It is really not a matter of going green. It has little to do with doing the right thing. It is pretty much about a bottom-line business decision.

That was the context of the second Atmosphere America Natural Refrigerants Conference that took place this summer in Washington, D.C. The approach was a very unsentimental business case for wider use in North America, especially the U.S., of such refrigerants as ammonia (R-717), CO2 (R-744), and the HC propane (R-290).

“There is a sense of momentum when it comes to naturals,” said Marc Chasserot, managing director, Shecco, who moderated the two-day event. “There is something happening here.” And while much of the conference featured case histories of ongoing refrigeration projects involving natural refrigerants, Chasserot acknowledged that a major impact will only come when many more end users and service contractors see that there is a cost-effectiveness and energy-efficiency distinctive compared with f-gas refrigerants most commonly in use.

That was the focus of a state-of-the-industry panel session that examined where naturals were being used and their track record.

CO2: A Ready Refrigerant

“R-744 Refrigerant Ready for Today’s Market” was the presentation of Marc-Andre Lesmerises, CEO of Carnot Refrigeration with a particular focus on CO2’s use in a transcritical system.

“The demonstration of the benefits of the transcritical CO2 refrigeration system is now well accepted by several supermarket chains,” he said. “Several other markets (are) following (such as) distribution centers, ice rinks, mobile air conditioning, and (stationary) air conditioning.”

In terms of supermarkets, he noted a rapid growth of such systems in Canada. Regarding ice rinks, he said a mechanical equipment change-out would allow the use of CO2 at existing sites. “The retrofit is easy if you have the right team. Ice rink projects are actually at parity with HFC technology when you include the heat reclaim capability in the initial cost.”

He did point out that there is no one-fits-all approach, and skilled engineers and labor are the keys for the success.

CO2: A North American Perspective

Taking a look at “Advances in CO2 Supermarket Refrigeration in North America” was Scott Martin, director of sustainable technologies, Hillphoenix.

He looked at systems that still incorporate HFCs, but are designed to reduce the amount of HFC needed. These included secondary CO2 and CO2 cascade, both of which allow more than a 50 percent reduction in HFCs. He also noted a more recent CO2 booster system that is HFC-free.

In a CO2 secondary or pumped system, liquid CO2 is circulated to provide refrigeration and “a simple system design has on-off solenoid operation for temperature control.” For CO2 cascade, there is a direct expansion CO2 system on the lower cascade and an HFC-based DX system on the upper cascade. This, he said, “eliminates all low-temp HFC charge.” He said that since 2006, 100 secondary and 30 cascade systems have been installed in North America.

The newer approach — the CO2 booster system — has 800 systems in 12 countries including 20 in North America. It has an adiabatic gas cooler to allow for more subcritical operating hours. There is also parallel compression of CO2 flash gas.

CO2 and Ammonia

Taking a look at using an ammonia and CO2 supermarket system was Mark Tomooka, director of applied technology development, Mayekawa USA. The idea, he said, was to lower the amount of ammonia needed onsite to fewer than 500 pounds, which would reduce the regulatory aspects of larger charges of ammonia. This “proves competitive operation to existing technology,” he said, referencing an application that currently operates on a 250 pound ammonia charge, saying the approach has “established operation and maintenance procedures” that uses “modular type units and compact construction.”

Regarding R-744, he said “Most commercial interest is focused on CO2 applications with ammonia system interest increasing.”

For next-generation systems, he said, “Characterizing system parameters are key. Initial projects should be collaborations based on capturing best system knowledge with a clear understanding of project requirements, proper expectations, and defined goals.”

The Regulatory Aspect

While most attention to natural refrigerants is based on efficiencies and costs, there is still a regulatory landscape, which was discussed by Masood Ali, manager of center of excellence for alternative systems, Heatcraft Worldwide Refrigeration.

He noted, for example, that European f-gas regulations are pointing to an HFC phasedown of 79 percent by 2030 and a ban on new equipment using refrigerants that have a global warming potential (GWP) higher than 150. He said, “Regulations that start in Europe quickly migrate to California and regulations that start in California quickly migrate to the U.S. federal level.”

Meanwhile, he said the supplier base of components for equipment using natural refrigerants is increasing but there is still a “lack of economies of scope and scale. While the gap exists in product range, costs are driving down.

“Natural refrigerants have an energy-efficiency advantage. Natural refrigerants hedge against uncertainty due to (f-gas) refrigerant cost increase/taxes on HFC (in some countries) and increase in energy costs.”

Still to be sorted out, he said, are installation costs (“there is conflicting information, a lack of familiarity, and awareness by the contractors”), and the need for more training for service technicians.

Publication date: 9/16/2013 

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