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Household refrigerator/freezers are the most popular major appliance in the world. Because they are located in the kitchen, refrigerators are the most visible major appliance. As a result, many global environmental issues related to refrigerants and energy efficiency are illustrated through examples using household refrigerators.

Putting the global warming and ozone depletion issues into scientific perspective as they relate to refrigerators, however, produces a different relationship than the public may perceive between household appliances and these issues of international concern. The amount of CFC's used by household refrigerators was less than 2% of all CFC's used worldwide before the 1996 phaseout took place. After this phaseout of CFC's in non-article 5 (developed) countries, 75% of all CFC uses were eliminated with not-in-kind technologies. Less than 2% of all global warming gases covered under the Kyoto Protocol are fluorocarbons that replaced CFC's.

The energy consumed by household refrigerators is less than 2% of all energy consumed in the US. In spite of the relatively small impact these household products have on the global environment, appliance manufacturers worldwide are committed to further reducing this impact, both in terms of the ozone depletion of the refrigerants and foams incorporated into designs and the energy consumed to maintain a safe food supply.

The decision to replace CFC's in all products worldwide was made under the Montreal Protocol and in the United States under the Clean Air Act. In all developed countries, household refrigerators were redesigned to perform without CFC's by the end of 1996. In the US, as in many other countries in the developed world, this redesign was undertaken by assessing the replacements for CFC's in terms of product performance, ozone depletion, global warming, toxicity, flammability, economics, and energy efficiency. These undertakings resulted in several different solutions globally.

Fluorocarbons play two roles in home refrigerators --- refrigerant and foam insulation blowing agent. Table 4-1 summarizes the progression that has occurred in the choice of the typical refrigerant and blowing agent, as the phase out of ODS's continues.

Table 4-1: Refrigerant and Foam Blowing Agent Alternatives and Not-in-Kind Technology Alternatives for Home Refrigerators

The US appliance industry was guided in its effort to replace CFC's by the US Environmental Protection Agency's (EPA) Clean Air Act regulations. The Significant New Alternatives Program (SNAP) approves chemicals and technologies that can be used to replace ozone depleting chemicals. The SNAP regulations were influenced by US Department of Energy (DOE) regulations relating to the impact of the energy efficiency of each CFC replacement. The direct global warming of each replacement chemical was noted as well.

The SNAP list of approved CFC replacements is a result of EPA's analysis of all CFC and HCFC alternatives relative to their ozone depletion, safety (toxicity and flammability), global warming, and energy efficiency, among other factors. The SNAP list includes fluorocarbon, hydrocarbon, and several not-in-kind technologies. Most of the US appliance industry has adopted fluorocarbon replacements for CFC's.

Efforts to replace CFC's in Europe were most heavily influenced by the direct global warming impact of each replacement chemical. This impact was especially prevalent in Northern Europe. Subsequently, hydrocarbon technologies were the predominant chemical used to replace CFC's in Northern Europe. Companies manufacturing household refrigerators in Southern Europe have adopted a mix of solutions to the problem of CFC replacement. Many companies in this region use a fluorocarbon refrigerant (HFC-134a) and a hydrocarbon foam-blowing agent (cyclopentane and mixtures with n-pentane).

Japanese manufacturers have utilized all of the refrigerant and blowing agent options. HFC-134a has predominated as the primary refrigerant option, but isobutane has been utilized as well. In 2000, approximately 40% of Japanese refrigerator production used HFC-141b blown foam and 60% used hydrocarbon blown foam. Both HFC and HC blowing agents are being considered for replacing HCFC-141b.

Developing countries have followed several basic routes thus far in addressing CFC use in household refrigerator designs. Many nations have developed full fluorocarbon designs while others have incorporated hydrocarbons fully or partially into their products. The last route is to continue to use CFC's because of economic considerations and uncertainty caused by criticism of fluorocarbon technologies, and the high cost and safety issues associated with hydrocarbons.

The basis for these decisions is dependent on a number of complex variables. Assessments take into account aspects such as the basic design, government regulations, manufacturability, corporate and regulatory safety requirements, energy efficiency, international regulations, workplace safety, warehousing, transportation, consumer usage, service, and disposal procedures.

