Multi-stage sCO2 Turbo-generator for Scaling and Efficiency
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Solution Overview
Problem
Turbomachinery-based power plants face challenges in scaling down for smaller power generation applications, as lower mass flow rates result in low specific speeds and inefficiencies, and electrical machines struggle to match operating speeds with turbomachinery components, leading to design complexity and leakage issues.
Innovation Solution
A multi-stage turbo-generator design for supercritical CO2 power blocks, featuring cascading turbine generator units connected in series, with each unit operating at optimal speed, and a voltage controller to regulate shaft speed, eliminating the need for additional couplings and bearings, and using high-speed electric generators for efficient power conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single large turbo-generator is used, then power output is high, but manufacturing complexity and cost increase significantly
Solution Approach 1:
The patent divides a single large turbo-generator into multiple smaller turbo-generators operating in parallel. Each smaller unit can be manufactured independently with simpler processes, yet the combined output achieves the desired total power level. This segmentation resolves the contradiction by allowing high power output through aggregation of multiple simple units rather than manufacturing one complex large unit.
2Productivity
If high rotational speeds are used in turbomachinery, then efficiency increases, but matching with electrical machines becomes difficult
Solution Approach 1:
The patent employs variable speed drives and power electronics to dynamically adjust the rotational speeds of individual turbo-generators. This allows each unit to operate at its optimal efficiency speed while the electrical output is synchronized to grid requirements. The dynamic speed control resolves the contradiction by decoupling the mechanical optimal speed from the electrical synchronization requirement.
3Speed
If gear boxes are used to match speeds, then speed compatibility is achieved, but CO2 leakage risk increases
Solution Approach 1:
The patent replaces mechanical gear boxes with direct-drive configurations combined with variable speed electrical controls. This substitution eliminates the need for shaft seals and mechanical couplings that would create leakage paths for supercritical CO2, thereby maintaining speed compatibility through electrical control rather than mechanical transmission.
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 design achieves high efficiency and simplicity, with low pressure drop in inter-stage piping and high conversion efficiencies, reducing production costs and maintenance, while preventing CO2 leakage through hermetic operation.
Implementation Method 1
a turbine with a supercritical CO2 input and a supercritical CO2 output
Implementation Method 2
a generator with an electrical input and power output
Implementation Method 3
Each of plurality of active rectifiers converts the power output of a generator to direct current
Data Source
AI summary
A supercritical CO2 turbo-generator system includes multiple turbine generator units, a direct current bus, a plurality of active rectifiers, and a voltage controller. Each turbine generator unit includes a turbine with a supercritical CO2 input and a supercritical CO2 output, a generator with an electrical input and power output, a shaft connecting the turbine and generator, and a speed sensor for sensing shaft speed. The turbine generator units are connected in a cascading series with the input of a first turbine generator unit connected to a heated supercritical CO2 source and the input of each subsequent turbine generator unit is connected to the output of a prior turbine generator unit. The voltage controller monitors the speed sensor of the turbine generator units and varies the load on each generator to control shaft speed. Each active rectifier converts the power output of a generator to direct current, and the power from multiple active rectifiers is combined by the direct current bus.