Fridge of the Future: ORNL's Refrigeration R&D

By Carolyn Krause

Fears about warming the globe may change the way we chill our foods. Concern about global warming, as expressed in the President's Climate Change Action Plan of 1993, is the latest motivation for putting future American refrigerators and freezers on a strict energy diet. A current national goal is to design an environmentally sound refrigerator-freezer by 1998 that uses half as much energy as 1993 models.

Interest in designing a more energy-efficient refrigerator is not new. It first became a goal almost 20 years ago. In the 1970s, the United States was relying on increasingly unstable supplies of imported oil for fuel, and energy prices began to rise. Utilities balked at building additional power plants because of rising costs and investment risks. As a result, a premium was placed on developing energy-efficient appliances, culminating in the passage of the National Appliance Energy Conservation Act of 1987.
In the late 1980s, refrigerator design was again a target of engineers because of the need to change the refrigerant and insulation used. The reason: the Montreal Protocol called for the phasing out of substances containing chlorofluorocarbons (CFCs) by the year 2000 because they were thought to be destroying the earth's stratospheric ozone layer. Ozone shields humans from solar rays that can cause skin cancer and cataracts. Among the CFCs to be phased out are common refrigerants like R-12 and the refrigerator insulation blowing agent R-11.
Today, the ozone-friendly refrigerant R-134a has been designated to replace CFC-containing refrigerants in new refrigerators because of its lack of chlorine, the main chemical element causing ozone depletion. However, it may become a target for future phaseout because it contributes to global warming, although much less so than CFCs. In that event, its likely replacement will be a hydrocarbon such as isobutane or propane. These natural refrigerants will have to be "engineered around" in a new refrigerator design because they are flammable. Thus, their widespread use may slow global warming but raise the risk of house fires.

Brooks Lunger, a guest user at ORNL's Buildings Technology Center from DuPont, checks instrumentation on test refrigerators.

Large Energy User

Home refrigerators are a significant user of world electricity; hundreds of millions are currently in use, and 58 million new units are manufactured worldwide each year. In the United States, refrigeration systems (including air conditioners and heat pumps) account for 41% of the energy consumed by residential and commercial buildings. The buildings sector requires about 36% of the energy used in the United States. If no improvements are made, energy use in the buildings sector is projected to climb 37%—from 29 quads (quadrillion British thermal units) today to 40 quads—by 2010.

The goal of the Department of Energy's Refrigeration Systems Program, in which ORNL's Buildings Technology Center (BTC) plays a large role, is to develop and market advanced refrigeration systems to reduce the projected energy consumption in U.S. buildings by 10% in 2010. There are several reasons for the current energy reduction goal. They include saving money, reducing reliance on imported oil, and helping utilities avoid risky capital investments in new power plants to meet escalating demands for electricity during certain times of day.

The most compelling reason to curb demand for electricity is to slow global warming. Fossil fuels used for electricity production are a large source of atmospheric carbon dioxide, a greenhouse gas that may alter the climate. Energy use in buildings accounts for 36% of carbon dioxide emissions produced in the United States, suggesting that buildings may have a significant impact on outdoor as well as indoor environments.

ORNL's Role

ORNL has been heavily involved in the refrigerator redesign efforts of the past two decades. Today the Laboratory has the largest and most comprehensive refrigerator-freezer research program supported by DOE. ORNL has the expertise and experience to help meet the challenge of increasing energy efficiency of refrigeration. Since 1977, ORNL's contributions to developments of commercial refrigerator-freezers and other refrigeration equipment include

BTC is now working on developing a highly energy-efficient refrigerator-freezer that uses an efficient and environmentally acceptable refrigerant and insulation. This work is being done under cooperative research and development agreements (CRADAs) with the largest manufacturers in the refrigeration industry.

ORNL also will play a role in DOE's latest effort to save energy. In addition to developing new highly efficient refrigerators, DOE seeks to help industry sell existing energy-efficient refrigeration equipment.

