Fuel Cell Coolant Preheating Using Outgoing Air for Freeze Start
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Solution Overview
Problem
Fuel cell systems face challenges in starting up at freezing temperatures due to ice buildup, requiring additional heating methods that increase costs and prolong startup times, and existing solutions like heaters or ice buffers are costly and inefficient.
Innovation Solution
The method involves using a heat exchanger to heat the coolant in the fuel cell system with the heat from outgoing air, eliminating the need for external heaters and reducing ice tolerance measures, allowing for a rapid start without additional thermal power by integrating a heat exchanger into the cooling circuit or outgoing air path, enabling direct or indirect heat transfer from outgoing air to coolant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external heaters or ice buffers are installed to prevent freezing during startup, then the ice tolerance of the fuel cells is increased, but additional costs and system complexity are incurred
Solution Approach 1:
The fuel cell system uses its own outgoing air (which contains waste heat) to heat the coolant during startup, making the system self-sufficient for heating without requiring external heaters or ice buffers. The outgoing air that would otherwise be discarded is now utilized to serve the heating need internally.
Solution Approach 2:
The system recovers the waste heat from the outgoing air that would normally be discarded to the environment. This recovered heat is then used to warm the coolant during startup, converting a waste resource into a useful heating source.
2Reliability
If the coolant flow rate is reduced to prevent fuel cell freezing during startup, then the freeze protection is improved, but the startup process is prolonged
Solution Approach 1:
The system converts the harmful cold outgoing air into a beneficial heating source by passing it through the heat exchanger where it transfers heat to the coolant. This transforms the cold air that could contribute to freezing into a useful heating medium that accelerates startup.
Solution Approach 2:
The heat exchanger acts as an intermediary device that facilitates heat transfer from the outgoing air to the coolant. This mediator enables efficient thermal energy transfer without direct contact between the gases and coolant, solving the heating problem while maintaining system integrity.
3Productivity
If additional heaters are installed to heat the coolant during startup, then the startup speed is improved, but additional costs and energy consumption are incurred
Solution Approach 1:
The system recovers waste heat from the outgoing air that would otherwise be discarded, using it to heat the coolant during startup. This eliminates the need for additional thermal power from external heaters while maintaining fast startup performance.
Solution Approach 2:
The fuel cell system heats its own coolant using its own outgoing air, making the heating process self-sufficient without requiring external energy input. The system serves its own heating needs internally during startup.
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 enables a quick start at freezing temperatures without additional heaters, reduces hydrogen consumption, and lowers costs by utilizing the heat from outgoing air to warm the coolant, thus enhancing the freeze-start capability of the fuel cell system.
Implementation Method 1
the coolant is heated using at least one heat exchanger before entering the fuel cell stack, whereby the outgoing air exiting the fuel cell stack is used as a heat source
Data Source
AI summary
The invention relates to a method for operating a fuel cell system (1), in which air is supplied to a fuel cell stack (2) via an air intake path (3) and outgoing air emerging from the fuel cell stack (2) is removed via an outgoing air path (4), and in which a coolant of a cooling circuit (5) is conducted through the fuel cell stack (2) in order to remove the waste heat. According to the invention, in a starting situation, in particular when starting the fuel cell system (1) at freezing temperatures, the coolant is heated using at least one heat exchanger (6, 7) prior to entering the fuel cell stack (2), wherein the outgoing air emerging from the fuel cell stack (2) is used as a heat source.The invention further relates to a fuel cell system (1) for carrying out the method.