Thermocline Control in Thermal Energy Storage
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Solution Overview
Problem
Single-tank heat storage devices suffer from temperature degradation, leading to inefficient operation and increased material costs due to thermocline degradation, which results in fluctuating heat transfer fluid temperatures and reduced utilization factors.
Innovation Solution
A method of controlling the thermocline region in heat storage devices by removing heat transfer fluid from the thermocline region and adjusting its temperature by mixing it with fluid from upper or lower temperature regions, ensuring a constant outflow temperature and reducing thermocline width, thereby enhancing the utilization factor and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If heat transfer fluid is continuously removed from the thermocline region during charging and discharging, then the utilization factor is increased, but the outflow temperature becomes fluctuating and unstable
Solution Approach 1:
The patent applies local quality by differentiating the treatment of heat transfer fluid from different vertical regions. Fluid from the upper temperature region is mixed with fluid from the thermocline region during charging, while fluid from the lower temperature region is mixed with thermocline fluid during discharging. This localized mixing strategy maintains stable outflow temperature while preserving the utilization factor benefit.
Solution Approach 2:
The patent introduces upper and lower temperature regions as intermediary zones that mediate the interaction between the thermocline region and the external system. These intermediary regions provide temperature-buffered fluid that stabilizes the outflow temperature while allowing continuous thermocline utilization.
2Stability of the object's composition
If the thermocline region width is increased to provide thermal buffer, then the temperature stability is improved, but the utilization factor decreases and material costs increase
Solution Approach 1:
The patent changes the operational parameters by implementing selective mixing based on charging/discharging mode. During charging, upper region fluid is introduced to the thermocline; during discharging, lower region fluid is introduced. This dynamic parameter change maintains narrow thermocline width while ensuring temperature stability through appropriate fluid selection.
Solution Approach 2:
The patent applies dynamics by making the mixing strategy adaptive to the operational mode. The system dynamically switches between different mixing configurations based on whether it is charging or discharging, allowing the thermocline to maintain optimal width while providing temperature stability through mode-dependent fluid mixing.
3Stability of the object's composition
If heat transfer fluid is extracted and reheated using a heat exchanger, then the outflow temperature is stabilized, but the device complexity and material costs increase
Solution Approach 1:
The patent applies self-service by using the thermal energy already present in the upper and lower temperature regions to stabilize the thermocline fluid temperature. During charging, the warm upper region fluid naturally cools the extracted thermocline fluid; during discharging, the cooler lower region fluid naturally heats it. This eliminates the need for external heat exchangers.
Solution Approach 2:
The patent merges the temperature stabilization function with the existing fluid circulation system. Instead of adding a separate heat exchanger system, the invention combines the mixing of upper/lower region fluids with the thermocline extraction process, achieving temperature stability through integrated fluid manipulation.
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 method allows for precise control of thermal stress and temperature in heat storage devices, increasing the utilization factor and reducing material costs by maintaining a constant heat transfer fluid temperature, thus improving the efficiency of systems connected to the thermal energy storage.
Implementation Method 1
adjusting its temperature by mixing it with fluid from upper or lower temperature regions
Implementation Method 2
removing heat transfer fluid from the thermocline region and adjusting its temperature by mixing it with fluid from upper or lower temperature regions
Implementation Method 3
Heat storage devices enable dispatchable thermal energy from intermittent solar energy
Implementation Method 4
a body of heat transfer fluid comprising an upper temperature region comprising heat transfer fluid having a temperature above a upper threshold temperature, a lower temperature region comprising heat transfer fluid having a temperature below a lower threshold temperature and a thermocline region separating the upper and lower temperature regions
Data Source
AI summary
The present invention to provide a method of operating a thermal energy storage device comprising a body of heat transfer fluid, said body of heat transfer fluid comprising an upper temperature region comprising heat transfer fluid having a temperature above a upper threshold temperature, a lower temperature region comprising heat transfer fluid having a temperature below a lower threshold temperature and a thermocline region separating the upper and lower temperature regions and comprising heat transfer fluid having a temperature above a lower threshold temperature and below an upper threshold temperature, wherein during charging of the thermal energy storage device, heat transfer fluid is removed from the thermocline region of the body of heat transfer fluid and when the temperature of the heat transfer fluid being removed from the thermocline region of the body of heat transfer fluid rises above a maximum temperature, said heat transfer fluid being removed is brought to a temperature equal to or below said maximum temperature, wherein the maximum temperature is above the lower threshold temperature and/or wherein during discharging of the thermal energy storage device, heat transfer fluid is removed from the thermocline region of the body of heat transfer fluid and when the temperature of the heat transfer fluid being removed from the thermocline region of the body of heat transfer fluid falls below a minimum temperature, said heat transfer fluid being removed is brought to a temperature equal to or above said minimum temperature, wherein said minimum temperature is below the upper threshold temperature.