Among the researchers who have led the more recent developments in BTC's $1-million-a-year refrigeration research program are Van Baxter, Phil Fairchild, Steve Fischer, Patrick Hughes, Keith Rice, Jim Sand, John Tomlinson, and Ed Vineyard, all of the Energy Division, and Tom Kollie, Ron Graves, and Ken Wilkes, all of the Metals and Ceramics Division. Several of these researchers have been influential in their fields.

In three of the past five years, Sand and Vineyard have won American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) technical paper awards; the award recognizes the best papers presented at the annual meetings of the international organization. Vineyard has participated on technical panels for ASHRAE, the Super Efficient Refrigerator Program of the Consortium for Energy Efficiency, the Association of Home Appliance Manufacturers (AHAM), and the United Nations Environment Programme (which in 1991 and 1994 produced Technical Progress on Protecting the Ozone Layer, to which he contributed a chapter). Sand is a member of an advisory committee for the Materials Compatibility and Lubricant Research program of the Air-Conditioning and Refrigeration Institute (ARI), which sponsors research aimed at solving the equipment problems resulting from the use of alternative refrigerants. He also was a panelist for a February 10, 1994, video conference on CFC refrigerant recovery and replacement, which was broadcast by satellite to a wide regional audience in the Southeast.

Baxter was the recipient of ASHRAE's 1982 Willis H. Carrier Award. Fairchild, who helped establish ORNL's research program on CFC alternative refrigerants, is an adviser to ARI's Research and Technology Committee; in 1987 he gave testimony at U.S. Senate Joint Subcommittee Hearings on Stratospheric Ozone Protection and Substitutes for Ozone-Depleting Chemicals. These and other ORNL researchers have also helped steer the refrigeration industry in a new direction through their work as influential members of ASHRAE's Refrigeration Technical Advisory Committee.

Advanced Refrigerator Model and Compressor

In 1977, ORNL engineers led by Virgil Haynes in the Energy Division were asked by DOE's predecessor agency to work with subcontractor firms to develop a more efficient refrigerator. Funds received by ORNL paid for the work of subcontractors selected by the Laboratory.

In one project, ORNL engineers worked with engineers from Amana, a refrigerator manufacturer, to develop a more efficient refrigerator-freezer. To help them, they used a computer model of a refrigerator developed in 1977 by Arthur D. Little, Inc., under an ORNL subcontract. Amana performed field tests of different models of refrigerators to determine which ones were most efficient. ORNL provided technical guidance and expertise for all this work.

The engineers focused on vapor-compression refrigeration. In this device, a refrigerant under low pressure is evaporated in a coiled pipe called an evaporator. To get energy to evaporate, the refrigerant pulls heat away from the refrigerator compartment, chilling it to the desired temperature. A compressor draws away the evaporated refrigerant, compresses the vapor, and passes it to a condenser, where it gives off the heat it had absorbed to the kitchen air. The increased pressure and loss of heat forces the refrigerant to condense into a liquid. The liquid refrigerant is expanded to the lower pressure, reducing its temperature, and then is returned to the evaporator. Throughout these cycles, a thermostat regulates the temperature inside the refrigerator by switching the compressor on and off.

To design a more efficient refrigerator, Amana and ORNL engineers decided to increase the insulation thickness in the refrigerator's walls from 1/2 inch to 2 inches, install an anti-sweat switch, move the fan to a better location, improve compressor efficiency, and increase heat exchanger areas. They elected to have two evaporators instead of one—one evaporator for maintaining freezer temperature at 0-5°F and the other for holding the refrigerator at 40°F for fresh food. Because electric heaters are used for defrosting, they decided to save additional energy by setting the refrigerator-freezer for automatic defrost every 4 days instead of every 18 hours.

The collaborating engineers showed that refrigerator efficiency could be increased by these changes. Although these changes would raise the cost of the appliance, they argued that the difference could be made up by reduced long-term operational costs through decreased use of electricity.

