Volume 1, Issue 1-2 -

Asymmetric and symmetric magnetoelectric (ME) laminates structures of piezoelectric macro-fiber composite (MFC)/nickel (Ni) were fabricated and investigated their ME and magneto-mechano-electric (MME) energy harvesting responses to an applied magnetic/mechanical stimulations. Both the structures strongly revealed the dependence of ME voltage coefficient ( α ME ) on applied magnetic field directions with an important feature of a zero-bias field ME response. This is much more beneficial for designing the magnetic field sensors. The fabricated MFC/Ni structures exhibited good energy harvesting response to applied simultaneous magnetic/mechanical vibrations of lab magnetic stirrer. The electric power was successfully harnessed from magneto-mechanical stimulations; the resulting potential and power were up to ~20 V p–p and ~6 μW respectively, which are quite enough power to light a commercial red LED with traditional rectifier circuit and capacitor. Hence, the present MFC/Ni ME generators provide their future feasibility having self-biasing feature for designing the magnetic field sensors as well as for powering small consumer electronic devices and wireless sensor network systems by exploiting mechanical/magnetic stimulations from surrounding.

Shape Memory Alloys (SMAs) exhibit temperature-dependent cyclic deformation. SMAs undergo reversible phase transformation with heating that generates strain which can be used to develop heat engine. In this study, we build upon the concept where environmental heat is first converted into mechanical energy through SMA deformation and then into electrical energy using a microturbine. This SMA heat engine was tailored to function as a miniature energy harvesting device for wireless sensor nodes applications. The results showed that 0.12 g of SMA wire produced 2.6 mW of mechanical power which was then used to drive a miniature electromagnetic generator that produced 1.7 mW of electrical power. The generated electrical energy was sufficient to power a wireless sensor node. Potential design concepts are discussed for further improvements of the SMA heat engine for the wireless sensing platform.

The step toward the fabrication of nanodevices with low cost and improved performance is of high demand; therefore, in the present study, different flexible substrates like common paper, textile fabric, plastic and aluminum foil have been utilized to harvest electrical energy. ZnO nanorods (NRs) were grown by using low-temperature aqueous chemical growth method. The obtained ZnO NRs were highly dense, well aligned, uniformly distributed over the substrates and exhibited good crystal quality. The structural study was carried out by using X-ray powder diffraction and scanning electron microscopy. The piezoelectric properties of ZnO NRs were investigated by the help of an atomic force microscope using contact mode. The measurements of generated piezoelectricity were around 16.2 mV, 23.2 mV, 38.5 mV and 43.3 mV for common paper, textile fabric, plastic and aluminum foil, respectively. This investigation is an important step in order to study the effect of different substrates influencing the magnitude of the output voltage under identical growth and measurement conditions. We expect that this study will help identify the most suitable flexible substrate for harvesting energy. It also offers a promising alternative powering source for the next generation nanodevices using non-conventional substrates like aluminum foil. Moreover, the use of aluminum foil as flexible and low cost substrate may pave the way to develop devices in different fields including energy harvesting.

There is growing need for the green, reliable, and cost-effective power solution for the expanding wireless microelectronic devices. In many scenarios, these needs can be met through a small-scale wind energy portable turbine (SWEPT) that operates near ground level where wind speed is of the order of few meters per second. SWEPT is a three-bladed, 40 cm rotor diameter, direct-drive, horizontal-axis wind turbine that has very low cut-in wind speed of 1.7 m/s. It operates in a wide range of wind speeds between 1.7 m/s and 10 m/s and produces rated power output of 1 W at wind speed of 4.0 m/s. The wind turbine is capable of producing electrical power up to 9.8 W at wind speed of 10 m/s. The maximum efficiency of SWEPT was found to be around 21% which makes it one of the most efficient wind turbines reported at the small scale and low wind speed. These advancements open many new opportunities for embedding and utilizing wireless and portable devices.

“Politico-engineering” in the twenty-first century is generating “Piezoelectric Actuator Renaissance” in the area of sustainability and crisis technologies in particular. This paper reviews the recent advances in materials, designing concepts, and new applications of piezoelectric actuators and describes the future perspectives of this area.

