Green Appliances Come in Several Shades
May 31, 2007
Responding to legislative pressure and soaring energy costs, manufacturers of large household appliances are developing more energy-efficient products.
Responding to legislative pressure, environmental initiatives, soaring energy costs and increasing consumer demand, manufacturers of air conditioners, dishwashers, refrigerators, washing machines, water heaters and other large household appliances are developing more energy-efficient products. The goal is to reduce excess electricity, gas and water consumption.
The U.S. Department of Energy (DOE, Washington, DC) claims that refrigerators alone account for 12 percent of residential energy use. That’s because it’s an appliance that is constantly running. The DOE is authorized to enact energy efficiency rules for a broad range of appliances. However, it is way behind in updating old ones and enacting new ones.
Despite recent hype, green appliances are not a new concept. Indeed, engineers at Oak Ridge National Laboratory (Oak Ridge, TN) have conducted extensive research on the subject over the last few decades. As a result, it costs less to own and operate most appliances today vs. 35 years ago. One major innovation-an improved refrigerator-freezer compressor-saved consumers more than $6 billion in energy costs between 1980 and 1990.
Appliance manufacturers have offered energy-efficient models for many years. “It’s a subject that’s been getting a lot more voice now, but we’ve been involved with this issue since the early 1970s,” notes J.B. Hoyt, director of regulatory affairs at Whirlpool Corp. (Benton Harbor, MI). “Energy efficiency standards have existed in the appliance industry since the late 1970s. As a result, today’s refrigerators use one-quarter of the amount of energy that they did 30 years ago.”
Whirlpool claims that annual average kilowatt-hour usage of its refrigerators dropped 74 percent between 1972 and 2007. General Electric Co. (Fairfield, CT) claims that its latest generation of refrigerators use 40 percent less energy than conventional models sold in 2001, and 50 percent less than models manufactured before 1993. Manufacturers have also dramatically improved the efficiency of washing machines, cutting energy use by as much as 70 percent.
“Appliance standards rank with automobile fuel economy standards as the two most effective federal energy-saving policies,” says William Prindle, acting executive director of the American Council for an Energy-Efficient Economy (Washington, DC). “As old appliances wear out and are replaced, savings from existing standards will steadily grow.”
For instance, in January 2006, a new mandatory rating for central home air conditioners went into effect, resulting in a 30 percent jump in efficiency. By 2010, Prindle predicts savings will total more than 250 billion kilowatt hours, or 6.5 percent of projected electricity use.
Why Go Green?“Energy efficiency is a form of product differentiation,” explains Mike Deneen, appliance industry analyst at the Freedonia Group Inc. (Cleveland). “It helps drive replacement demand in the marketplace. But, it’s certainly not a fad. The shift toward green products is here to stay, and demand will continue to grow in the future.”
Ken Monnier, vice president of engineering at Emerson Climate Technologies (Sidney, OH) says energy efficiency is one of the major components of the global warming reduction programs currently underway in many parts of the world. “With electric generation for residential and commercial applications representing over a third of the CO2 emissions in the United States, lowering the amount of electricity used in any appliance is very important,” he points out.
“Legislation being written in many states, and federal programs like Energy Star, all help to promote energy efficiency and provide incentives to homeowners to buy the most energy-efficient products,” says Monnier. “Supporting these efforts makes good environmental sense and good business sense.”
That sentiment was reflected in a recent nationwide survey conducted by the Copper Development Association Inc. (CDA, New York). Participants were asked about their knowledge of energy issues and what determined their choices of home appliances. They ranked several factors that impacted their purchasing decisions, such as fuel choice (electricity vs. natural gas), price, energy efficiency, brand name, product features, availability and appearance.
“In all regions, energy efficiency replaced price as the key determinant in making an appliance purchase,” says Dr. John Cowie, vice president of strip, sheet and plate products and project manager of the association’s copper motor rotor program. “A majority of U.S. households now assert that they will make an extra effort to buy energy-efficient appliances in the future.”
According to the survey, 75 percent of respondents said energy efficiency was a very important factor in their purchase of appliances during the past year. And, 84 percent claim that energy efficiency will be a “very important consideration” in making future purchasing decisions.
The study discovered that 25 percent of the respondents would be willing to pay 15 percent to 25 percent more for higher-efficiency appliances. Many respondents also reported seeing energy efficiency-related advertising.
“The reasons for this heightened awareness of energy efficiency could certainly be credited to current factors, including unstable energy prices and a struggling U.S. economy,” says Cowie.
