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Energy-Efficient Appliances PUBLIC ACCESS

Washing Machines and other Household Devices are being Redesigned for Greater Efficiency, So Consumers can begin to think Green as they keep Clean.

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Associate Editor

Mechanical Engineering 120(03), 94-97 (Mar 01, 1998) (3 pages) doi:10.1115/1.1998-MAR-6

Washing machines and other household devices are being redesigned for greater efficiency. Key to creating an energy-efficient washer is to cut the use of water, because 85 to 90 percent of the energy used in washers goes to heating the water. This is typically accomplished by a front-loading unit with a tub that rotates around a horizontal axis. Studies by Electric Power Research Institute (EPRI), Palo Aldo, CA, show that horizontal-axis machines use about one-third less water and two-thirds less energy than the vertical-axis machines that have captured almost the entire U.S. market. Maytag Laundry Appliances Research and Development’s new front-loading Neptune washer features a horizontal-axis tub that is angled up 15 degrees to improve visibility and access. Rather than agitating wash loads in a full tub of water like standard top loaders, the Neptune washer substitutes a clothes-dryer-like tumbling action that dunks fabrics in a smaller volume of water.

HOME-APPLlANCE BUYERS HAVE always looked at low prices and desirable features as key to selecting washing machines, refrigerators, and the like. Rarely is environmental acceptability high up on the list of consumers' needs. As federal regulations have gotten stricter and green consciousness has 'grown in the public's mind, however, appliance manufacturers are giving greater emphasis to developing new products that use less energy than earlier models.

Unfortunately, the appliance industry is not especially known for technological innovation. "The appliance business is a very competitive market," said John Kesselring, manager of residential systems for the Electric Power Research Institute (EPRI) in Palo Alto, Calif. With cost control being critical, companies tend to' go for cheaper options in designing app liances, he said, "but there's a n'larket transformation going on right now." Part of that conversion is a greater focus on improved energy efficiency: "It's the biggest change in 30 years," he said.

Last year, for example, May tag Laundry Appliances in Newton, Iowa, introduced its Neptune frontloading washer, a high-end model that not only saves electricity and water but also cleans clothing better than standard top loaders, which is perhaps more important for consumers. "Energy efficiency is not a big draw for your average appliance consumer," Kesselring said. "If a new washer doesn't do a better job cleaning clothes, nobody cares."

Key to creating an energy-efficient washer is to cut the use of water, because 85 to 90 percent of the energy used in washers goes to heating the water. This is typically accomplished by a front-loading unit with a tub that rotates around a horizontal axis. "Horizontalaxis machines can wash with less water because you are not completely submersing the clothes," said Donald Erickson, manager of horizontal-axis washerdesign engineering at Maytag Laundry Appliances Research and Development. Front loaders substitute the tumbling action of a clothes dryer for the push-pull agitation of a top-loading or vertical-axis washer, lifting clothes up and dropping them back into a smaller volume of water.

Horizontal-axis machines have long dominated the European market. Studies by EPRI show that such machines use about one-third less water and two-thirds less energy than the vertical-axis machines that have captured almost the entire U.S. market. However, horizontal-axis washers generally have smaller capacities and longer wash cycles, and typically cost three times as much as top loaders.

Maytag's new front-loading Neptune washer features a horizontal-axis tub that is angled up 15 degrees to improve visibility and access.

Grahic Jump LocationMaytag's new front-loading Neptune washer features a horizontal-axis tub that is angled up 15 degrees to improve visibility and access.

In 1991, the U.S. Department of Energy (DOE) announced that it was going to issue strict energyefficiency requirements for washers. "To meet the anticipated requirements, several of the manufacturers went to horizontal-axis designs," Kesselring said. M ter a long delay, the DOE recently revived plans for its tougher standards, which are now slated to be released in 1999 and will take effect as soon as 2002. Two large appliance makers, Frigidaire and Amana, have already introduced front loaders that save moderate amoun ts of water and energy.

