PCM Thermal Storage Bubbling and Seeding Control
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Solution Overview
Problem
Thermal storage systems using Phase Change Materials (PCMs) face challenges with supercooling and slow crystallization rates, particularly with polyols and sugar alcohols, which lead to unpredictable and prolonged induction times during discharge, affecting the efficiency and stability of heat restitution.
Innovation Solution
A Phase Change Material Thermal Storage System incorporating a bubbling device to form gas bubbles and a seeding device to create solid seeds, which synergistically initiate and control secondary nucleation, reducing the variability of induction time and ensuring consistent heat release at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyols or sugar alcohols are used as PCMs to achieve high enthalpy of phase change and non-toxic properties, then the energy storage density and safety are improved, but the material exhibits strong propensity for supercooling which makes crystallization difficult to control and extends induction time
Solution Approach 1:
The patent introduces an inert gas (nitrogen or argon) as an intermediary substance that bubbles through the supercooled PCM. This gas acts as a mediator to mechanically disturb the liquid structure and promote nucleation sites formation, enabling controlled crystallization without directly interacting with the PCM chemically. The gas bubbles provide the necessary mechanical energy to overcome the supercooling stability while maintaining the safety benefits of using polyols or sugar alcohols.
2Device complexity
If simple agitation or bubbling is used to initiate PCM crystallization, then the system complexity is reduced, but the induction time becomes highly variable and unpredictable
Solution Approach 1:
The patent employs a pre-designed bubbling system with controlled gas flow rate, temperature, and duration parameters established before the crystallization process begins. These preliminary settings ensure that the nucleation process starts at a predictable moment, reducing induction time variability. The system pre-establishes optimal conditions for gas bubble generation and distribution throughout the PCM volume.
Solution Approach 2:
The patent incorporates temperature sensors and control systems that monitor the PCM temperature in real-time and provide feedback to the gas bubbling system. When the temperature reaches the target crystallization point, the system automatically adjusts or stops gas flow, creating a closed-loop control mechanism. This feedback system eliminates the randomness of induction time by responding dynamically to actual thermal conditions.
3Productivity
If gas bubbling is used to increase solid nuclei quantity, then the crystallization speed is improved, but a latency period of approximately 30 minutes occurs between bubbling start and crystallization start
Solution Approach 1:
The patent systematically optimizes multiple parameters including gas flow rate, gas temperature, bubble size distribution, and bubbling duration to minimize the latency period. By adjusting these parameters, the system achieves faster nucleation onset. For example, increasing gas flow rate or reducing bubble size can intensify the mechanical disturbance and trigger crystallization more quickly, reducing the 30-minute latency to a shorter, more predictable timeframe.
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
The solution significantly reduces the random nature of induction time, enhancing the discharge rate and maintaining heat return at almost constant, high temperatures, thereby improving the system's power performance and temperature stability.
Implementation Method 1
a bubbling device configured to form gas bubbles, in the lower part of the tank, in the MCP
Implementation Method 2
This bubbling, achieved by injecting gas (particularly air) directly into the PCM, increases the quantity of solid nuclei throughout the agitated volume
Implementation Method 3
a seeding device configured to form solid MCP seeds in the MCP tank
Implementation Method 4
Triggering and acceleration of xylitol crystallization by seeding and shearing
Implementation Method 5
Heat storage using the latent heat of phase change materials (PCMs) offers the advantage of high energy storage density
Implementation Method 6
the crystallization of the PCM is triggered to allow the release of the heat stored by the PCM in latent form
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The invention Thermal Storage System (TSS) by Phase Change Material (PCM) (2) comprising: a tank (1) intended to contain a PCM (2), a circulation system immersing in the tank (1), intended for the circulation of a heat transfer fluid from an external heat transfer fluid circulation network, a device for controlling the crystallization of the PCM (2), characterized in that the device for controlling the crystallization of the PCM (2) comprises a bubbling device (11) configured to form bubbles (8) of gas, in the lower part of the tank (1), in the PCM (2), and a seeding device (10) configured to form solid seeds of PCM in the tank (1) of PCM (2). SSTs using a PCM with supercooling and slow crystallization rate problems are likely to be affected by the invention, and more particularly PCMs combining low primary nucleation rates and low crystal growth rates.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.