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Abstract:
The second law of thermodynamics is a big hit with the beret-wearing college crowd because of its implicit existential crunch. The tendency of a closed systems to become increasingly disordered if no energy is added or removed is a popular, if not depressing, "things fall apart" sort-of-law that would seem to confirm the adolescent experience.

Tiny generators turn waste heat into power

Washington, DC | Posted on September 28th, 2010

Now a joint team of Ukrainian and American scientists has demanded more work and less poetry from the second law of thermodynamics, proposing a novel "pyroelectric" method to power tiny devices using waste heat.

Using tiny structures called ferroelectric nanowires, they can rapidly generate an electrical current in response to any change in the ambient temperature, harvesting otherwise wasted energy from thermal fluctuations. Their report appears in the Journal of Applied Physics, which is published by the American Institute of Physics.

Explains lead researcher Anna Morozovska of the National Academy of Sciences of Ukraine, "The second law of thermodynamics rules modern life: Through all kinds of industry, humans consistently produce an enormous amount of waste heat. However, the laws of thermodynamics do not exclude rescuing some of this energy by harvesting the thermal fluctuations to produce electricity."

Pyroelectrictricity can play key role in consumer electronics, says Morozovska, and recovering this heat in the form of pyroelectric energy may bring about a new era of "tiny energy." Pyroelectric nanogenerators could be extremely useful for powering specific tasks in biological applications, medicine and nanotechnology, particularly in space because they perform well in low temperatures.

In an investigation of the pyroelectric properties of ferroelectric nanowires, the team analyzed how the pyroelectric coefficient corresponds to the radius of the wire and its coupling. They found that the smaller the wire radius, the more the pyroelectric coefficient diverges until a critical radius at which the response changes to paraelectric (above the Curie temperature). This so-called "size effect" could be used to tune the phase transition temperatures in ferroelectric nanostructures, thus enabling a system with a large, tunable, pyroelectric response.

In theory, the use of rectifying contacts could enable the polarized ferroelectric nanowire to generate a giant, pyroelectric, direct current and voltage in response to temperature fluctuations that could be harvested and detected using a bolometric detector. Such a nanoscale device would not contain any moving parts and could be suitable for long-term operation in ambient applications such as in-vitro biological systems and outer space. The researchers calculate that these little nanogenerators would have very high efficiency at low temperatures, decreasing at warmer temperatures.

The article, "Pyroelectric response of ferroelectric nanowires: Size effect and electric energy harvesting" by Anna N. Morozovska, Eugene A. Eliseev, George S. Svechnikov, and Sergei V. Kalinin appears in the Journal of Applied Physics. jap.aip.org/resource/1/japiau/v108/i4/p042009_s1

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About American Institute of Physics
The American Institute of Physics is a federation of 10 physical science societies representing more than 135,000 scientists, engineers, and educators and is one of the world's largest publishers of scientific information in the physical sciences. Offering partnership solutions for scientific societies and for similar organizations in science and engineering, AIP is a leader in the field of electronic publishing of scholarly journals. AIP publishes 12 journals (some of which are the most highly cited in their respective fields), two magazines, including its flagship publication Physics Today; and the AIP Conference Proceedings series. Its online publishing platform Scitation hosts nearly two million articles from more than 185 scholarly journals and other publications of 28 learned society publishers.

About Journal of Applied Physics

Journal of Applied Physics is the American Institute of Physics' (AIP) archival journal for significant new results in applied physics; content is published online daily, collected into two online and printed issues per month (24 issues per year). The journal publishes articles that emphasize understanding of the physics underlying modern technology, but distinguished from technology on the one side and pure physics on the other. See: jap.aip.org/

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