Graphite Block Thermal Storage for Phase Change Pressure Control
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Solution Overview
Problem
Previous thermal energy storage systems using silicon metalloid materials face issues with pressure build-up and enclosure fissuring due to expansion and contraction, and poor heat transport efficiency, particularly in arrangements with sintered graphite rods.
Innovation Solution
A thermal energy storage apparatus featuring a contiguous block of sintered graphite with precision-bored holes for heat storage elements and electric heating elements, along with a containment vessel made of silicon carbide that preferentially expands to manage phase change stress, and a Carnot cycle heat engine for efficient energy conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon metalloid material is stored in separate enclosures before being inserted into refractory material, then the material can be protected during handling, but the continual pressure build-up and collapse during phase changes results in fissuring of the enclosure
Solution Approach 1:
The invention divides the system into two functional parts: a reusable refractory graphite block (heat-absorbing material) and replaceable silicon metalloid ingots (heat storage elements). The refractory block maintains structural integrity and contains machined holes for ingot insertion, while the silicon ingots are handled as separate replaceable units. This segmentation allows the strong refractory material to provide structural support while the silicon material performs its phase change function, resolving the contradiction between protection during handling and enclosure integrity.
2Loss of energy
If silicon metalloid ingots are placed directly in contact with refractory heat-absorbing material, then heat transport efficiency is improved, but the metalloid is absorbed by the graphite on undergoing phase change to liquid form
Solution Approach 1:
The invention introduces refractory ceramic material as an intermediary layer between the silicon metalloid ingots and the graphite heat-absorbing material. This intermediary serves dual functions: it maintains intimate thermal contact for efficient heat transport while preventing the harmful absorption of liquid silicon by the graphite. The ceramic barrier allows thermal energy transfer during phase changes without allowing material mixing, thus resolving the contradiction between heat transport efficiency and prevention of substance loss.
3Reliability
If canisters are used to store silicon metalloid in interleaved arrangement with sintered graphite rods, then heat storage is enabled, but the canisters are prone to cracking particularly in the region of the grooves
Solution Approach 1:
The invention extracts the problematic canister structure entirely and replaces it with a simplified direct-contact design. Instead of using enclosed canisters with grooves that are prone to cracking, the silicon metalloid ingots are placed directly into machined holes in the refractory graphite block. This eliminates the weak canister structure while maintaining heat storage capability through the phase change material's inherent properties and its direct thermal contact with the refractory block.
4Loss of energy
If silicon metalloid material undergoes phase change from solid to liquid, then thermal energy is absorbed for storage, but significant pressure build-up occurs on the enclosure
Solution Approach 1:
The invention converts the harmful pressure build-up during phase change into a beneficial self-regulating mechanism. The refractory graphite block's mechanical strength contains the pressure, while the design allows the silicon material to expand and contract within its designated space. The pressure generated during melting actually ensures intimate contact between the silicon and the refractory ceramic, optimizing heat transfer. During solidification, the pressure release creates voids that accommodate volume changes. This transforms the harmful pressure effect into a feature that enhances thermal contact and energy storage efficiency.
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 design prevents fracturing and enhances heat transport by embedding heat storage elements within a machinable graphite block, allowing for controlled heating and efficient energy storage and release, while maintaining structural integrity and optimizing thermal efficiency.
Implementation Method 1
the silicon metalloid material would absorb thermal energy as it underwent a phase change from a solid to a liquid
Implementation Method 2
the thermal energy stored within the silicon metalloid material
Implementation Method 3
on undergoing a phase change from liquid to solid, there is an expansion of the material rather than contraction
Implementation Method 4
a block of a heat-absorbing material, and a plurality of heat storage elements, the heat storage elements including a phase change material stored in a containment vessel; wherein each heat storage element is in thermal contact with the block of heat-absorbing material
Implementation Method 5
a Carnot cycle heat engine for efficient energy conversion
Data Source
AI summary
A thermal energy storage apparatus, including: a block of a heat-absorbing material, and a plurality of heat storage elements, the heat storage elements including a phase change material stored in a containment vessel; wherein each heat storage element is in thermal contact with the block of heat-absorbing material.