Superconducting DC Generator for Wind Turbines
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Solution Overview
Problem
Conventional direct drive generators for wind turbines face limitations in torque density and weight at higher power ratings, and AC generators require costly and unreliable power conversion systems for grid connection.
Innovation Solution
A superconducting direct current (DC) generator with a stationary annular field winding and rotating armature, utilizing superconducting coil magnets and a commutator assembly to transfer DC current, which is cooled by vaporized and re-condensed cryogenic liquids, allowing for high torque density and reduced weight, and potentially eliminating or simplifying the first stage of the power conversion system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional direct drive generators are used to increase power rating above 6 MW, then electrical power generation capacity is improved, but weight increases making the generator too heavy for wind turbine towers
Solution Approach 1:
The patent applies parameter changes by transitioning from conventional copper windings to superconducting materials, fundamentally changing the electrical conductivity parameter. This allows the generator to achieve higher power density without proportional weight increase, as superconductors can carry much higher current densities with zero resistance, reducing the amount of conductor material needed while maintaining or increasing power output capability.
Solution Approach 2:
The patent employs composite materials by combining superconducting materials with appropriate structural and cooling system components. The generator integrates superconducting windings, cryogenic cooling systems, and structural supports into a unified composite structure that achieves high power-to-weight ratio suitable for wind turbine applications.
2Power
If conventional direct drive generators are used to increase power rating, then electrical power generation capacity is improved, but torque density decreases requiring larger and heavier components
Solution Approach 1:
The superconducting material enables parameter changes in magnetic field strength and current density, allowing the generator to produce higher torque per unit volume. The zero-resistance property of superconductors allows sustained high current densities in the windings, creating stronger magnetic fields that interact with the rotor to generate higher torque density at the same physical size.
3Adaptability or versatility
If AC generators are used with power electronics converters for grid connection, then adaptability to grid requirements is improved, but system complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the need for complex bidirectional power electronic converters by generating DC directly at the generator output. This removes the rectification stage and associated control complexity, leaving only the necessary inversion stage for grid connection, thereby simplifying the overall power conversion system while maintaining grid adaptability.
Solution Approach 2:
Instead of the conventional approach of generating AC and then converting to DC for certain applications, the patent inverts the sequence by directly generating DC and then converting to AC for grid connection. This reversal eliminates the need for rectifiers and simplifies the power electronic interface, particularly beneficial for wind turbine applications where direct DC generation can be achieved through the superconducting generator design.
4Ease of manufacture
If conventional generators are used, then ease of manufacture is maintained, but reliability decreases due to gearbox requirements and conversion losses
Solution Approach 1:
The patent applies mechanics substitution by replacing the mechanical gearbox system with a direct-drive configuration. The superconducting generator is designed to operate directly at the low rotational speeds of the wind turbine rotor, eliminating the need for mechanical gear multiplication. This substitution removes the gearbox—a known reliability concern—from the system while the superconducting technology enables the generator to operate efficiently at these lower speeds.
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 solution enables a lightweight DC generator capable of generating 10 MW or more, reducing costs and increasing reliability by providing high torque density and simplifying power conversion, while maintaining efficiency and reliability.
Implementation Method 1
The field winding includes superconducting coil magnets
Implementation Method 2
cooling the superconducting coil magnets to a superconducting condition using a cooling liquid that is at least partially vaporized as it cools the coils
Implementation Method 3
condensing the vaporized cooling liquid in a re-condenser elevated above the DC generator, wherein the condensed cooling liquid flows by gravity to the superconducting coil magnets
Implementation Method 4
generating electrical current in the armature by the rotation of the armature around the stationary field winding
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
Disclosed is a direct current generator 22 including an annular armature 24 connectable to rotate with a rotating component of a wind turbine 10 and a stationary annular field winding 26 coaxial to the armature 24 and separated by a gap from the armature 24. The field winding 26 is configured to include superconducting coil magnets 68 and a support structure connectable to an upper region of a tower of the wind turbine 10. The direct current generator 22 further including a commutator assembly 90 configured to transfer DC current generated by the rotating armature 24 to a power conversion system 100.