Supercritical CO2 Power Cycle for Waste Heat Recovery
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Solution Overview
Problem
Current waste heat recovery systems face limitations in efficiency and complexity due to fluctuating waste heat conditions and the need for multiple-cycle systems, which increase system complexity and maintenance requirements.
Innovation Solution
A heat engine system utilizing a working fluid in a supercritical carbon dioxide cycle with dual- and single-cycle modes, featuring heat exchangers, expanders, recuperators, and pumps, along with a plurality of valves to optimize operating range and efficiency by switching between modes based on heat source temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple independent cycle systems are used to handle fluctuating waste heat conditions, then the system can maintain efficiency across different operating conditions, but the system complexity increases due to additional components, control requirements, and maintenance needs
Solution Approach 1:
The patent implements a dynamic single-cycle system with variable geometry components (variable inlet guide vanes, adjustable nozzles, and controllable valve arrangements) that allow the system to adapt to fluctuating waste heat conditions. This enables a single cycle to operate efficiently across a wide range of temperatures and pressures without requiring multiple fixed-cycle systems, thereby maintaining adaptability while minimizing complexity.
2Device complexity
If a single heat exchanger is used in the heat engine system, then the system complexity is minimized, but the operating range and efficiency are limited when waste heat conditions fluctuate
Solution Approach 1:
The patent utilizes parameter changes by operating the carbon dioxide working fluid across different thermodynamic states (subcritical and supercritical phases) within a single heat exchanger. By controlling pressure and temperature parameters and using variable geometry components to adjust mass flow rates, the system can adapt to a wide range of waste heat conditions while maintaining efficient operation with minimal system complexity.
3Productivity
If the heat engine system is designed for optimal efficiency at specific temperatures, then maximum energy conversion is achieved, but the system cannot effectively handle waste heat conditions outside the optimal range
Solution Approach 1:
The patent designs a universal heat engine system using carbon dioxide as a working fluid that can operate efficiently across both subcritical and supercritical states. The single-cycle configuration with variable geometry components and controllable valve arrangements enables the system to maintain high energy conversion efficiency across a broad spectrum of waste heat temperatures, eliminating the need for multiple specialized cycle systems while preserving optimal performance.
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 system achieves optimized operating efficiency and minimized complexity by adapting to varying waste heat conditions, effectively recovering thermal energy and generating mechanical or electrical energy across a broader range of temperatures.
Implementation Method 1
configured to transfer thermal energy from the heat source stream to the working fluid within the working fluid circuit
Implementation Method 2
each of the first and second heat exchangers is fluidly coupled to and in thermal communication with the high pressure side of the working fluid circuit
Implementation Method 3
a first expander fluidly coupled to and downstream of the first heat exchanger on the high pressure side of the working fluid circuit and a second expander fluidly coupled to and downstream of the second heat exchanger
Implementation Method 4
The first recuperator may be configured to transfer thermal energy from the working fluid received from the first expander to the working fluid received from the first and second pumps
Data Source
AI summary
Aspects of the invention disclosed herein generally provide heat engine systems and methods for recovering energy, such as by generating electricity from thermal energy. In one configuration, a heat engine system contains a working fluid (e.g., sc-CO2) within a working fluid circuit, two heat exchangers configured to be thermally coupled to a heat source (e.g., waste heat), two expanders, two recuperators, two pumps, a condenser, and a plurality of valves configured to switch the system between single/dual-cycle modes. In another aspect, a method for recovering energy may include monitoring a temperature of the heat source, operating the heat engine system in the dual-cycle mode when the temperature is equal to or greater than a threshold value, and subsequently, operating the heat engine system in the single-cycle mode when the temperature is less than the threshold value.