Pumped Heat Storage Integration with Coal-Fired Power Units
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Solution Overview
Problem
Existing energy storage systems struggle with efficient and fast conversion of electrical energy into thermal energy for storage and back to electrical energy, particularly in the context of grid stability and resilience, especially with high penetration of renewable energy sources like solar.
Innovation Solution
A Pumped Heat Electric Storage (PHES) system integrates a working fluid loop with heat exchangers and turbines, utilizing thermal storage media to convert electrical energy into thermal energy during charge mode and generate electricity during generation mode, with components like molten salt steam generators and recuperative heat exchangers to enhance efficiency and flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional energy storage systems are used, then energy storage capacity is provided, but conversion efficiency between electrical and thermal energy is low
Solution Approach 1:
The system utilizes phase transitions of the working fluid (between liquid and vapor states) in the heat exchangers to enable efficient heat transfer. During charge mode, the working fluid absorbs heat from the thermal storage medium during condensation, and during discharge mode, it absorbs heat from the thermal storage medium during evaporation, achieving high roundtrip efficiency through these phase change processes
Solution Approach 2:
The system changes the physical parameters of the working fluid (temperature, pressure) to optimize heat transfer efficiency. By controlling the temperature and pressure parameters of the working fluid as it cycles through the heat exchangers, the system achieves efficient energy conversion between electrical and thermal forms
2Speed
If energy storage systems are designed for fast cycling, then response time is reduced, but system complexity increases
Solution Approach 1:
The heat exchangers are designed to perform multiple functions: during charge mode they transfer heat from the thermal storage medium to the working fluid, and during discharge mode they transfer heat from the working fluid to the thermal storage medium. This multi-functionality enables fast cycling without requiring separate systems for charging and discharging, thereby reducing overall system complexity
Solution Approach 2:
The system employs dynamic control of the working fluid flow and heat exchanger operations to enable rapid mode switching between charge and discharge. The ability to quickly adjust the operational state of the heat exchangers and working fluid circulation allows the system to respond rapidly to grid demands while maintaining manageable complexity through coordinated control
3Quantity of substance
If thermal storage media are used for energy storage, then energy density is improved, but heat transfer efficiency decreases
Solution Approach 1:
The working fluid acts as an intermediary between the thermal storage medium and the heat exchangers. It circulates through the heat exchangers, absorbing and releasing heat to the thermal storage medium, thereby enabling efficient heat transfer while maintaining high thermal energy storage capacity in the thermal storage medium
Solution Approach 2:
The working fluid undergoes phase transitions (condensation and evaporation) in the heat exchangers, which provide highly efficient heat transfer mechanisms. These phase changes allow rapid and efficient heat exchange with the thermal storage medium, overcoming the potential heat transfer efficiency losses associated with using thermal storage media
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
The PHES system provides high roundtrip efficiency, fast cycling, and rapid mode switching, enhancing grid stability and resilience, enabling spinning reserve capabilities without fossil fuel consumption, and supporting rapid energy shifts.
Implementation Method 1
a heat engine or heat pump, a heat exchanger may be employed to transfer heat between a thermal storage material and a working fluid
Implementation Method 2
One or more motor/generators may be used to obtain work from the thermal energy in the system, preferably by generating electricity from mechanical energy received from the turbine
Implementation Method 3
a first compressor system and a first turbine system; a working fluid loop comprising a charge-mode working fluid loop arranged to circulate a working fluid through, in sequence, the charge compressor system
Data Source
AI summary
The present disclosure provides pumped heat energy storage systems that can be integrated with a Coal Fired Energy Generation Unit (CF-EGU) to repurpose CF-EGUs as thermal energy storage systems. A pumped heat energy storage system of the present disclosure can store thermal energy by operating as a heat pump with heat discharge occurring as a result of heat engine operation of the pumped heat energy storage system and/or a steam cycle of the CF-EGUs to provide heating thereto. For example, thermal energy can be exchanged via working fluids flowing between the pumped heat energy storage systems and the CF-EGUs to drive turbines that provide power to generators while repurposing equipment from the CF-EGUs to create energy.