Cantilever beams are widely used for designing transducers for low-frequency vibration energy harvesting. However, in order to keep the dimensions within reasonable constraints, a large tip mass is generally required for reducing the resonance frequency below 100 Hz which has adverse effect on the reliability. This study provides a breakthrough toward realizing low-frequency micro-scale transduction structures. An analytical out-of-plane vibration model for standalone arc-based cantilever beams was developed that includes provisions for shear and rotary inertia, multidirectional arcs, and multiple layers. The model was applied to a multilayered cantilever beam (10-mm wide and 0.1-mm thick) composed of three arcs, and the results indicate that the fundamental bending mode of the beam was 38 Hz for a silicon substrate thickness of 100 μm. The model was validated with modal experimental results from an arc-based cantilever made out of aluminum.

The thermoelectric energy conversion is described in terms of fluxes of extensive variables entropy and charge, which gives a clear meaning to the figure of merit and to the power factor. Strength and sign of coupling of entropy current and electrical current is decisive for the function of a thermoelectric generator, which was built from n-type and p-type oxide ceramics to be suitable for the high-temperature range. For n-type and p-type legs, Zn 0.98 Al 0.02 O and Ca 3 Co 4 O 9 -derived ceramics, respectively, were used. Microstructure of both materials was investigated to some detail by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy including elemental analysis. N-type Zn 0.98 Al 0.02 O shows sub-micrometre precipitates of ZnAl 2 O 4 spinel. P-type Ca 3 Co 4 O 9 -derived ceramic is a multi-phase composite as the starting powder decomposed partly during sintering. The thermoelectric materials show different temperature slopes of the power factor with the p-type material reaching 1.8 mW cm −1 K −2 at 1,000 K and the n-type reaching 1.6 mW cm −1 K −2 at 1,050 K. For the 10-leg thermoelectric generator, a figure of merit of zT = 0.10 was estimated at maximum electrical power output when the hot side was at 1,023 K, and a temperature difference of 200 K was applied.

We report a levitation-induced vibration energy harvester based on a double-repulsion configuration in the moving magnet composite. Computational modeling clearly illustrated the advantages of the double-repulsion configuration over the single-repulsion and no-repulsion configurations. Double-repulsion configuration provided the best dynamics (displacement and velocity) and output response (voltage). Based on the modeling results, an AA battery-sized harvester with the double-repulsion configuration was fabricated. The harvester exhibited high power response at low frequencies (12.9 mW at 1 g and 16 Hz) and also exhibited a high normalized power density at low excitations (15.33 mW cm −3 g −2 at 0.25 g and 13 Hz). The harvester was used to charge a cellphone at 4.7 V DC.

A fully functional, self-sufficient body-worn energy harvesting system is presented in this paper. The system is designed for passively capturing energy from human motion, with the long-term vision of supplying power to portable, wearable, or even implanted electronic devices. Compared with state-of-the-art vibrational systems, the system requires no external power supplies and can bootstrap from zero-state-of-charge to generate electrical energy from walking, jogging, and cycling; convert the induced AC voltage to DC voltage; and then boost and regulate the DC voltage to charge a Li-ion-polymer battery. Measurements show that at open-load the system turns on when the input is above 1 V pk and turns off when the input drops below about 600 mV pk with no measurable standby power consumption. Tested under normal human activities (walking, jogging, and cycling) when worn on different parts oze body, the 70 cm 3 system is shown to charge a 3.7 V rechargeable battery at charge rates ranging from 33 μW to 234 μW.

A design methodology is proposed for electronic systems powered by energy harvesting. The methodology first considers the operating environment. It then evaluates the supply-side (the attributes of the harvester), the demand-side (the engineering application or load which receives and uses the converted power), and the power conditioning needed between supply and demand. A test case is presented in which the vibrations of an electromagnetic device are harvested, converted, and used to power a wireless sensor node. Such a node is being used for the condition based monitoring of manufacturing equipment.

Thermoelectric properties of zinc oxide (ZnO) are largely influenced by its electrical property. In this paper, we investigated the correlation between the electrical resistivity and synthesis temperature for aluminum (Al)-modified ZnO. At constant Al doping, the electrical resistivity of ZnO exhibited sharp decrease with increase in sintering temperature due to the increased carrier density resulting from Al 3+ substitution on Zn 2+ sites. Photoluminescence analysis showed that segregation of Al in secondary phase, ZnAl 2 O 4 , promotes Zn 2+ vacancy formation and consequently compensates the free electrons that dominate the electrical behavior at relatively low sintering temperature. The mechanism controlling the large change in electrical resistivity of dense ZnO, ranging from insulator (~10 7 Ω cm) to semiconducting regime (~ 0.1 Ω cm) has been discussed.