Maytag appliance engineers were well aware of these issu es when they instituted plans to develop a new front-loading washing machine. "We've known for a long time that high-efficiency washer technology in Europe has held promise with its cleaning ability and its energy and water savings," said Curran Cotton, May tag's vice president of research and development for laundry products, "but we also knew there were certain features- such as convenience, capacity, and accessibilitythat North American consumers weren't willing to sacrifice." In partic ular, May tag engineers were concerned with the smaller wash load capacity as well as the inconvenience of bending over and stooping to load and unload horizontal-axis machines.

When the DOE began considering the more-stringent standards, May tag approached EPRI; the two had developed a relationship from previous programs. Their joint six-year project to develop a new horizontal-axis machine kicked off in 1992.

The biggest issue confronting design engineers was the limited tub access of front loaders. T he May tag team solved that and the bend-and-stoop problem by tilting the spinner axis of the stainless-steel tub up 15 degrees and making the opening as large as possible. The upward tilt improved visibility and reach, as did expanding the opening diameter to 15 inches. The resulting widemouthed, ergonomically designed tub has a capacity of 2.9 cubic feet-20 percent more usable capacity than standard top loaders.

However, these major design changes "broke the cabinet," Erickson said. The new nonorthogonal orientation of the heavy internal components weakened the structure. The team had to redesign the cabinet, particularly the top cover and door, to accommodate the tilted tub. Reinforcing members were added to strengthen the cabinet, and "we moved the door opening back at the top and sloped the upper front so the door breaks the top plane," he added.

The baffle system was also redesigned to move the clothes toward the raised front. The baffies, which line the interior of the tub, not only have to improve item circulation in the wash without any tangling but also have to scoop up water so it can rain down on the tumbling clothes. "It took a lot of development work, mostly done by trial and error, to come up with the six half-baffies in the Neptune's tub," Erickson said. This technology plus the greater concentration of detergent in the smaller water volume result in improved cleaning of fabrics.

To shorten the Neptune's total operating cycle time, May tag en engineers installed a faster-spinning tub. The machine's higher spin speed of 800 rpm means 30 percent more water extraction than standard units, which translates into 25 to 30 percent shorter drying times. Such speeds, however, can cause severe vibration and even "walking" if the load is not properly distributed in the tub. The engineers therefore developed a special load-distribution and vibration-isolation system. The addition of a tuned absorber to the washer door created a simple spring-mass damper system tuned to go into resonance at 800 rpm, Erickson said. The spring mass moves with the washer but 180 degrees out of phase, thus absorbing energy.

In this system, the machine controller, which is mounted rigidly to the cabinet, communicates with the motor controller and the motor tachometer. As spin speed approaches 800 rpm, both the cabinet and the machine controller's circuit board start to shake from side to side. An accelerometer attached to the board also vibrates, creating an electrical signal proportional to vibrational ' amplitude. Once the motor is up to speed, the machine controller determines the rotation at which the accelerometer output is the lowest. The motor controller then sets the rotation to the speed at which the tuned absorber can cancel out the most vibration.

The engineers chose a switched-reluctance electric motor from St. Louis-based Emerson Electric to drive the Neptune's tub because they wanted a maintenancefree, low-noise, high-efficiency motor with infinitely variable-speed control. According to Erickson, the brushless motor was a first for the appliance industry.

Finally, because the average U.s. consumer uses too much detergent for a horizontal-axis machines, the prospect of excess sudsing was also a design issue. May tag Therengineers developed a electronic sensing system that de- tects and controls oversudsing.

In real-world tests, the Neptune washer showed water Kesselsavings of 38 percent and energy savings of 56 percent. The machine uses about 6 gallons of water in the wash cycle, which means a total water use of 25 gallons; a stan- enerdard vertical-axis washer uses enerdard vertical-axis washer uses highwash/ rinse cycle. The new ma chine was also shown to clean better than top loaders, particu lady tough stains such as grass, blood, and "ring around the collar." Despite the higher price tag of the new model-typical- mily at least twice the average $220 to $550 cost of top- loading U.S. machines-con apartsumers seem to be happy with the Neptune. Sales are going well, and May tag has reportedly increased production to meet demand.