Amana built and sold a more efficient refrigerator that incorporated these changes. "Its major features were a delayed defrost, increased insulation, and a dual evaporator," says Sand. "But it was on the market for only a few years because it had some moisture problems in the fresh food compartment."

However, the refrigerator model developed under ORNL subcontract and later improved and validated by ORNL researchers is still in use today. It will be used by Indian manufacturers to develop more-efficient single-door refrigerators for India. ORNL is assisting the effort to develop more-efficient but affordable appliances in India and China through a DOE program called Assisting Deployment of Energy Practices and Technologies (ADEPT). For the Indian project, BTC evaluated the energy performance of refrigerators made by five different Indian companies and suggested design changes to improve their efficiency. Improved efficiency is deemed necessary to keep demand for electricity under control in a country that lacks resources for adding power plants. The demand for power will rise because the portion of the population that uses refrigerators is expected to increase from 6% now to nearly 60% by 2010.

In a November 17, 1994, letter to DOE officials, Tom Wilbanks, corporate fellow in ORNL's Energy Division, wrote: "Quite clearly, the ADEPT project is viewed as a major success in India—a model of bilateral cooperation. Besides leading to a new joint venture between Amana and Voltas, it is credited with encouraging Whirlpool's entry into the Indian market (purchasing Frigidaire's share in Kelvinator-India). The results of ORNL's tests of five Indian home refrigerators have led directly to a decision by the Bureau of Indian Standards to [tighten] the voluntary efficiency standard for Indian refrigerators. . . . In addition, the Indian Institute of Technology (IIT) has added an environmental chamber to its refrigeration R&D lab as a direct result of [an IIT professor's] participation in the April 1994 workshop in Oak Ridge and his observation of ORNL's testing approaches."

A related project in the late 1970s that was an unusually big success was the development of a more efficient refrigerator compressor by engineers from industry. ORNL was technical monitor for this project with Columbus Products, which later became White Westinghouse and then Americold Compressor Company. In 1981, the subcontractor, by incorporating design changes to the motor, suction muffler, and compressor valve assembly, developed a compressor that uses 44% less energy than conventional units of the same size. The compressor is part of product lines of Americold Compressor and Frigidaire. This compressor technology has helped reduce annual refrigerator energy use from 1500 kilowatt hours (kwh) to 900 kwh per year in 1990. Between 1980 and 1990, according to DOE, the energy-efficient refrigerator compressors saved U.S. consumers $6 billion in energy costs. The more efficient compressor is one of three achievements cited as "notable successes" in DOE's 1991 Refrigeration Systems Program Summary report, and it was recently awarded a DOE Pioneer Award.

Another ORNL-led project that received a DOE Pioneer Award resulted from a collaboration of the Laboratory's Energy Division and Foster-Miller Associates (FMA), H. E. Butt Grocery, and Friedrich Commercial Refrigeration. The project goal was to reduce electricity consumption in supermarket refrigeration systems, which use nearly 2% of the electricity consumed in the United States. The research led to improvements in refrigeration systems that cut energy use in U.S. supermarkets by 30%, reducing energy bills by about $4 billion since the mid-1980s. About 80% of supermarkets now use the advanced system.

An improved microprocessor controller that modulates the compressor capacity to meet changing refrigeration loads accounted for about half of the efficiency gain. The remaining improvement came from further refinements developed by manufacturers sponsored by the Electric Power Research Institute. In addition to cost savings, the reduced energy consumption by supermarkets avoided the emission of almost 10 million metric tons of carbon.

Concern about CFCs

After development of a computer model and a more efficient refrigerator and compressor by 1981, refrigerator research at ORNL lay dormant for 6 years. Then in 1987-88, the CFC issue emerged because of concern about the thinning ozone layer. Suddenly, funding became available from DOE to develop CFC-free insulation and CFC-free refrigerants for refrigerators.

During this time, DOE's Roof Research Facility at ORNL was dedicated as a national user facility to help industry develop longer-lasting energy-efficient roofs. Soon after, this facility became concerned with developing and testing CFC-free roof insulations. It added a room with apparatus for evaluating the energy performance of CFC-free insulations and CFC-free refrigerants for refrigerators, air conditioners, and heat pumps.

