Supercritical CO2 Heat Engine with Sequential Recuperators
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Solution Overview
Problem
Existing heat engine systems are inefficient in converting thermal energy to mechanical or electrical energy, particularly under high-temperature and high-pressure conditions, leading to high costs per kilowatt and requiring large heat exchangers.
Innovation Solution
The heat engine system incorporates a working fluid circuit with multiple heat exchangers and recuperators sequentially and alternately disposed on the high-pressure side, utilizing carbon dioxide in a supercritical state to efficiently transfer thermal energy, and includes an expander and driveshaft to convert pressure drops into mechanical energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional Rankine cycles with steam are used to convert waste heat to electrical energy, then the system can operate at high temperatures, but the heat exchangers required become very large and costly
Solution Approach 1:
The patent changes the working fluid from water/steam to carbon dioxide and operates it in a supercritical state, fundamentally altering the thermodynamic parameters. This allows the system to achieve high temperature heat addition while maintaining compact heat exchanger sizes due to the unique properties of supercritical CO2, which has higher density and heat capacity compared to steam at similar conditions.
Solution Approach 2:
The patent utilizes the phase transition properties of carbon dioxide by operating it in a supercritical state rather than traditional liquid-vapor cycles. This eliminates the need for large two-phase heat exchangers and allows for more efficient heat transfer throughout the cycle, reducing overall heat exchanger area while maintaining high temperature operation.
2Device complexity
If poorly designed heat engine systems are used for heat to electrical power conversion, then the system complexity may be reduced, but the efficiency of conversion decreases and cost per kilowatt increases
Solution Approach 1:
The patent divides the heat engine system into multiple distinct components including separate heat exchangers, a supersonic turbine, and associated flow control elements. This segmentation allows each component to be optimized for its specific function, achieving high overall efficiency while maintaining manageable system complexity through modular design.
Solution Approach 2:
The patent incorporates dynamic flow control through variable area nozzles and adjustable guide vanes in the supersonic turbine, allowing the system to adapt to varying operating conditions. This dynamic capability maintains high efficiency across different load conditions without requiring overly complex control systems.
3Use of energy by moving object
If large heat exchangers are used to handle high pressures and temperatures in heat engine systems, then the heat transfer capability is sufficient, but the total cost of the heat engine system increases significantly
Solution Approach 1:
By changing to supercritical CO2 as the working fluid, the patent achieves higher density and improved heat transfer coefficients, which allow for significantly reduced heat exchanger sizes compared to traditional steam cycles. This reduces both material costs and manufacturing complexity while maintaining adequate heat transfer capability.
Solution Approach 2:
The patent replaces traditional mechanical heat exchanger designs with compact heat exchangers optimized for supercritical fluid flow characteristics. This substitution leverages the unique thermodynamic properties of supercritical CO2 to achieve efficient heat transfer in a much smaller, more cost-effective package.
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 configuration reduces the required heat transfer area, increases power output, and minimizes the use of costly heat exchangers, achieving greater than 15% net system output power under various ambient conditions.
Implementation Method 1
Each of the recuperators may be fluidly coupled to the working fluid circuit and configured to transfer thermal energy between the high pressure side and the low pressure side of the working fluid circuit
Implementation Method 2
Each of the heat exchangers may be fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit. The heat exchangers may be configured to be fluidly coupled to and in thermal communication with a heat source, and configured to transfer thermal energy from the heat source to the working fluid within the high pressure side
Implementation Method 3
The expander may be fluidly coupled to the working fluid circuit and disposed between the high pressure side and the low pressure side and configured to convert a pressure drop in the working fluid to mechanical energy
Implementation Method 4
The system pump may be fluidly coupled to the working fluid circuit between the low pressure side and the high pressure side of the working fluid circuit and configured to circulate or pressurize the working fluid within the working fluid circuit
Implementation Method 5
The cooler may be in thermal communication with the working fluid in the low pressure side of the working fluid circuit and configured to remove thermal energy from the working fluid in the low pressure side of the working fluid circuit
Data Source
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AI summary
Provided herein are heat engine systems and methods for transforming energy, such as generating mechanical energy and/or electrical energy from thermal energy. The heat engine systems may have one of several different configurations of a working fluid circuit. One configuration of the heat engine system contains at least four heat exchangers and at least three recuperators sequentially disposed on a high pressure side of the working fluid circuit between a system pump and an expander. Another configuration of the heat engine system contains a low-temperature heat exchanger and a recuperator disposed upstream of a split flowpath and downstream of a recombined flowpath in the high pressure side of the working fluid circuit.