Rather than agitating wash loads in a full tub of water like standard top loaders (top), the Neptune washer substitutes a clothes-dryer-like tumbling action that dunks fabrics in a smaller volume of water (bottom).

Grahic Jump LocationRather than agitating wash loads in a full tub of water like standard top loaders (top), the Neptune washer substitutes a clothes-dryer-like tumbling action that dunks fabrics in a smaller volume of water (bottom).

EPRI engineers are currently developing a countertop microwave dryer that is expected to dry small loads of clothing faster and more efficiently than conventional dryers.

Grahic Jump LocationEPRI engineers are currently developing a countertop microwave dryer that is expected to dry small loads of clothing faster and more efficiently than conventional dryers.

Appliance engineers are also working to reinvent the clothes dryer. EPRl researchers expect microwave clothes-drying technology to be as much as 65 percent faster than conventional dryers. Mter eight or nine years of R&D aimed at developing a full-size microwave dryer, EPR! is now pursuing a countertop version that should have broader market potential.

In a standard dryer, air is heated to approximately 350°F; the heat, once transferred to the surface of the wet clothing, then evaporates the water. The later stages of drying are particularly inefficient: Heat must penetrate the fabric's interior to vaporize moisture there, but the vapor escaping from the fabric cools the material, which must then be reheated to continue the process. Because of the need to heat the fabric, its surface gets as hot as 150°F, shrinking it and cutting service life.

Microwaves, however, can penetrate the surface of wet clothing and heat the water inside directly, so the fabric in a microwave dryer stays cooler-typically no hotter than 110°F to 115°E A flow of warm air passing through the dryer carries the evaporated moisture away. This drying process is both shorter and cooler, so it is gentler on clothing. The shrinkage of cottons is largely eliminated, and heat-sensitive (delicate) fabrics such as wool can be dried safely by microwaves.

EPRI's multiyear effort to develop a full-size microwave dryer culminated in the mid-1990s with the successful demonstration of several prototypes. Unfortunately, the two companies that had shown the most interest-Ther mo Energy Corp. and ASTeX/ Gerling Laboratorie decided against commercialization. EPRI "had difficulty in attracting manufacturers to commercialize it," Kessel ring said, because current technology can meet DOE energy-use standards for dryers relatively easily. Another hindrance was the fact that the technology to be used in ener gy-efficient dryers was not as well known as that in the highwash efficiency washers. "What was clear," he said, "was that first cost was going to be much higher than current machines."

In early 1997, EPRl researchers shifted their focus to developing a countertop or personal mily crowave dryer, which is expect- ed to have a much wider appeal than full-size units with apartsumers ment and dormitory residents as well as operators of upscale hotels and health clubs. The countertop model, which would be the size of a microwave oven, should be able to dry clothing more quickly. "It works just like a microwave oven," Kesselring said. "Drying speed and efficiency depend on the size of the load."

The long effort to develop full-size units has yielded other results as well. EPR! researchers have developed and tested a better hum..idity sensor that automatically shuts off the machine when the clothes are dry, so no timer is needed and no energy is wasted overdrying clothes. In addition, a rapid-response safety sensor "very quickly detects indications of excessive heating [such as] small amounts of gaseous by-products of combustion," Kesselring said, and automatically shuts the unit off if a foreign metal object threatens to scorch fabrics or start a fire.

The countertop dryer, like its oven counterpart, would supplement rath er than replace existing technology. Consumers could use it both for smaller loads needed in a hurry and for delicate materials that could be damaged by a conventional drye r. Furthermore, because eve rything in the countertop dryer except for the sensors and a rotating drum would be from components already in use, its development and production should be relatively swift and inexpensive. As a result, its anticipated retail price-about $150, roughly the same as a standard microwave oven-would be far lower than a $] ,000 full-size unit.

EPRl recently completed a market study (to be pub lished later this year) that showed a high level of consumer inferest in the new microwave product. The potential market in the United States is said to be some 100 million households, not including hotels, dorms, and other locations. EPRI has initiated design and is talking with potential manufacturers to have a prototype ready for testing by the end of this year.

Energy efficiency is not yet a big draw for the average consumer of washing machines and other appliances.