Ed Vineyard checks instrument readings during a test of chlorine-free refrigerant mixtures and alternatives to the coolant HCFC-22.

In 1993, the user facility was renamed the Buildings Technology Center. Researchers from industry used this center not only for roof research but also for development of more-efficient appliances. Just as ORNL's early refrigeration researchers had collaborated with industrial firms through subcontracts, the Laboratory's current researchers became involved with the refrigeration industry through collaborative agreements and CRADAs. The focus of these agreements has been energy-efficient, environmentally acceptable refrigerators and other refrigeration equipment.

Concern about Global Warming

In June 1992, the international Earth Summit meeting was held in Brazil. Concerns about global warming were strongly expressed, and the United States was urged to reduce its emissions of carbon dioxide. The U.S. pledge to restrict carbon dioxide emissions through increased energy efficiency and other measures was formulated in President Clinton's Climate Change Action Plan of 1993. This plan exerts additional pressure on the refrigeration industry to design, manufacture, and market energy-efficient appliances that use environmentally acceptable refrigerants and insulations. In addition, the Energy Policy Act of 1992—legislation passed by Congress that was based on information gathered for DOE's National Energy Strategy—gives DOE the authority and responsibility to pursue energy efficiency actively.

The problem is that CFCs contribute not only to ozone depletion but also to global warming. In fact, their contribution to global warming is second only to that of carbon dioxide, which accounts for 80% of greenhouse gas emissions in the United States. However, replacing CFCs with ozone-friendly compounds such as hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs) would still affect global warming. HCFCs and HFCs are also greenhouse gases, but their direct impact on global warming is much smaller than that of CFCs. However, widespread use of some CFC alternatives in refrigeration systems would result in larger consumption of electricity from fossil fuel plants. Thus, emissions of carbon dioxide would increase, speeding up global warming. Clearly, the substitute refrigerants would have an indirect impact (energy-related) as well as a direct impact (emission-related) on global warming. The combined effect is called the total equivalent warming impact (TEWI).

The concept of TEWI and of indirect and direct effects of greenhouse gases on global warming was developed by Steve Fischer, Patrick Hughes, and Phil Fairchild, all of ORNL's Energy Division, and analysts from Arthur D. Little, Inc., for the first CRADA at the Laboratory. The agreement involved ORNL and the Alternative Fluorocarbons Environmental Acceptability Study, a consortium of 12 of the world's largest producers of fluorocarbons. The work was started in December 1990 and completed in December 1991 with the publication of Energy and Global Warming Impacts of CFC Alternative Technologies.

Under the CRADA, ORNL evaluated the relative performance, subsequent carbon dioxide emissions, and net global climate change potential of CFC alternatives in building energy-related applications. ORNL investigated alternative refrigerants; insulation materials and systems; and advanced refrigeration, air-conditioning, and heating technologies. Consortium members contributed technical expertise on refrigerant alternatives. The CRADA was extended and a second report was issued in December 1994. The extension focused on investigating several alternative technologies to fluorocarbon-based vapor-compression refrigeration.

"The direct effect on global warming of a refrigerant leaking from refrigerators is less than the indirect effect on global warming of carbon dioxide from their energy use," Sand says. "For leaking automobile air conditioners, the direct effect of the leaks on global warming is larger than the indirect effect of burning gasoline. But for refrigerators the indirect effect of consuming electricity inefficiently from fossil fuel plants is much larger than the direct effect of refrigerant leaks. So, for environmental reasons, emphasis should be placed on improving energy efficiency of refrigerators to reduce carbon dioxide releases."