According to Richard Babyak, editor of Appliance Design magazine, a sister publication of ASSEMBLY, green appliances come in many different shades. “I am generally wary of using the term ‘green,’ due to its vagueness,” notes Babyak. “Green can refer to energy efficiency in electrical consumption, energy efficiency in gas consumption, water conservation in wet appliances, use of recyclable materials, or use of refrigerants and blowing agents [with low global warming potential]. So, it is possible for an appliance to be green in one aspect, and distinctly non-green in another aspect.
“And, when talking about recycling, there is also a difference between potentially recyclable and actually being recycled,” adds Babyak. “For example, many plastic parts, like a polypropylene dryer drum, are technically recyclable. In actual practice, they typically aren’t. Most scrap dealers simply shred an appliance, use magnets to get the steel, and the plastic goes into landfill as fluff.”
Nevertheless, the U.S. appliance industry touts more environmentally friendly options and features than ever. Appliance manufacturers have been spending millions of dollars on new components that reduce electricity, gas and water consumption. For instance, GE has invested more than $400 million in R&D for energy-efficiency components during the last 5 years.
“In 2006 alone, we invested $55 million in [energy-efficient] appliances to create 309 new models,” claims James Campbell, president and CEO of GE Consumer & Industrial (Louisville, KY). “That’s a 31 percent increase over 2005.” The company says 50 percent of its product lineup can be classified as highly efficient appliances.
Whirlpool claims that it has invested approximately $500 million in North America alone to design and manufacture energy- and water-efficient products in the past 5 years. The company offers nearly 600 energy-efficient appliances.
“Appliance manufacturers are trying to satisfy both government mandates, as well as consumer desires for energy-efficient product,” notes James Rutz, director of marketing at Tecumseh Compressor Group (Tecumseh, MI). “The old saying is still true: ‘The total is greater than the sum of the parts.’ To achieve efficient finished goods, manufacturers need intelligently designed components that work well together to produce an efficient end product.” In addition to compressors, those components include motors, pumps, sensors, switches and digital controls.
Federal RegulationsThe green movement in the U.S. appliance industry began with federal regulations, such as a government initiative called Energy Star. It is a voluntary, market-based program that has existed since 1992. Energy Star is jointly administered by DOE and the U.S. Environmental Protection Agency (Washington, DC). Products that meet certain requirements in categories such as air conditioners, dishwashers, furnaces, refrigerators and washing machines are allowed to display a blue-and-white star logo.
However, the program has been controversial. For instance, appliance manufacturers conduct their own tests and submit the results. In addition, only the top 25 percent of products in each category were originally supposed to receive the Energy Star label. Last year, more than 80 percent of all dishwashers were awarded the designation.
Several recent developments are expected to further stimulate interest in green appliances. The European Committee of Manufacturers of Domestic Equipment (CECED, Brussels, Belgium) has called for a worldwide approach to energy efficiency. It wants legislative measures enacted to ensure energy performance standards as an alternative to the continuous updating of voluntary agreements that the industry introduced in Europe a decade ago.
According to CECED president, Magnus Yngen, patchy government enforcement of the European Union’s energy labeling scheme has undermined the appliance industry’s ability to reach the next phase of voluntary measures. “Too many governments are not stopping careless or unscrupulous operators from marketing products that claim better energy efficiency than they actually deliver,” warns Yngen, who also serves as head of major appliances in Europe for AB Electrolux (Stockholm).
The CECED is launching a market testing program using independent laboratories to check products sampled from the market against the performance claims stated on their labels. Results will be made public later this year.
Last month, the Association of Home Appliance Manufacturers (AHAM, Washington, DC) announced that its members will establish new mandatory federal energy efficiency standards, including new Energy Star thresholds. Manufacturers will receive tax credits for the production of super-efficient products that dramatically increase efficiency levels. It includes first-ever national minimum water efficiency standards for clothes washers and dishwashers.
“The accord represents a landmark consensus agreement between industry and energy and water advocates to increase the energy and water efficiency of many home appliance products,” says Joseph McGuire, AHAM president.
How to Go GreenGoing green affects the way that appliances are designed and assembled. For instance, engineers rely on a wide variety of sensors, switches and digital controls to measure and monitor energy consumption. Those extra components make assembly more complex.
“Front-load washers are a good example,” says Whirlpool’s Hoyt. “They use variable-speed motors, which require sophisticated electronics to manage and monitor functionality.”
