US could follow Europe with CO2

USA: The US Department of Energy’s largest r&d laboratory is predicting that American supermarkets could follow Europe by switching to CO2 refrigeration.

The influential Oak Ridge National Laboratory (ORNL) is currently carrying out a number of trials of new refrigerants including CO2 in supermarket applications.

“Each supermarket has a lot of refrigerant in its system—two to four thousand pounds—and about 20% of that leaks out every year. That’s a lot of greenhouse gas into the atmosphere,” said Brian Fricke, who works in ORNL’s Buildings Technologies Research and Integration Centre.

In his lab, Fricke is looking particularly at the problems of low system efficiencies when using CO2 refrigeration in warmer climates. “In warmer climates, CO2 uses more energy, but it doesn’t have anywhere near the environmental impact of leaking refrigerant,” Fricke said. CO2 cascade systems are an obvious answer and the ORNL is looking at these in tandem with R404A.

“CO2 is only going to get more and more popular as time goes by,” Fricke said.

R448A tests

In addition to investigating CO2’s refrigeration qualities, Fricke has also partnered with Honeywell to study N40, Honeywell’s HFC/HFO blend replacement for R404A that, unlike CO2, could be used in an R404A system.

Now carrying the ASHRAE designation R448A, the new Honeywell refrigerant comprises R32 (26%), R125 (26%), R1234yf (20%), R134a (21%) and 1234ze(E) (7%). It is non-flammable, non-toxic and has a GWP of 1,300.

The ORNL considers that for supermarkets looking to be more green but don’t have the resources to install a whole new CO2 system, R448A can be an attractive alternative.

Besides having a lower GWP, R448A is more efficient than R404A. Following tests where Fricke compared R404A and N40 under various temperatures in the same refrigerant system, Fricke found that N40 increased the efficiency of the system by around 10%.

“It would be nice to have a refrigerant that could replace R404A that would perform the same or better and also have a lower GWP. That’s the intent of N40, to be a replacement of R404A,” Fricke said.

Life-cycle calculation software

With the University of Maryland, Fricke has helped design a LCCP software tool which calculates the CO2 equivalent emissions over the entire operating lifetime of a refrigeration system.

The software takes into account the CO2 emissions related to all aspects of refrigeration including manufacture, transport, assembly, maintenance, electricity usage, refrigerant leakage, teardown and recycling.

“LCCP even takes into account the emissions associated with making a part within the refrigeration system,” Fricke said. “By considering these factors, buyers can consider environmental factors more easily. The ultimate goal would be to use LCCP as a global tool to study regional differences in refrigeration. The United States could be compared with Japan, or Europe with India, he said.

The work is supported by DOE’s Office of Energy Efficiency and Renewable Energy, Building Technologies Office. ORNL has cooperative research and development agreements (CRADAs) with Honeywell and with refrigeration systems manufacturer Hillphoenix.

Reputation

Oak Ridge National Laboratory is DOE’s largest multi programme science and energy laboratory, with scientific and technical capabilities spanning the continuum from basic to applied research. These resources enable the lab to tackle an exceptionally wide range of R&D assignments, from fundamental nuclear physics to applied R&D on advanced energy systems. In addition, ORNL has a well-deserved reputation for combining insights from fundamental science with an in-depth technical understanding of applied systems to deliver practical solutions to real-world problems.