Nanotube thermocells hold promise for converting heat waste to energy

ATLANTA, GEORGIA — A study published in the American Chemical Society's journal Nano Letters reveals that thermocells based on carbon nanotube electrodes might eventually be used for generating electrical energy from heat discarded by chemical plants, automobiles and solar cell farms.

The research was a joint collaboration between Baratunde Cola, assistant professor in the George W. Woodruff School of Mechanical Engineering at Georgia Tech, and an international team of researchers from the U.S., Australia, China, India and the Philippines.

Cola, director of Georgia Tech’s NanoEngineered Systems and Transport Research Group (NEST), described the study as a breakthrough in efficiently harvesting electrical energy from various sources of exhaust or wasted heat.

Efficiently harvesting the thermal energy currently wasted in industrial plants or along pipelines could also create local sources of clean energy that in turn could be used to lower costs and shrink an organization’s energy footprint.

The new thermocells use nanotube electrodes that provide a threefold increase in energy conversion efficiency over conventional electrodes.

One of the demonstrated thermocells looks just like the button cell batteries used in watches, calculators and other small electronics. One key difference, however, is that these new thermocells can continuously generate electricity, instead of running down like a battery. The research netted other thermocells, as well, including electrolyte-filled, textile-separated nanotube sheets that can be wrapped around pipes carrying hot waste streams from manufacturing or electrical power plants.  The temperature difference between the pipe and its surroundings produces an electrochemical potential difference between the carbon nanotube sheets, which thermocells utilize to generate electricity.

The research team estimates that multi-walled carbon nanotubes in large thermocells could eventually produce power at a cost of about $2.76 per watt from freely available waste energy, compared with a cost of $4.31 per watt for solar cells, which can only be used when the sun is shining. On a smaller scale, button cell-sized thermocells could be used to power sensors or electronic circuits.

The new thermocells take advantage of the exceptional electronic, mechanical, thermal and chemical properties of carbon nanotubes. The nanotubes’ giant surface area and unique electronic structure afforded by their small diameter and nearly one-dimensional structure offer high current densities, which enhance the output of electrical power and the efficiency of energy harvesting.

Adapted from Georgia Institute of Technology news release.

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