The need to reduce hydrofluorocarbon (HFC) refrigerant charge and emissions from supermarket refrigeration systems has becoming increasingly clear over the past ten years. By the end of the last decade, the next generation of Second Nature systems began entering the market and the key to these systems success was their use of carbon dioxide (CO2) as a working fluid.

A number of reasons have factored into the search for alternatives to HFCs. Foremost among these were environmental concerns that lead initially to international agreements (i.e., Montreal and Kyoto Protocols) and then to regulations such as Section 608 of the Clean Air Act that banned the venting of CFC (e.g., R-11, R-12, etc.), and HCFC (e.g., R-22, R-401A, etc.) refrigerants. More recently proposed rule changes by governments at home and aboard (i.e., European Union F-gases regulations) have sought to even further reduce emissions of all synthetic refrigerants including HFCs (e.g., R-404A, R-410A, R-507, etc.). The impact of these regulatory pressures on system operators has added economic justifications to the move away from their use as not just the penalties for leaks has increased, but the taxation on their use (in Europe) has directly added to their cost.

As of 2010, no new equipment using R-22 could any longer be produced for sale in the US. By 2015, R-22 omestic production will be by limited by 90% to 1989 levels all but curtailing the use of any equipment except with existing or reclaimed stocks of R-22. Finally, in 2020, what little remaining production of R-22 there is will cease. In the years ahead, these trends are only expected to intensify with a more aggressive phasing-out of HCFCs and phasing-down of HFCs likely.

Clearly, the overarching need for sustainable approaches to refrigeration has strengthened as these forces upon the market have intensified. Consequently, refrigerant manufacturers have responded with a number of alternative approaches intended to address the environmental challenges supermarkets face. But despite various advances made by new synthetic alternatives such as R-1234yf that have no ozone depletion potential and very low global warming potential, costs for these options are expected to be high. For many, therefore, a more promising path points toward natural alternatives.

Favorable Characteristics of CO2
CO2 (R-744) has several key characteristics that make it an ideal choice as a refrigerant. To start with it is colorless, odorless, and naturally available in the atmosphere where as of mid-2011, it was measured at 392 ppm (0.039% by volume). Approximately 50% heavier than air, it is produced through natural processes including the carbon cycle in which it occurs as a product of respiration in animals and from fermentation of organic compounds. The most common means by which it is produced is through the liquefaction of air.

As a refrigerant, its high volumetric cooling capacity means that small pipe dimensions and small compressor swept volumes can be used. Because of its low liquid and gas viscosity, only small pressure losses occur in piping systems. Other R-744 benefits include high heat transfer coefficients and compatibility with most materials since it is noncorrosive and nontoxic. For companies that are focused on sustainability, responsible corporate citizenship, and smaller carbon footprints, CO2 is an attractive choice.

The rational for choosing CO2 include these qualities:
• Colorless, odorless, and naturally occurring in the atmosphere
•Approximately 50% heavier than air
•Non-flammable and actually suppresses combustion
•High volumetric cooling capacity (small pipe dimensions and small compressor swept volume)
•Low viscosity in liquid and gas pipes (small pressure losses)
•High heat transfer coefficients
•Compatible with most materials: noncorrosive, nontoxic
• Companies are increasing sustainability, responsible corporate citizenship, and smaller carbon footprints.

Compared to other refrigerants , CO2 is extremely affordable. At 2011 prices around $1 per pound, it is truly an inexpensive refrigerant. Coleman grade (99.99% pure) used for refrigeration must be dry, but it can readily be obtained from welding companies and other industrial gas suppliers. As of late 2010, a fifty-pound cylinder of Coleman grade CO2 from one supplier was priced at around $61.

CO2 Systems
Manufacturers have pursued a number of different approaches to using CO2 in commercial refrigeration systems. In addition to low-temperature secondary systems like those already in use in the U.S., other approaches include those that use subcritical cascade and transcritical refrigeration. Subcritical systems have been around for more than ten years in various configurations. More recently, European transcritical systems have grown from just a few in 2006, to more than a thousand since then. Transcritical systems, particularly booster systems, continue to gain in popularity.

