Calcium Oxide Thermal Storage With Microwave-Assisted Dehydration
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Solution Overview
Problem
Existing thermal energy storage systems face challenges such as low energy density, high manufacturing costs, complex engineering, significant energy losses, and inefficient heat transfer, particularly in sorption storage concepts using zeolites and other materials.
Innovation Solution
The use of calcium oxide as a storage material that undergoes a hydration reaction to calcium hydroxide, which is then converted back into calcium oxide, utilizing microwave radiation and a catalyst to enhance dehydration, combined with ettringite as an additional storage material, to achieve high energy density and efficient heat transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If zeolite storage material is used to achieve high energy density, then energy density is improved, but heat transfer efficiency deteriorates due to high heat transfer resistances
Solution Approach 1:
A metallic foam structure serves as an intermediary between the zeolite storage material and the heat exchanger, facilitating efficient heat transfer while maintaining high energy density. The foam's high surface area and porous structure enable effective thermal coupling without compromising the storage capacity of the zeolite.
2Loss of energy
If zeolite is applied as thick layer on metallic supports to improve heat transfer, then heat transfer efficiency is improved, but cyclic stability deteriorates
Solution Approach 1:
Metallic foam with controlled porosity is used as the support structure, allowing the zeolite to be applied as a thin, stable layer rather than a thick coating. The foam's three-dimensional network provides mechanical stability and thermal conductivity while accommodating the zeolite in a configuration that maintains cyclic stability.
3Loss of energy
If water tank is heavily insulated to reduce energy losses, then energy loss is reduced, but space requirement increases
Solution Approach 1:
A composite insulation system combining vacuum technology with reflective barriers is employed to achieve superior thermal isolation with minimal thickness. The vacuum eliminates conductive and convective heat transfer, while reflective layers provide radiative barrier, together reducing energy losses without significantly increasing the tank volume.
4Quantity of substance
If high desorption temperatures are used to achieve optimal energy density in zeolite, then energy density is improved, but application range deteriorates
Solution Approach 1:
The metallic foam heat exchanger acts as a thermal intermediary that enables efficient heat transfer at lower operating temperatures. This allows the zeolite to operate in a temperature range that expands application versatility while maintaining high energy density through optimized heat exchange surface area.
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 approach enables flexible, high-capacity thermal energy storage with minimal losses, achieving discharge temperatures significantly higher than charging temperatures and reducing manufacturing costs, while eliminating the need for secondary heat exchangers and minimizing installation effort.
Implementation Method 1
calcium oxide is used as storage material, which releases heat in a lime cycle and is hydrated to calcium hydroxide
Implementation Method 2
converted back into calcium oxide by absorbing heat
Implementation Method 3
utilizing microwave radiation and a catalyst to enhance dehydration
Implementation Method 4
is insulated by a vacuum
Data Source
Figure 1~2
Figure 3
AI summary
A method for storing and releasing thermal energy using a storage device involves using calcium oxide as the storage material. This material releases heat in a cold cycle and is hydrated to calcium hydroxide, which is then converted back into calcium oxide while absorbing heat. This heat storage device can absorb direct and diffuse solar radiation to flexibly store thermal energy.