Wasted Energy: and Electricity:

Discussion in 'General Science & Technology' started by paddoboy, Feb 8, 2017.

  1. paddoboy Valued Senior Member

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    Material can turn sunlight, heat and movement into electricity—all at once
    February 7, 2017

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    Credit: Marina Shemesh/public domain
    Many forms of energy surround you: sunlight, the heat in your room and even your own movements. All that energy—normally wasted—can potentially help power your portable and wearable gadgets, from biometric sensors to smart watches. Now, researchers from the University of Oulu in Finland have found that a mineral with the perovskite crystal structure has the right properties to extract energy from multiple sources at the same time.

    Perovskites are a family of minerals, many of which have shown promise for harvesting one or two types of energy at a time—but not simultaneously. One family member may be good for solar cells, with the right properties for efficiently converting solar energy into electricity. Meanwhile, another is adept at harnessing energy from changes in temperature and pressure, which can arise from motion, making them so-called pyroelectric and piezoelectric materials, respectively.



    Read more at: https://phys.org/news/2017-02-material-sunlight-movement-electricityall.html#jCp
     
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  3. paddoboy Valued Senior Member

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    http://aip.scitation.org/doi/10.1063/1.4974735


    Ferroelectric, pyroelectric, and piezoelectric properties of a photovoltaic perovskite oxide


    ABSTRACT
    A perovskite solid-solution, (1-x)KNbO3-xBaNi1/2Nb1/2O3-δ (KBNNO), has been found to exhibit tunable bandgaps in the visible light energy range, making it suitable for light absorption and conversion applications, e.g., solar energy harvesting and light sensing. Such a common ABO3–type perovskite structure, most widely used for ferroelectrics and piezoelectrics, enables the same solid-solution material to be used for the simultaneous harvesting or sensing of solar, kinetic, and thermal energies. In this letter, the ferroelectric, pyroelectric, and piezoelectric properties of KBNNO with x = 0.1 have been reported above room temperature. The investigation has also identified the optimal bandgap for visible light absorption. The stoichiometric composition and also a composition with potassium deficiency have been investigated, where the latter has shown more balanced properties. As a result, a remanent polarization of 3.4 μC/cm2, a pyroelectric coefficient of 26 μC/m2 K, piezoelectric coefficients d33 ≈ 23 pC/N and g33 ≈ 4.1 × 10−3 Vm/N, and a direct bandgap of 1.48 eV have been measured for the KBNNO ceramics. These results are considered to be a significant improvement compared to those of other compositions (e.g., ZnO and AlN), which could be used for the same applications. The results pave the way for the development of hybrid energy harvesters/sensors, which can convert multiple energy sources into electrical energy simultaneously in the same material.
     
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  5. Q-reeus Valued Senior Member

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    Right before donning a wired-up-everywhere energy harvesting suit & shoes groovy combo, a disturbing thought flashes - "Jack of all trades, and master of none."
    But who knows - they laughed at the notion of millions of commuters jet-packing to and from work. Some folks just have no vision. But they get left in the dust.
     
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  7. exchemist Valued Senior Member

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    Interesting. However I confess to some scepticism about the claim to produce electricity from heat. As I understand it, pyroelectricity, which the reported material exhibits, results from a change in the degree of polarisation (partial charge separation) of the crystal with change in temperature. So you only get tiny amounts of change in electric charge (corresponding to an even tinier current over time) when the temperature changes, as the crystal absorbs or emits heat. I have great difficulty seeing this as a source of useful electric current. The rate of doing work seems far too low.

    The other modes of generation look more helpful, as it is easier - to my mind at least - to envisage some kind of constant motion or exposure to light that would produce a continuous current.
     
  8. Q-reeus Valued Senior Member

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    Indeed. A thing called Carnot Cycle, coupled to very modest delta T. But honestly, this smacks of 5-mnute wonder gimmickery for film stars to flash at a party. Wearable energy harvesting devices must somehow reliably and repeatedly electrically connect to whatever - watch, mobile phone. And also disconnect. Easily and conveniently both ways. And being K based Perovskites, questions over all-weather & wash'n'wear durability comes to mind. Best of luck to the team.
     
  9. exchemist Valued Senior Member

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    Yes, I didn't know anything about pyro-electricity until now, but the descriptions seem to focus more on the voltage produced as a function of temperature rather than any current, perhaps for obvious reasons!

    Efficiency will be abysmal, certainly. One has the image of a person jumping in and out of a centrally heated house in winter for several hours just to charge his watch battery.

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  10. Q-reeus Valued Senior Member

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    Brilliantly spotted! Of course! It's really part of a very clever government agenda to fight the obesity epidemic. No-one likes exercise as a drudgery chore, but make them think they are cutting-edge tech savvy while also helping to 'save energy' and defeat global warming. While actually getting fit and healthy, thus staving off the nightmare projections of uncontrollable medical bills as the young-to-middle-aged obese become the aging obese clogging up hospital wards etc.

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  11. paddoboy Valued Senior Member

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    In essence, another one of these science possibilities where the possible benefits demand further research.
     

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