Environmentally Acceptable Refrigerants Identified

In 1990, ORNL researchers tested DuPont refrigerant blends proposed as substitutes for R-12, the commonly used refrigerant that contains CFCs. They identified an HCFC blend of R-22/R-152a/R-124 as an ozone-friendly chemical that could be even more energy efficient than the common refrigerant R-12 if the refrigerator were properly redesigned to increase heat transfer and improve the refrigerant circuit arrangement.
"We helped DuPont make its refrigerant blend more efficient," Ed Vineyard says. "DuPont made the blend using the results of our computer model. We tested this blend and many other HCFC blends. We suggested changes in the blend's composition to improve its efficiency. DuPont made the changes, and we wrote scientific papers on the new blend."

The ORNL researchers had tested numerous alternative refrigerants supplied by DuPont and Pennwalt using the Laboratory's Alternative Refrigerants Calorimeter Facility. In examining each refrigerant, they measured its energy performance (the electrical energy required to operate the appliance using the refrigerant) and its refrigeration capacity (the ability of the fluid to absorb heat—a measure of the cooling output). The ratio of the refrigeration capacity to the electrical energy input is the coefficient of performance (COP). The alternative refrigerants that have the highest COPs were considered the best candidates for future refrigerators.

Charlie Hardin (now retired) sets up a breadboard refrigeration loop to test heat transfer performance of zeotropic mixture alternatives to HCFC-22.

Vineyard, Sand, and others have used a computer model of a detailed refrigerator system to evaluate the energy savings for several design modifications of a refrigerator using an alternative refrigerant such as HFC R-134a. The design options included use of a more efficient compressor, increased evaporator and condenser size, door gaskets to reduce energy losses, improved cabinet and door insulation, and high-efficiency fan motors. Laboratory refrigerator prototypes were built and tested to verify the model's analytical results experimentally. The modeled and experimental results were generally in agreement. The differences observed guided the researchers in improving the model.

Partly as a result of the influence of ORNL researchers Sand and Vineyard on AHAM's Refrigeration Technical Advisory Committee, the refrigeration industry adopted R-134a as the refrigerant of the future.

"Just as you must switch from an internal combustion engine to a diesel engine if you want to use diesel fuel instead of gasoline," Sand says, "we found that the refrigerator design had to be changed to use R-134a as a refrigerant."

"It is not easy to change from a refrigerant used for 40 years," Vineyard says. "To use 134a, the refrigerator had to be redesigned in a short time because after 1995 it will be illegal to build a refrigerator that uses only R-12 because this refrigerant will be phased out."

"We faced several complications in the rush to redesign the refrigerator for the new refrigerant," Sand says. "For example, we learned that the conventionally used lubricating oil is not compatible with 134a. So we tried a different oil. But we found out that this oil dissolves insulation for the compressor motor, causing it to burn out. So we tried a different oil, but it plugged up the expansion valve. As you can see, the ripple effect of one change necessitates a cascade of changes that jacks up the cost of the refrigerator."

Because of these problems, DOE and the Air-Conditioning and Refrigeration Technology Institute are jointly funding research to determine the compatibility of structural materials and lubricants with refrigerants being considered as replacements for restricted CFC compounds.

"Some environmentalists complain that the refrigeration industry is slow to manufacture environmentally sound refrigerators," Sand says, "but the reason for the delay is that it takes time to develop and test a system that accommodates a change in refrigerants. If enough time is not taken to conduct tests, a financial disaster could occur. Recently, a leading manufacturer of refrigerators lost almost a billion dollars replacing damaged refrigerators. For these new models, the company had decided to use a new compressor design. But the new compressors failed in consumers' homes after a few weeks of operation, so the company lost a considerable amount of money."

HFCs such as R-134a have been favored over CFCs because they are less of a threat to the ozone layer. However, HFCs have since fallen into disfavor in some quarters because they are greenhouse gases that have long atmospheric lifetimes. R-134a absorbs infrared radiation emitted by the earth's surface in the spectrum not absorbed by other gases.

"The ultimate refrigerant of the future," Sand says, "could be hydrocarbons like isobutane or propane if HFCs fall victim to global warming concerns. Hydrocarbons are 4 to 5% more efficient than R-12, they don't destroy the ozone layer, and they don't contribute to global warming. Isobutane is a propellant used to replace CFCs in spray cans, and propane is found in crude petroleum and natural gas. European refrigerator manufacturers are now switching to hydrocarbons."

