Fuel Cell Cold Start via Motor Winding Joule Heating

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Solution Overview

Problem

Cold-starting a fuel cell system in a motor vehicle at temperatures below freezing point is challenging due to limited available electric loads and operational constraints, which hinder the heating-up and warm-up phases, affecting the vehicle's operational availability.

Innovation Solution

The method involves consuming a defined quantity of output power from the fuel cell system during the heating-up and warm-up phases by using a power consumption means, such as an electric motor, to convert the power into power loss, thereby increasing the loading of the fuel cell system and reducing the duration of the cold start phase. This is achieved by impressing a suitable current into the winding of an electric motor, allowing the drive enable signal to be issued earlier, enabling the vehicle to start sooner.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the fuel cell system is loaded with electric secondary loads during cold start, then the heating-up phase duration is extended, but the vehicle operational availability is improved

Engineering Contradiction:

Improvevehicle operational availabilityVSAvoidheating-up phase duration

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The patent implements periodic loading of the fuel cell stack by alternately connecting and disconnecting electric secondary loads during the heating-up phase. This periodic action creates temperature fluctuations that accelerate the warm-up process while still achieving the necessary operating temperature, thereby reducing overall heating duration while maintaining vehicle availability.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The control unit dynamically adjusts the loading parameters of the fuel cell stack by varying the connection state of electric secondary loads. By changing the electrical load parameters periodically, the system optimizes the heating rate while ensuring the fuel cell reaches operational temperature, resolving the contradiction between heating duration and vehicle availability.

Inventive Principle:

Principle #35Parameter changes

2Duration of action of moving object

If the output power of the fuel cell system is consumed by power consumption means during heating-up phase, then the heating-up phase duration is reduced, but energy efficiency is worsened

Engineering Contradiction:

Improveheating-up phase durationVSAvoidenergy efficiency

Core Design Contradiction:

Duration of action of moving objectVSUse of energy by moving object

Solution Approach 1:

The patent converts the wasted energy from power consumption means into beneficial thermal energy for heating the fuel cell stack. By directing the consumed power to heat the cooling liquid circulating through the fuel cell, the system transforms what would be energy loss into useful heating, thereby reducing heating-up duration without significant energy efficiency penalty.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The cooling liquid serves as an intermediary medium that transfers thermal energy from the power consumption means to the fuel cell stack. This intermediary approach allows efficient heat transfer and distributes the thermal energy uniformly throughout the fuel cell, achieving rapid heating while managing energy consumption effectively.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If the drive enable signal is issued earlier during warm-up phase, then vehicle operational availability is improved, but the fuel cell system may operate below optimal temperature

Engineering Contradiction:

Improvevehicle operational availabilityVSAvoidfuel cell operating temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The control unit continuously monitors the temperature of the fuel cell stack and the state of electric secondary loads, using this feedback to determine the optimal moment to issue the drive enable signal. By implementing feedback control, the system ensures that the drive enable signal is issued at the precise moment when the fuel cell reaches sufficient operating temperature, balancing vehicle availability with optimal operating conditions.

Inventive Principle:

Principle #23Feedback

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 significantly reduces the duration of the cold start phase, allowing the vehicle to become fully operational earlier, although it results in a reduction of energy efficiency as the converted power does not contribute to the electric motor's effective power, but it ensures quicker initialization of the operating phase.

Implementation Method 1

converting the consumed quantity of the output power into power loss by impressing a suitable current into at least one winding of an electric motor

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS9583774B2Method for cold starting a fuel cell system and fuel cell system of a motor vehicle

Publication Date: 2017.02.28 CELLCENTRIC GMBH & CO KG

AI summary

The operational availability of a motor vehicle with a fuel cell is increased by providing that a defined quantity of the output power of the fuel cell system is consumed by a power consumption component in the heating-up phase and/or in the warm-up phase and that the consumed quantity of the output power is converted into power loss by impressing a suitable current into at least one winding of an electric motor which is to be energized.