Reciprocating sCO2 Piston System for Sub-Megawatt Power Generation
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Solution Overview
Problem
The design and manufacturing of sub-megawatt turbomachinery for supercritical carbon dioxide (sCO2) systems pose significant challenges due to complex blade geometry, high-speed rotor dynamics, and high costs, making them commercially unviable.
Innovation Solution
A system for generating mechanical power using supercritical carbon dioxide, comprising a twin cylinder reciprocating system with a larger expansion cylinder and a smaller compression cylinder, connected by heat exchangers to manage the high-temperature and high-pressure CO2, optimizing the thermodynamic Brayton cycle for efficient power generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If sCO2 turbines are designed to operate at high rpms (50-100 k rpm) to compensate for low blade heights, then adequate power can be produced, but the complexity of blade geometry increases and manufacturing costs skyrocket
Solution Approach 1:
The patent replaces the traditional high-speed rotating turbine mechanism with a reciprocating piston-cylinder mechanism. This substitution eliminates the need for complex high-speed rotor dynamics, critical speed considerations, and intricate blade geometries. The reciprocating system operates at lower speeds while producing adequate power through volumetric displacement, thereby simplifying manufacturing and reducing costs.
2Power
If sCO2 turbines spin at very high rpms to produce adequate power, then power generation is achieved, but shaft seals, bearings, and rotor dynamics become severe constraints
Solution Approach 1:
The patent substitutes the high-speed rotating turbine with a reciprocating piston system that operates at much lower speeds. This eliminates the severe constraints associated with high-speed rotor dynamics, including shaft seal reliability, bearing life, and critical speed issues. The reciprocating mechanism achieves reliable power generation through simple, robust components that operate within acceptable mechanical limits.
3Power
If sub-megawatt sCO2 turbomachinery is designed with watchmaker's precision, then adequate power can be produced, but the cost skyrockets making it commercially unviable
Solution Approach 1:
The patent replaces the precision-critical high-speed turbine with a reciprocating piston system that tolerates standard manufacturing variations. The reciprocating mechanism does not require the same level of dynamic balancing, shaft alignment, and component precision as high-speed turbines. This substitution dramatically reduces manufacturing costs and improves commercial viability while maintaining adequate power output.
4Shape
If sCO2 expands from 210 bar to 0.05 bar in a steam turbine, then large change in density occurs facilitating larger blade heights, but the turbine size becomes very large
Solution Approach 1:
The patent changes the operating parameters of the sCO2 cycle, specifically operating at higher minimum pressures (avoiding expansion to 0.05 bar). This parameter change results in smaller density ratios across the expansion device, which allows for more compact reciprocating cylinder designs. The reciprocating system accommodates these parameter changes efficiently, achieving compact sizes suitable for sub-megawatt applications.
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 proposed system achieves efficient mechanical power generation with improved thermal efficiencies and reduced costs by optimizing the design of the twin cylinder system and heat exchanger configuration, addressing the challenges of sub-megawatt sCO2 turbomachinery.
Implementation Method 1
A heat exchanger is provided between the compression cylinder and the expansion cylinder. The heat exchanger cools the CO2 received from the expansion cylinder.
Implementation Method 2
The compression cylinder pressurizes the CO2 cooled by the first heat exchanger.
Implementation Method 3
The sCO2 received from the outlet port of the compression cylinder expands in the expansion cylinder to drive a piston to generate mechanical energy.
Implementation Method 4
A second heat exchanger is provided between the compression cylinder and the expansion cylinder. The second heat exchanger heats the sCO2 received from the outlet port of the compression cylinder.
Data Source
AI summary
A system for generating mechanical power using super critical carbon dioxide (sCO2) is disclosed. The system includes at least one expansion cylinder (5) housing a first piston (5a) and at least one compression cylinder (6) housing a second piston (6a). A first heat exchanger (C) is fluidically connected to the compression cylinder (6) and the expansion cylinder (5), and a second heat exchanger (H) is fluidically connected to the compression cylinder (6) and the expansion cylinder (5). The first heat exchanger (C) cools the CO2 received from the expansion cylinder (5), and the compression cylinder (6) pressurizes the CO2 cooled by the first heat exchanger (C). The second heat exchanger (H) heats the CO2 from the compression cylinder (6) and supplies to the expansion cylinder (5). The high temperature and high-pressure CO2 drives the first piston (5a) housed inside the expansion cylinder (5) to generate mechanical energy.