Global shipping is about to get its first ever “natural” refrigerant, in the form of a carbon dioxide-based system developed by Carrier Transicold. The company is a division of refrigeration expert Carrier Corp., which has been pushing for energy conservation and lower greenhouse gas emissions. Compared to conventional shipping container refrigerants with a global warming potential of up to 3260, the new system has a potential of only one. That’s quite an accomplishment — but what in the heck is global warming potential?
Global Warming Potential and Refrigerants
Global Warming Potential (GWP) is a relative scale that refers to the contribution that a particular mass of greenhouse gas is estimated to make to global warming, calculated over a given period of time. Carbon dioxide is the benchmark, so it gets a GWP of one. Hydrofluorocarbons are conventional refrigerants that happen to be “high GWP” gases, with a far more potent effect on global warming than carbon dioxide. According to the U.S. EPA, high GWP gases only account for about 2 percent of total greenhouse gas emissions in the U.S., but their extreme potency makes them a priority for reduction.
Carbon Dioxide Refrigeration
Carrier’s new system replaces hydrofluorocarbons with the refrigerant form of carbon dioxide, known by its industry designation R-744. Carrier is just one of a growing list of companies that are replacing hydrofluorocarbons with carbon dioxide, and it is believed to be the first to apply the new technology to refrigerated shipping containers. The new system also includes energy efficiency improvements such as a gas cooler/condenser coil designed to maximize heat transfer, and a “smart” controller that adjusts for cooling loads and temperature control. So far, Carrier has tested the system with global shipping giant Hapag-Lloyd, and plans to expand the test runs in 2011.
A Sea Change for Refrigeration
Ironically, hydrofluorocarbons were introduced in order to stem the ozone depletion caused by an earlier generation of refrigerants. Hopefully, third-generation alternatives like carbon dioxide will avoid going down the road of unintended consequences, and just stick to reducing greenhouse gas pollution. Among the other promising new technologies are magnet-based refrigerating systems, hydrocarbon refrigerants such as isobutane and propane, and an “elastic” metal alloy that could replace liquid coolants.
Image: Shipping containers by Jim Bahn on flickr.com.
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