Scientists convert processor heat back to electricity

Posted by Wolfgang Gruener

Chicago (IL) – Perhaps AMD and Intel should not have abandoned the Gigahertz-race and bunsen-burner processors after all: Scientists from the University of Utah today said that they can convert waste heat into sound and electricity.

There soon may be a rather unusual method to cool down your overclocked rig: Physicist Orest Symko and his research team at the University of Utah said they succeeded in building small devices that turn heat into sound and then into electricity. The findings, which are part of a 5-year, $2 million project to develop “tiny thermo-acoustic refrigerators”, will be presented at the annual meeting of the Acoustical Society of America this Friday.

According to Symko, most of the heat-to-electricity acoustic devices are housed in cylinder-shaped "resonators" that fit in the palm of a 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 injected, the heat builds to a threshold and moving air produces sound. The sound is then converted into electricity by using "piezoelectric" devices that are squeezed in response to pressure, including sound waves, and change that pressure into electrical current. Only about 20% of the sound energy is lost when pressure is converted to electricity, Symko said.

 

So, how efficient is the conversion of waste heat into electricity overall? Symko said that the efficiency depends on its application and temperature differences – the higher the difference between a source heat and the temperature within the cylinder, the greater the efficiency. He believes the technology can be about 20 – 25% efficient initially, with greater efficiencies to be reached down the road, depending on the application. However, he told TG Daily that the technology could enable solar cells, which are up to 40% efficient in high-end applications and typically reach efficiencies of less than 20% in mass market products, to bump efficiencies to more than 50%.

For microprocessors, the technology could be used as a supporting cooling technology: Ironically, the technology increases its efficiency with greater temperatures – the hotter a processor the more sense the energy conversion technology makes.    

An obvious concern of the technology would be noise: Symko said that the technology can produce very loud sounds “to impress people.” However, noise can be shielded and become a non-issue, he told us. The scientists are also working on ultrasonic devices that would eliminate any noise for the human ear.

Symko plans to test the devices within a year to produce electricity from waste heat at a military radar facility and at the university’s hot-water-generating plant. Within two years, the physicist believes that the devices could be used as an alternative to solar cells for converting sunlight into electricity and as a new way to generate electricity from heat that now is released from nuclear power plant cooling towers.

Of course, there cooling of server, desktop and laptop computers is another application for the technology: Symko told us that a thermo-acoustic cooling device for a computer could cost about $100 to $200, when it goes into production.