"Hydrocarbon refrigerants have one problem," Vineyard says. "They are flammable. That's why hydrocarbons, which are natural refrigerants, were not originally selected for electric refrigerators. Vendors will have to deal with lawsuits that may arise from expected increases in refrigerator-related house fires. They will have to worry about the risk of fire in factories that store hydrocarbon refrigerants and in hydrocarbon tanks in trucks used by refrigerator service people. To reduce the fire risk to homeowners, we will have to engineer around such refrigerants and keep them hermetically sealed. But there will always be a small risk that they could leak out into defroster heaters or catch electrical sparks and ignite. We hope to study these problems for the Environmental Protection Agency."

Friendly Insulation

R-11, an insulation blowing agent that contains CFCs, was once used to blow polyurethane foam into refrigerators. Now HCFC-141b, which contains chlorine, is used as the common blowing agent; the problem with it is that chlorine can attack the ozone layer. Today the goal is to insulate new refrigerators with a combination of vacuum insulation and foam blown with a non-ozone-depleting chemical. "This combination," says Ken Wilkes, "is expected to be very efficient but more expensive and with uncertain reliability."

Two types of vacuum insulation being developed and tested at ORNL are powder evacuated panels (PEPs) and an insulation that contains fibrous glass. Because the insulating value of these materials is several times greater than current refrigerator insulation, they could save $10 to $20 a year in electricity per unit. But vacuum insulations are more costly than foam insulation.

In vacuum insulations, powder or fiber is sealed in evacuated envelopes. "Vacuum insulations," says Wilkes, "are like boxes of coffee grounds packed in vacuum except the grounds are insulating powders or fibers and the packages are made of plastic or steel sheets."

In 1981 Arthur D. Little, Inc., and ORNL looked into developing vacuum insulations for refrigerators, ovens, and mobile homes to improve energy efficiency. At ORNL, David McElroy made laboratory measurements of properties and performance of materials in vacuum insulations. He determined the insulating value of the fine powders and the ability of evacuated envelopes of different materials to support the load of the atmosphere without collapsing.

For vacuum insulations, durability is a key issue. If they are not durable, they develop holes and air leaks in, destroying the vacuum. In addition, air molecules can diffuse through plastic envelopes, even if they have no holes. In some Japanese refrigerators, vacuum insulations have been known to lose their vacuum in a year. They must be made durable for 15 to 20 years, the expected lifetime of refrigerators.

At ORNL, Tom Kollie (now retired from the Metals and Ceramics Division) developed a procedure for measuring the lifetime of various vacuum insulations. ORNL researchers are now measuring the lifetime and thermal resistance of vacuum insulation samples. They are developing computer models to account for heat flow around the panel edges. In general, they have found that the thermal resistivity of vacuum insulations exceeds that of conventional insulation by 3 to 7 times, or more.

Evacuated panels contain fibrous glass or ceramic or metallic powders. Vacuum insulation jackets are made of plastic sheets or steel foils. They will be embedded in foam in the refrigerator door and wall. From the outside in, the refrigerator of the future may consist of a steel skin, vacuum insulation panels about 1 inch thick, about 1 to 2 inches of insulating foam blown with a non-ozone-depleting chemical instead of a chlorine-containing agent, and a plastic inner wall. The foam will give the steel wall structural rigidity.

Currently, ORNL researchers are evaluating vacuum insulations under CRADAs with PPG, Aladdin Industries, DuPont, VacuPanel, and the AHAM, which represents all major refrigerator manufacturers ranging from Amana to General Electric to Whirlpool. The goal of the research is to develop fillers and vacuum envelopes that offer increased thermal resistivity and longer lifetimes while decreasing cost.

