Intermediate Thermal Storage Tank Layout for Efficient TEES Heat Transfer
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Solution Overview
Problem
Existing 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 thermal storage medium usage.
Innovation Solution
A thermoelectric energy storage system with a transcritical cycle and a heat exchanger design that includes multiple storage tanks and an internal stream splitter to minimize temperature differences between the working fluid and thermal storage medium, optimizing the flow rate of the thermal storage medium to enhance round-trip efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heat transfer occurs over large temperature differences in conventional TEES systems, then heat transfer rate increases, but round-trip efficiency decreases due to thermodynamic irreversibilities
Solution Approach 1:
The thermal storage medium circuit is segmented into multiple storage tanks (hot storage tank, intermediate storage tank, cold storage tank) with different temperature levels. This segmentation allows heat transfer to occur in stages across smaller temperature differences, reducing thermodynamic irreversibilities while maintaining effective heat transfer rates.
Solution Approach 2:
Different regions of the thermal storage system are assigned different temperature characteristics. The hot storage tank operates at high temperature, the cold storage tank at low temperature, and the intermediate storage tank at medium temperature. This local differentiation optimizes heat transfer efficiency at each stage while minimizing overall energy losses.
2Loss of energy
If multiple storage tanks and stream splitters are added to minimize temperature differences, then round-trip efficiency improves, but device complexity increases
Solution Approach 1:
The intermediate storage tank serves multiple functions: it acts as a thermal buffer between hot and cold storage, provides a medium for heat exchange during both charging and discharging cycles, and enables flow rate modulation. The stream splitter also performs multiple roles by distributing thermal storage medium to different heat exchangers and enabling flexible system operation modes.
Solution Approach 2:
The system utilizes the thermal energy already stored in the intermediate storage tank to facilitate heat transfer processes, reducing the need for external energy input. The circulating pumps and stream splitters are controlled to automatically optimize flow distribution based on system conditions, minimizing manual intervention.
3Loss of energy
If flow rate of thermal storage medium is optimized to minimize temperature differences, then heat transfer losses decrease, but control complexity increases
Solution Approach 1:
The system incorporates temperature sensors and flow meters that continuously monitor the thermal state of the storage medium and working fluid. This feedback information is used to automatically adjust the flow rates through the intermediate storage tank and stream splitters, optimizing heat transfer efficiency while maintaining simple operation through automated control.
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 minimizes temperature differences and maximizes round-trip efficiency, reducing capital costs and heat transfer losses, thereby improving the overall efficiency of energy storage and retrieval.
Implementation Method 1
heat transfer from a hot working fluid to a thermal storage medium during the heat pump cycle and back from the thermal storage medium to the working fluid during the heat engine cycle
Implementation Method 2
The rate of flow of the thermal storage medium in the heat exchanger is modified in order to minimize temperature difference between the working fluid and the thermal storage medium
Implementation Method 3
Thermal energy can be stored in the form of sensible heat via a change in temperature
Implementation Method 4
the conversion of heat to mechanical work in a heat engine is limited to the Carnot efficiency
Implementation Method 5
a heat pump requires work to move thermal energy from a cold source to a warmer heat sink. Since the amount of energy deposited at the hot side is greater than the work required by an amount equal to the energy taken from the cold side, a heat pump will 'multiply' the heat
Data Source
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AI summary
A system and method for storing electric energy in the form of thermal energy is described. A thermoelectric energy storage system comprises a working fluid circuit for circulating a working fluid through a heat exchanger (16) and a thermal storage medium circuit for circulating a thermal storage medium, the thermal storage medium circuit having at least one hot storage tank (24), one intermediate temperature storage tank (22) and one cold storage tank (20) connected together via the heat exchanger (16). The flow rate of the thermal storage medium in the heat exchanger (16) is modified in order to minimize temperature difference between the working fluid and the thermal storage medium during charging and discharging cycles.