Hybrid CAES with Thermal Storage for Compression Losses
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Solution Overview
Problem
Conventional compressed air energy storage (CAES) systems are inefficient and costly due to high compression pressures, energy losses from compressive heating, and cooling on expansion, making them non-competitive for energy storage solutions.
Innovation Solution
A low-cost hybrid energy storage system (LCHESS) that combines compressed air energy storage with high-temperature thermal energy storage (HTES) using a Brayton cycle, where energy is stored as thermal energy in HTES units and converted back to compressed air for efficient energy deployment, reducing the need for high-pressure air storage and minimizing energy losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional CAES systems store energy at high pressure, then energy storage capacity is improved, but compression costs and energy losses increase
Solution Approach 1:
The system segments the energy storage function into two separate components: compressed air storage and thermal energy storage. The compression process stores energy as both pressurized air and thermal energy in separate tanks, allowing independent optimization of each storage medium and reducing the energy losses associated with single high-pressure storage.
Solution Approach 2:
A heat exchanger serves as an intermediary component that transfers thermal energy from the compression process to the thermal energy storage tank. This mediator captures the waste heat that would otherwise be lost, converting it into usable stored energy and significantly reducing the overall energy losses of the system.
2Quantity of substance
If conventional CAES systems compress air to high pressure, then energy storage density is improved, but compression costs increase
Solution Approach 1:
The system divides the expensive high-pressure compression function from the storage function. Air is compressed to moderate pressure and the energy is stored as thermal energy in a separate tank, eliminating the need for expensive ultra-high-pressure compression equipment while maintaining high energy storage density through the thermal component.
Solution Approach 2:
The system changes the storage parameter from purely mechanical (pressurized air) to thermal (heated air in thermal storage). This parameter change allows energy to be stored at lower pressures, dramatically reducing compression costs while maintaining or improving overall energy storage density through the high-capacity thermal storage medium.
3Productivity
If conventional CAES systems use high-pressure storage, then energy deployment efficiency is improved, but cooling losses on expansion increase
Solution Approach 1:
The thermal energy storage tank acts as an intermediary that captures and stores the thermal energy generated during compression. During expansion, this stored thermal energy is released to preheat the expanding air, serving as a mediator that recovers what would otherwise be lost cooling energy and significantly reduces expansion cooling losses.
Solution Approach 2:
The system implements a feedback loop where thermal energy from compression is stored and then fed back during expansion to preheat the air. This feedback mechanism ensures that the thermal energy generated during the compression phase is reused during expansion, minimizing energy losses and improving overall deployment efficiency.
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 LCHESS system achieves efficient and cost-effective energy storage and deployment by utilizing thermal energy storage to augment compressed air systems, reducing reliance on high-pressure air storage and minimizing inefficiencies, thus providing a competitive alternative for energy storage solutions.
Implementation Method 1
The HTES units receive energy from a source and store the energy as thermal energy, and transfer the energy to fluid flowing through the flow paths
Implementation Method 2
The first compressor generates a stream of compressed air to an outlet. The first flow junction connected to the outlet directs a first portion of the compressed air stream to a hot fluid heat exchanger
Implementation Method 3
A low-cost hybrid energy storage system (LCHESS) that combines compressed air energy storage with high-temperature thermal energy storage (HTES) using a Brayton cycle
Implementation Method 4
A first flow junction connected to the outlet directs a first portion of the compressed air stream to a hot fluid heat exchanger
Data Source
AI summary
An energy storage-combined cooling, heating and power (S-CCHP) system for a building receives energy from a source, for example an intermittent source, and stores the energy in first and second high temperature energy storage (HTES) units. A Brayton cycle using the first HTES unit produces hot and pressurized air that is further heated in the second HTES unit. The heated air drives a turbine to generate electricity for the building. A portion of the compressed air from the Brayton cycle is diverted to a hot water heat exchanger, then to another turbine to produce electricity to the building. The hot water heat exchanger heats water for the building and the other turbine exhaust cools water for building cooling. Heat exchangers are strategically placed to optimize the thermal efficiency of the cycle. In some embodiments the heat transfer fluid is humidified to improve thermal energy transfer properties.