Packed-Bed Thermal Storage with Gaseous Heat Carrier
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Solution Overview
Problem
Current thermal electricity storage systems face inefficiencies due to high operating pressures, complex operations, and high material and maintenance costs, particularly in systems using liquid salt and refrigerants, which limit current-to-current efficiency and increase the complexity of the systems.
Innovation Solution
The implementation of a thermal power storage device utilizing a fixed-bed storage system with gaseous heat carriers operating at ambient pressure, eliminating the need for multiple heat exchangers and optimizing temperature interaction between the hot and cold sides, thereby reducing material requirements and operational complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If liquid salt or liquid salt mixture is used as storage medium, then thermal energy storage is achieved, but the temperature range is limited between 230°C and 570°C, reducing storage capacity
Solution Approach 1:
The patent changes the physical state parameter of the storage medium from liquid to solid granular form, and replaces liquid salt with solid materials like rocks, ceramics, or metal oxides that can withstand higher temperatures without melting or decomposing, thereby expanding the operational temperature range and storage capacity
Solution Approach 2:
The patent uses composite material structures where solid granular storage materials are combined with gas-phase heat transfer media (air or inert gases), creating a system that leverages the high heat capacity of solids and the excellent heat transfer properties of gases to achieve both high storage capacity and efficient thermal exchange
2Loss of energy
If multiple gas-liquid heat exchangers are installed, then efficient heat transfer is achieved, but system complexity and material requirements increase significantly
Solution Approach 1:
The patent extracts the liquid phase from the heat transfer medium and removes it entirely, replacing it with gas-phase heat transfer media that eliminate the need for complex gas-liquid heat exchangers, thereby simplifying the system structure while maintaining efficient heat transfer
Solution Approach 2:
The patent merges the storage medium and heat transfer medium into a single phase (gas phase), where the same gas that transfers heat also serves as the working fluid for the thermodynamic cycle, eliminating the need for separate heat exchanger systems and reducing overall device complexity
3Loss of energy
If high operating pressures are used, then power-to-power efficiency is improved, but material requirements and maintenance costs increase
Solution Approach 1:
The patent employs pneumatic principles by using gas-phase heat transfer media that operate at lower pressures compared to liquid systems, reducing the mechanical strength requirements for system components while maintaining efficient heat transfer through optimized gas flow dynamics and pressure differentials
4Temperature
If liquid storage medium is used in cold storage system, then cooling is achieved, but the temperature range is limited by freezing point and evaporation
Solution Approach 1:
The patent changes the phase parameter of the cold storage medium from liquid to solid granular material, which can be cooled to very low temperatures without freezing or evaporating, thereby expanding the achievable temperature range and providing greater flexibility in cold storage applications
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 achieves higher current-to-current efficiency and simplifies operations by reducing pressure requirements, material needs, and maintenance costs, while maintaining high temperature spreads, thus enhancing the overall efficiency and reliability of thermal energy storage.
Implementation Method 1
The heat transfer medium flows through the storage material and transfers heat to or from the storage material
Implementation Method 2
The gaseous heat transfer medium is conveyed through the high-temperature heat storage unit and the cold storage unit
Implementation Method 3
The compressor and the turbine are coupled to an electric machine... adiabatic compression and adiabatic expansion
Implementation Method 4
After expansion in the turbine, the gaseous working fluid has a very low temperature
Implementation Method 5
A first heat exchanger is arranged between an outlet of the compressor and an inlet of the turbine... A second heat exchanger is arranged between an outlet of the turbine and an inlet of the compressor
Data Source
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AI summary
The invention relates to a system and a method for storing electrical energy which are based on a closed thermodynamic cycle. They make it possible to store electrical energy in a very efficient, cost-effective, and safe manner. No environmentally hazardous or expensive materials are required. The system comprises a compressor, a turbine, and two packed-bed storage units which are operated at different temperature levels. In order to load the packed-bed storage units, the cycle is operated as a counterclockwise heat pump process. In this process, the heat generated at the outlet of the compressor is released at a high temperature level into a first packed-bed storage unit and stored therein. The "cold" produced during the subsequent expansion of the gaseous working medium in a turbine is stored in a second packed-bed storage unit. This requires mechanical energy which is provided by an electrical machine. In order to discharge the energy storage system, the cycle is operated in reverse (i.e. as a clockwise cycle). Before entering the compressor, the working medium is cooled with the cold stored in the second packed-bed storage unit and, after compression, absorbs the heat from the high-temperature packed-bed storage system. The hot working medium at high pressure is expanded by means of the turbine and thus energy is generated.