Scientists at Oak Ridge National Laboratory, working in conjunction with the U.S. Department of Energy and General Electric, have built a prototype ultrasonic clothes dryer that does not use heat. The dryer uses piezoelectric transducers to generate high-frequency vibration that mechanically extracts moisture from wet fabric.
The research group began work on the technology in October 2014 in response to the DOE's call for a new clothes dryer technology that could increase the energy factor from 3.7 to 5.43 lb/kWh without significantly increasing the dry time. The group set an early proof of concept goal of drying a fabric sample less than 4 square inches in less than 20 minutes. Testing showed that their mechanical design could dry a 14 square inch sample in around 7.5 minutes, exceeding the goal.
The research group projects that the new dryer can dry a medium load of laundry in about 20 minutes, less than half the average time it would take a heat-based machine. The new technology produces less lint than a conventional dryer because lint is created when hot air blows small bits of fiber off of clothing during the dry cycle. The absence of heat also eliminates overdrying and ensures that clothes run through the dryer will better retain their shape and color after many dry cycles.
Most significantly, ultrasonic drying saves energy over conventional heat drying through shorter dry times and lack of heating. The research group tested a fabric sample using ultrasonic cold drying and thermal drying at four different temperatures, including room temperature. As shown in the above graph, the ultrasonic-dried sample dried in only 14 seconds, as compared to nearly 500 seconds at 80 degrees Celsius. This represents two orders of magnitude in dry time improvement.
According to the DOE, 1% of U.S. energy—between $7.5 and $9 billion annually—is spent on drying clothes. Ultrasonic drying won't hit the commercial market for several years, but its effect on drying energy, time and quality could be significant.