Cold Thermal Storage for Excess Heat in Closed Brayton Cycles
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Solution Overview
Problem
Inefficiencies in closed cycle heat engines and heat pumps require excess heat removal, leading to suboptimal performance and increased cooling demands, particularly in Brayton cycle systems where polytropic efficiencies of turbomachinery are less than 100%, necessitating additional cooling heat exchangers and fluids.
Innovation Solution
Incorporating a cold thermal storage medium that heats up during the discharge cycle and is then cooled, allowing waste heat to be stored and reused in the charge cycle, eliminating the need for additional cooling heat exchangers and decoupling instantaneous cooling power from immediate heat dissipation needs, thereby reducing cooling power requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If excess heat is removed from the system to close the thermodynamic cycle, then the cycle can be completed, but additional cooling heat exchangers and cooling fluids are required, increasing system complexity
Solution Approach 1:
The patent combines the cold thermal storage medium's cooling function with the excess heat removal function. The same heat exchanger that cools the CTS medium also removes excess heat from the working fluid, merging two functions into one component and eliminating the need for separate cooling heat exchangers.
Solution Approach 2:
The heat exchanger serving the cold thermal storage medium is designed to perform multiple functions: cooling the CTS medium during charge cycle and removing excess heat from the working fluid during discharge cycle. This multi-functionality reduces the total number of heat exchangers required in the system.
2Loss of energy
If additional cooling heat exchangers are added to remove excess heat, then heat removal is achieved, but system complexity and component quantity increase
Solution Approach 1:
The cold thermal storage medium system serves itself by using its own heat exchanger to remove excess heat from the working fluid. The CTS medium absorbs the excess heat that would otherwise require separate cooling equipment, making the system self-sufficient and reducing component requirements.
3Productivity
If cooling power is increased to handle immediate heat dissipation needs, then heat removal efficiency improves, but cooling power requirements and energy consumption increase
Solution Approach 1:
The cold thermal storage medium is pre-cooled during the charge cycle before the discharge cycle begins. This preliminary cooling action allows the system to handle heat dissipation during discharge without requiring high instantaneous cooling power, as the CTS medium is already in a low-temperature state ready to absorb heat.
Solution Approach 2:
The system uses periodic charging and discharging cycles of the CTS medium. During charge, the CTS medium is cooled; during discharge, it absorbs excess heat. This periodic operation smooths out the cooling power requirements, avoiding the need for continuously high cooling power and reducing overall energy consumption.
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 approach enhances overall system efficiency by storing waste heat in the cold thermal storage medium, allowing for smaller cooling power usage over a longer time, and maintains system performance without additional cooling heat exchangers or fluids.
Implementation Method 1
a cold side heat exchanger in thermal contact with the working fluid and in thermal contact with the cold side thermal storage medium
Implementation Method 2
excess heat in a discharge cycle may be stored in the cold side of the heat engine prior to removal
Implementation Method 3
a cooling heat exchanger configured to remove heat from the working fluid
Implementation Method 4
a turbine, and a compressor... A motor/generator may be used to obtain work from the thermal energy in the system
Data Source
AI summary
Extra heat in a closed cycle power generation system, such as a reversible closed Brayton cycle system, may be dissipated between discharge and charge cycles. An extra cooling heat exchanger may be added on the discharge cycle and disposed between a cold side heat exchanger and a compressor inlet. Additionally or alternatively, a cold thermal storage medium passing through the cold side heat exchanger may be allowed to heat up to a higher temperature during the discharge cycle than is needed on input to the charge cycle and the excess heat then dissipated to the atmosphere.