The Wet-TSA DAC captures CO2 from the air using a rotor. When applied to air conditioning and ventilation, utilizing the exhaust air allows for effective CO2 capture, as the exhaust already contains approximately three times the CO2 concentration of the outside air due to human respiration. Furthermore, the air from which CO2 has been removed has a CO2 concentration similar to the outside air. Therefore, in areas with exceptionally high outside temperatures or poor air quality, removing and purifying CO2 from exhaust or outside air before reuse improves comfort and energy efficiency.

Outside CO2 concentrations are particularly high in large metropolitan areas. Data shows that the average CO2 concentrations in major Indian cities are:

* Delhi: 900-1200 ppm

* Mumbai: 800-1000 ppm

* Bangalore: 750-900 ppm

This document introduces an energy-saving CO2 liquefaction and dry ice production system that combines a Wet-TSA (Wet-TSA) air CO2 capture and concentration system, a system for compressing, cooling, and liquefying the captured high-concentration CO2 gas, and a system for producing dry ice from the liquefied CO2 gas.

Conventionally, liquefied CO2 was recovered and utilized as a by-product from petroleum refining facilities, but after use, the recovered CO2 is ultimately released into the atmosphere, increasing the atmospheric CO2 concentration. Furthermore, in the future, the depletion of conventional liquefied CO2 sources is expected due to the reduction of plastics and fossil fuels. In addition, conventional methods involve filling heavy, high-pressure containers with liquefied CO2 gas from petroleum refining facilities and transporting it to demand areas, resulting in increased CO2 emissions.

In the future, the demand for dry ice is expected to increase. It is necessary for the widespread use of frozen foods and the associated transportation. Converting refrigerated transport vehicles to electric vehicles (EVs) would also increase the weight of the batteries used for the refrigeration units. Replacing batteries and refrigeration equipment with green dry ice increases the load capacity of frozen goods, while reducing the load on the return journey, enabling the transport of more refrigerated foods. Furthermore, dry ice will be necessary for small-lot deliveries of frozen and refrigerated goods by drones, which are expected to become more widespread in the future. Since green dry ice uses CO2 recovered from air conditioning exhaust in urban areas, it will not worsen CO2 concentrations in urban areas.

The dry ice production system, which uses air conditioning air as a CO2 source, can be installed even on remote islands. If locally produced and consumed dry ice is available, it could revolutionize the distribution of local products, particularly those from remote islands where sales have previously been difficult.

Since the dry ice production system utilizes green liquefied CO2, it is also possible to supply liquefied CO2 for purposes other than dry ice. If technology is developed to convert CO2 into fuel or valuable materials, it will be possible to introduce this system into factories, allowing them to procure CO2 internally. This would also be a positive factor in carbon credit certification.