Band 3, Heft 2 -

An experimental investigation of an integrated piezo-electric based energy harvester and an organic energy storage device is performed. The energy is harvested from a vibrating composite unimorph beam. The storage device is made out of an organic semiconductor material and storage elements from synthesized nanoparticles. The semiconducting polymer is obtained by blending poly (vinyl alcohol) and poly (acrylic acid) in crystal state polymers with sorbitol acting as the plasticizer. Zinc-Oxide nanoparticles with a diameter size between 50 and 70 nm are used as charge storage elements. A piezoelectric energy generation element made out of macro-fiber composite is used to harvest the energy from the vibrating beam. The harvested energy is stored in the organic capacitor. The performance of the organic device is evaluated through its comparison with commercial capacitors. The results show that the voltage produced was high enough to store the harvested energy in the organic capacitor. The charge and energy levels of the organic capacitor are reported.

Dynamic vibration absorption is a passive technique for suppressing unintended vibrations. Optimal absorption of energy from a vibration source entails the determination of absorber parameters such as resonant frequency and damping. In the present work, we propose a method to obtain these parameters for a generic case of large number of identical vibration absorbers placed on a vibration source. We discuss an iterative procedure to find the optimum absorber resonant frequency and damping by minimizing the total energy absorbed by the system. We also analyse the influence of damping of the entire set of absorbers on the total energy absorbed and the effect of the absorber mass on the bandwidth of absorption. The proposed method is verified by analysing the response of a set of cantilever absorber beams placed on a vibrating cantilever plate. The resonant frequencies of the system with different number of absorbers are verified experimentally. We identify, using our method, the absorber mass, resonant frequency and damping of the absorber at which significant amount of energy supplied to the system flows into absorbers. A potential application of this method in the context of energy harvesting is the design of harvesters for a given vibration source. We emphasize through our work that monitoring energies in the system and optimizing them is both rational and vital for designing multiple harvesters that absorb energy from a given vibration source optimally.

We investigate the performance of a piezoelectric energy harvester with nonlinearity induced by wrinkles. Linear and nonlinear regimes are detected in the electric response of the device when sweeping the intensity of the external excitation. Those regimes are related to the activation of a nonlinear mechanical response that appears when increasing the excitation amplitude. The wrinkles have been found to improve the power density and the normalized power density, in a certain noise power range.

The goal of this study was to design a micro wind turbine having dimensions on the order of 1–10 cm 3 for powering wireless sensor nodes. Using the parametric study based upon a computational model, the coupling factor between the blade and generator section was significantly enhanced. Building upon the formulation for the coupling factor, we derived efficiency metric for the rotational generators. A prototype was designed based upon the analytical study conducted through the combination of blade element momentum theory and ANSYS magnetics to match the performance of the generator to that of the blades. The blade diameter and depth was 72 mm and 9 mm, respectively. The generator diameter was 26 mm with total volume of 18.1 cm 3 . It was found that the micro wind turbine generated DC output power of 12.39 mW, 49.03 mW and 102.61 mW at 3.7 m/s, 6 m/s and 8 m/s wind speeds, respectively. The power density was computed to be 0.304, 1.204, and 2.52 mW/cm 2 , respectively, which are higher than all the other results reported in the literature.

Cover letter An autonomous flyback converter was designed for energy harvesting from Microbial Fuel Cells (MFCs). The circuit was optimized to minimize the losses and maximize the efficiency. A Maximum Power Point Tracking (MPPT) algorithm was implanted in the converter to extract the maximum power available from MFC. Discontinuous conduction mode operation of the flyback allows controlling the MPP operation by impedance matching. The flyback can start-up at low voltage, around 300 mV. The output open circuit voltage is about 20 V and the voltage at MPP is 6.4 V with a maximum efficiency of 71.2%. Abstract : Microbial fuel cells (MFCs) use bacteria as the catalysts to oxidize organic matter and generate electricity. This energy can be used to supply low power electronic systems. A power management unit between the MFCs and the load is required to adapt the voltage and control the operation. The low voltage and low power characteristics of MFCs prohibit the use of standard converter topologies since the threshold voltage of standard CMOS transistors in CMOS technology is higher than the output voltage of MFCs. A low-voltage start-up sub-circuit is required to charge a primary capacitor to supply the driver. A specific sub-circuit is also required to control the operation of MFCs for Maximum Power Point Tracking (MPPT) issues. An optimized Discontinuous Conduction Mode (DCM) autonomous flyback converter for energy harvesting is presented for ambient sources, like MFCs. The converter is designed, fabricated, and tested. An MPPT algorithm is integrated in the system to control the operation and to extract the maximum available power from the MFC. The converter is able of start and step-up MFC output voltage to a value higher than 3 V under load. The peak efficiency of the converter is 71.2%.

