Fuel Cell System Sub-Zero Activation Pump Control
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Solution Overview
Problem
Fuel cell systems face challenges in supplying high hydrogen concentration fuel gas at sub-zero temperatures, leading to freezing issues and reduced fuel efficiency, particularly due to the limitations of check valves and circulation pumps at activation.
Innovation Solution
A fuel cell system with a controller, temperature sensor, fuel gas supplier, and circulation pump configuration that stops the circulation of fuel off-gas at sub-zero temperatures to prevent freezing and ensures high hydrogen concentration supply, thereby eliminating freezing and enhancing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fuel off-gas is circulated through the ejector at sub-zero temperatures, then the fuel cell can be activated, but the fuel gas concentration decreases and freezing occurs
Solution Approach 1:
The system dynamically adjusts the circulation pump operation based on temperature conditions. At sub-zero temperatures, the circulation pump is controlled to stop or reduce operation, preventing the circulation of fuel off-gas that would otherwise dilute the hydrogen concentration. This dynamic control allows the system to maintain high hydrogen concentration fuel gas supply while still enabling activation capability when needed.
Solution Approach 2:
The system changes the operational parameters of the circulation pump based on temperature readings. When the temperature drops below freezing point, the pump operation parameter is changed from continuous circulation to stopped or reduced circulation, thereby preventing freezing and maintaining high hydrogen concentration in the supplied fuel gas.
2Loss of energy
If fuel off-gas circulates continuously, then fuel efficiency decreases, but system complexity is reduced
Solution Approach 1:
The system employs temperature feedback control where a temperature sensor monitors the fuel cell temperature and provides feedback to the control unit. Based on this feedback, the control unit adjusts the circulation pump operation accordingly. This feedback mechanism enables the system to stop circulation at sub-zero temperatures to maintain fuel efficiency while using a relatively simple control structure.
3Device complexity
If check valve is used to prevent backflow, then device complexity is reduced, but reliability at sub-zero temperatures deteriorates
Solution Approach 1:
The system replaces the purely mechanical check valve approach with a controlled pump system. Instead of relying on the check valve's mechanical backflow prevention mechanism which may fail or freeze at sub-zero temperatures, the system uses the circulation pump's controlled operation to prevent backflow. This substitution of mechanical passive prevention with active controlled prevention improves reliability in cold conditions.
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 system effectively supplies high hydrogen concentration fuel gas to the fuel cell, quickly eliminates freezing, and increases fuel efficiency by controlling the circulation pump's operation based on temperature readings.
Implementation Method 1
when the fuel gas flow path in the fuel cell is frozen at the time of activation at sub-zero temperatures
Implementation Method 2
an ejector disposed in the fuel gas supply flow path
Implementation Method 3
a gas-liquid separator disposed in the fuel off-gas discharge flow path
Data Source
AI summary
A fuel cell system wherein, at the time of activating the fuel cell system, the controller determines whether or not the temperature of the fuel cell detected by the temperature sensor is equal to or less than a temperature corresponding to activation at sub-zero temperatures, and wherein, when the controller determines that the temperature of the fuel cell detected by the temperature sensor is equal to or less than the temperature corresponding to the activation at sub-zero temperatures, the controller sends a command to the fuel gas supplier to supply the fuel gas to the fuel cell, and the controller controls rotation of the circulation pump to stop a flow of the fuel off-gas in the circulation flow path.