-rich state to suppress oxidation and consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the fuel cell system is left unused, then the system can be idle, but carried carbon in the cathode-side catalyst is oxidized leading to power generation performance degradation
Solution Approach 1:
The control means performs preliminary action by calculating the molar quantities of hydrogen and oxygen before the system is left unused, and adjusts the hydrogen supply to achieve a molar ratio of 2 or more. This preliminary adjustment of gas composition prevents carbon oxidation that would otherwise occur during idle time, thereby maintaining power generation performance while allowing the system to remain idle.
2Reliability
If hydrogen is supplied to prevent carbon oxidation, then power generation performance is maintained, but excessive hydrogen consumption occurs
Solution Approach 1:
The control means changes the critical parameter of hydrogen supply by calculating the precise molar quantities of hydrogen and oxygen in the supply/discharge systems. By adjusting the hydrogen supply to achieve a molar ratio of 2 or more (rather than arbitrary hydrogen supply), the system maintains power generation performance while minimizing excessive hydrogen consumption through optimized parameter control.
3Ease of operation
If air is sucked from cathode outlet side during system stop, then the system can be ventilated, but oxygen diffuses to anode side causing abnormal potential and carbon oxidation
Solution Approach 1:
The control means creates a hydrogen-rich inert environment by supplying hydrogen to achieve a molar ratio of 2 or more during system stoppage. This hydrogen-rich atmosphere prevents oxygen from causing carbon oxidation even if air is present, effectively creating a protective environment that eliminates the harmful effect of abnormal potential generation while allowing system ventilation.
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
Prevents carbon oxidation and excessive hydrogen consumption, maintaining power generation performance by controlling the molar ratio of hydrogen and oxygen, thereby suppressing abnormal potential generation.
Implementation Method 1
oxygen in the air becomes involved in an electrochemical reaction, and eventually a voltage (this will be referred to as an abnormal potential in the present description) is generated regardless of the stopped state of the system
Implementation Method 2
carried carbon in a cathode-side catalyst is sometimes oxidized
Implementation Method 3
air is sucked from a cathode outlet side to enter a fuel cell, and the air sometimes diffuses from a cathode side to an anode side
Data Source
AI summary
It is prevented that when a system is left unused, carried carbon ion a cathode-side catalyst to lower a power generation performance. The molar quantities of hydrogen and oxygen in a fuel gas supply/discharge system and an oxidizing gas supply/discharge system with respect to a fuel cell are calculated, and control is performed so that the molar ratio of hydrogen and oxygen which can chemically be reacted in a fuel gas and an oxidizing gas during the stop of the fuel cell is 2 or more. Hydrogen is preferably supplied in accordance with the magnitude of a cell voltage in the fuel cell so as to maintain the molar ratio. Moreover, a gas passage in the oxidizing gas supply/discharge system is preferably provided with an inlet valve and an outlet valve for sealing the oxidizing gas in the gas passage.