Fuel Cell Water Management via Self-Service Drying
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Solution Overview
Problem
Existing fuel cell systems face challenges in managing retained water, which leads to decreased power generation performance and potential freezing issues, especially during system stoppages, without requiring additional scavenging gas supply units or enlarging the system size.
Innovation Solution
A fuel cell system with a power generation control unit that operates in normal-time and stop-time drying modes to actively manage retained water by adjusting power generation, temperature, and gas flow rates, eliminating the need for scavenging gases and reducing system size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a scavenging gas supply unit is added to discharge retained water after power generation stop, then retained water can be effectively removed, but the system size and complexity increase
Solution Approach 1:
The fuel cell stack itself is utilized to generate heat for vaporizing retained water through controlled power generation after stop instruction, eliminating the need for external heating devices or scavenging gas supply units. The system uses its own power generation capability to solve the water retention problem.
Solution Approach 2:
The control unit adjusts power generation parameters (current, voltage, load) after stop instruction to optimize heat generation for vaporizing retained water. By dynamically changing operational parameters, the system achieves effective water removal without additional hardware.
2Speed
If power generation is continued at high output to warm up the fuel cell stack, then warming-up speed increases, but retained water quantity increases causing flooding
Solution Approach 1:
The control unit implements periodic or phased power generation control after stop instruction, adjusting output levels to balance heat generation needs with water vaporization requirements. This staged approach allows controlled warming while preventing excessive water accumulation.
Solution Approach 2:
The system dynamically adjusts power generation parameters (current, voltage, load) to optimize the balance between heat generation for warming and water vaporization. By changing operational parameters in response to retained water conditions, the system prevents flooding while maintaining warming efficiency.
3Reliability
If retained water is discharged during normal power generation, then flooding is suppressed, but power generation performance decreases due to reduced hydrogen and air supply
Solution Approach 1:
The system performs retained water discharge operations during normal power generation before stop instruction, when power generation performance can be maintained. This preliminary action removes excess water that would otherwise cause flooding during subsequent stop periods.
Solution Approach 2:
The control unit rapidly discharges retained water during brief intervals during normal operation, then quickly returns to optimal power generation mode. This brief, intensive discharge action removes water without significantly impacting overall power generation performance.
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
Effectively reduces retained water, prevents freezing, and ensures efficient power generation startup by actively managing water levels during both normal operation and system stoppages without enlarging the system or requiring additional energy sources.
Implementation Method 1
a fuel cell that has a membrane electrode assembly which includes an electrolyte membrane
Implementation Method 2
water vapor (moisture) is generated in the cathode and portion of the generated water permeates an electrolyte membrane toward the anode side
Implementation Method 3
air moving toward the cathode is humidified by a humidifier
Data Source
AI summary
A fuel cell system includes a fuel cell stack having a membrane electrode assembly and an internal reactant gas passage, a unit that detects or estimates an actual retained water quantity (R.W.Q.), and a power generation control unit having a normal-time mode, a normal-time drying mode and a stop-time drying mode. In the normal-time drying mode, the fuel cell stack is caused to generate electric power while being dried more than in the normal-time mode until the actual R.W.Q. is decreased to a target R.W.Q. In the stop-time drying mode, when the actual R.W.Q. is equal to or more than a flooding threshold at a time of detection of a system stop instruction, the fuel cell stack is caused to generate electric power while being dried more than in the normal-time drying mode until the actual R.W.Q. is decreased to a target R.W.Q.