Fuel Cell Shutdown Oxidant Consumption Control

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Solution Overview

Problem

Existing fuel cell systems face deterioration issues during start-up and leaving periods due to the hydrogen front and hydrogen peroxide generation, which are exacerbated by the need for hydrogen concentration monitoring and control, leading to inefficiencies and increased deterioration over time.

Innovation Solution

Implementing a control mechanism that consumes oxidant gas during shutdown by terminating fuel gas supply after a predetermined period, balancing start-up and leaving period deterioration based on system shutdown duration, thereby suppressing hydrogen front and hydrogen peroxide generation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If hydrogen concentration monitoring and control are implemented during the leaving period, then start-up deterioration due to hydrogen front is suppressed, but system efficiency decreases and operation becomes inconvenient

Engineering Contradiction:

Improvestart-up durabilityVSAvoidoperation convenience

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The fuel cell performs self-protection during shutdown by consuming residual oxidant gas through electrochemical reactions using stored fuel gas, eliminating the need for external monitoring systems or control operations during the leaving period

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The fuel cell executes gas consumption control during the shutdown period before start-up, pre-consumption of oxidant gas prevents hydrogen front formation at the next start-up without requiring real-time monitoring or control during operation

Inventive Principle:

Principle #10Preliminary action

2Reliability

If the system shutdown period is extended, then start-up frequency is reduced, but deterioration during the leaving period accumulates due to hydrogen peroxide generation

Engineering Contradiction:

Improvestart-up durabilityVSAvoidleaving period deterioration

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The fuel cell converts the harmful oxidant gas that would otherwise cause hydrogen peroxide generation into a beneficial resource by using it for electrochemical reactions with stored fuel gas, transforming the shutdown period into a protective phase that eliminates both hydrogen front and hydrogen peroxide risks

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The system changes the chemical composition parameters of the gas environment during shutdown by controlling fuel gas supply to achieve complete consumption of oxidant gas, transforming the harmful oxidizing atmosphere into a safe inert or fuel-rich atmosphere

Inventive Principle:

Principle #35Parameter changes

3Reliability

If oxidant gas is consumed during shutdown, then start-up deterioration is suppressed, but additional fuel gas consumption occurs during the shutdown period

Engineering Contradiction:

Improvestart-up durabilityVSAvoidfuel gas consumption

Core Design Contradiction:

ReliabilityVSLoss of substance

Solution Approach 1:

The fuel cell maintains continuous protective action during shutdown by sustaining fuel gas supply to consume oxidant gas, ensuring the fuel electrode remains in a safe atmosphere throughout the entire shutdown period rather than using intermittent or post-shutdown measures

Inventive Principle:

Principle #20Continuity of useful action

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 effectively reduces start-up deterioration by managing oxidant gas concentration during short shutdowns and minimizes leaving period deterioration by allowing fuel gas consumption by outside air during longer shutdowns, achieving a balanced suppression of deterioration factors.

Implementation Method 1

a fuel cell is known which generates power by making a fuel gas (hydrogen, for example) supplied to a fuel electrode and an oxidant gas (the air, for example) supplied to an oxidant electrode electrochemically react with each other

Methodology Applied

Scientific EffectElectrochemical reaction: Fuel Cell

Implementation Method 2

hydrogen peroxide is generated by the reaction of hydrogen in the fuel cell with the air entering through a sealing portion

Methodology Applied

Scientific EffectChemical reaction: Oxidation

Data Source

PatentUS8765315B2Fuel cell system and method of controlling fuel cell system

Publication Date: 2014.07.01 NISSAN MOTOR CO LTD

AI summary

Deterioration at the start-up and deterioration during the leaving period are suppressed in a good balance. As a system shutdown process, a controller (30) causes consumption of the air (oxygen) present in an oxidant electrode of a fuel cell stack (1) (oxygen consumption control). Further, after the termination of the oxygen consumption control, the controller (30) performs control to set a medium pressure hydrogen valve (13) and a hydrogen pressure adjustment valve (14) in a closed state. The controller (30) thereby causes hydrogen to be held in a passage located between the medium pressure hydrogen valve (13) and the hydrogen pressure adjustment valve (14). During a system shutdown period, a predetermined amount of hydrogen (medium pressure hydrogen) held in the hydrogen supply passage (L1) at a position between the medium pressure hydrogen valve (13) and the hydrogen pressure adjustment valve (14) can be supplied to the fuel electrode of the fuel cell stack (1) through a bypass passage (L2).