Green cooling with CO2
Man-made refrigeration gases threaten the Earth’s climate. The use of natural compounds like CO2 is an effective counter-measure.
By Petter Nekså, Chief Research Scientist, and Anne Karin T. Hemmingsen, Senior Research Scientist, SINTEF
Earlier this month, almost 200 of the world’s nations agreed to reduce the use of the potent HFC greenhouse gases, man-made compounds used to extract heat from air cooling installations, frozen goods counters, refrigerators and heat pumps. In the past, HFC gases were used instead of other man-made gases because these damaged the atmosphere’s ozone layer. One option for preventing this kind of problem again is to use natural compounds as refrigeration gases.
Could result in cuts of 0.5 degrees C
First the background: The agreement on cutting HFCs was reached during a summit in Rwanda. According to Vidar Helgesen, the Norwegian Minister of Climate and Environment, the agreement is probably the single biggest action that will give the greatest global reduction in greenhouse gas emissions. It may actually reduce global warming by up to half a degree Celsius by the end of the century, compared with a future based on “business as usual”.
Molecule for molecule, the greenhouse effect of HFC compounds is vastly greater than that of CO2. This autumn, the climate minister has taken part in a media campaign, focusing on two Norwegian fishing trawlers whose cooling plants use no HFC gases and are a good example of how the HFC problem can be solved. Instead, these cooling gases have been replaced by one of nature’s own chemical compounds, CO2.
Better than HFC compounds by far
Yes, CO2is also a greenhouse gas, but the amount of CO2 that leaks from cooling installations is so small as to cause insignificant damage, compared with emissions from power stations and industrial processes. At SINTEF and NTNU we have been working on this type of “back to nature” concept for almost thirty years. Much of the CO2-based cooling and heat pump technology in today’s world has its roots in this research.
Among other things, this applies to the CO2-based trawler installations highlighted by Helgesen, CO2-based freezers and refrigerated counters that are now spreading from supermarkets in Europe to other parts of the world, and CO2-based heat pumps for use in domestic water supplies. Several million of these kinds of units have been installed in Japan alone.
Air conditioning in your car
CO2-based interior cooling of cars is on its way – an innovation that may be introduced in top-of-the-range models from Daimler Chrysler in 2017, according to the manufacturer.
Our development of this technology is the result of a precautionary principle: In practice one can never guarantee that man-made refrigeration and cooling gases will not lead to environmental problems once they have been brought into use. If nature’s own compounds are used instead, the danger is eliminated.
Natural compounds moHowever, the “carbon footprint” of a cooling installation is not only determined by coolant leakage. What really determines the impact of an installation is its energy consumption. In this respect, a transition from HFC to CO2 in freezer and refrigerated counters in our climatic zone is good news. At northern latitudes, CO2-based installations are in fact at least as energy-efficient as HFC installations – usually more so.
Hence, the use of natural compounds in cooling installations and heat pumps is an important theme of “HighEFF”, Norway’s new industrial energy efficiency research team that was established by the Research Council of Norway.
CO2 is not the only substance from nature’s “laboratory” which is of interest in this connection. In HighEFF we are also looking at compounds like ammonia, hydrocarbons – and water.
Tropical regions can benefit, too
It’s likely that societies in tropical regions, whose cooling requirements are naturally considerable, will be able to benefit from Norwegian research in this field. In a recently started Norwegian-Indian collaboration, we have a major project under way which will demonstrate whether CO2-based freezing and refrigeration concepts can achieve satisfactory energy consumption even in hot regions of the sub-continent.
All in all we believe that many of the world’s cooling needs can be satisfied using natural substances. In that case we need no longer fear that solving one environmental problem will lead to new environmental problems.
This article was first published in Dagens Næringsliv on Friday, 21 October 2016 and is reprinted here with the permission of DN.