Refrigerators represent another type of device that can be significantly improved by making them more energyefficient. Engineers at the DOE's Oak Ridge National Laboratory in Oak Ridge, Tenn., have developed and demonstrated a "fridge of the future" that uses half as much as energy as today's refrigerator/ fi:eezers. Frigidaire Corp. in Dublin, Ohio, has signed a three-year agreement with the lab to develop a commercial version.

In the redesign effort, a popular size and style unitone with a 20-cubic-foot capacity and a top-mounted freezer-was altered to cut energy use by half, from 2 kilowatt-hours per day to 1. This reduction exceeds the decrease called for 'in a new federal rule, announced in April 1997, that requires refrigerators sold in 2001 to use 30 percent less electricity than those on the market today. The prototype unit is the result of a cooperative research and development agreement between Oak Ridge and the Appliance Research Consortium, a subsidiary of the Association of Home Appliance Manufacturers.

"Basically, we made a lot of incremental, cost-effective improvements that came together to produce really significant energy savings," said Ed Vineyard, a research engineer in Oak Ridge's Energy Division. Many of those alterations were intended to accommodate the change from the banned chlorofluorocarbon refrigerant R -12 to the more environmentally acceptable R-134a.

The first alteration was to in stall vacuum insulation panels, which operate like large flat thermos bottles, around the freezer com.partment to reduce heat gain. "Due to the high cost of vacuum insulation pan el, however, we used them only around the freezer," Vineyard said. The rest of the prototype refri gerato r is insulated with 1 inch of blown polyurethane foam, thickened to 2 inches in the doors. " I think vacuum panels may one day be cost-effective for refrigerators," he said. "Not only do they save energy but they also enable the designer to win valuable extra space inside the refrigerator."

The next step was to replace the three ac motors that drive two fans and a compressor with electrically commutated dc motors. "The lower-power motors use less electricity and release less heat that must be removed from the compartment," Vineyard said. The new design's variable-speed evaporator fan, for example, uses only 2 watts; previous models need 10 to 12 watts.

A reciprocating, variable-speed compressor that is about 10 percent more efficient than conventional types resolved several tough performance and reliability questions in finding a new compressor to work with R-134a, he said. The compressor, supplied by Americold Compressors in Cullman, Ala., features larger pistons to compensate for R-134a's somewhat lower heat capacity. In addition, it uses an ester-based oil instead of mineral-based oil.

Finally, the automatic defrost control, which removes ice from refrigerant coils daily to improve their heattransfer properties, was replaced with an adaptive or demand defrost function. The system relies on refrigerantcircuit sensors to ensure that defrosting occurs only when needed-perhaps every other day in the summer and once a week in the winter, depending on humidity and the number of times the door is opened. "A standard system defrosts every 10 hours of compressor run time," Vineyard said, or every 20 hours of real time. "We put a temperature sensor on the suction line. As frost builds up on the coils, the temperature of the suction line drops, which indicates it's time to defrost."

Vineyard said that the forthcoming commercial refrigerator model may modulate the compressor speed according to the demand for cooling. During mealtimes, for example, the compressor would run at high speed to meet the extra load create by frequent door openings. A low-speed, energy- saving mode would kick in at night and between meals.

He estimated that the prototype would cost about $106. more to buy than a similar conventional refrigerator but would save about $16 in electricity every year.

As with all the new designs for washing machines and dryers, widespread adoption of the more efficient refrigerator would mean significant energy savings. "Some 125 million refrigerators in the United States consume approximately 1.5 percent of the energy used in the country," Vineyard said. " If the energy used in units now in homes was reduced to 1 kilowatt-hour per day, refrigerators would consume only about on half of 1 percent of the nation's energy, saving almost $6.5 billion annually."

Countertop microwave dryers should have considerable appeal for residents of small apartments.

Oak Ridge researchers used Christmas tree lights as internal heat sources to test their prototype refrigerator for reverse heat loss.

Grahic Jump LocationOak Ridge researchers used Christmas tree lights as internal heat sources to test their prototype refrigerator for reverse heat loss.

Copyright © 1998 by ASME
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