In North America over the past decade, supermarkets have begun adopting some of these approaches to CO2. So far, CO2 secondary fluid systems have been used for low-temperature applications. Following on the success of these systems, subcritical cascade (DX) systems have seen increasing use in low-temperature applications and some retailers have now begun to look even further at transcritical booster systems. Early in 2012, for instance, Canadian retailer Overwaitea Food Group became the first user on the continent of a new generation of transcritical booster systems in one of their Vancouver, British Columbia stores.

The overwhelming success of CO2 as a refrigerant and the different types of systems in which it is used has convinced more and more companies that it is a tremendously effective approach to sustainable and efficient refrigeration.

Bill Katz is a technical writer for the Hill PHOENIX Learning Center. He can be reached at William.katz@hillphoenix.com

ASHRAE/NIST Conference to Focus on Alternative Refrigerants
Alternative low global warming potential refrigerants will be in the spotlight at the American Society of Heating, Refrigeration, and Air Conditioning Engineers/National Institutes of Standards & Technology (ASHRAE/NIST) Conference, “Moving Toward Sustainability,” Oct.29-30, 2012, at the National Institute of Standards and Technology, located in Gaithersburg, MD.

Papers will be presented on refrigerant alternatives and technologies, environmental effects of refrigerants, new refrigerant performance considerations, and natural refrigerants.

“For each application, some refrigerants are better than others, but I don’t think there’s one given refrigerant to fit all needs,” says Tom Watson, 2012-2013 ASHRAE president, and chief engineer, Daikin-McQuay. “There never has been and I don’t suspect there ever will be. For food processing, however, ammonia is the clear leader,” Watson says.

“The idea of the conference is to get people together who are dealing with different types of refrigerants, such as halocarbons, HFOs, CO2., and other types, to start talking together on what makes sense for each application.”

Attendees must register in advance, because there will be no onsite registration due to security requirements at the government facility. Registration closes on Oct. 18. Find more information here

Late Breaking News
Bristol, England-based A-Gas International, one of the world’s largest independent suppliers of refrigerants, associated environmental services, and speciality gases and chemicals, has completed the acquisition of Houston, TX-based Coolgas Inc., a leading independent supplier and distributor of refrigerants to the US. market. The terms of the transaction were not disclosed.

The transaction represents the fifth strategic acquisition by A-Gas in 2012, and forms part of its growth-through-acquisition strategy, which is being executed in the UK and internationally. Founded in 1994 by Jesse Combs, Coolgas has grown to become one of the leading independent distributors of refrigerants in the US. The Coolgas “refrigerants made simple” philosophy reflects its focus on customer service that has enabled it to grow to become a national participant. Coolgas has recently commissioned a new refrigerant storage and packaging facility in Houston, and has distribution centers in California, Utah, Arizona, Indiana, Michigan, Maryland, and Georgia, ensuring that Coolgas is close to its customers in any location.

A-Gas acquired refrigerant reclamation and halocarbon management specialists RemTec International, Bowling Green, OH, in July 2012.

“Jesse Combs and his management team have built a great business in the U.S. refrigerant sector, and we’re delighted to add it to our rapidly expanding presence in this important market,” says John Rutley, executive chairman and founder of A-Gas International. “The fit with our recently acquired business — RemTec — is perfect, and allows us to offer a full range of products and services to our customers in the world’s largest refrigerant market.”

“I feel honored that A-Gas saw Coolgas as a strategic fit and entry point into the U.S. refrigerants’ distribution business,” says Jesse Combs, CEO, Coolgas. “Our team of professionals have a customer service mindset that I believe sets Coolgas apart from the rest of the industry. I have the upmost confidence that the A-Gas team will support and grow upon our “refrigerants made simple” philosophy for many years to come.”