Assessment of the environmental impact of domestic refrigerators...

Refrigerators are one of the largest energy consumers in residential buildings. According to the IIR, about 2 billion domestic refrigerators and freezers are in service worldwide and consume almost 4% of global electricity (1).

The authors of a recent article (2) in the International Journal of Refrigeration (IJR) present a new method for assessing the environmental effects of domestic refrigerators by using the life cycle climate performance (LCCP).

LCCP comprises direct emissions, which are related to the environmental effects of refrigerant leaks, and indirect emissions which comprise four components: emissions from energy consumption, manufacturing of materials, manufacturing of refrigerant, and disposal of units.

As asserted by Yunho Hwang – one of the authors of this article – in an IIR Informatory Note (3), LCCP is a holistic metric for quantifying the environmental impacts of HVAC&R units over their lifetime and should be an essential tool in the future selection, development and implementation of these units.

Based on a literature review, the authors of the IJR article found that there were very few relevant LCCP assessment studies on recent domestic refrigerators. Moreover, most of the studies focused on refrigerants. However, the LCCP assessment carried out by these authors shows that refrigerator performance and equipment manufacturing were the dominant factors in total CO₂ emissions.

Therefore, energy and material-related factors, such as refrigerator cycle options, materials used, insulation, and power sources, were primarily investigated by these researchers. A simulation model was developed with experimental data and used for the LCCP evaluation of various vapour compression cycle options.

A single evaporator cycle was selected as the baseline. Dual evaporator cycles as well as ejector and two-stage cycles were considered.

The main conclusions of the study are the following:

For household refrigerators using R600a as a working fluid, direct emissions are almost negligible. Energy consumption and equipment manufacturing emissions constitute 90% and 9% of the total emissions respectively.
Dual evaporator cycles, such as the serial, bypass, and parallel-circuit cycles indicate 2.0%, 3.8%, and 7.9% respectively lower CO₂ emissions than the baseline cycle, thanks to improved energy consumption.
Total emissions from the ejector and two-stage cycle decrease by 11.1% and 14.7%, respectively. Adding more components to these advanced vapour compression cycles results in a slight increase in the equipment manufacturing emissions, but total emissions decrease and system efficiency has improved.
The use of an aluminum scroll condenser instead of steel in household refrigerators reduces total emissions by 2% to 2.5%.
When vacuum insulation panels are applied on the sides, back, top, bottom, and doors of the refrigerator, total emissions are reduced by 7.7%.
In a power supply scenario in 2030 with 20% renewable energy, total emissions are expected to be reduced by 13% in the baseline scenario, 19.9% in the parallel-circuit cycle, and 26% in the two-stage cycle. If 100% renewable energy is used, total emissions will be reduced by 82.4%.

In the future, if the supply of renewable energy is increased, refrigerator materials and refrigerant will be more critical factors to the LCCP of household refrigerators. Future research would focus on the use of low-GWP refrigerants and low-emingitt materials.

Sources:

(1) https://iifiir.org/en/fridoc/the-role-of-refrigeration-in-the-global-economy-2019-142028

(2) Choi S. et al, Environmental effect evaluation of refrigerator cycle with life cycle climate performance : Download in FRIDOC (free for IIR members after logging in).

(3) https://iifiir.org/en/fridoc/harmonization-of-life-cycle-climate-performance-methodology-139940

Assessment of the environmental impact of domestic refrigerators using LCCP