Intermediate Tank Thermoelectric Storage for Lower Heat Transfer Loss
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Solution Overview
Problem
Thermoelectric energy storage systems face limitations in round-trip efficiency due to thermodynamic irreversibilities, particularly in heat transfer over large temperature differences, leading to high capital costs and inefficiencies in existing solutions like large heat exchangers or phase change materials.
Innovation Solution
A thermoelectric energy storage system utilizing a transcritical thermodynamic cycle with a heat exchanger and thermal storage medium circuit, including hot, intermediate, and cold storage tanks, where the flow rate of the thermal storage medium is modified to minimize temperature differences and optimize heat exchange, using an internal stream splitter to control flow rates and maintain efficient heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If large heat exchangers are used to transfer heat over large temperature differences, then heat transfer capability is improved, but capital cost increases significantly
Solution Approach 1:
The thermal storage system is segmented into multiple temperature zones (hot, intermediate, cold storage tanks) rather than using a single large heat exchanger. This segmentation allows heat transfer to occur across smaller temperature differences in each zone, reducing the overall heat exchanger size and capital cost while maintaining heat transfer capability.
Solution Approach 2:
An intermediate storage tank is introduced as a mediator between the hot and cold storage tanks. This intermediate zone facilitates heat transfer by breaking down the large temperature difference into smaller steps, thereby reducing the required heat exchanger area and capital investment.
2Quantity of substance
If phase change materials are used to store thermal energy, then storage density is improved, but system complexity and cost increase
Solution Approach 1:
The system uses sensible heat storage with fluid thermal storage media instead of phase change materials. By changing the storage mechanism from latent heat (phase change) to sensible heat (temperature change), the system reduces complexity while maintaining adequate storage density through the use of intermediate storage zones.
3Productivity
If heat transfer over large temperature differences is used to improve heat pump performance, then charging efficiency is improved, but thermodynamic reversibility decreases
Solution Approach 1:
The heat transfer process is segmented into multiple smaller temperature difference steps across hot, intermediate, and cold storage zones. This segmentation reduces thermodynamic irreversibility by minimizing the temperature gradient during heat transfer, thereby improving overall thermodynamic efficiency while maintaining charging performance.
4Power
If the thermal storage medium flow rate is increased to improve heat exchange, then heat transfer rate is improved, but temperature differences increase
Solution Approach 1:
The system incorporates flow control mechanisms that adjust the thermal storage medium flow rate based on temperature conditions. By using feedback control, the system optimizes the balance between heat transfer rate and temperature difference, ensuring efficient heat exchange while minimizing thermal gradients through dynamic flow rate adjustment.
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 round-trip efficiency by reducing temperature differences and minimizing capital costs, achieving improved energy storage and retrieval with reduced heat transfer losses.
Implementation Method 1
heat transfer in the heat exchanger
Implementation Method 2
thermal storage medium circuit for circulating a thermal storage medium
Implementation Method 3
the working fluid undergoes a transcritical process during heat transfer in the heat exchanger
Implementation Method 4
a heat exchanger, and a working fluid circuit for circulating a working fluid through the heat exchanger
Data Source
AI summary
A system and method are provided for storing electric energy in the form of thermal energy. A thermoelectric energy storage system includes a working fluid circuit for circulating a working fluid through a heat exchanger, and a thermal storage medium circuit for circulating a thermal storage medium. The thermal storage medium circuit includes at least one hot storage tank, an intermediate temperature storage tank, and a cold storage tank connected together via the heat exchanger. A proportion of the storage medium is redirected to or from the intermediate storage tank from or to the hot or cold storage tank, joining another proportion which flows directly between the cold and hot storage tank.