17-06-2013, 04:51 PM
NANOGENERATOR
[attachment=55580]
ABSTRACT
Nanofiber-based piezoelectric energy generators could be scalable power sources applicable in various electrical devices and systems by scavenging mechanical energy from the environment. This review article highlights recent advances in nanofiber nanogenerators, discusses their operation principles and addresses performance issues including energy conversion efficiencies and possible false artifacts during experimental characterizations. Piezoelectric nanogenerators made of PVDF (polyvinylidene fluoride) or PZT (lead zirconate titanate) and fabricated by means of electrospinning processes such as conventional, modified or near-field electrospinning (NFES) are the key focuses of this paper. Material and structural analyses on fabricated nanofibers using tools such as XRD (X-ray diffraction), FTIR (Fourier transform infrared), SHG (second harmonic generation), PFM (piezoresponse force microscopy) and Raman spectroscopy toward the fundamental characterizations of piezoelectric nanofibers are also described. We summarize the report by highlighting recent nanogenerator developments and future prospects including high power nanogenerators, energy storage/regulation systems and fundamentals on piezoelectricity.
Introduction:
Nanogenerator is an energy harvesting device converting the external kinetic energy into an electrical energy based on the energy conversion by nano-structured piezoelectric material. Although its definition may include any types of energy harvesting devices with nano-structure converting the various types of the ambient energy (e.g. solar power and thermal energy), it is used in most of times to specifically indicate the kinetic energy harvesting devices utilizing nano-scaled piezoelectric material after its first introduction in 2006.
Although still in the early stage of the development, it has been regarded as a potential breakthrough toward the further miniaturization of the conventional energy harvester, possibly leading the facile integration with the other types of energy harvester converting the different types of energy and the independent operation of mobile electronic devices with the reduced concerns for the energy source, consequently.
Geometrical Configuration:
Depending on the configuration of piezoelectric nanostructure, the most of the nanogenerator can be categorized into 3 types: VING, LING and "NEG". Still, there is a configuration that do not fall into the aforementioned categories, as stated in other type.
Other type:
The fabric-like geometrical configuration has been suggested by Professor Zhong Lin Wang in 2008. The piezoelectric nanowire is grown vertically on the two microfibers in its radial direction, and they are twined to form a nanogenerator.One of the microfibers is coated with the metal to form a schottky contact, serving as the counter electrode of VINGs. As the movable microfiber is stretched, the deformation of the nanostructure occurs on the stationary microfiber, resulting in the voltage generation. Its working principle is identical to VINGs with partial mechanical contact, thus generating DC electrical signal.
Applications:
Nanogenerator is expected to be applied for various applications where the periodic kinetic energy exists, such as wind and ocean waves in a large scale to the muscle movement by the beat of a heart or inhalation of lung in a small scale. The further feasible applications are as follows.
HOW IT WORKS:
A key innovation that led to the nano wire generator is a new electrode design. Fabrication begins with growing an array of vertically-aligned nanowires approximately half a micron apart on gallium arsenide, sapphire or flexible polymer substrate.
Zinc oxide nanowires grown on a gallium nitride substrate.A layer of zinc oxide is grown on top of the substrate to collect the current. Also fabricated is a‘zigzag’ silicon electrode that contains thousands of nano-scale tips made conductive by a platinum coating. The electrode is then lowered on top of the nano wire array, leaving just enough space so that a significant number of the nano wires are free to flex with in the gaps created by the tips.Moved by mechanical energy such as waves or vibration, the nanowires periodically contact the tips, transferring there electrical charges. To vibrate the electrode, the researchers packaged the device, put it in water and exposed to the ultrasonic waves. As the zigzag electrode moves up and down, its peaks push and bend the nano wires, which generate electric current that the electrode collects simultaneously.
Compressing the wires or vibrating them left or right makes all the current add up in the same direction. By capturing the tiny amounts of current produced by hundreds of nano wires kept in motion, the generator outputs a direct current in the nanoampere range.
Before that happens, additional development will be needed to optimize current production. For instance, though nanowires in the arrays can be grown to approximately the same length — about one micron – there is some variation. Wires that are too short cannot touch the electrode to produce current, while wires that are too long cannot flex to produce electrical charge.
Conclusion:
• Researchers expect that with optimization, the nano generator could produce as much as 4 watts per cubic centimeter based on a calculation for a single nano wire.
• One day by placing these into people's shoes we can generate electricity when walking.
• Powering the simple electronic devices.
• The principle and nanogenerator demonstration could be the basis for new self powered nano devices that can harvest electricity from environment for application such as implantable bio-medical devices, wireless sensors, and portable electronics.
