Miniaturized piezoelectric energy harvester for battery‐free portable electronics

This paper describes a miniaturized energy harvester based on the interaction of two permanent magnets placed on both ends of a folded cantilever made with piezoelectric thin films. A unique design of the folded cantilever structures is developed to efficiently collect ambient vibrational energy over a wide frequency bandwidth for the operation of battery‐free electronic devices. The output performance of the two energy harvesters is observed to improve significantly through the use of the mutual coupling technique. The folded cantilever structure also demonstrates improved space efficiency compared with the conventional rectangular cantilever design. A wide frequency band and sufficient energy‐harvesting ability were successfully achieved by the optimally manufactured device. The maximum output power of the miniaturized energy harvester was 41.6 μW with an impedance of 0.3 MΩ. Furthermore, a pedometer was powered completely by the energy harvester without the need for any battery and external power source, demonstrating the potential of the proposed design for self‐powered electronics applications in a vibrational environment.     

A piezoelectric based energy harvester for simultaneous energy generation and vibration isolation

A vibration isolator with energy harvesting abilities is presented in this work. The developed device is able to isolate the environment from vibration of appliances, such as household electrical generators, domestic refrigerators, microwave oven, and automobile's engine, and at the same time convert the vibration to electrical energy. The resulting energy produced by the device can be utilized to operate the wireless condition monitoring units. The developed device composed of piezoelectric disc embedded in silicone rubber and is able to exhibit a resonance at 56‐Hz frequency. When subjected to a sinusoidal force, an open circuit voltage of 1.7 V is generated by the devised harvester. Furthermore, the device generated an optimum power of 2.12 mW at a matching load of 340 kΩ and frequency (resonant) of 56 Hz. However, while operating in the isolation region, it is capable of producing a load voltage of 0.87 and 0.25 V and power of 1.8 and 0.51 mW at 1.4 and 3.5 frequency ratios, respectively.     

Flexible liquid metal coil prepared for electromagnetic energy harvesting and wireless charging

This paper reported a study on a flexible liquid metal coil (LMC) for electromagnetic collection from the transmission line for self-powered sensor and electromagnetic generation for wireless charging of cellular telephone. The room temperature liquid metal of Galinstan was perfused to elastic silicone tube, which is then terminated with gallium-plated copper wire. The as-prepared liquid metal wire can sustain stretching, twisting, and bending with large deformation, and has a good electrical contact stability with the external circuit. The LMC based magnetic energy harvester was then designed and demonstrated to collect the magnetic field energy induced by a wire carrying alternating current. The power of 260 mW was obtained for the wire carrying current of 10 A. The flexible toroidal inductor was fabricated and tested for magnetic energy harvesting. The flexible spiral-shaped LMC was also designed and demonstrated to power cellular telephone through wireless charging. The present study opens the way for further applications of elastic LMC in electromagnetic energy harvesting and charging.     

Review of vibration‐based energy harvesting technology: Mechanism and architectural approach

Energy harvesting technologies are growing rapidly in recent years because of limitation by energy storage and wired power supply. Vibration energy is abundant in the atmosphere and has the potential to be harvested by different mechanisms, mainly through piezoelectric and electromagnetic means. Various architectural structures were also designed for several operating conditions, namely, resonance frequency and range thereof, acceleration, and energy extraction from several motions. The advantages and disadvantages were elaborated on, and improvements on ideas from current research were discussed in this review.     

A new IoT‐based smart energy meter for smart grids

The significant increase in energy consumption by the growth of the population or by the use of new equipment has brought big challenges to the energy security as well as the environment. There is a need that consumers can track their daily use and understand consumption standards for better organizing themselves to obtain financial and energetic efficiency. With the improvement of smart networks technology for better energy supply, a smart meter is not just a simple measurement gadget anymore, but it has additional functions including smart equipment control, bidirectional communication that allows integration of users and networks, and other functionalities. Smart meters are the most fundamental components in smart power grids. Besides, the meters used with a management system can be utilized for monitoring and controlling home appliances and other gadgets according to the users' need. A solution of an integrated and single system should be more efficient and economical. Smart measurement systems allow monitoring the energy consumption of the final consumers while providing useful information about the energy quality. The information provided by these systems is used by the operators to enhance the energy supply, and different techniques can be also applied for this end, such as charge scheduling, management from the demand side, and non‐intrusive load monitoring. The Internet of Things (IoT) is becoming a great ally in the management of smart distribution and energy consumption in smart systems scenarios. To address these issues, this paper proposes and demonstrates a new smart energy meter following an IoT approach and its associated costs and benefits. The developed device incorporates several communication interfaces. In order to easily integrate with any monitoring software solution, the meter has a multi‐protocol connection. Finally, the provided solution is validated and demonstrated in real‐life environments and it is also under use.     

