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issue: November 2003 APPLIANCE European Edition

European Edition: Engineering Refrigerators
The Effect of Blowing Agents on Energy Use and Climate Impact of a Refrigerator


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by Dr. Robert W. Johnson, RWJ Consulting Inc. and Jim Bowman, Honeywell International

The phase-out of CFC-11 as a foam-blowing agent, as called for under the Montreal Protocol, is well underway. The most common replacements with zero ozone depletion potential have been c-pentane and mixtures of c-pentane with other hydrocarbons, along with some HFCs, including HFC-134a and HFC-245fa.

Although HFCs account for only a small fraction of total greenhouse gas emissions, the global warming potential of most HFCs is quite large. This raises legitimate questions regarding the appropriateness of using HFCs as replacement blowing agents for foam. Refrigerators, however, make their largest contribution to global warming in an indirect manner as a result of the energy that they consume. Therefore, manufacturers have made different choices for the replacement, depending on their assessment of the relative merits of the available options. In Europe, hydrocarbons have been chosen because of the importance placed on direct emissions of global warming substances. Conversely, in North America, strict energy standards and factory safety regulations have led to HFCs (mostly HFC-245fa) as the preferred approach.

This study attempts to analyze the relative merits of the two most popular options (a cyclopentane/pentane blend and HFC-245fa) through a limited life cycle analysis (LCA), considering only items related to the choice of blowing agent and its influence on the energy consumption and the total global warming impact, or "life cycle climate performance" (LCCP) of a refrigerator. Emissions and energy consumption at the blowing agent and refrigerator factories are included, but energy consumption associated with parts unrelated to the blowing agent is not considered. While expanding the analysis to include the items omitted in this study would be interesting, the final results would not change because the omitted items would be similar for both products considered.

Product Information and Key Data

The refrigerator considered in the study is a 358-L "combi" type product that has a fresh food section at the top and a freezer section at the bottom, which is popular in Europe. Both sections have a "direct-cool" type refrigeration system. The refrigerant used in the products was R-600a. The pentane blend foam formulation used for the products tested was the same as is used for that model in production. The blowing agent (0.393 kg) was a blend of 70-percent cyclopentane and 30-percent isopentane. The HFC-245fa formulation used for the comparison was the same as is used in a large North American refrigerator factory (0.985 kg of HFC-245fa was used).

The products were similar in all respects except the foam formulation and blowing agent. Energy tests were conducted per the ISO test procedure on three products of each type. Results were averaged for purposes of comparison. The Pentane Model (currently in production) used 455 kWh/year, and the HFC-245fa model used 398 kWh/yr. Analysis of the data indicated more than 90-percent confidence that the mean is within 2 percent of the true population mean for both products.

Values used for other parameters important to the study are shown in Table 1. Carbon intensity values for Europe are EIA estimates for the year 2000[1]. Product lifetime is assumed to be 15 years.

Ê

Table 1. Key Data
Item Value Units Source
Carbon Intensity Ð All Europe 0.41 kg CO2 /kWh EIA Est.[1]
Energy Intensity Highway Transport 3000 BTU / ton-mile EIA[2]
Energy Intensity Waterborne Transport 411 BTU / ton-mile EIA[2]
GWP Ñ HFC-245fa 950 Ê IPCC[3]
GWP Ð c-pentane, n-pentane 3 Ê IPCC[4]
Natural Gas (Energy) to produce HFC-245fa 0.017 MCF / lb Honeywell
Electricity to produce HFC-245fa: 1.83 kWh / lb Honeywell
CO2 Emissions for production of pentane 1.2 kg CO2 / kg APME[5]
Natural Gas (refrigerator factory) 0.041 MCF/product Whirlpool
Electricity (refrigerator factory) 7.16 kWh/product Whirlpool
Assumed product useful life 15 Years Ê


Disposal Practices

The UNEP Task Force on Collection, Recovery, and Storage conducted a study of current disposal practices in North America, Europe, and Japan in 2001 [6]. The report estimates that in 2001, approximately 60 percent of the foam from refrigerators decommissioned in Europe would go to landfills. Presumably, most would be shredded for recovery of the metal, and the foam would be sent to the landfill, with no recovery of the blowing agent. Under these conditions, a recent study at the Danish Technical University (DTU) indicates that about 20 percent of the blowing agent will escape at the time of shredding, and the remainder will escape over time [7]. The UNEP report indicates that disposal practices are expected to change in response to European Union (EU) directives. Therefore, this study considered one case where 60 percent of products go to landfills and another case, where new practices are used and 10 percent go to landfills.

Foam Aging

Energy consumption measurements are usually made on new products. However, because foam degrades, energy consumption may increase over time. This increases global warming emissions due to electricity consumption of the product. The Appliance Research Consortium sponsored a study at Oak Ridge National Laboratories to measure aging effects for several blowing agents [8]. Results of that study and another study involving tests on full products [9] were used to create a model for foam aging to predict energy consumption of products over their useful life. The model, together with the measured initial consumption, was used to estimate energy consumption of the products over a 15-year period.

