Thermal Energy Storage System Using Ice Slurry Phase Change Material
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Solution Overview
Problem
Existing energy storage systems face inefficiencies due to thermocline degradation and the need for large quantities of materials with decreasing specific heat capacity at lower temperatures, leading to increased costs and reduced system performance.
Innovation Solution
A thermal energy storage system utilizing a thermodynamic circuit with a gaseous working fluid, a motor/generator system, and a latent TES system with ice slurry as a phase change material, which maintains a steep temperature gradient and efficient energy transfer by using ice slurry in a two-phase form to set a lower temperature limit, reducing the need for large quantities of materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a thermal energy storage system uses gravel as TES medium in both hot and cold containers, then the system can store and release thermal energy, but the specific heat capacity decreases with temperature causing the cold container to need more gravel than the hot container, increasing costs
Solution Approach 1:
The patent introduces a phase change material (PCM) with a specific melting point to maintain a minimum temperature in the cold TES container. This parameter change (using PCM phase transition at a defined temperature) prevents the temperature from dropping too low, thereby maintaining the specific heat capacity of the gravel and reducing the amount of gravel needed in the cold container while preserving energy storage efficiency
Solution Approach 2:
The phase change material acts as an intermediary between the cold TES container and the environment. It absorbs or releases latent heat to maintain the minimum temperature boundary, preventing excessive cooling that would reduce the specific heat capacity of the gravel and require larger quantities of storage material
2Duration of action of stationary object
If the thermocline zone width increases during repeated charging/discharging cycles, then the temperature gradient flattens (thermocline degradation), but this decreases the overall efficiency of the system
Solution Approach 1:
The patent applies preliminary anti-action by using a phase change material to prevent thermocline degradation before it significantly impacts system performance. The PCM maintains a sharp temperature gradient at the cold container boundary through phase transition, counteracting the natural tendency of the thermocline to broaden during repeated cycling, thereby preserving system efficiency over extended operation
3Reliability
If encapsulated particulate PCM is used to prevent melting and solidifying, then the gas can traverse the PCM, but if granules are too small the costs increase and volume relative to heat transfer becomes too small, while if granules are too large thermal transfer is not adequate
Solution Approach 1:
The patent employs a fluidized bed approach where gas flow fluidizes the PCM granules, enhancing heat transfer through increased contact and mixing. This pneumatic mechanism allows the system to use larger, more cost-effective granules while maintaining adequate thermal transfer efficiency, as the fluidization process compensates for the reduced surface area-to-volume ratio of larger particles
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 configuration enhances energy storage efficiency by maintaining a steep thermocline, reducing material requirements, and optimizing costs, while allowing for flexible design and retrofitting of existing systems.
Implementation Method 1
A thermal energy storage system utilizes a thermodynamic circuit with a gaseous working fluid, a motor/generator system, and a latent TES system with ice slurry as a phase change material
Implementation Method 2
a latent TES system with ice slurry as a phase change material, which maintains a steep temperature gradient and efficient energy transfer by using ice slurry in a two-phase form
Implementation Method 3
When there is surplus electricity, a compressor is driven by an electrical engine, increasing the temperature of gas by compression
Implementation Method 4
When there is a demand for electricity, the compressed hot gas is released from the first TES container through an expander which drives an electrical generator for recovering the electrical energy
Implementation Method 5
thermal energy is exchanged through the thermally conducting wall between the gaseous working fluid in the gas flow circuit and the latent working fluid
Implementation Method 6
In order to prevent the paraffin from melting and solidifying into a solid mass, which would prevent the gas from traversing the PCM, the paraffin is encapsulated and provided as a granular material
Data Source
AI summary
Thermal energy storage system with phase change material and method of its operation An energy storage system (100) comprises a hot thermal energy storage medium (5′) and a cold thermal energy storage medium (4′), which are interconnected in a thermo-dynamic gas flow circuit. An energy converter with a motor/generator system (1A, 1B) is functionally connected to a compressor/expander system (2) for converting between electrical energy and thermal energy of the gaseous working fluid in the thermodynamic fluid circuit. A latent thermal energy storage working fluid is thermally connected to the gas flow circuit through heat exchanger (8) for providing a limit for the temperature in the cold TES medium (4′).