The company has even gone one step further with its HyCool product, which uses the enhanced thermoelectric cooling with R-410a refrigerant. At press time, the refrigerator was scheduled to be previewed at the 2009 Housewares Show in March.

Both NuCool and HyCool still have the size limitations of traditional thermoelectric cooling systems, but Haier is working toward bigger goals. "NuCool at this moment is available in 1.7 cu ft and 2.8 cu ft, with plans to develop a 3.2 cu ft model in the near future," Hedaya tells APPLIANCE. "We believe larger than that will not be efficient enough. In that regard, we are working with researchers on more eco friendly coolants for larger capacity refrigerators."

Another advancement coming in a small package is a mini refrigeration compressor from Aspen Compressor, LLC (Marlborough, MA, U.S.; www.aspencompressor.com). Based on a technology used to cool military personnel and electronics, the component is said to produce as much cooling capacity as many reciprocating compressors that have 10 times its weight and volume. And unlike the AC-powered reciprocating compressors used in many refrigerated appliances, the mini compressor evolved from a rotary design containing a DC motor.

The unit's overall volume of 12 in3 and weight of 1.3 pounds makes it the smallest and lightest refrigeration compressor commercially produced today, according to S. Ronald Wysk, Aspen's vice president of business development. "For downsizing to such physical dimensions, our design team concluded that a rotary compressor had better scalability than other types," he says.

According to Wysk, rotaries are able to operate at higher speeds than reciprocating compressors due to a less complex valve mechanism. "At the time this development effort began, the smallest rotary compressor in production had a displacement of 7.0 cc, a factor of 5 times the displacement of our baseline compressor (1.4 cc). This represented a significant leap due to the much smaller machined parts and the high-precision requirements of the manufacturing process,” he explains.

The unit's brushless DC motor and sensorless drive also help keep size down. "To produce the same amount of torque, an equivalent AC motor would have to be considerably larger," Wysk explains. "The volume of gas compressed at 7,000 RPM is about twice the quantity of that using a 3,500 RPM AC motor. In a sense, this compressor can be compared in its own context to that of a Formula One race car—it’s very light, quite small, and very powerful."

According to Wysk, the major challenge in designing the compressor was the "unprecedented" small size of the pump assembly parts that had to be manufactured with very tight tolerances to ensure optimum performance. "The compressor lubrication system also had to be proven in order to assure long-term reliability," Wysk adds. "To address these issues and produce a reliable compressor cost-effectively, our engineers conceived and developed a proprietary manufacturing process with precision high speed machining and assembly equipment."

Applications for the mini compressor include countertop appliances used in kitchens and laboratories, as well as portable and compact refrigerators used in mobile applications. The component can be used with a range of refrigerants and with low, medium, and high backpressure conditions. "The characteristics of rotary compressors are such that they are more tolerant to high return gas temperatures and pressures," Wysk says. "The mini compressor was originally designed for operation on R-134a, but has also been used with low temperature refrigerants including R-404a, R-507a, and R-508a. It has also been successfully incorporated in a two-stage system, where it has achieved evaporator temperatures down to minus 100ºC."