Brake Resistor Cooling Control for Fuel Cell Vehicle Braking
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Solution Overview
Problem
Fuel cell vehicles face challenges in cooling the brake resistor, which is essential due to the need for efficient energy dissipation during braking events, particularly when the fuel cell system's power ramp-down rate is slower than the vehicle's, leading to potential degradation and thermal stress.
Innovation Solution
A control unit detects upcoming brake events and predicts resistor temperature, actively cooling the resistor if it exceeds a temperature criterion, using shared cooling components like a compressor or cooling system to ensure a slow power ramp-down and prevent degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the fuel cell system power is ramped down quickly to match vehicle power during braking events, then the vehicle power response is improved, but the fuel cell system degradation increases
Solution Approach 1:
The control unit predicts upcoming brake events and proactively adjusts the fuel cell system power before the actual braking occurs. This preliminary action allows the fuel cell to ramp down gradually while still meeting the vehicle's power demands through coordinated control with the battery and resistor, thereby preventing degradation while maintaining vehicle performance.
2Temperature
If the brake resistor is cooled continuously, then the resistor temperature is maintained below threshold, but the fuel cell system efficiency decreases due to shared cooling resources
Solution Approach 1:
The control unit continuously monitors the brake resistor temperature and dynamically adjusts the cooling strategy based on real-time temperature readings and predicted brake events. Cooling is activated only when necessary to maintain resistor temperature below the threshold, allowing the shared cooling system to serve both the fuel cell and resistor efficiently without continuous operation.
Solution Approach 2:
Instead of continuous cooling, the system uses periodic cooling cycles triggered by temperature thresholds and predicted brake events. The control unit activates cooling intermittently based on the resistor's thermal state and upcoming braking requirements, reducing overall cooling energy consumption while maintaining safe operating temperatures.
3Device complexity
If the brake resistor is cooled using shared cooling components, then the system complexity is reduced, but the cooling capacity for the fuel cell may be insufficient
Solution Approach 1:
The control unit dynamically allocates the shared cooling capacity between the fuel cell and brake resistor based on real-time operational conditions, temperature requirements, and predicted events. This dynamic control allows a single cooling system to adaptively serve multiple components with different cooling demands without requiring separate dedicated cooling systems.
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 prevents resistor overheating and fuel cell degradation by optimizing cooling during power ramp-down, extending the lifespan and ensuring stable performance of both components.
Implementation Method 1
The auxiliary brakes convert brake energy to heat dispersed to ambient... The energy dissipating resistor dissipate the excessive kinetic energy into heat
Implementation Method 2
the resistor may be cooled using a liquid cooling system which is also used to cool the fuel cell... the resistor may be cooled using a compressor which is also used to provide air to the fuel cell
Data Source
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AI summary
A vehicle fuel cell system (20) comprising an energy dissipating resistor (40) arranged in connection with a control unit (50), wherein the control unit (50) is configured to detect an upcoming brake event by the vehicle (10) within a time period, wherein the control unit (50) is configured to predict a temperature of the resistor (40) at an onset of the upcoming brake event, and wherein the control unit (50) is configured to actively cool the resistor (40), in preparation for the upcoming brake event, if the predicted temperature of the resistor (40) at the onset of the upcoming brake event fails to satisfy a temperature acceptance criterion.