Thermal Storage System Crystallization Control via Two-Phase Solvent
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Solution Overview
Problem
Thermal storage systems using Phase Change Materials (PCMs) face challenges with supercooling and slow crystallization speeds, particularly with polyols like xylitol and sorbitol, which hinder efficient heat storage and release due to their strong propensity to supercooling, making it difficult to control crystallization and thus limiting their implementation in large-scale applications.
Innovation Solution
A Thermal Storage System (TSS) that includes a vessel with a circulation system and a device for controlling crystallization by injecting a two-phase solvent into the PCM, where the solvent changes state from liquid to gas, generating agitation and accelerating crystallization, and is evacuated to manage pressure and recycle the solvent, thereby enhancing crystallization speed and control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If polyols are used as PCM, then enthalpy of change of state is improved, but crystallization speed deteriorates
Solution Approach 1:
Nucleation agents are introduced as intermediary substances that facilitate the crystallization process. These agents provide predefined nucleation sites that trigger and accelerate crystal formation in polyols, solving the slow crystallization issue while preserving the high enthalpy advantage of polyol PCMs.
Solution Approach 2:
The crystallization process is accelerated by changing physical parameters such as applying mechanical agitation, ultrasonic treatment, or controlled cooling rates. These parameter changes overcome the natural slow crystallization tendency of polyols while maintaining their high enthalpy of change of state.
2Object-affected harmful factors
If polyols are used as PCM, then non-toxicity is improved, but supercooling propensity worsens
Solution Approach 1:
Nucleation agents serve as mediators that prevent supercooling by providing nucleation sites. These agents are carefully selected to be compatible with the non-toxic nature of polyols, ensuring that the ecological advantages are maintained while reliability is improved.
Solution Approach 2:
Nucleation agents are pre-added to the polyol PCM before operation. This preliminary action ensures that nucleation sites are already present when cooling occurs, preventing supercooling from happening and ensuring reliable crystallization at the expected temperature.
3Speed
If nucleation agents are added to accelerate crystallization, then crystallization speed is improved, but device complexity worsens
Solution Approach 1:
The nucleation agents are incorporated directly into the PCM material itself, allowing the system to self-trigger crystallization without requiring external complex devices. The PCM contains its own crystallization catalyst, eliminating the need for separate nucleation device systems.
4Reliability
If mechanical agitation is applied to trigger crystallization, then crystallization control is improved, but energy consumption worsens
Solution Approach 1:
Nucleation agents act as intermediaries that enable crystallization to start with minimal or no mechanical agitation. The nucleation sites provided by these agents allow crystallization to proceed spontaneously or with very light stirring, dramatically reducing the energy required compared to systems requiring intensive mechanical agitation.
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 significantly improves the crystallization speed and control of PCMs, enabling more efficient heat storage and release, overcoming the limitations of supercooling and enhancing the performance of thermal storage systems.
Implementation Method 1
injecting a two-phase solvent into the PCM (2), in the liquid state, in the lower part of the tank (1), and the evacuation of the solvent in the gaseous state in the upper part of the tank (1)
Implementation Method 2
The solvent is two-phase so as to change state on contact with the PCM having stored heat. In this way, the addition of two-phase solvent in the MCP contributes to favorably modifying the properties of the MCP and therefore accelerating the rate of crystallization while allowing the heating of the solvent introduced in the liquid state in contact with the MCP. The increase in the temperature of the solvent in contact with the MCP causes it to boil, generating bubbling of the solvent in the MCP, thus triggering the crystallization of the MCP.
Implementation Method 3
A Thermal Storage System (TSS) that includes a vessel with a circulation system and a device for controlling crystallization
Data Source
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AI summary
The present invention relates to a Thermal Storage System (TSS) using a Phase Change Material (PCM) (2) comprising a tank (1) for containing a PCM (2), and a circulation system immersed in the tank (1) for circulating a heat transfer fluid from an external heat transfer fluid circulation network. The system is characterized in that it includes a device for controlling the crystallization of the PCM, comprising: an injection module configured to inject a two-phase solvent in liquid form into the lower part of the tank (1), and an evacuation module configured to evacuate the two-phase solvent in gaseous form into the upper part of the tank, opposite the lower part. All TSSs whose PCMs have issues with supercooling and slow crystallization rates are likely to be relevant to the invention.The present invention will find application in urban, rural, or industrial heating and/or cooling networks, as well as in solar energy storage. The invention may also find applications in housing, off-grid thermal transport (trucks, boats, etc.), and the thermal management of embedded systems.