In the pictures,University of Utah physicist Orest Symko demonstrates how heat can be converted into sound by using a blowtorch to heat a metallic screen inside a plastic tube, which then produces a loud tone, similar to when air is blown into a flute. Symko and his students are developing much smaller devices that not only convert heat to sound, but then use the sound to generate electricity. The devices may be used to cool electronics, harness solar energy in a new way, and conserve energy by changing waste heat into electric power.
As on June 4 2007,Symko expected the devices could be used within two years as an alternative to photovoltaic cells for converting sunlight into electricity. The heat engines also could be used to cool laptop and other computers that generate more heat as their electronics grow more complex. And Symko foresees using the devices to generate electricity from heat that now is released from nuclear power plant cooling towers.
Using sound to convert heat into electricity has two key steps. Symko and colleagues developed various new heat engines (technically called "thermoacoustic prime movers") to accomplish the first step: convert heat into sound.
Then they convert the sound into electricity using existing technology: "piezoelectric" devices that are squeezed in response to pressure, including sound waves, and change that pressure into electrical current.
Most of the heat-to-electricity acoustic devices built in Symko's laboratory are housed in cylinder-shaped "resonators" that fit in the palm of hand. Each cylinder, or resonator, contains a "stack" of material with a large surface area -- such as metal or plastic plates, or fibers made of glass, cotton or steel wool -- placed between a cold heat exchanger and a hot heat exchanger.
When heat is applied -- with matches, a blowtorch or a heating element -- the heat builds to a threshold. Then the hot, moving air produces sound at a single frequency, similar to air blown into a flute.Longer resonator cylinders produce lower tones, while shorter tubes produce higher-pitched tones.
The advantages of the Devices are they convert heat to sound and then to electricity and lack moving parts, so such devices will require little maintenance and last a long time. They do not need to be built as precisely as, say, pistons in an engine, which loses efficiency as the pistons wear.
The devices won't create noise pollution. First, as smaller devices are developed, they will convert heat to ultrasonic frequencies people cannot hear. Second, sound volume goes down as it is converted to electricity. Finally, it's easy to contain the noise by putting a sound absorber around the device.
Nowadays,studies are going on to improve the efficiency of acoustic conversion of heat to sound.One of the student built the device 1.5 inches long and half inch wide and worked to improve amount of heat converted to sound rather than escaping.It is also seen that by increasing air pressure, a smaller temperature difference between heat exchangers is needed for heat to begin converting into sound.Also work is being done to mount the devices together to form an array which must be "coupled" to produce the same frequency of sound and vibrate in sync.
Various metals were used to build supports to hold 5 of the devices at once.It was found that the devices could be synchronized if a support was made of a less dense metal such as aluminum and, more important, if the ratio of the support's weight to the array's total weight fell within a specific range. The devices could be synchronized even better if they were "coupled" when their sound waves interacted in an air cavity in the support.
It was also found that a resonator would be more efficient than a cylider because in a resonator sound waves keep circling through the device with nothing to reflect them.while in cylider shaped sound waves bounce against the ends of the cylinder.
Likewise many experiment are being done with the device to make it usable and worth of the $2million which had been spent on it!!!