The US appliance industry redesigned household refrigerators without CFC's after accounting for national and international regulatory requirements. The US consuming public is accustomed to large, auto-defrost refrigerators that perform for twenty years or more without significant service. The goal of US manufacturers was to replace CFC's in household refrigerators without changing the performance expectations of the American consumer, therefore, the transition needed to be transparent. Fluorocarbons provided this advantage.

The refrigerants that have been used to replace CFC-12 in domestic refrigerators are HFC-134a and isobutane. As indicated in Table 4-1, the Montreal Protocol phase-out of CFC-12 resulted in the adoption of non-ozone depleting HFC-134a in much of the world and of non-ozone depleting isobutane (HC-600a) in parts of Europe, particularly Germany.

A detailed discussion of the design and manufacturing factors that need to be considered when replacing CFC-12 with HFC-134a or isobutane is contained in [UNEP, 1998, Section 3]. The key considerations for applying HFC-134a and isobutane are:

• To replace CFC-12 with HFC-134a, a small increase (~18%) in compressor displacement was required and the compressor lubricant was changed from mineral oil to a synthetic, polyolester (POE) lubricant. Other material compatibility considerations were addressed --- e.g., XH7 or XH9 mole sieve dryer instead of XH6 typically used with CFC-12, and motor insulation material. In production, better control of both moisture and overall internal refrigeration system cleanliness is required, due to the hydroscopic nature of POE lubricants and the detergency of POE lubricants. Various oils and waxes that have been used as cutting fluids, motor winding lubricants, and drawing lubricants in system component fabrication are not soluble with HFC-134a, so their use should be avoided. HFC-134a is chemically stable in a sealed refrigeration system. When moisture is controlled to allowable levels, the HFC-134a charge will last for the life of the refrigerator. Manufacturers have implemented the necessary process procedures to maintain low moisture and contamination levels, which has resulted in improved reliability in the field, compared to earlier, CFC-12 based units. While these issues are not technically complex, they must be addressed in a competent manufacturing operation.
• To replace CFC-12 with isobutane requires nearly twice (80% larger) the compressor displacement. Lubricant, material compatibility issues, and historic cleanliness practices that have been applied to CFC-12 are all suitable for isobutane. Both HFC and HC servicing and manufacturing requires care in this regard, but it is not difficult.
• The flammability of isobutane typically requires that the product is configured so that electrical components are isolated from areas with potential refrigerant leaks. In no-frost designs, the design of the defrost heater must preclude it becoming an ignition source. In manufacturing, flammable vapor safe charging and repair stations are needed --- among other things, hydrocarbon vapor monitoring, proper ventilation, and explosion proof factory electrical systems are needed. Instead of brazing operations to seal charged systems, lock ring joints are used. The small charge size requires higher precision charging equipment.

As indicated in Table 4-1, the Montreal Protocol phase-out of CFC-11 foam blowing agent was followed by the widespread use of HCFC-141b and cyclopentane. HCFC-141b has one of the higher ODP values among the transitional alternatives; in the U.S. and Japan it has been put on an earlier phase-out schedule than other transitional alternatives. The non-ozone depleting alternatives include several HFCs, as well as pentane and cyclopentane. Foam blowing agents like nitrogen and carbon dioxide result in much higher foam thermal conductivities, and while they are used in other foam applications, are not serious candidates for this application.

In qualitative terms, production foaming equipment for manufacturing home refrigerators is readily available for both HFC and hydrocarbon blowing agents. Cyclopentane foaming systems are already fully operational with necessary fire safety provisions --- extra ventilation, explosion-proof electricals, and hydrocarbon vapor monitors --- included and adding to the capital cost (note that for application in the US additional features along with VOC emission controls would be required; European VOC regulations are just coming into play). The changeover from HCFC-141b to alternatives is currently in process, and will be complete in the U.S. by January 1, 2003. The HFC blowing agents with the best thermal performance (e.g., HFC-245fa, HFC-365mfc) result in foams having thermal conductivity comparable to HCFC-141b foams and about 10% lower than cyclopentane blown foam [AHAM Research Consortium results].

