For a long time, traditional thermal power generation has been the main form and backbone of electricity production in China. Driven by the goals of peaking carbon emissions and achieving carbon neutrality, the scale and proportion of renewable energy applications have significantly increased and will continue to grow at a faster rate. However, most renewable energy sources have the characteristics of intermittency, randomness, and volatility, such as wind energy, solar energy, etc. Therefore, it is necessary to rely on large-scale and multi form energy storage systems to provide support for the large-scale application of renewable energy.

There are various types of existing energy storage technologies, each with its own advantages and disadvantages in terms of functionality and performance. Compressed air energy storage (CAES) and pumped hydro energy storage (PHES) are energy storage technologies suitable for long-term storage and large-scale energy conversion. However, the engineering implementation of these two technologies has higher requirements for geographical environment and cannot form a good coupling with distributed energy systems. In addition, low energy storage density and large-scale energy storage facilities are major drawbacks of such systems.

CO₂ has a high critical temperature, is easy to liquefy, and replacing air with it as the storage working fluid in compressed gas energy storage systems can increase energy storage density to a certain extent. Furthermore, using compressed CO₂ energy storage systems can promote the reuse of captured carbon, making it a good method for carbon sequestration. Moreover, the engineering implementation of compressed CO₂ energy storage systems has low requirements for geographical environment and is suitable for integration with distributed energy systems.

However, traditional compressed CO₂ energy storage systems still have shortcomings. In any type of CO₂ energy storage system, it is necessary to add a thermal storage unit to increase energy storage efficiency. Therefore, the loss caused by heat transfer during thermal storage and release cannot be avoided, and methods to reduce this loss should be sought. Additionally, since low-pressure side CO₂ cannot be directly released into the atmosphere like compressed air, a large number of storage tanks are needed, resulting in large volumes of low-pressure side CO₂ storage tanks, low energy storage density, and high system construction costs. Although some scholars have proposed underground storage solutions (hard rock caves, salt caverns, abandoned coal mines, saline aquifers, underwater, etc.) for CO₂ storage, these solutions rely on special geographical environments and do not fundamentally solve the problem.

This thesis proposes new solutions to address some of the shortcomings of previous compressed CO₂ energy storage systems. A new heat transfer mode is proposed to improve the heat transfer efficiency of compressed CO₂ energy storage systems by utilizing phase change latent heat to address the issue of severe heat loss in the heat exchange components of energy storage systems; The results show that within a certain temperature range, using mixed phase change working fluids can effectively reduce the entropy production rate of heat exchange systems, improve heat transfer performance, and reduce the waste of low-grade heat energy. A stamping based packaging scheme for phase change thermal storage materials is proposed to address the issues of multiple production processes and high costs in conventional phase change thermal storage schemes; The results show that the proposed phase change thermal storage capsule packaging scheme has good sealing and compressive performance, and its manufacturing method is extremely simple with low production costs, making it very suitable for large-scale application in engineering. For the problem of low energy storage density and high construction cost caused by the large volume of low-pressure side CO₂ storage tanks, this thesis proposes a new high-density and low-cost low-pressure side gas storage scheme based on chemical absorption method. Through theoretical analysis methods such as system model construction, theoretical derivation, program writing, and simulation calculation, the physical characteristics of the new compressed CO₂ energy storage system are studied; The results show that the proposed new compressed CO₂ energy storage system based on chemical absorption method has a very high energy storage density, which is 6-10 times higher than general similar systems. Within the calculation range, the maximum energy storage density can reach 19.97 kWh/m3, and the maximum round-trip efficiency is 0.663.