1. What is R744?
R744 is the chemical reference for carbon dioxide (CO2) used as refrigerant. It is a naturally occurring substance that can be applied as a working fluid in different heating and cooling applications, due to its excellent heat transfer properties and its high volumetric cooling capacity.
2. Are R744 and CO2 the same thing?
Yes. According to industry standards, each refrigerant receives a nomenclature starting with the letter R (for Refrigerant) and a number, which follows an order depending on the "family" the substance belongs to. R744 / R-744 is hence the standard nomenclature for CO2 used as a refrigerant: "7" indicates the natural fluid while "44" refers to the fluid's weight. The term R744 is applied when referred to the refrigerant itself, and CO2, and/ or CO2 Technology is used when referring to an application or use.
3. What are the main characteristics of R744?
- Environmentally friendly, with a Global Warming Potential = 1
A more detailed explanation of each of these features follows below.
4. Why is R744 environmentally friendly?
Applying R744 in vapour compression applications reduces significantly the amount of greenhouse gas (GHG) emissions released into the atmosphere, which is at the origin of climate change. Besides, R744 systems, in many applications, have the potential to be more efficient than current systems in most climate conditions, and therefore indirect emissions of GHG resulting from energy consumption are also reduced.
For example: Given that, on average, Mobile Air Conditioning (MAC) is activated about 60% of the time a car is in use over its lifetime, the choice of the low global warming refrigerant R744 is a key element for improving the environmental performance of a car. For other applications, such as heat pump water heating or commercial refrigeration, the potential for emission reduction by using R744 is also significant.
For more details see the section Environment under Mobile Air Conditioning.
5. Does R744 have any impact on the Ozone layer?
No, R744 does not contribute in any way to the depletion of the ozone layer.
6. Is R744 flammable?
No, R744 is not flammable and presents no risks in case of interaction with other substances or chemical blends. CO2 is applied in many fire extinguishers.
7. Is R744 toxic?
R744 is not toxic at moderate concentrations. Given the small system charge used for heating and cooling applications, R744 thus presents minimal health risks. In the US, for example, this is reflected by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) with the common standard ASHRAE 34, which lists R744 as Safety Class A1 - a low toxic, non-flammable refrigerant.
When inhaled at high concentrations, however, carbon dioxide can lead to a risk of asphyxiation, since it displaces oxygen. In such case it would produce a sour taste in the mouth and a stinging sensation in the nose and throat combined with dizziness.
8. Where does the CO2 used in refrigeration come from?
The refrigerant used in heat pumps is an industrial waste product. Some industrial companies have developed systems to extract CO2 from their plants to process it and sell it as a refrigerant.
9. For which applications is R744 suitable?
R744 can be applied in most heating and cooling systems such as Mobile Air Conditioning (MAC) in vehicles and buses, vending machines, coolers, commercial cabinets for supermarkets, containers and climate control systems for residences. CO2 Technology (R744) has also shown to be extremely efficient in heating water. This explains the success of the Japanese "EcoCute" Heat Pump Water Heaters, which can also be combined efficiently with floor heating. As an illustration, in Japan more than 300,000 CO2 based EcoCute units of water heaters were sold in 2006.
10. What are the main benefits of R744 in commercial refrigeration?
R744-based commercial refrigeration and freezing features:
- Reduced emissions of greenhouse gases
- Space savings for piping arrangements (self-contained system)
- Reduced costs of piping arrangements and insulation
- Energy efficiency
11. What is the state of development in this field?
There are several ongoing projects with R744 at advanced degrees of completion. Some refrigeration cabinets working with R744 are already part of supermarkets in Europe (i.e. Scandinavia, UK, Switzerland, Belgium), and large-scale production of components could follow soon if the market conditions evolve favourably.
12. What other applications is R744 used in most frequently?