PEMFC Stack Rapid Preheating via Bypass Circuit
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Solution Overview
Problem
Conventional polymer electrolyte membrane fuel cells (PEMFCs) face inefficiencies due to catalyst poisoning by CO by-products and require lengthy coolant heating, delaying start-up operations.
Innovation Solution
A method for rapid preheating of the PEMFC stack using a coolant system with a by-pass line, heating element, and valve control to minimize coolant volume and heating time, allowing for quicker temperature increase and efficient start-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional high temperature PEMFC uses a coolant system to heat the fuel cell stack to operating temperature, then the temperature control is improved, but the start-up time is significantly increased due to the time required to heat the coolant
Solution Approach 1:
The coolant system is segmented into two separate circuits: a first coolant circuit that circulates coolant through the cooling plates during normal operation, and a second coolant circuit that independently heats coolant during start-up. This segmentation allows the heating function to operate independently without being constrained by the volume of coolant in the entire system, thereby reducing start-up time while maintaining temperature control capability.
Solution Approach 2:
A heat exchanger is introduced as an intermediary component in the second coolant circuit to rapidly heat a small volume of coolant. This heat exchanger acts as a mediator between the heating source and the fuel cell stack, enabling efficient heat transfer to a minimized coolant volume, which significantly reduces the time required to reach operating temperature.
2Reliability
If the operating temperature of a conventional PEMFC is kept below 100°C to prevent polymer electrolyte membrane drying, then the membrane is protected, but catalyst poisoning by CO increases and operation efficiency is reduced
Solution Approach 1:
The system dynamically adjusts operating temperature based on operational phase: during start-up, the temperature is rapidly increased to 120°C or higher to minimize catalyst poisoning and improve efficiency; during normal operation, the temperature is maintained below 100°C through the coolant system to prevent membrane drying. This dynamic temperature adjustment allows the system to optimize for different operational requirements at different times.
Solution Approach 2:
The fuel cell stack is preheated to 120°C or higher before normal operation begins through the second coolant circuit. This preliminary heating action reduces catalyst poisoning by CO during the critical start-up phase, improving initial operation efficiency without compromising long-term membrane durability, as the membrane is subsequently protected during normal operation.
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 method significantly reduces the time required to reach operating temperature, enhancing start-up efficiency and minimizing catalyst poisoning, thus improving PEMFC performance and reducing start-up delays.
Implementation Method 1
a heating element that heats coolant in the by-pass line
Implementation Method 2
a heat exchanger installed between the first flow line and the coolant reservoir
Data Source
AI summary
A method of starting a polymer electrolyte membrane fuel cell (PEMFC) stack by rapidly increasing its temperature. The PEMFC stack includes: a first flow line connected to cooling plates; a second flow line connected to the cooling plates; a coolant reservoir; a heat exchanger; a by-pass line; a heating element; a first valve installed between the first flow line and the heat exchanger; and a second valve that selectively connects the coolant reservoir, the second flow line, and the by-pass line. The method of starting a PEMFC stack includes: closing the first valve and controlling the second valve so that the second flow line and the by-pass line are connected to each other, and the coolant in the coolant reservoir is not connected to the second flow line and the by-pass line; and heating the coolant in the by-pass line.