Phase Change Thermal Storage with External Seed Trigger
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Solution Overview
Problem
Current systems fail to effectively store and release thermal energy generated from transient sources like solar power for long periods without significant loss, as existing methods like hot water tanks are inefficient for long-term storage and release.
Innovation Solution
A modular thermal energy storage apparatus using a phase change material like sodium acetate trihydrate, housed in a container with a sidewall fitting for external fluid connection and an external seed crystal reservoir trigger assembly that induces solidification of the phase change material to release thermal energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If thermal energy is stored in hot water tanks with thermal insulation, then thermal energy can be stored and transported, but the thermal energy dissipates to the external environment through conduction over time, making it ineffective for long-term storage
Solution Approach 1:
The patent utilizes the phase transition of sodium acetate trihydrate from liquid to solid state, which releases latent heat of fusion (125-150 kJ/kg). This phase change mechanism allows for high-density thermal energy storage that can be maintained indefinitely in the supercooled liquid state or released on-demand during solidification, eliminating the continuous thermal dissipation problem of hot water tanks.
Solution Approach 2:
The system pre-cools the phase change material below its freezing point to create a supercooled liquid state that is metastable and can store thermal energy indefinitely without spontaneous solidification. This preliminary cooling action enables the material to maintain its thermal energy storage capacity over extended periods without the continuous heat loss characteristic of conventional thermal storage systems.
2Quantity of substance
If solar thermal systems use conventional thermal storage, then thermal energy can be collected and stored, but significant solar collector area is required to achieve adequate storage capacity
Solution Approach 1:
The high latent heat of fusion of sodium acetate trihydrate (125-150 kJ/kg) enables compact thermal energy storage with high energy density. This allows sufficient thermal energy storage capacity to be achieved in a much smaller volume, thereby reducing the required solar collector area compared to conventional thermal storage systems that rely on sensible heat storage in water or other fluids.
3Ease of operation
If phase change material is stored in a flexible pouch for manual manipulation, then the pouch must be sufficiently translucent to locate the disc, sufficiently small to allow external manipulation, and sufficiently flexible to allow flexion
Solution Approach 1:
The trigger mechanism for inducing solidification is extracted from the bulk phase change material and placed in a separate, easily accessible location. The trigger assembly includes a seed crystal reservoir and delivery mechanism that can be actuated externally without requiring manipulation of the entire pouch, thereby enabling easy operation while accommodating larger storage volumes.
Solution Approach 2:
A separate trigger assembly acts as an intermediary between the user and the phase change material. This trigger mechanism delivers a seed crystal to initiate solidification without requiring direct manipulation of the phase change material itself, allowing the pouch to be larger and less flexible while maintaining ease of operation.
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 solution allows for efficient long-term storage and controlled release of thermal energy, reducing energy loss and enabling the use of solar thermal systems with reduced solar collector area, thereby lowering costs.
Implementation Method 1
a phase change material which may exist in a melted or solid state
Implementation Method 2
such a phase change material undergoes a phase transition from solid to liquid at an elevated temperature and when cooled, remains stable in a higher energy supercooled liquid state
Implementation Method 3
The supercooled liquid sodium acetate trihydrate then crystalizes around the seed crystal, and in the process of solidifying, releases stored thermal energy
Implementation Method 4
exposes the supercooled liquid sodium acetate trihydrate to the trapped seed crystal
Implementation Method 5
allowing for the transfer of thermal energy across the first fluid flow plate from the phase change material to the heat exchange fluid
Data Source
AI summary
A thermal energy storage apparatus is disclosed. The apparatus may include a base and fluid flow plates which cooperate with the base to define a cavity; a phase change material contained within the cavity; an external seed crystal reservoir trigger assembly at least partially positioned within the phase change material; and end plates which cooperate with the fluid flow plates to define fluid flow channels. The apparatus may include a housing that holds a heat exchanger and phase change material. Inlet and outlet ports allow for the ingress and egress of a heat exchange fluid into the fluid flow channels or heat exchanger. In operation, actuation of the external seed crystal reservoir trigger assembly to an open state induces solidification of at least a portion of the phase change material from a supercooled liquid state to a solid state, releasing thermal energy, allowing for the transfer of thermal energy across the fluid flow plates or heat exchanger from the phase change material to the heat exchange fluid.