Two-Thermal-Bath Thermoelectric Storage for Round-Trip Efficiency
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Solution Overview
Problem
Existing thermoelectric energy storage systems have limited round-trip efficiency due to constraints imposed by the second law of thermodynamics, coefficient of performance, and temperature differences, leading to significant energy loss during charging and discharging cycles.
Innovation Solution
A thermoelectric energy storage system with a working fluid circuit and thermal storage medium circuit, where the second heat exchanger is switchably connected to different thermal baths during charging and discharging cycles to minimize temperature differences, optimizing the coefficient of performance and energy recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a single thermal bath is used for both charging and discharging cycles, then the system structure is simplified, but the round-trip efficiency is limited due to unavoidable temperature differences
Solution Approach 1:
The single thermal bath is segmented into two separate thermal baths with different temperature levels. The first thermal bath operates at a higher temperature during the charging cycle, while the second thermal bath operates at a lower temperature during the discharging cycle. This segmentation allows each bath to be optimized for its specific function, reducing temperature differences during heat transfer and improving overall round-trip efficiency.
Solution Approach 2:
The system changes the temperature parameter of the thermal baths based on the operational cycle. During charging, the first thermal bath is maintained at a higher temperature to minimize the temperature difference with the working fluid. During discharging, the second thermal bath is maintained at a lower temperature to maximize the temperature difference and improve heat engine efficiency. This dynamic parameter adjustment resolves the contradiction between energy loss and system complexity.
2Productivity
If the temperature difference between thermal bath and storage tank is maximized, then heat transfer rate increases, but the capability of heat to do work decreases
Solution Approach 1:
Different temperature differences are applied locally to different thermal baths based on their specific functions. The first thermal bath uses a minimized temperature difference during charging to preserve heat work capability, while the second thermal bath uses a maximized temperature difference during discharging to enhance heat transfer rate and power generation. This localized optimization resolves the contradiction between heat transfer rate and heat work capability.
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 the round-trip efficiency of the thermoelectric energy storage system while minimizing system costs, allowing for more effective energy storage and retrieval with lower electricity input during charging and higher energy recovery during discharging.
Implementation Method 1
a first heat exchanger for transferring thermal energy between the working fluid and the thermal storage medium
Implementation Method 2
a second heat exchanger for transferring thermal energy between the working fluid and the thermal bath
Implementation Method 3
converts the heat back to electricity in a discharging cycle
Data Source
AI summary
An exemplary system and method for storing and retrieving energy in a thermoelectric energy storage system is disclosed. The thermoelectric energy storage system includes a working fluid that is circulated through a first and second heat exchanger, and a thermal storage medium that is circulated through the first heat exchanger. The second heat exchanger is in connection with a first thermal bath during a charging cycle and with a second thermal bath during a discharging cycle. In this way roundtrip efficiency is improved through minimizing the temperature difference between the first thermal bath and the hot storage tank during charging, and maximizing the temperature difference between the second thermal bath and the hot storage tank during discharging.