High pressure, high effect
Carbon dioxide (R744) has an ODP of zero, a GWP of one and is virtually unlimited. It is also very cheap: many industrial processes produce CO2 as a by-product. It is suitable for compact air-conditioning systems, deep-freeze warehouses and, for example, supermarket refrigeration. Another field of application is cascade systems for sub-zero temperatures, where ammonia systems form the first stage and CO2 systems the second.
Over the past few decades, carbon dioxide has established itself as a refrigerant mainly in stationary applications, including domestic hot-water heating, but it can also be used for mobile air conditioning, cooling or heating in vehicles or on ships. Due to the high pressures involved, CO2 refrigeration systems are relatively compact and can also be used for smaller output ranges.
The high "power density" also proves to be an advantage for replacement investment. Old systems with synthetic refrigerants can be replaced by compact CO2 systems without space problems.
Think about your design
Due to the high pressures required in CO2 refrigeration systems (or heat pumps), a special design of the compressors and the entire refrigeration system is required. In addition to pressure-resistant components, this can mean additional work for sensors and control technology.
The narcotic or suffocating effect of CO2 plays a subordinate role when used as a refrigerant. The filling quantities are typically so small that no lethal concentration can form in the room (even in a technical center). For example, the filling quantity in Germany is limited to 0.07 kg/m³ in accordance with DIN EN 378.