How products are made more energy efficient often relates to the specific appliance. “For example, rating the energy efficiency of a washing machine is a complex formula,” explains Babyak. “There is the direct electrical consumption of its motor. There is the indirect energy consumption of hot water, where the energy is actually expended in the home’s water heater, and the indirect consumption of energy by the clothes dryer, which is affected by how much water is spun out of the clothes during the washer’s spin cycle. Bumping up the spin speed in a washer therefore reduces energy consumption in the dryer.
“On the water side, a front-load washer typically uses a third of the water of a conventional top-load washer,” adds Babyak. “But, since so many people love their top loaders, both Whirlpool and GE came out with low water usage top loaders that don’t fill up the tub like conventional top loaders. Both their designs eliminate the traditional agitator and require novel approaches to moving clothes around.”
In a refrigerator or air conditioning unit, there are different paths to improving energy efficiency, each with its pluses and minuses. “In a fridge, you can use a more efficient compressor and motor, a better heat exchanger, or thicker or better insulation, and adaptive defrost controls,” Babyak points out. “There are tradeoffs with each. A better motor is higher cost. Thicker insulation reduces interior space.”
Air conditioning presents similar challenges to engineers. “You can go with a variable-capacity compressor, a more efficient motor, or bigger and better heat exchangers,” says Babyak. “Again, each has its tradeoffs in cost and system design.”
Another aspect to energy efficiency is the concept of standby energy, which is the amount of energy consumed by an appliance when not performing its main function, such as the clock on an oven.
“Standby energy is decreased by designing more efficient power supplies and more efficient charging circuits,” explains Babyak. “This usually means different and more costly types of semiconductor devices on the circuit board.”
Challenges and OpportunitiesAppliance manufacturers and suppliers have been focusing their efforts on electric motors, because many products use motors to control fans, compressors, pumps and other items. However, motors have a notorious thirst for electricity. In fact, the DOE reports that 60 percent to 65 percent of the total energy produced in the United States is consumed by electric motors.
“Traditionally, the electric motors used in domestic appliances have been induction machines, operating at fixed speed and relying upon relatively unsophisticated and inefficient regulation techniques, such as mechanical gearboxes or duty cycling,” notes Graham Robertson, vice president of global marketing at International Rectifier Corp. (El Segundo, CA). “Replacing these motors with variable speed, permanent magnet alternatives could cut wasted energy by as much as 50 percent.”
In addition to reducing energy consumption, the lower losses and higher torque per amp associated with permanent magnet motor technology allows engineers to specify a smaller and lighter motor to maintain the target temperature in a refrigerator or air conditioning application, for example.
“This not only saves space and weight, but also allows a lower cost motor and eases mechanical design,” Robertson points out. “Permanent magnet motors, which are the technology of choice for most variable-speed appliance applications, also tend to incorporate smaller quantities of expensive raw materials, such as steel, compared to induction motors.
“Variable-speed motor operation also leads to greater reliability and longevity, as well as reduced acoustic noise,” adds Robertson. “Overall, the promise of a lower purchase price and lower running costs should make variable-speed domestic appliances attractive to the buying public.”
“Energy efficiency is interesting for big motors, where you can save real money if you use less electrical power,” adds Dr. Urs Kafader, chief technical engineer at Maxon Motor (Sachseln, Switzerland). “Generally, the bigger the motor, the higher the relative losses and the lower the efficiency.”
Kafader says high efficiency is obtained by careful design of the motor parts that cause losses, such as brush commutation, bearings and laminated iron stack. “High-efficiency motors use parts with lower tolerance levels,” he points out. “This usually increases costs.”
Several different motor technologies can improve energy efficiency in appliance applications. “Both DC and brushless DC (BLDC) motors are interesting,” says Kafader. “It depends on the application and the requirements.”
Traditional DC motors “have limited life, but for many applications, it is sufficient by far,” explains Kafader. “They are also simpler to control. Brushless DC motors have longer life, less early failures and can run at very high speeds. However, they need electronic commutation and control is more complex.”
Besides the motor itself, energy can be saved by a high efficiency design of the drive screws and gearing. “This is usually where you lose most of the power,” notes Kafader.
Electric motor manufacturers are experimenting with different materials, such as substituting copper parts with aluminum or plastic components. “Copper is very expensive, so everyone’s looking at alternatives, such as aluminum,” says Jack Huether, senior vice president of marketing and sales at Emerson Appliance Solutions (St. Louis). “But, there are performance and cost tradeoffs. For instance, while aluminum is less expensive, it doesn’t transfer electricity as well.”
According to International Rectifier’s Robertson, permanent magnet synchronous motors (PMSM) are becoming the preferred solution over traditional three-phase induction motors. “A PMSM motor is more efficient than an induction motor and uses less steel and copper than an induction motor of the same power rating,” he explains. “In the past few years, the cost of magnetic materials has dropped. Therefore, the PMSM is not only more efficient, but less expensive than the induction motor.”
