Energy Scavenging Devices Research Articles

Analysis of energy harvesters for highway bridges

This article investigates the possibility of piezoelectric energy harvesters as energy scavenging devices in highway bridges. The structural vibration due to the motion of a load (vehicle) on the bridge is considered as the source of energy generation for the harvester. The energy generated in this way can be useful for wireless sensor networks for structural health monitoring of bridges by reducing or even eliminating the need for battery replacement/recharging. A highway bridge model with a moving point load is investigated and a linear single-degree-of-freedom model is used for the piezoelectric energy harvester. Two types of harvesters, namely, the harvesting circuit with and without an inductor, have been considered and the energy generated for a single vehicle has been estimated. These results may be used, together with traffic statistics, to obtain the variation of average power and thus, for a given application, help to design the energy management system.

Pore analysis of obliquely deposited nanostructures by krypton gas adsorption at 87 K

The porous nature of high surface area and large aspect ratio nanorods arrays make them strong candidates for a range of applications from catalyst supports to energy scavenging devices. The glancing angle deposition (GLAD) technique is a straightforward and flexible method for ensuring control of morphology and porosity in nanorod arrays. Quantifying the porous nature of nanostructured columnar arrays, fabricated using the GLAD technique, is critical for understanding and optimizing the performance of devices fabricated using this method. The mesoporosity and pore volume of these GLAD nanorod arrays have thus been characterized using gas adsorption (krypton adsorption at 87.3 K) and scanning electron microscopy (SEM) image analysis techniques. To characterize the obliquely deposited amorphous titanium dioxide (TiO 2) and silicon dioxide (SiO 2) samples, top-down SEM images of the films were also analyzed which allowed us to determine the mean distance between columns. SEM image analysis permitted for estimation of inter-column porosity of films deposited at angles from 65° to 85°, while krypton analysis allowed for the identification of mesoporosity in films from 45° to 85°. Our results provide a comprehensive characterization of GLAD film porosity which will be vital for the design of devices for a diverse set of applications from photonics to sensing to microfluidics.

Dynamic Analysis of a Motion Transformer Mimicking a Hula Hoop

Hula-hoop motion refers to the spinning of a ring around a human body; it is made possible by the interactive force between the moving ring and the body. Inspired by the generic concept of hula-hoop motion, this study proposes a novel motion transformer design that consists of a main mass sprung in one translational direction and a free-moving mass attached at one end of a rod, the other end of which is hinged onto the center of the main mass. It is expected that the transformer is capable of transforming linear reciprocating motion into rotational motion. In addition, the transformer could be integrated with coils, magnets, and electric circuits to form a portable energy scavenging device. A thorough dynamic analysis of the proposed transformer system is conducted in this study in order to characterize the relationships between the varied system parameters and the chance of hula-hoop motion occurrence. The governing equations are first derived with Lagrange’s method, which is followed by the search for steady-state solutions and the corresponding stability analysis via the homotopy perturbation method and the Floquet theory. Direct numerical simulation is simultaneously performed to verify the correctness of the approximate analysis. In this manner, the feasibility of the proposed design and the occurrence criteria of hula-hoop motion are assessed.

Distribution Analysis of Hydrogenases in Surface Waters of Marine and Freshwater Environments

BackgroundSurface waters of aquatic environments have been shown to both evolve and consume hydrogen and the ocean is estimated to be the principal natural source. In some marine habitats, H2 evolution and uptake are clearly due to biological activity, while contributions of abiotic sources must be considered in others. Until now the only known biological process involved in H2 metabolism in marine environments is nitrogen fixation.Principal FindingsWe analyzed marine and freshwater environments for the presence and distribution of genes of all known hydrogenases, the enzymes involved in biological hydrogen turnover. The total genomes and the available marine metagenome datasets were searched for hydrogenase sequences. Furthermore, we isolated DNA from samples from the North Atlantic, Mediterranean Sea, North Sea, Baltic Sea, and two fresh water lakes and amplified and sequenced part of the gene encoding the bidirectional NAD(P)-linked hydrogenase. In 21% of all marine heterotrophic bacterial genomes from surface waters, one or several hydrogenase genes were found, with the membrane-bound H2 uptake hydrogenase being the most widespread. A clear bias of hydrogenases to environments with terrestrial influence was found. This is exemplified by the cyanobacterial bidirectional NAD(P)-linked hydrogenase that was found in freshwater and coastal areas but not in the open ocean.SignificanceThis study shows that hydrogenases are surprisingly abundant in marine environments. Due to its ecological distribution the primary function of the bidirectional NAD(P)-linked hydrogenase seems to be fermentative hydrogen evolution. Moreover, our data suggests that marine surface waters could be an interesting source of oxygen-resistant uptake hydrogenases. The respective genes occur in coastal as well as open ocean habitats and we presume that they are used as additional energy scavenging devices in otherwise nutrient limited environments. The membrane-bound H2-evolving hydrogenases might be useful as marker for bacteria living inside of marine snow particles.

Dynamic Simulation of an Electromechanical Energy Scavenging Device

This paper presents a multi-physic modeling of an electromechanical energy scavenging device. A permanent magnet, connected to the inner liner of a tyre, is accelerated along a guide by the tyre deformation during car motion; by interacting with coils it generates a power which is conditioned by a proper electronic interfaced to an external load. The energy conversion process takes into account the simulation of different phenomena like: dynamic behavior of the seismic mass, electromagnetic coupling between moving mass and coils, transfer of the generated power to an external load by means of a nonlinear circuit interface. An integrated model of the cascaded energy steps is developed inside the Simulink environment. A good agreement is found in the comparison between theoretical model and experiments. The accurate modeling of the energy conversion device is a breakthrough in the modeling of these kinds of devices and allows to reach interesting power/volume ratios: small dimensions (about one cubic centimeter) and relatively high power output (more than one milliwatt).

