Water-Based Refrigerants

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East Hartford, Connecticut
Project Term:
09/02/2010 - 03/16/2012

Critical Need:

New and more efficient cooling methods are needed to reduce building energy consumption and environmental impact. Residential and commercial buildings currently account for 72% of the nation’s electricity use and 40% of its CO2 emissions each year, 5% of which comes directly from air conditioning. The refrigerants used in air conditioners are potent greenhouse gases (GHGs) that may contribute to global climate change. Because the majority of cooling systems run on electricity and most U.S. electricity comes from coal-fired power plants that produce CO2, there is a pressing need to support improvements that increase the efficiency of these technologies and enable substantial reductions in GHG emissions.

Project Innovation + Advantages:

United Technologies Research Center (UTRC) is developing an efficient air conditioning compressor that will use water as the refrigerant. Most conventional air conditioning systems use hydrofluorocarbons to cool the air, which are highly potent GHGs. Because water is natural and non-toxic, it is an attractive refrigerant. However, low vapor density of water requires higher compression ratios, typically resulting in large and inefficient multi-stage compression. UTRC’s design utilizes a novel type of supersonic compression that enables high-compression ratios in a single stage, thus enabling more compact and cost-effective technology than existing designs. UTRC’s water-based air conditioner system could reduce the use of synthetic refrigerants while also increasing energy efficiency.

Potential Impact:

If successful, UTRC’s air conditioning compressor would enable cost-effective and energy efficient use of water as a refrigerant—decreasing the use of conventional, polluting refrigerants.


Increased energy efficiency would decrease U.S. energy demand and reduce reliance on fossil fuels--strengthening U.S. energy security.


Refrigerants with polluting emissions could account for up to 10%-20% of global warming by year 2050. UTRC's technology could help to eliminate the use of these refrigerants.


Widespread adoption of this technology could increase energy efficiency of air conditioners and refrigerators--providing consumers with cost savings on energy bills.


ARPA-E Program Director:
Dr. Ravi Prasher
Project Contact:
John Misselwitz
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