Transcritical depressurization liquefaction method and device for carbon dioxide energy storage system

The invention relates to a transcritical depressurization liquefaction method and device for a carbon dioxide energy storage system, and belongs to the technical field of compressed gas energy storage. The method comprises the following steps: cooling supercritical carbon dioxide with fixed temperature and fixed pressure intensity, introducing the cooled supercritical carbon dioxide into a throttle valve, and carrying out pressure reduction and self-condensation to obtain liquid carbon dioxide. The throttling valve is arranged at the outlet of the after-stage cooler to replace a condenser so that carbon dioxide can be converted into liquid to be stored in the liquid storage tank, and compared with a matched refrigerator and the condenser for cooling of a heat pump unit adopted by a conventional gas energy storage system, the throttling valve is simple in structure and convenient to operate. A large amount of electric quantity and matched auxiliary equipment for providing cooling capacity required by a convent