Vacuum panel insulation has attracted considerable technical interest over the past decade, and has been developed with a variety of fillers and envelope materials. However, the reality is that vacuum panels require tight quality control and are one of the least cost-effective refrigerator design options for energy efficiency. Furthermore, their reliability has not been demonstrated. Foam insulation is required in conjunction with vacuum panels for structural integrity of the cabinet. Vacuum panels are not a viable foam replacement option for refrigerators produced worldwide and have not been considered in this study.

Refrigerators differ considerably in design as well as function in different regions of the world. The predominant design in Europe is about a 10 cubic foot manual defrost all-refrigerator unit popular in a culture where everyday market visits are commonplace. Weekly or bimonthly grocery shopping in the US has resulted in the most common design being 18 to 22 cubic foot automatic defrost refrigerator/freezers. The European designs have fewer internal electricals to contend with in their decision to utilize a small hydrocarbon charge. The US designs have numerous electrical components, and, because of their large size, would require a larger hydrocarbon refrigerant charge. Therefore, zero ozone depleting HFC-134a was chosen as a CFC replacement refrigerant.

As discussed below, approaches to energy efficiency vary from country to country, as do the product configurations that meet the preferences and resources of consumers in those countries. The U.S. has had a system of mandatory energy efficiency standards in place for more than two decades. Refrigerator standards went into effect in 1990, 1993 with the latest revision going into effect in July 2001. Europe introduced its first energy standards in 1999.

Foam aging has an impact on the lifetime average energy consumption of any refrigerator using plastic and foam wall insulation. Due to foam aging (the gradual diffusion of the blowing agent out of the foam and/or the diffusion of air into the foam), the thermal conductivity of the foam increases over time. As a result, the cabinet heat leak increases over time.

Figure 4-1 [from Johnson, 2000] summarizes energy test data over time for full-size, functional refrigerators with several different foam blowing agents. The energy consumption increases, but at different rates for each blowing agent. HFC-245fa foam exhibits the most gradual increase in energy consumption. Figure 4-2, from Wilkes, compares the change of thermal conductivity of foam panels blown with different blowing agents versus time. Consistent with Figure 4-1, HFC-245fa foam thermal conductivity increased more slowly than any of the other foams tested. HFC-245fa foam conductivity increased at only half the rate of conductivity increase of cyclopentane foam.

Figure 4.1: Comparison of Foam Aging --- Effect of Aging on Refrigerator Energy Consumption [From Johnson, 2000 ]

Figure 4.2: Comparison of Foam Aging --- Effect of Aging on Foam Thermal Conductivity [From Wilkes, 2001]

4.2.1.4.1 US Requirements

In the U.S., the National Appliance Energy Conservation Act (NAECA) sets maximum energy consumption levels of home refrigerators and other domestic appliances. In July, 2001 a new energy efficiency standards level took effect, requiring, on average, a 30% reduction in energy consumption from the standard levels which had been in effect since January, 1993. Prior to July, 2001, the allowable energy of a typical 18 cubic foot no-frost, top freezer model (with a 4.5 cu. ft. freezer), was 688 kWh/year (1.89 kWh/day). In 2001, the allowable energy consumption for this prototypical refrigerator was reduced to 480 kWh/year (1.32 kWh/day).

4.2.1.4.2 International Requirements

The US rulemaking process that is followed under NAECA requires that the standard level is economically feasible, that is, cost-effective to the consumer. The July 1, 2001 standard levels were set with the assumption that HFC-245fa or an equivalent chemical, which provides comparable insulating performance to HCFC-141b, would be available as a foam-blowing agent. If HFC-245fa had not emerged as a realistic option during the rulemaking, alternate standard levels 10% higher would probably have been included in the final rule for HCFC-free refrigerators [Federal Register, April 28, 1997]. Thus, if hydrocarbons were the only available blowing agent, maximum energy consumption levels would have been set 10% higher. For the typical 18 cubic foot refrigerator, the resulting maximum energy consumption standard would have been 528 kWh/yr, instead of 480 kWh/year.

The international community has undertaken energy efficiency mandates for home appliances in a similar fashion to the current US regulations. The EU has mandatory energy efficiency requirements for refrigerators that took effect on September 1, 1999. These regulations are currently under review for more stringent efficiency levels in the years 2005-2006.

