Supercritical CO2 Cooling for Electric Machine Power Density
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Solution Overview
Problem
Conventional cooling systems for electric machines, such as air, hydrogen, and water cooling, face inefficiencies and increased complexity, weight, and cost due to their limitations in heat management, which affect the machine's power density and lifespan.
Innovation Solution
The use of supercritical carbon dioxide (SCO2) as a working medium in a heat exchanger to directly cool heat generating components of electric machines, eliminating the need for complex auxiliaries and allowing for a closed loop system that increases power density without adding weight or footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If hydrogen cooling is used to cool the rotor and stator, then cooling effectiveness is improved, but device complexity and weight increase due to reinforced casing and auxiliary systems
Solution Approach 1:
The patent extracts the harmful and complex auxiliary systems (seal oil systems, blowers, valves, pressure regulators, gas driers, monitoring systems) from the hydrogen cooling system, replacing them with a simplified direct CO2 cooling approach that eliminates these dependencies while maintaining cooling effectiveness
Solution Approach 2:
The patent changes the cooling medium from hydrogen to CO2, and operates CO2 in supercritical state (above 31°C and 73.8 atm) to achieve superior heat transfer properties. This parameter change eliminates the need for complex hydrogen management systems while providing effective cooling
2Temperature
If water cooling is used to directly cool components, then cooling effectiveness is improved, but device complexity increases due to purity maintenance requirements and sealing systems
Solution Approach 1:
The patent removes the complex sealing and purity maintenance systems required by water cooling by replacing water with CO2 as the cooling medium. CO2's inherent properties eliminate the need for demineralizers, driers, filters, and complex sealing arrangements
Solution Approach 2:
The patent uses CO2 as an inert cooling medium that does not conduct electricity and does not require purity maintenance like water. This creates a simplified cooling environment without the need for complex sealing or water treatment systems
3Device complexity
If air cooling is used to cool the rotor and stator, then device complexity is reduced, but power density decreases due to lower cooling effectiveness
Solution Approach 1:
The patent changes from air cooling to supercritical CO2 cooling, utilizing CO2's superior heat transfer coefficients in supercritical state. This parameter change enables higher power density while maintaining relatively simple system architecture, achieving both goals simultaneously
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
SCO2 cooling enhances the efficiency and power density of electric machines by directly contacting copper windings and reducing the need for auxiliary systems, while maintaining a compact design and reducing the complexity of cooling systems.
Implementation Method 1
SCO2 cooling enhances the efficiency and power density of electric machines by directly contacting copper windings
Implementation Method 2
supercritical carbon dioxide (SCO2) as a working medium in a heat exchanger to directly cool heat generating components
Implementation Method 3
The electric machine may include a heat exchanger to cool a fluid that cools at least one heat generating component, where the SCO2 is a working medium of the heat exchanger and the working medium is heated during the heat exchange
Implementation Method 4
The heated working medium may be discharged to the atmosphere, put in to a container, used as a coolant in a further component, or used as a working medium in a further component
Data Source
AI summary
Systems and methods are provided to cool a heat producing component in an electrical machine system. The electrical machine includes a supercritical carbon dioxide (SCO2) wherein the SCO2 is a working medium of a heat exchanger that is arranged in the electrical machine system to cool a fluid that cools the heat producing component and/or wherein the SCO2 directly cools at the heat producing component.