Polyol-Salt Inert Mixture for Thermal Energy Storage
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Solution Overview
Problem
Current phase change materials for thermal energy storage, such as paraffinic, fatty acid, hydrated salt, eutectic salt, and polyol materials, face limitations including low thermal conductivity, slow crystallization kinetics, flammability, chemical aggression, and sub-cooling phenomena, which affect their efficiency and stability in thermal energy storage applications.
Innovation Solution
An inert mixture comprising specific polyols (like glycerol, erythritol, and inorganic salts with a nucleating agent, such as carbon powder, is developed, with a molar ratio of polyol to salt between 99:1 and 50:50, enhancing thermal conductivity, stability, and eliminating sub-cooling issues, suitable for a wide temperature range from -40 °C to 200 °C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If paraffinic phase change materials are used for thermal energy storage, then the material provides adequate phase change temperature ranges, but the thermal conductivity is low and flammability is moderate
Solution Approach 1:
The patent applies composite materials by combining paraffinic phase change materials with inorganic salts (such as nitrates, sulfates, or halides) and nucleating agents. This composite structure allows the mixture to maintain the advantageous phase change temperature characteristics of paraffins while the inorganic salt component provides enhanced thermal conductivity and chemical stability, thereby resolving the contradiction between temperature performance and reliability.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the composition ratios of polyols, inorganic salts, and nucleating agents in the inert mixture. By optimizing these parameters, the material achieves improved thermal conductivity and reduced flammability while maintaining appropriate phase change temperatures for thermal energy storage applications.
2Reliability
If hydrated salts are used for thermal energy storage, then the thermal conductivity is high and phase transition energy is high, but the material is chemically aggressive towards metal components and unstable after a few cycles due to phase segregation
Solution Approach 1:
The patent employs composite materials by formulating an inert mixture of polyols, inorganic salts, and nucleating agents. The polyol component serves as a stable base that is not chemically aggressive towards metal components, while the inorganic salt provides high phase transition energy. The nucleating agent prevents phase segregation during cycling, thereby maintaining composition stability and chemical inertness throughout multiple thermal cycles.
Solution Approach 2:
The patent uses the polyol as an intermediary substance that mediates between the inorganic salt and metal components of the storage device. The polyol layer prevents direct contact and chemical reaction between the salt and metal surfaces, eliminating corrosion issues while still allowing thermal energy transfer. This intermediary approach resolves the contradiction between high energy density and chemical stability.
3Temperature
If eutectic mixtures of salts are used for thermal energy storage, then the phase change temperature is suitable, but the material cannot be used in the envisaged applications due to temperature range limitations
Solution Approach 1:
The patent achieves universality by creating an inert mixture system that can operate across a wide temperature range from -40°C to 200°C. By selecting appropriate combinations of polyols, inorganic salts, and nucleating agents, the same basic formulation approach can be adapted to different temperature requirements, making the material suitable for diverse applications including refrigeration, building thermal management, and industrial heat storage.
4Use of energy by moving object
If polyols are used for thermal energy storage, then the thermal capacity is high, but significant sub-cooling phenomena occur leading to deviation between phase change temperatures during heating and cooling
Solution Approach 1:
The patent introduces nucleating agents as intermediary substances that facilitate consistent phase change behavior. These nucleating agents provide stable crystallization sites that prevent supercooling phenomena, ensuring that the phase change temperature remains consistent during both heating and cooling cycles. This resolves the contradiction between maintaining high thermal capacity and achieving temperature consistency.
Solution Approach 2:
The patent applies preliminary action by incorporating nucleating agents into the polyol-inorganic salt mixture before use. These agents pre-establish the conditions for controlled crystallization, ensuring that phase change occurs at the intended temperature without significant sub-cooling. This preliminary preparation eliminates temperature deviation issues while preserving the high thermal capacity of polyols.
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 inert mixture exhibits improved thermal energy storage capabilities with high phase change energy, chemical stability, and absence of sub-cooling phenomena, making it suitable for electric energy production, steam production, and building/air-conditioning sectors, with enhanced thermal conductivity and prolonged material stability.
Implementation Method 1
phase change materials, which use a phase change process of the material to store thermal energy. The phase change takes place in well-defined and different temperature and pressure ranges
Implementation Method 2
at least one nucleating agent selected from the group consisting of carbon powder, metal powder, and silicon carbide
Data Source
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AI summary
This invention relates to an inert mixture comprising: at least one polyol selected from the group consisting of: glycerol, erythritol, mannitol, pentaerythritol, xylitol, dulcitol, sorbitol, ribitol, maltitol, and inositol; at least one inorganic salt soluble in said polyol, said inorganic salt being of at least one metal selected from the group consisting of: lithium, sodium, potassium, calcium, magnesium, strontium, barium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, and aluminum and of at least one anion selected from the group consisting of: a halide, a silicate, and a sulfate; and at least one nucleating agent selected from the group consisting of carbon powder, metal powder, and silicon carbide; wherein: the molar ratio of the at least one polyol to the at least one inorganic salt is in the range from 99:1 to 50:50; and the at least one nucleating agent is present in the form of particles having a size in the range from 1 to 50 microns, measured by the laser diffractometry method according to the ISO standard 13320:2009 (E), and the use thereof to store thermal energy. The present invention also relates to a thermal energy storage device which includes the inert mixture according to the present invention and a method of thermal energy storage which includes the use of such a device.