Tiny generators turn waste heat into power

September 28, 2010, American Institute of Physics

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.

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

Using called ferroelectric nanowires, they can rapidly generate an in response to any change in the , harvesting otherwise wasted energy from thermal fluctuations. Their report appears in the .

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 . 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.

Explore further: Startup to develop new solid-state technology at UCLA for use in medical imaging

More information: 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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not rated yet Sep 28, 2010
Is this a team partnered with those from this article below?

"Quantum physicists turn waste heat into power"

Have they discovered a different effect related to waste heat being converted to electricity, or is this based on the same principles?

I gather this could be useful in nano-robots as a primary or secondary power supply either in implants in people or as "maintenance robots" in spacecraft, which would be literally powered by the waste heat from the craft's primary systems.

If these are two unrelated effects then it appears they've just found a huge potential increase in efficiency.

If they are using the same principles then I guess it's two different ways to skin the same cat.
not rated yet Sep 30, 2010
I think the introduction of this news is somewhat exagerated.

The 2nd principle contains no poetry although many ones have interpreted it in different (questionable) ways.

Moreover in my opinion the article described here does not directly address the 2nd principle but rather the maximisation of the efficiency in electrically active closed systems.

Nice topic of research otherwise and it is useful that physorg advertises it.

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