Canada and Mexico have identical energy efficiency regulations as the US for refrigerators sold in their countries. Japan is developing mandatory regulations for refrigerator efficiency as part of their country's commitment to the Kyoto Protocol. Many other countries are considering voluntary and mandatory energy efficiency requirements for household refrigerator/freezers.

4.2.1.4.3 Developing Countries' Limited Resources

As developing countries improve their quality of living, refrigerators become more desirable in homes. One third of all the food in developing countries goes to waste because of a lack of refrigeration. The increased usage of household refrigeration is placing a demand on limited resources in developing countries. Efficient refrigerator designs are going to be a critical aspect to the successful incorporation of home refrigeration in developing countries.

In North American products, refrigerator designs are subject to a trade-off between manufacturing cost and energy efficiency. The design measures that could reduce energy consumption --- more efficient compressors, fan motors, larger heat exchangers, thicker walls, etc. --- add to the total product cost. It is noteworthy that the energy efficiency of HFC-134a versus isobutane is not significantly different, while the refrigerator thermal-mechanical design is otherwise similar. However, the U.S. appliance industry has estimated that the safety measures needed to use isobutane in a U.S. style refrigerator would add $15 to $30 to the direct manufacturing cost, which could result in a retail price increase between $35-$70. The rationale for mandating the use of isobutane would be in its lower direct global warming potential. However, when 90% of the original refrigerant charge is recovered at the end of the product life, the direct warming impact is considerably reduced:

• Only 10% of a typical 5 ounce refrigerant charge (14 grams) is actually emitted to the atmosphere
• For HFC-134a, the warming impact of 0.014 Kg of emitted refrigerant is only 19 Kg of CO2 equivalent (based on a GWP for HFC-134a of 1313). In the U.S., 29 kWh of electric energy consumption is the same as the emission of 19 Kg of CO2. Therefore, over the 20 year life of a refrigerator, a decrease in energy consumption of 0.3% will be equivalent to the HFC-134a lost in a products' lifetime.
• The U.S. appliance industry estimated that a 1% reduction in energy adds $3 to direct manufacturing cost, so the cost of a 0.3% efficiency improvement could be approximately $2 at retail, if these costs are passed through.

In other words, it is 30 times more cost effective to gain this incremental improvement in warming impact through a small improvement in energy efficiency than changing to isobutane refrigerant.

The LCCP impact of a refrigerator consists of the indirect warming impact of the energy consumption and the direct warming impact of any refrigerant and blowing agent that is actually emitted over the complete life cycle of the refrigerator Only the refrigerant and blowing agent that is actually emitted to the atmosphere has a warming impact. With current practices, refrigerant is charged into new refrigerators with negligible losses to the atmosphere and is contained throughout the life of the refrigerator. End of life refrigerant recovery is mandated, with only a small portion of the charge lost to atmosphere during the recovery process. Therefore, less than 10% of the refrigerant charge is actually emitted to the atmosphere.

Regarding the foam blowing agent direct emissions, after a small loss during foaming, the foam blowing agent is contained with the closed cells of the foam and by the inner liner and outer wrapper (outer sheet metal skin). Over time, blowing agent gradually diffuses out of the foam. At the end of the useful life of the refrigerator, options for disposal include land filling, shredding and land filling, or incineration. Initial research [Kjeldsen and Scheutz, 2002] indicates that less than 25% of the blowing agent may be released upon shredding and before being land filled. Once the foam has been land filled, diffusion to the atmosphere is very slow. Moreover, recent laboratory and field studies [Scheutz and Kjeldsen, 2002] indicate that microbes in the soil breakdown a variety of fluorchemicals such as CFC 11 and 12 and HCFC-22, further reducing the amount emitted to the atmosphere. Additional research is being conducted to determine the extent to which these microbes also breakdown HFC blowing agents such as HFC-245fa.

The TEWI of a 22 cubic foot side-by-side refrigerator-freezer that meets the July, 2001 U.S. energy standards was analyzed by [Johnson, 2000], for three different combinations of refrigerant and blowing agent alternatives as follows:

• Isobutane refrigerant with HC foam
• HFC -134a refrigerant with 134a foam
• HFC-134a refrigerant with 245fa foam (assumed 10% lower energy consumption than the above 2 combinations). Note that recently reported data on the insulating performance of HFC-134a blown foam formulations shows improved insulating performance and reduced energy penalties, ranging from 4% to 7% versus HFC-245fa blown foam [Gurechi, 1998].