[attachment=55580]
ABSTRACT
Nanofiber-based piezoelectric energy generators could be scalable power sources applicable in various electrical devices and systems by scavenging mechanical energy from the environment. This review article highlights recent advances in nanofiber nanogenerators, discusses their operation principles and addresses performance issues including energy conversion efficiencies and possible false artifacts during experimental characterizations. Piezoelectric nanogenerators made of PVDF (polyvinylidene fluoride) or PZT (lead zirconate titanate) and fabricated by means of electrospinning processes such as conventional, modified or near-field electrospinning (NFES) are the key focuses of this paper. Material and structural analyses on fabricated nanofibers using tools such as XRD (X-ray diffraction), FTIR (Fourier transform infrared), SHG (second harmonic generation), PFM (piezoresponse force microscopy) and Raman spectroscopy toward the fundamental characterizations of piezoelectric nanofibers are also described. We summarize the report by highlighting recent nanogenerator developments and future prospects including high power nanogenerators, energy storage/regulation systems and fundamentals on piezoelectricity.
Introduction:
Nanogenerator is an energy harvesting device converting the external kinetic energy into an electrical energy based on the energy conversion by nano-structured piezoelectric material. Although its definition may include any types of energy harvesting devices with nano-structure converting the various types of the ambient energy (e.g. solar power and thermal energy), it is used in most of times to specifically indicate the kinetic energy harvesting devices utilizing nano-scaled piezoelectric material after its first introduction in 2006.
Although still in the early stage of the development, it has been regarded as a potential breakthrough toward the further miniaturization of the conventional energy harvester, possibly leading the facile integration with the other types of energy harvester converting the different types of energy and the independent operation of mobile electronic devices with the reduced concerns for the energy source, consequently.
Geometrical Configuration:
Depending on the configuration of piezoelectric nanostructure, the most of the nanogenerator can be categorized into 3 types: VING, LING and "NEG". Still, there is a configuration that do not fall into the aforementioned categories, as stated in other type.
Other type:
The fabric-like geometrical configuration has been suggested by Professor Zhong Lin Wang in 2008. The piezoelectric nanowire is grown vertically on the two microfibers in its radial direction, and they are twined to form a nanogenerator.One of the microfibers is coated with the metal to form a schottky contact, serving as the counter electrode of VINGs. As the movable microfiber is stretched, the deformation of the nanostructure occurs on the stationary microfiber, resulting in the voltage generation. Its working principle is identical to VINGs with partial mechanical contact, thus generating DC electrical signal.
Applications:
Nanogenerator is expected to be applied for various applications where the periodic kinetic energy exists, such as wind and ocean waves in a large scale to the muscle movement by the beat of a heart or inhalation of lung in a small scale. The further feasible applications are as follows.
HOW IT WORKS:
A key innovation that led to the nano wire generator is a new electrode design. Fabrication begins with growing an array of vertically-aligned nanowires approximately half a micron apart on gallium arsenide, sapphire or flexible polymer substrate.
Zinc oxide nanowires grown on a gallium nitride substrate.A layer of zinc oxide is grown on top of the substrate to collect the current. Also fabricated is a‘zigzag’ silicon electrode that contains thousands of nano-scale tips made conductive by a platinum coating. The electrode is then lowered on top of the nano wire array, leaving just enough space so that a significant number of the nano wires are free to flex with in the gaps created by the tips.Moved by mechanical energy such as waves or vibration, the nanowires periodically contact the tips, transferring there electrical charges. To vibrate the electrode, the researchers packaged the device, put it in water and exposed to the ultrasonic waves. As the zigzag electrode moves up and down, its peaks push and bend the nano wires, which generate electric current that the electrode collects simultaneously.
Compressing the wires or vibrating them left or right makes all the current add up in the same direction. By capturing the tiny amounts of current produced by hundreds of nano wires kept in motion, the generator outputs a direct current in the nanoampere range.
Before that happens, additional development will be needed to optimize current production. For instance, though nanowires in the arrays can be grown to approximately the same length — about one micron – there is some variation. Wires that are too short cannot touch the electrode to produce current, while wires that are too long cannot flex to produce electrical charge.
Conclusion:
• Researchers expect that with optimization, the nano generator could produce as much as 4 watts per cubic centimeter based on a calculation for a single nano wire.
• One day by placing these into people's shoes we can generate electricity when walking.
• Powering the simple electronic devices.
• The principle and nanogenerator demonstration could be the basis for new self powered nano devices that can harvest electricity from environment for application such as implantable bio-medical devices, wireless sensors, and portable electronics.