Advanced compressed air energy storage (advanced adiabatic compressed air energy storage, supercritical compressed air energy storage, etc.) recovers and stores the heat of compression generated during the compression process and releases it during the energy release process, which solves the need for traditional compressed air energy storage. The problem of burning fossil energy has the advantages of high energy storage efficiency, large energy storage capacity, and no carbon dioxide emissions. It is currently one of the most promising large-scale power energy storage technologies. Among them, heat storage is one of the key factors affecting the performance of advanced compressed air energy storage systems.
Recently, the Research Institute of Engineering Thermophysics of the Chinese Academy of Sciences has proposed a new type of indirect atmospheric heat storage technology based on sensible heat storage (Figure 1(a)). The system adopts an atmospheric pressure packed bed (Figure 1(b)) instead In the high pressure heat storage device, atmospheric pressure air driven by the pump is used as the intermediate heat transfer medium to obtain the heat of the compressed air through the heat exchanger, and is transferred to the rock particles accumulated in the packed bed through direct contact heat exchange for sensible heat storage. Obviously, atmospheric pressure heat storage technology instead of high-pressure heat storage, high-efficiency direct contact heat exchange, and inexpensive rock particles as sensible heat storage media make this type of indirect atmospheric heat storage system low in cost, high in efficiency, and highly reliable. With such advantages, the proposal of this technology is a key technological innovation for the Institute in the direction of large-scale and industrialized development of advanced compressed air energy storage.
Recently, in order to gain a deep understanding of the operating mechanism and characteristics of this type of indirect atmospheric heat storage system, researchers rely on the Zhongguancun compressed air energy storage basic test platform to conduct experimental studies on the operating performance and influencing factors of key packed bed heat storage devices. And monitoring the temperature distribution and temperature change process inside the packed bed during the heat storage/release test through multiple thermocouples (Fig. 1(b)) arranged at the central axial and two radial positions inside the packed bed. Fig. 2) The dynamic heat transfer characteristics of the stored bed heat storage device during heat storage and heat release are obtained under different storage/release air flow directions and regenerative temperatures, and the packed bed is analyzed from the perspective of energy and exergy. The overall performance of the heat storage cycle.
The results show that the thermal conductivity, axial convection, and air flow pore structure inside the packed bed all affect the dynamic heat transfer characteristics of the packed/released process packed bed, especially the axial natural convection and air flow pore structure. The pressure and velocity distribution of air in the packed bed can be influenced, thereby affecting the heat transfer performance of the air in the packed bed; the main factor affecting the temperature dynamic characteristics of the packed bed is the naturalness of the packed bed in the axial direction of the packed bed. Convection effect: When the hot air is used to flow from top to bottom in the regenerative process, the solution corresponding to the normal-temperature air flowing from bottom to top in the heat release process can effectively inhibit the natural convection in the axial direction of the packed bed; the thermal efficiency of the heat storage cycle of the packed bed The enthalpy efficiency can be increased by 9% and 5% when compared with the opposite direction of storage/release hot air flow (Figure 3); increasing the storage temperature also helps to improve the performance of the packed bed heat storage cycle.
The above work was supported by the National Natural Science Foundation of China and the National High-Tech Research and Development Program ("863"). The research results have been published in the International Journal Energy.
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