Fridge of the Future

ORNL researchers are now working under a CRADA with the Appliance Industry–Government CFC Replacement Consortium, a subsidiary of AHAM. The goal of the CRADA is to design a new refrigerator-freezer of conventional size by 1998 that is 50% more efficient than the 1993 federal standard. This "next-generation" refrigerator must use environmentally acceptable materials.

Some of the innovative concepts being investigated by engineers from ORNL and the refrigeration industry include highly efficient adjustable-speed compressors, dual-evaporator refrigerators, compact heat exchangers, advanced insulations, and refrigerant blends. The "fridge of the future" is expected to have PEPs and foam insulation, extended surface heat exchangers for the condenser and dual evaporator, an environmentally friendly refrigerant, direct-current electrically commutated motors for the two fans that blow air past the condenser and dual evaporator, and an expansion valve.

The refrigerator firms have proposed changes and sent their best components and improved versions to ORNL for testing. ORNL tests units containing the best components from the different companies. ORNL then gives participants test results and suggests changes to further improve component and refrigerator design.

Refrigerator of the future.

A new CRADA is being negotiated between ORNL and an undisclosed large refrigerator manufacturer. The goal is to develop the most energy-efficient unit using advanced door gaskets (with better seals to reduce energy losses), improved defrost, advanced insulation, and a different evaporator-compressor-condenser cycle.

Helping Designers of Heat Pumps

ORNL research has had an impact on the development of more-efficient heating and cooling equipment as well as refrigerators. This equipment includes gas-fired and electric-driven heat pumps.

In the 1980s, C. Keith Rice together with Steve Fischer and other staff in ORNL's Energy Division developed a computer model that has become a valuable tool for heat pump designers. The model allows designers to determine the effects of newly designed individual system components on performance of new heat pump and air-conditioner designs. The ORNL computer code has been widely used by U.S. manufacturers to design highly efficient air-to-air heat pumps and air conditioners. The Trane Company uses the model together with its own expert system to cut component design time by 75%. According to DOE, application of this model has contributed to the development of heat pump systems that use 20% less energy than conventional systems. This development is another of the three achievements cited as "notable successes" in DOE's 1991 Refrigeration Systems Program Summary report.

Bill Miller inspects a facility for testing heat exchanger designs for advanced heat pump systems.

ORNL also manages a program for DOE that has guided industry in producing more-efficient heating and cooling equipment. A new technology that doubles the efficiency of gas heating—a gas-fired heat pump called the GAX system—has been developed. ORNL engineers are working with a leading company and gas utilities to market this technology (see the following article).

Marketing Efficient Appliances

Developing highly efficient appliances is not the only way to reduce appliances' use of energy. Another way is to increase sales of appliances already on the market that are "energy savers." These include $1200 refrigerators that will save buyers $1200 over 10 years in electricity costs.

"DOE is focusing more on helping vendors sell their efficient appliances than on developing new ones," Sand says. "This is the softer side of DOE. It is selling the sizzle rather than the steak."

"The DOE sticker will be on future appliances to lend credibility to vendors' claims that energy savings from a product will eventually pay for its initial cost," Vineyard says. "Because DOE has name recognition and a reputation for energy expertise, appliance vendors want DOE's name on their efficient products to help them sell. DOE wants to help the vendors because it knows that convincing consumers to replace yesterday's inefficient appliances with today's more efficient ones will save energy."

The DOE sticker will also be useful to salesmen and customers. It will help them identify the high-efficiency appliances for which some electric utilities give rebates.

The refrigerator of the future will likely also bear a DOE sticker because it will use half as much energy as today's refrigerator. Saving energy benefits many groups. Consumers enjoy lower electricity bills and may use their savings to buy other products, stimulating the economy. Commercial and industrial firms using more-efficient refrigeration equipment may use their savings to hire more workers. Electric utilities may be able to avoid building new power plants. The nation has less of a need to rely on imported oil for electricity production. And, environmentalists and policymakers have less concern that refrigerators will contribute to thinning of the ozone layer and to global warming. In short, the refrigerator of the future will be environmentally acceptable. It is hoped that it will keep our food cold without making the globe too warm.

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