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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).

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 1999, approximately half of Japanese refrigerator production uses HFC-141b blown foam and half uses 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.

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 basic refrigerant replacements utilized 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.

When used as the refrigerant in a home refrigerator, key considerations for HFC-134a and isobutane are:

• To replace CFC-12 with HFC-134a, a small increase 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. 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. 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.
• To replace CFC-12 with isobutane requires nearly twice the compressor displacement. Lubricant and other material compatibility issues are minimal, but flammable vapor safe charging and repair stations are needed and the refrigerator design must account for the flammable refrigerant.

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, and 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, pre-foaming nitrogen purging, 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 a non-ozone depleting HFC is currently in process, with full-scale production a few years off. 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. 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 a 6 to 7 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 no 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 has its first energy standards going into effect on September 1, 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 Deeg, 1998] 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 Deeg, 1998]

Figure 4.2: Comparison of Foam Aging - Effect of Aging on Foam thermal Conductivity [From Wilkes, 1998]

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 takes effect, requiring, on average, a 30% reduction in energy consumption from the current standard levels which have been in effect since January, 1993. For the prototypical 18 cubic foot no-frost, top freezer model (with a 4.5 cu. ft. freezer), the allowable energy is currently 688 kWh/year (1.89 kWh/day). In 2001, the allowable energy consumption for this prototypical refrigerator will drop to 480 kWh/year (1.32 kWh/day). As a general rule, manufacturers design products with energy consumption approximately 5% below the standards level to ensure compliance. This is also done to accommodate some variability in individual component performance and cabinet manufacturing. Thus, future 18 cubic foot, no-frost, top freezer refrigerators in the U.S. will typically consume 456 kWh/year.

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 prototypical 18 cubic foot refrigerator, the resulting maximum energy consumption under standards would be 528 kWh/yr, instead of 456 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 take effect on September 1, 1999. These regulations are currently under review for more stringent efficiency levels in the years 2003-2004.

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.

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.

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 0.0142 Kg is only 19 Kg of CO₂ equivalent (based on a GWP plus manufacturing warming impact 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 following estimates the LCCP for a typical current U.S. refrigerator and for future refrigerators meeting the new energy efficiency standards that take effect in July 2001. For future refrigerators, two basic design options are examined.

• HFC based - HFC-134a refrigerant and HFC-245fa blowing agent
• Hydrocarbon based - Isobutane refrigerant and cyclopentane blowing agent

In addition, the LCCP is calculated for a current refrigerator, meeting current efficiency standards and using HFC-134a refrigerant and HCFC-141b blowing agent.

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 emitted from the refrigerator. Representative energy consumption was estimated in the previous section and is used here to calculate the direct impact. Refrigerant and blowing agent emissions, in terms of the initial charge of each, are assumed to be:

• Refrigerant
  • 90% of original charge recovered at end of life, i.e., lifetime emissions of 10% of the original charge
• Blowing agent
  • Up to 5% loss during production
  • 1/2% per year loss while in service, based on aging data [Wilkes, 1998; Deeg, 1998; Johnson, 1999]
  • 1% per year loss after disposal, on the basis of recently published data [Johnson, 1999] indicating that the blowing agent diffusion half-life from unfaced, aged foam is on the order of 75 years for a variety of fluorocarbon blowing agents.

Figure 4-3 compares the LCCP for the current U.S. refrigerator and for HFC and HC based future refrigerators that will meet the July, 2001 efficiency standard, as discussed in 4.2.1.4.1. The direct warming for the HFC alternative has been calculated based on emission of 100% of the blowing agent. But, as indicated above, the actual rate of diffusion of blowing agent out of foam that is contained between impervious surfaces is extraordinarily slow. Over the normal life of the refrigerator on the order of 15% of the original blowing agent is actually lost into the atmosphere. After disposal, the loss of the remainder stretches over a period of the order of one hundred years or more. Even with the highly conservative assumption of eventual 100% blowing agent loss, the LCCP for HFC based and HC based refrigerators is essentially comparable.

Figure 4-3: LCCP for Domestic Refrigerator in the U.S.

The results from an LCCP perspective demonstrate that HFC and HC options for the future are essentially equivalent. The LCCP of the future HFC refrigerator will be 30% less than the LCCP of current refrigerators, a reduction far in excess of the warming impact of the maximum possible HFC emissions. It is important to remember that the IPCC states that GWP values are accurate to +/- 25% and that GWP values themselves are being continuously updated.

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, in the order of hundreds of millions of dollars.

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 attempt has been made to estimate the magnitude of this cost, but in the U.S. legal environment the impact could 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 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. The 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.

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