Nanoscale materials and devices for future communication networks

New discoveries in materials on the nanometer- length scale are expected to play an important role in addressing ongoing and future challenges in the field of communication. Devices and systems for ultra-high-speed short- and long-range communication links, portable and power-efficient computing devices, high-density memory and logics, ultra-fast interconnects, and autonomous and robust energy scavenging devices for accessing ambient intelligence and needed information will critically depend on the success of next-generation emerging nanomaterials and devices. This article presents some exciting recent developments in nanomaterials that have the potential to play a critical role in the development and transformation of future intelligent communication networks.

Modeling, fabrication and stress compensation of an epitaxial thin film piezoelectric microscale energy scavenging device

This paper focuses on a renewable power source for wireless sensor nodes via energy scavenging using thin film piezoelectrics. The novelty of this research is the growth of epitaxial PZT on a Si platform. The films were grown with good consistency using pulsed laser deposition. Using the optimized piezoelectric film properties, an analytical model was generated to predict the output power for a single cantilever, 5.5 nW/beam. Further, if arrays of the cantilevers were packed into a cubic centimeter, the output power would be 80–200 µW cm−3. A microfabrication technique was developed to manufacture the cantilevers using standard low-temperature procedures. As the devices demonstrated a significant residual stress upon release, an analytical model was created to predict the residual stress in the films from the high-temperature growth step. A neutral argon bombardment technique was then established to compensate for these stresses and to develop a planar usable device. The initial device fabrication was successful and testing was done to determine resonant frequency, quality factor and output power. The experimental resonant frequency response compared well with what was determined by the model, but the quality factor was 95, which was lower than expected. The output power per cantilever was 24.5 pW over a 510 MΩ load operating over an input vibration of 10 m s−2 and at resonant frequency (976 Hz).

Performance of Li-ion secondary batteries in low power, hybrid power supplies

Small, portable electronic devices need power supplies that have long life, high energy efficiency, high energy density, and can deliver short power bursts. Hybrid power sources that combine a high energy density fuel cell, or an energy scavenging device, with a high power secondary battery are of interest in sensors and wireless devices. However, fuel cells with low self-discharge have low power density and have a poor response to transient loads. A low capacity secondary lithium ion cell can provide short burst power needed in a hybrid fuel cell–battery power supply. This paper describes the polarization, cycling, and self-discharge of commercial lithium ion batteries as they would be used in the small, hybrid power source. The performance of 10 Li-ion variations, including organic electrolytes with Li x V 2O 5 and Li x Mn 2O 4 cathodes and LiPON electrolyte with a LiCoO 2 cathode was evaluated. Electrochemical characterization shows that the vanadium oxide cathode cells perform better than their manganese oxide counterparts in every category. The vanadium oxide cells also show better cycling performance under shallow discharge conditions than LiPON cells at a given current. However, the LiPON cells show significantly lower energy loss due to polarization and self-discharge losses than the vanadium and manganese cells with organic electrolytes.

Model of a single mode energy harvester and properties for optimal power generation

The process of acquiring the energy surrounding a system and converting it into usableelectrical energy is termed power harvesting. In the last few years, the field of powerharvesting has experienced significant growth due to the ever increasing desire to produceportable and wireless electronics with extended life. Current portable and wireless devicesmust be designed to include electrochemical batteries as the power source. The use ofbatteries can be troublesome due to their finite energy supply, which necessitates theirperiodic replacement. In the case of wireless sensors that are to be placed in remotelocations, the sensor must be easily accessible or of disposable nature to allow the device tofunction over extended periods of time. Energy scavenging devices are designed to capturethe ambient energy surrounding the electronics and covert it into usable electrical energy.The concept of power harvesting works towards developing self-powered devices that donot require replaceable power supplies. The development of energy harvestingsystems is greatly facilitated by an accurate model to assist in the design of thesystem. This paper will describe a theoretical model of a piezoelectric based energyharvesting system that is simple to apply yet provides an accurate prediction of thepower generated around a single mode of vibration. Furthermore, this modelwill allow optimization of system parameters to be studied such that maximalperformance can be achieved. Using this model an expression for the optimalresistance and a parameter describing the energy harvesting efficiency will bepresented and evaluated through numerical simulations. The second part of this paperwill present an experimental validation of the model and optimal parameters.

Resonance tuning of piezoelectric vibration energy scavenging generators using compressiveaxial preload

Vibration energy scavenging, harvesting ambient vibrations in structures for conversioninto usable electricity, provides a potential power source for emerging technologies includingwireless sensor networks. Most vibration energy scavenging devices developed todate operate effectively at a single specific frequency dictated by the device’sdesign. However, for this technology to be commercially viable, vibration energyscavengers that generate usable power across a range of driving frequencies mustbe developed. This paper details the design and testing of a tunable-resonancevibration energy scavenger which uses the novel approach of axially compressing apiezoelectric bimorph to lower its resonance frequency. It was determined that an axialpreload can adjust the resonance frequency of a simply supported bimorph to24% below its unloaded resonance frequency. The power output to a resistiveload was found to be 65–90% of the nominal value at frequencies 19–24% belowthe unloaded resonance frequency. Prototypes were developed that produced300–400 µW of power at driving frequencies between 200 and 250 Hz. Additionally,piezoelectric coupling coefficient values were increased using this method, withkeff values rising as much as 25% from 0.37 to 0.46. Device damping increased 67% underpreload, from 0.0265 to 0.0445, adversely affecting the power output at lower frequencies. Atheoretical model modified to include the effects of preload on damping predictedpower output to within 0–30% of values obtained experimentally. Optimal loadresistance deviated significantly from theory, and merits further investigation.