Refrigerant and blowing agent emissions, in terms of the initial charge of each, were assumed by Johnson to be:

• Refrigerant
  • 80% of original charge recovered at end of life ,i.e., lifetime emissions of 20% of the original charge (as stated previously, only 10% of the original charge is actually emitted to the atmosphere, but for conservative purposes, 20% was assumed in this analysis)
• Blowing agent
  • Up to 5% loss during production
  • ½% per year loss while in service (based on measurements of blowing agent remaining in refrigerator foam after 17 years of use)
  • At disposal, 50% of blowing agent destroyed, the remainder lost to atmosphere (again, a conservative estimate used by Johnson, compared to results published by Kjeldsen as noted above)

Figure 4-3 compares the TEWI over time, based on these assumptions, for the 3 combinations of refrigerant and blowing agents described above. Based on the recently reported improved insulating performance with HFC134a blowing agent, the TEWI plot for HFC-134a would fall between the plots for hydrocarbons and for HFC-245fa. Energy is the predominant contribution to the TEWI for all three blowing agent options, as shown by Figure 4-4.

Figure 4-3: TEWI Over Time for Domestic Refrigerator in the U.S.

The results from an LCCP perspective demonstrate that HFC and HC options are essentially equivalent. Figure 4-4 shows that in the U.S., the direct effect from loss of blowing agent and refrigerant accounts for less than 10% of the total warming impact., making it clear that it is more important to work on energy consumption

Figure 4-4: Breakdown of Energy, Refrigerant, and Blowing Agent Contributions to the TEWI of an HFC Based Domestic Refrigerator in the U.S.

Home refrigerators are mass-produced at high rates, with extensive automation throughout. The remarkably low prices paid by consumers are due largely to the continuing innovations in manufacturing processes that have been developed by the manufacturers. The impact of refrigerant and blowing agent on manufacturing process requirements is an important factor in the choice of refrigerants. HFC refrigerants with POE lubricants have imposed a new level of system cleanliness and moisture control requirements, while use of hydrocarbons requires that fire safety and local air pollution (VOC) regulations be met.

In the manufacturing environment, several specific safety measures must be taken:

• For cyclopentane or pentane foam, fixture ventilation, explosion proof electricals, hydrocarbon vapor concentration monitoring and alarms and emergency ventilation are among the safety measures that are needed to ensure a fire-safe, explosion-safe operation. An estimate of the additional capital cost of these safety measures for the U.S. appliance industry, with a total capacity of approximately ten million refrigerators per year, is $250 million [Johnson, 1999].
• For isobutane refrigerant, the evacuation and charging stations require explosion proof electricals, hydrocarbon vapor monitors and alarms, and emergency ventilation. No industry-wide estimate of these costs has been prepared, but the costs across the industry would be substantial.

Beyond the manufacturing environment, the costs of safety include the liability from potential accidents, a cost that will be reflected in the product liability insurance premiums paid by the manufacturers. No publicly available data exists to estimate the magnitude of this cost and risk, but in the U.S. legal environment the impact would be significant.

HFC-134a and the HFC foam blowing agents are exempt from volatile organic compound (VOC) emission regulations because they are sufficiently stable that they do not enter into the photochemical reactions involved in the formation of "smog" and ground level ozone. Both isobutane and the pentanes are subject to US VOC regulations. Depending on plant location and applicable local regulations, the small amounts of isobutane refrigerant that escapes during changing and of cyclopentane blowing agent that escapes during foaming must be captured by appropriate pollution control equipment, adding to the investment and operating costs of the manufacturing operation.

With hydrocarbon refrigerants and blowing agents, warehousing and transportation arrangements must take the possibility of refrigerant leaks and outgassing of flammable blowing agents into account. No significant hazards exist with HFCs in this area.

Worldwide production of household refrigerators reaches 65 million annually. Virtually all of the households in developed countries have a refrigerator with an approximate worldwide saturation of fifty percent. With this large number of refrigerators in service, even seemingly minor safety risks must be accommodated.

