Scientists fight climate change with an unlikely ally: CO2

India’s air conditioning and cold storage sectors may have recorded over 7% growth in just the last five years but experts find the trend “uncool”. Reason? The high demand for cooling devices has led to an increase in synthetic hydrofluorocarbon refrigerant use, which is, in turn, heating up the atmosphere.

Instead, scientists from four institutes and a think tank in India are now working with their counterparts in Norway in a unique partnership to back the adoption of a natural refrigerant, and the candidate is an unlikely one: carbon dioxide (CO2). Unlikely, because this is a compound that is often seen as the culprit behind climate change.

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But scientists say nothing can be further from the truth. To corroborate their claims, they are now developing a range of testbed cooling units from air-conditioners to cold storage containers operating on CO2.

The Norwegian government-funded project involves scientists from the Indian Institute of Science (IISc), IIT-Madras, BITS, Central Institute of Fisheries Technology and the Council for Energy, Environment and Water (CEEW), working with the Norwegian University of Science and Technology.

“The idea that CO2 is the contributor to climate change is a misconception,” said Pramod Kumar, Associate Professor in the Department of Mechanical Engineering at the IISc.

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“Its global warming potential (GPW) is just 1. In contrast, synthetic refrigerants such as R134A (which is commonly used) have a global warming potential of 1,430. So, the margins are huge,” said Kumar, who is among those scientists involved in the Indo-Norwegian collaboration which has been dubbed INDEE+.

But why carbon dioxide? “As per international commitments, we have to start phasing out refrigerants with 150 global warming potential or more. Among all the gases we can use as a replacement, carbon dioxide is the best choice because of its extremely low global warming potential,” said Assistant Professor Satyanarayanan Seshadri of the Department of Applied Mechanics, IIT-Madras, who is also involved in the collaborative project.

While a laboratory under Professor Prakash M Maiya at IIT-Madras has already developed a CO2-based air conditioning unit, the Norwegian involvement comes in handy in adapting the technology to the Indian climate.

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Scientists noted two challenges in using CO2: one, it is generated at high pressure, creating engineering problems. Second, because of India’s high general ambient temperature of 31C, there is some difficulty condensing it into liquid form.

Having this gas condense into liquid is vitally important to achieving cooling. “We are now using this pilot programme to make viable commercial testbeds. This is where we are working with the Norwegian University of Science and Technology to get these technological issues sorted out,” Dr Seshadri added.

The programme will see the deployment of four pre-commercial CO2-using cooling units at five different locations: a supermarket in Bengaluru, an industrial building, a fishery (for cold storage), and an Akshay Patra community kitchen where hot and cold water can be delivered.

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