Results and Discussions


Figure 1. Product Lifetime Energy Consumption

The energy consumption of the refrigerators for a 15-year life was estimated using the data from Table 1 and the aging model discussed above. Results are shown in Figure 1. The 12-percent initial energy consumption advantage for the HFC-245fa products grows to about 15 percent when aging effects over the life of the product are considered. This significant advantage in energy performance should be highly valued in most markets, including the EU, which is dependent on imports for much of its energy supply [10].

The aforementioned data and assumptions were used in LCCP calculations that were made, considering sales into the European market, including Eastern Europe. In all cases analyzed, the dominant factor in the LCCP analysis is the indirect emissions of CO2 due to energy consumption of the product over its useful life. Even in the case where 60 percent of the HFC-245fa products are assumed to be shredded and sent to landfills after decommissioning, more than 80 percent of the global warming effect is due to electricity consumption of the product.


Current practices - 60 percent sent to a landfill. (CLICK for larger image.)

Future practices - 10 percent sent to a landfill). (CLICK for larger image.)

Figure 2A and 2B. Emissions Comparison of current practices to future practices.
Results of the LCCP analysis are summarized in Figure 2, which shows two scenarios. The graph on the left reflects the case where disposal practices are assumed to be unchanged from those in place in 2001. The graph on the right reflects the case where disposal practices are assumed to change in response to EU directives for recycling and recovery so that only about 10 percent of the blowing agent that remains in a product at the end of its useful life escapes to the atmosphere.

The relative insignificance of the miscellaneous items that are considered in the LCA is clearly seen. Emissions associated with energy consumed during the production process and transportation is significantly less than that associated with energy consumption of the product or direct emissions of the blowing agent over the long term. The same is true for blowing agent emissions in the factories.

Although Europe is of particular interest because of the debate regarding the use of HFCs in that market, it is also important to consider the total warming impact of similar products in other regions.


Figure 3. Warming Impact Comparison. CLICK for larger image.
Calculations were made for other countries, using estimates for carbon intensity from EIA data [1] and disposal practice assumptions as follows: 50 percent of decommissioned products in the U.S., Australia, and New Zealand would go to shredders and landfills; 80 percent in Brazil, China, and India would go to shredders and landfills; and 5 percent in Japan would go to shredders and landfills. It is clear from the results that a product foamed with HFC-245fa would have a lower climate impact in all of these regions, except Brazil, which has large hydroelectric resources (see Figure 3).

Conclusions

With current foam formulations, the use of HFC-245fa as a blowing agent, instead of a cyclopentane and n-pentane blend, offers a significant advantage in energy consumption for refrigerator/freezer types considered in this study. The advantage was more than 12 percent for initial energy consumption and when foam aging is considered, the advantage is approximately 15 percent over the life of the product.

The two blowing agents considered in this study are similar in terms of LCCP. In Europe, the pentane product would have about a 3-percent advantage with 2001 disposal practices. But, if disposal practices improve, as called for in EU directives, the HFC-245fa product has nearly a 10-percent advantage. In the other markets considered, the HFC-245fa products would typically have an advantage of between 5 and 10 percent, except in Brazil. By far the dominant item in LCCP is the energy consumption of the product and the associated emissions from the electricity generation system. Emissions due to energy consumption during manufacture and transportation of the blowing agent and refrigerator are negligible in comparison.

Considering the many challenges faced by appliance producers and the strong need to both save energy resources and limit global warming emissions, both HFCs and hydrocarbons should be considered good long-term options for refrigerator insulating foam blowing agents.

References

1. Total Emissions Attributed to Electricity Generation - Source EIA estimates, Kevin Lillis 202-586-1395, Personal Communication.

2. Measuring Energy Efficiency in the United States' Economy: A Beginning, October 1995, Energy Information Administration, Office of Energy Markets and End Use, U.S. Department of Energy, Washington, DC, U.S. 20585.

3. Climate Change 2001: The Scientific Basis, IPCC Report, Working Group.

4. IPCC Second Assessment Report (1995).

5. I. Boustead, Ecoprofiles of Plastics and Related Intermediates, APME, Brussels, 1999.

6. UNEP Report of the Technology and Economic Assessment Panel: Volume 3A Report of the Task Force on Collection, Recovery and Storage, April 2002.

7. Scheutz and Kjeldsen, Determination of the Fraction of Blowing Agent Released from Refrigerator/Freezer Foam after Decommissioning the Product, Environment & Resources DTU, January 2002.

8. Wilkes, Gabbard, and Weaver, Aging of Polyurethane Foam Insulation in Simulated Refrigerator Panels - One-Year Results with Third-Generation Blowing Agents, Earth Technologies Forum, Washington, DC, U.S., 1999.

9. Robert W. Johnson, The Effect of Blowing Agent on Refrigerator/Freezer TEWI, Polyurethanes Conference 2000, Boston, MA, U.S., Oct. 8-11, 2000.

10. Green Paper: Towards a European Strategy for the Security of Energy Supply, presented by the Commission of the European Communities, Brussels, Nov. 29, 2000.

 

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