A prototype flexible thermoelectric generator fabricated with bulk materials is presented. Mineral-fiber band and copper tape are used as flexible substrate and electric connectors, respectively, to coil up the constructed thermoelectric device under investigation. The applied active thermoelectric materials are Ca3Co4O9${\rm{C}}{{\rm{a}}_{\rm{3}}}{\rm{C}}{{\rm{o}}_{\rm{4}}}{{\rm{O}}_{\rm{9}}}$ ceramic and Cu-Ni alloy for hole and electron conduction, respectively. Thermal parallel and electric series connections of the mentioned materials were realized in the prototype flexible thermoelectric generator. The device delivered an open-circuit voltage of 16.52 mV and a short-circuit current of 19.40 μA${\rm{\mu A}}$ with a temperature difference of ΔTTEG=31 K${\rm{\Delta}}{{\rm{T}}_{{\rm{TEG}}}}{\rm{= 31\ K}}$ for the hot side temperature of 420 K. The device exhibits an approximately 3 cm long stripe that include four basic units (n-p pair and electric connector).

The article is devoted to researching the practical application of the magnetoelectric effect for the development of energy harvesting devices, in particular for the design of magnetoelectric synchronous generator. The energy harvesting devices are designed to provide by the energy of remote or nonvolatile electronic devices that don’t require the high power consumption. General dimensions of the generator were as follows: diameter of 12 cm, thickness of 2.4 cm. The model of generator comprising eight ME elements with dimensions of one element of 40×10×0.5 mm at the frequency of the alternating magnetic field of 38 Hz provides the output constant voltage of 1.12 V and current of 3.82 microamps. Variable voltage before the rectifier was of 1.7 V. Total generated power was of 4.28 µW. The studies of resonant and non-resonant mode of ME element were carried out. Resonance mode of ME element provides a much greater output power. Designed generator can be applied in the construction of wind power sets, hydrogenerators, turbogenerators and other power generation equipment.

The magnetoelectric (ME) effect has been investigated in lead zirconate titanate (PZT) thin film deposited on nickel foil using chemical solution deposition (CSD) technique. The synthesized PZT thin films are found to possess perovskite structure without presence of any intermediate layer. PZT thin film deposited on nickel foil exhibits a good ferroelectric property with a high remnant polarization of about 86 µC/cm 2 .The ferroelectric loop has been modeled using domain wall theory to verify the behavior of the ferroelectric domains. It is observed that deposition conditions, specially annealing temperature, play a crucial role in enhancing the magnetoelectric effect. A high ME coefficient of 220 mVcm –1 Oe –1 at a bias magnetic field of 50 Oe has been obtained due to enhanced magnetoelectric coupling between PZT film and nickel foil.

Paper is a material with a high Young’s modulus that vibrates sensitively due to environmental noise, voice, and sound. This study aims to create a triboelectric power generator to convert this sonic vibration energy into electrical energy to power microelectronics embedded on paper. A sonic wave has two wave modes, transverse and longitudinal, that propagate in paper; therefore, two types of triboelectric power generators were designed for trial simulation as the first step. A triboelectrically charged polytetrafluoroethylene sheet and a back electrode were attached to a paperboard. Another paperboard with a counter electrode attached was vibrated in the out-of-plane direction corresponding to transverse waves such that it would repeatedly move toward and away from the other paperboard. The generated power between the two electrodes reached 11.8 µW at 2 MΩ load. When comb-shaped electrodes were applied, manual strokes in the in-plane direction, corresponding to a longitudinal wave, induced voltage up to 8.2 V. The result suggested that sonic waves could be an electric power source for microelectronics in the future.