The use of natural refrigerants is nothing new in the refrigeration industry. In the early days of refrigeration, carbon dioxide (CO2) and ammonia were often the refrigerants of choice, but were later replaced by modern synthetic chemical options. Today, global phase-downs (and even bans) of hydroflourocarbon (HFC) refrigerants are part of an increasing effort to lower the global warming potential (GWP) in refrigeration and/or air conditioning systems. As a result, natural refrigerants, which often have little to no GWP, have come full circle and are being specified in commercial refrigeration systems more frequently. In my recent Making Sense webinar, I explored the viability of natural refrigerants and their implication on refrigeration system design.
The most common natural refrigerants returning to the commercial refrigeration landscape are propane (R-290), isobutene (R-600a), ammonia (R-717) and, most commonly, CO2 (R-744). While each refrigerant poses its own unique handing and operating parameters — from increased pressures and capacity to flammability and toxicity concerns — the ozone depletion potential (ODP) and GWP of natural refrigerants are virtually zero.
CO2 has many properties that make it an extremely viable refrigerant today:
- ODP = 0; GWP = 1
- Non-toxic, non-flammable, odorless
- Lower viscosity, meaning smaller line sizes vs. HFC piping systems
- Less sensitive to pressure drops
- Smaller refrigerant charge
- Less expensive than HFCs
- Better system performance vs. HFC systems under most conditions.
Like all natural refrigerants, the key to successfully using CO2 in modern refrigeration systems is to specify equipment that is designed for CO2 utilization. Globally, CO2-based refrigeration systems are gaining wider adoption than in the United States, and are typically based on one of the following system types: secondary, cascade and transcritical booster.
As we look for ways to reduce our collective carbon footprint in the future, there’s no question that CO2 (and other natural refrigerants) will be used more frequently in commercial refrigeration systems. It will become increasingly important for commercial retailers, system designers and contractors to understand the safety, performance, economic and environmental implications of the refrigeration systems that use this emerging class of natural refrigerants.
To listen to an archived recording of my webinar and learn more about natural refrigerants, please visit our Making Sense website, where we make sense of the issues that matter most in commercial refrigeration today.
Director — CO2 Business Development
Emerson Climate Technologies