Closed-Loop CO2 Energy Storage for Fast Grid Frequency Response
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Solution Overview
Problem
Existing energy storage systems struggle with flexibility in adjusting energy generation and storage to match non-programmable renewable sources and grid demands, lacking the ability to adjust output power proportionally and rapidly respond to frequency changes.
Innovation Solution
A hybrid system combining cyclic thermodynamic transformations (CTT) with a closed thermodynamic cycle (TC) using a working fluid like CO2, allowing for flexible energy management and rapid response, including fast ramping and grid frequency adjustment, using a closed circuit with tanks and heat exchangers to store and generate energy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional energy storage system is used, then energy can be stored and generated, but the system lacks flexibility to adjust energy generation and storage to match non-programmable renewable sources and grid demands
Solution Approach 1:
The system employs dynamic adjustment mechanisms where the thermodynamic cycle can rapidly transition between different operating modes (charging, discharging, heat pump mode) based on real-time grid demands and renewable energy availability. The controller dynamically adjusts the operation of compressors, turbines, and heat exchangers to provide flexible energy management that adapts to varying conditions.
Solution Approach 2:
The system changes operational parameters such as pressure, temperature, and flow rates of the working fluid to optimize performance under different conditions. By adjusting these parameters, the system can efficiently match energy generation with grid demands and handle non-programmable renewable energy sources effectively.
2Speed
If a conventional energy storage system is used, then energy can be stored, but the system cannot rapidly respond to frequency changes and grid demands
Solution Approach 1:
The system pre-charges energy storage tanks and pre-positions working fluid in different states during periods of low demand or high renewable energy availability. This preliminary action enables the system to rapidly respond to sudden frequency changes and grid demands without lengthy ramp-up times, as the energy and working fluid are already prepared and positioned.
Solution Approach 2:
The thermodynamic cycle operates in periodic cycles of compression, expansion, heat addition, and heat rejection. This periodic operation allows the system to rapidly cycle between energy storage and generation modes, providing quick response to frequency changes while maintaining stable power output through the rhythmic alternation of these thermodynamic processes.
3Productivity
If a hybrid system with closed thermodynamic cycle is used, then rapid response and flexible energy management are achieved, but the system complexity increases
Solution Approach 1:
The system merges multiple functions into integrated components: the working fluid serves both as the heat transfer medium and the energy storage carrier; the heat exchangers perform both heating and cooling functions; and the compressor-turbine assembly operates in both compression and expansion modes. This merging reduces the number of separate components needed while maintaining rapid response capability.
Solution Approach 2:
The thermodynamic cycle components are designed with multi-functionality: the working fluid can be in different phases (liquid, vapor, supercritical) for different operations; the heat exchangers can operate in reverse for heating or cooling; the turbine-compressor assembly can function as a prime mover or heat pump. This universality reduces overall system complexity while achieving rapid response and flexible energy management.
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
Enables flexible energy storage and generation, allowing for rapid adjustments to grid demands, including ultra-rapid frequency adjustments and reduced environmental impact, suitable for various applications including offshore use.
Implementation Method 1
The plant is configured to perform a closed cyclic thermodynamic transformation, first in one direction in a charge configuration and then in an opposite direction in a discharge configuration
Implementation Method 2
thermodynamic transformation from a point X to a point Y, where X coincides with Y; the TC unlike the CTT (Cyclic thermodynamic transformation) mentioned below does not have mass accumulations (significant for energy purposes) within the cycle
Implementation Method 3
using a closed circuit with tanks and heat exchangers to store and generate energy
Implementation Method 4
a compressor (3) configured to compress the working fluid
Implementation Method 5
a turbine (2) configured to expand the working fluid and rotate a shaft
Implementation Method 6
a generator (4b) configured to generate electrical energy from the rotation of the shaft
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A plant (1) for storing energy comprises a casing (5) for the storage of a working fluid other than atmospheric air, in gaseous phase and in equilibrium of pressure with the atmosphere; a tank (9) for the storage of said working fluid in liquid or supercritical phase with a temperature close to the critical temperature; wherein said critical temperature is close to the ambient temperature. The plant (1) is configured to perform a closed cyclic thermodynamic transformation (CTT), first in one direction in a charge configuration and then in an opposite direction in a discharge configuration, between said casing (5) and said tank (9); wherein in the charge configuration the plant (1) stores heat and pressure and in the discharge configuration the plant generates energy. The plant (1) is also configured to define a closed circuit and to perform a closed thermodynamic cycle (TC) in the closed circuit with at least a part of the working fluid, optionally while the plant (1) is in the charge configuration or in the discharge configuration.