Carnot continues CO2 development

OEM is marketing transcritical systems to industrial facilities while developing a CO2 condensing unit for retail and industrial applications.

John Miranda, Emergent Cold Technologies

Carnot Refrigeration, the Trois-Rivières, Quebec-based pioneer of transcritical CO2 refrigeration in North America, is continuing to find new customers and develop new technology for its CO2 systems, including supermarkets, cold-storage and food processing warehouses, ice rinks and data centers.

Helping in that endeavor is Emergent Cold Technologies, Geneva, Ill., which a year ago formed an agreement with Carnot to distribute its products and systems to customers in the U.S.

One of the newest sectors for Carnot’s transcritical systems is industrial. The OEM has installed several transcritical COsystems in industrial plants in Canada, and in June completed its second such installation in the U.S. at a Henningsen Cold Storage warehouse in Grandview, Wash.  

“More companies like Henningsen are going down the CO2 path,” said John Miranda, Emergent's founder and chief marketer, who was previously president of Guntner US, in an interview at the Global Cold Chain Expo in June.

Miranda sees transcritical CO2 as a good fit for spiral IQF (individual quick freezing) systems that require -40°F temperature. “We are currently building transcritical COrefrigeration systems for two food freezing projects in the New England region,” he said. “For minus 40°F, they think CO2 is more effective than ammonia, and they’re right.”

Miranda believes that CO2 can compete with ammonia at medium temperatures as well. He created an energy model (based on seasonalized weather data) comparing CO2and ammonia, and while ammonia prevails at the design point, CO2’s advantage increases as the ambient temperature drops.

"With CO2's ability to float head pressure to 50°F, and the increased coil surface of adiabatic gas coolers, CO2c an be more efficient at lower ambient temperatures than ammonia," he said.  “If you have a significant number of operating hours below 60°F, COwill have comparable or better energy, depending on the number of hours."

He acknowledged that areas like Florida, Eastern Texas and Louisiana are “tough areas” for CO2 and better for ammonia. But if the cost of "water energy"(water usage, sewer, water treatment and water-pump energy) associated with evaporative condenser systems is included, “then we’re less cost, even in those areas.”

The exceptional heat reclaim offered by CO2 for hot water and dehumidification in lieu of natural gas also helps CO2’s cost-savings argument.

For minus 40°F, they think COis more effective than ammonia, and they’re right.”
– John Miranda, Emergent Cold Technologies


One of the distinguishing features of the Henningsen system is that it’s a modular, rooftop unit, easily scalable to accommodate future expansion of the plant. This configuration also allows the end user to avoid building an equipment room in the plant, noted Miranda.

Carnot is now developing a smaller rooftop CO2 system – a condensing unit with two compressors that can be linked to one or two evaporators in the cooling area. “It could be an add-on unit for industrial, addressing spot requirements,” Miranda said.

The condensing unit will also serve as a heat pump, reversing the refrigeration cycle in order to defrost the evaporator coils. Like Carnot’s data center systems, the unit will be able to offer compression-free “free cooling” when ambient temperatures are low enough (about 40°F or less).

Another selling point for Carnot is the remote-monitoring service from its Quebec headquarters, which is tracking about 70 refrigeration systems for a monthly fee. “They can address about 90% of the activity remotely,” said Miranda. “For routine maintenance like changing oil filters, they coordinate with local maintenance people.”

Carnot collects data from its remote monitoring operation in order “to learn from the operating data and make the systems better,” said Miranda.

With the technological advances that transcritical CO2 has made in recent years – such as the addition of adiabatic condensers, ejectors, efficient heat reclaim and sensible defrost – "we see COas a viable solution for all industrial refrigeration applications," Miranda said.

By Michael Garry

Oct 03, 2018, 17:53




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