Ceramic-Graphite Composite for Stable High-Temperature Energy Storage
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Solution Overview
Problem
Existing high-temperature thermal energy storage (HT-TES) materials fail to simultaneously meet requirements of good thermal conductivity, temperature-independent electrical conductivity, robust mechanical properties, high temperature stability, and non-corrosivity, while being made from safe and abundant materials, leading to issues like thermal runaway and mechanical failure.
Innovation Solution
A composite material comprising a ceramic matrix with dispersed graphite flakes, where the ceramic is an oxide, carbide, boride, or nitride, and the graphite flakes are 20-35% by weight, forming a random continuous conductive pathway, with a porosity of 5-40%, enhancing thermal and electrical conductivity and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If refractory ceramics are used for HT-TES, then high temperature stability is achieved, but external heaters are required increasing system complexity
Solution Approach 1:
The ceramic material is doped to become electrically conductive, enabling it to self-heat through resistive heating when an electric field is applied. This eliminates the need for external heaters and associated complexity while maintaining high temperature stability up to 1500°C.
Solution Approach 2:
The electrical conductivity of the ceramic is modified through doping with conductive materials, transforming it from an insulator to a conductive material. This parameter change enables direct electrical heating while preserving the high temperature stability inherent to refractory ceramics.
2Productivity
If ceramics are doped to make them electrically conductive, then rapid self-heating is achieved, but conductivity varies widely with temperature causing thermal runaway
Solution Approach 1:
A composite material is created by combining doped ceramic particles with a binder matrix. The ceramic provides high temperature stability and thermal energy storage capacity, while the binder provides stable electrical conductivity across a wide temperature range. This composite structure achieves rapid self-heating while preventing thermal runaway through stable conductivity.
Solution Approach 2:
The composite structure distributes different materials in specific proportions (ceramic particles embedded in binder matrix) to create local regions with complementary properties. The ceramic regions provide thermal stability and energy storage, while the binder regions provide stable electrical conduction, achieving both rapid heating and thermal safety.
3Power
If good thermal conductivity is achieved to reduce temperature gradients, then power delivery rates increase, but material selection becomes more restricted
Solution Approach 1:
The composite structure combines ceramic particles with a conductive binder matrix, creating a material with enhanced thermal conductivity through the continuous binder phase. This allows selection from various ceramic types (alumina, silica, magnesia) while maintaining good thermal conductivity, increasing material versatility without sacrificing power delivery capability.
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 composite material achieves stable self-heating, withstands extreme temperature gradients and thermal cycling, and maintains electrical conductivity without significant variation, ensuring safety and efficiency in high-temperature thermal energy storage systems.
Implementation Method 1
The graphite flakes form a random continuous electrically conductive pathway in the composite material... allowing for direct electrical self-heating
Implementation Method 2
good thermal conductivity to reduce temperature gradients and increase power delivery rates
Data Source
AI summary
This disclosure provides systems, methods, and apparatus related to high-temperature thermal energy storage. In one aspect, a composite material includes a ceramic and graphite flakes dispersed in the ceramic. The ceramic serves as a matrix of the composite material. The ceramic is an oxide, a carbide, a boride, or a nitride. The graphite flakes are about 20 weight % to 35 weight % of the composite material. The composite material has a porosity of about 5% to 40%.