With HFC refrigerants and blowing agents, there is no significant consumer safety issue. HFCs are non-flammable and the refrigerant charge size is small in relationship to the room size and safe exposure levels. Specific design measures are required to address consumer fire safety issues with a hydrocarbon refrigerant. In European style refrigerators with cold-wall evaporators, double-wall construction is used, so a thick (2 mm) layer of the plastic inner liner material protects the evaporator. A potential danger that this addresses is puncturing the evaporator with an ice pick or other sharp object during manual defrosting. HC refrigerant charges must be limited to a small enough size so a hydrocarbon vapor concentration from a sudden release into a small kitchen will be well below the lower flammable limit.

Modern refrigerators are highly reliable. On average in the U.S., approximately 1.5% of refrigerators require service of the sealed refrigeration system in the field over the product's lifetime. American consumers tend to dispose of refrigerators after 15-20 years, generally before enough deterioration has accumulated to cause any systems failures. American consumers also enjoy an electric power supply system that has ample capacity, with "brownout" conditions of low voltage occurring infrequently. The same is generally the case in other developed countries. Nevertheless, 1.5 percent of refrigerator sealed systems do require servicing during their lifetime, and the service technician must consider the characteristics of refrigerants being utilized.

In developing countries, the frequent occurrence of low voltage conditions leads to compressor motor burnouts. Refrigerators may be serviced several times in their lifetime. The net effect is that sealed systems in refrigerators are serviced more often in developing countries and it is common practice to rebuilt welded-hermetic compressors.

Whether the refrigerant is HFC-134 or isobutane, technicians must be trained to handle these new refrigerants. With HFC-134a, controlling moisture and contamination are the primary considerations. With isobutane, procedures to work safely with the flammable refrigerant are paramount.

Before the refrigeration system is opened for servicing, the refrigerant should be recovered and recycled, or properly disposed of,regardless of the type. The design of safe recovery systems needs to account for both HFC and HC refrigerants.

Recovery of the refrigerant charge at disposal is mandated in most developed countries. Practices for disposing of the cabinet range from landfilling to shredding and incineration.

HFC refrigerants and foam blowing agents do not pose any significant hazards at disposal. Fire safety needs to be taken into account when disposing of a hydrocarbon refrigerator design. If the cabinet is shredded, hydrocarbon blowing agent can be released (even as most is retained in the foam) to form a flammable mixture in air.

Refrigerant designs vary with housing configurations, consumer preferences, food shopping and preparation habits, as well as climatic conditions. For example, in Northern Europe, manual defrost is satisfactory to most consumers, given the moderate climate conditions. In other areas, with warmer and more humid climates, consumers have shown a preference for no-frost models. In developing countries, design is driven toward simplicity and low cost. In each case, these differences and other factors drive the numerous choices of refrigerants and blowing agents.

Given the range of circumstances it is clear that one solution does not suit all requirements. Automatic defrost is approximately 95% of the U.S. market, whereas it is less than 10% of the European market. The typical European cold wall evaporator configuration accommodates hydrocarbon refrigerants safely. In the large no-frost refrigerators preferred by consumers in the U.S. and elsewhere, flammable refrigerant safety issues are more complex (and costly) to address effectively. The U.S. legal environment imposes significant financial risks on any refrigerator manufacturer who introduces flammable refrigerants into a market where other non-flammable alternatives are available.

The current international agreements addressing global environmental issues (the Montreal and Kyoto Protocols) already provide the guidelines needed to ensure that all refrigerant and blowing agent solutions are environmentally sound. The Montreal Protocol has provided for a reasonable, orderly, cost-effective phase-out of all ozone depleting substances. The comprehensive "basket" of greenhouse gases approach set under the Kyoto Protocol addresses global climate change in an integrated, comprehensive way. Both allow each individual country to develop its own most economically effective approach to meeting overall emission limits. With respect to refrigerators, the use of HFC refrigerants in refrigerators results in negligible emissions that can be most cost-effectively offset by even small energy efficiency improvements. HFC blowing agents, due to their superior insulating value, reduce total greenhouse gas emissions. Allowing for diversity of choice is critical to a successful global policy.