Robertson claims that air conditioning manufacturers in Japan already using permanent magnet motors expect a gain of up to 2 percentage points in efficiency, which will reduce energy losses by about 20 percent. Air conditioning manufacturers in China that are switching from fixed-speed induction motors to variable-speed PMSMs in the compressor expect to gain up to 40 percent in seasonal efficiency.
While delivering greater energy efficiency, permanent magnet variable-speed motor drive systems use three Hall-Effect sensors to detect the absolute rotor angle position. “Although eliminating the position and speed sensors is desirable, it has not previously been possible to implement a sensorless algorithm into existing microcontrollers,” says Robertson. “Historically, designing a sensorless PMSM controller has been a challenge.
“The most straightforward method measures the motor-winding currents and derives estimates of the rotor’s position and speed,” explains Robertson. “Direct measurements of motor-phase currents are expensive to implement and, in general, aren’t economical for many commercial appliance applications.”
Cost-effective sensorless designs make position and speed calculations based on an indirect current measurement. The controller computes the motor-winding currents from this indirect measurement and derives the rotor speed and torque from the winding-current calculations.
“Though practical in terms of implementation, sensorless controllers until recently have required the design team to combine pumping-systems knowledge, control algorithms expertise, and advanced programming abilities,” claims Robertson. “The latter are often unavailable in-house. Even when the requisite system-development skill set exists in-house, writing and testing the complex code can increase design risk, cost and cycle time.”
Robertson says the need to quickly and cost-effectively build control systems for PMSMs has created a demand for dedicated integrated circuits that can implement sensorless control. Semiconductor manufacturers such as International Rectifier have developed motor-control platforms comprising building blocks that appliance manufacturers can quickly bring together to create a finished variable-speed, sensorless drive design. “Platforms such as these accelerate the design process, cut component count, reduce risk and lower project costs,” notes Robertson.
Compressed Energy Plays a Key RoleIn addition to electric motors, compressors play a key role in energy-efficient appliances, especially air conditioners and refrigerators. “Energy-efficient compressors create a number of benefits for homeowners, such as energy savings and reduced condensing unit size,” says Emerson Climate Technologies’ Monnier. “Reduced energy savings can be achieved by increasing the efficiency of the compressor and by enabling the compressor to internally match the demand for air conditioning in the home throughout the seasons and over a wide range of operating conditions.
“Energy-efficient compressors take advantage of three factors to increase performance,” explains Monnier. “They utilize the most efficient motors to drive the compression mechanism; they are designed precisely to match the conditions for each application; and they compress gas using the most efficient method possible.”
However, achieving mechanical efficiencies in compressors and motors, such as minimizing re-expansion volume and frictional losses, “typically requires more sophisticated manufacturing capability,” notes Tecumseh’s Rutz. He says engineers must be aware that there are trade-offs when creating more energy-efficient appliance components.
“Often, ‘more efficient’ equates to more material in the motor and more expensive manufacturing processes,” claims Rutz. “At the same time, increased efficiency is often achieved by reducing the weight of moving parts, which in turn can reduce robustness.”
There are two ways to improve the efficiency of compressors. One approach involves reducing the amount of refrigerant that undergoes compression, which reduces load on the motor. Another alternative is to harness variable-speed motor technology. This saves energy by allowing engineers to achieve a better match of cooling load to energy consumed. But, it also increases complexity.
According to Monnier, the most efficient method available to compress gas today for air conditioning applications is with a scroll compressor. It uses two similar spiral compression elements to compress gas. One scroll is fixed to the compressor body. The other is driven by the motor and drive shaft, creating multiple pockets of gas and different pressures that gradually build to the optimal pressure level before being discharged into the system.
Single-speed motors are simple, reliable and inexpensive compared to variable-speed motors. However, variable-speed devices can save 20 percent or more in energy consumption; but they require sophisticated electronics that are expensive to design and produce, and add to assembly complexity.
“The assembly process differs when we move into direct current variable speed,” adds Rutz. “In these applications, there are special materials that require great care in handling and there is speed-sensing technology that must be incorporated into the product.
“Direct current, variable-speed motors operate quite differently than synchronous-speed alternating current motors,” Rutz points out. “Not only does speed need to be controlled, but also direction of rotation. At each start up, it is necessary to ascertain rotor positioning. All of this requires various sensors and intelligent electronics, some of which is packaged internal to the compressor.”