A study by an International Energy Agency (IEA)-sponsored program found that domestic unitary air conditioners (AC) using propane (R290) refrigerant have a lower Life Cycle Climate Performance (LCCP) than comparable units running with R410A, R32, R466B and R452B in 11 cities around the world.

The simulation study was conducted as part of IEA’s Technology Collaboration Programme on Heat Pumping Technologies (HPT TCP) – specifically, the program’s Annex 54 project, which studies heat pump systems with low-GWP refrigerants.

The program was described in the “2021 Progress Annual Report, HPT Annex 54 Tasks 1, 2 and 3,” which was published in January 2022. The report was compiled and edited by Tao Cao and Yunho Hwang of the Center for Environmental Energy Engineering, Department of Mechanical Engineering, at the University of Maryland in College Park, Maryland (U.S.).

LCCP measures the climate impact of HVAC&R systems as the sum of direct, indirect and embodied CO2e emissions generated over the lifetime of the system. Direct emissions include the release of refrigerants into the atmosphere, including annual leakage and losses during service and disposal of the unit. Indirect emissions are associated with the electricity powering the equipment, while embodiedemissions stem from, in this study, the refrigerant’s manufacturing process.

The study found that R410A units had the largest LCCP while R290 unitary AC had the lowest. However, the specific LCCPs depended on the particular location the appliance was in.

In College Park, Maryland, R290’s LCCP was estimated at about 63,000kg (138,891lbs) of CO2e, lower than R452B (70,000kg/152,324lbs), R32 (69,000kg/152,119lbs) and R410A (78,000kg/171,961lbs). The R466A was a special case because emissions data from its manufacturing process were not available; however, using an assumption of that value in the study, R466A’s LCCP was estimated to be 1.6% higher than R452B’s, or 71,120kg (156,793lbs) in the College Park example.

The refrigerant manufacturing process, which takes up to 3% of LCCP emissions, is a minor factor in LCCP compared with emissions from annual energy consumption and annual leakage, the report added. R290’s manufacturing emissions were the smallest.

In countries where the carbon intensity of electricity generation – or the grid emission factor (GEF) – is low, the annual refrigerant leakage rate from appliances has the biggest impact on the LCCP. For example, in low-GEF Switzerland and Sweden, the LCCP value can be decreased by 60% by replacing an R410A unit with an R290 unit because of the vast differences in the GWP of the refrigerants (2,100 and less than one, respectively).

On the other hand, where the GEF is high, meaning more carbon-intensive power sources are deployed to generate electricity, the equipment’s energy performance had the greatest influence on the LCCP value.

“The system efficiency has a 10 to 100 times greater impact on the HVAC system’s emissions than refrigerant leakage only in higher GEF countries,” the report said.

Country-based program

The HPT TCP, founded in 1978, is a global nonprofit organization whose goal is to accelerate the implementation of heat pumps and related heat pumping technologies, including air-conditioning and refrigeration. Only national governments may participate in the program. Member countries in Annex 54 include Austria, France, Germany, Italy, Japan, South Korea, Sweden and the U.S. as the operating agents.

In the LCCP simulation study, the unitary ACs were “stress tested” under multiple parameters (location, environment, climate and refrigerant) in the 11 cities: Miami; Phoenix; College Park (two locations); Atlanta; Tokyo; London; Basel; Kallax, Sweden; Shanghai and Beijing.

The 115kg (254lbs) units used fixed-speed compressors with a 10.55kW (3TR) capacity (12.3kW/3.5TR for cities in hot climate regions like Miami and Phoenix).

The study was based on usage in office buildings with higher occupant density and equipment loads than residential buildings.

In the global marketplace, R290-based residential ACs are being manufactured by a handful of companies in China and India, such as Godrej and Midea.

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