A heaving point absorber‐based triboelectric‐electromagnetic wave energy harvester: An efficient approach toward blue energy

This paper presents a hybridized triboelectric‐electromagnetic generator based on heaving point absorbers to harvest the energy of water waves. The device consists of a cylindrical freestanding grating triboelectric generator (TENG) and a 3‐phase tubular electromagnetic generator (EMG). The proposed system incorporates a slider which is capable of moving through a stator under the motion of a floating buoy. The floating component can heave up and down while facing water waves without being affected by the wave direction. The performance of the TENG and EMG units and corresponding electrical outputs are evaluated under various structural, dynamical, and electrical conditions. It is shown that the number of segments in the TENG unit, phase number in the EMG unit, and motion frequency in both harvesters are the key elements in the outputs of the hybridized system. For the first time, the effect of irregular wave motion on the TENG harvester performance is systematically explored using a well‐known wave spectrum. Also, the performance of the hybridized system for charging a storage unit is evaluated in details. The presented energy harvester shows a great potential toward harvesting the energy of water waves as well as hydrodynamic sensing applications. In addition, this research provides a framework for the exploration of irregular wave motion in TENG‐based energy harvesters.     

Experimental and numerical study on charging processes of an ice‐on‐coil thermal energy storage system

In this study, an external melt ice‐on‐coil thermal storage was studied and tested over various inlet conditions of secondary fluid—glycol solution—flow rate and temperature in charging process. Experiments were conducted to investigate the effect of inlet conditions of secondary fluid and validate the numerical model predictions on ice‐on‐coil thermal energy storage system. The total thermal storage energy and the heat transfer rate in the system were investigated in the range of 10 l min ^?1?V??60 l min ^?1. A new numerical model based on temperature transforming method for phase change material (PCM) described by Faghri was developed to solve the problem of the system consisting of governing equations for the heat transfer fluid, pipe wall and PCM. Numerical simulations were performed to investigate the effect of working conditions of secondary fluid and these were compared with the experimental results. The numerical results verified with experimental investigation show that the stored energy rises with increasing flow rate a decreasing tendency. It is also observed that the inlet temperature of the fluid has more influence on energy storage quantity than flow rate. Copyright © 2006 John Wiley & Sons, Ltd.     

Design,modeling, and analysis of a high performance piezoelectric energy harvester for intelligent tires

Basic parameters affecting vehicle safety and performance such as pressure, temperature, friction coefficient, and contact‐patch dimensions are measured in intelligent tires via sensors that require electric power for operation and wireless communication to be synchronized to the vehicle monitoring and control system. Piezoelectric energy harvesters (PEHs) can extract a fraction of energy that is wasted as a result of deflection during rolling of tires, and this extracted energy can be used to power up sensors embedded in intelligent tires. A new design of PEH inspired from Cymbal PEHs is introduced, and its performance is evaluated in this paper. Cymbal PEHs are proven to be useful in vibration energy harvesting, and in this paper, for the first time, the modified shape of Cymbal energy harvester is used as strain‐based energy harvester for the tire application. The shape of the harvester is adjusted in a way that it can be safely embedded on the inner surface of tires. In addition to the high performance, ease of manufacturing is another advantage of this new design. A multiphysics model is developed and validated to determine the output voltage, power, and energy of the designed PEH. The modeling results indicated that the maximum output voltage, the maximum electric power, and the accumulated harvested energy are about 3.5 V, 2.8 mW, and 24 mJ/rev, respectively, which are sufficient to power two sensors. In addition, the possibility is shown to supply power to five sensors by increase in piezoelectric material thickness. The effect of rolling tire temperature on the performance of the proposed PEH is also studied.     

Vibration‐based piezoelectric,electromagnetic, and hybrid energy harvesters for microsystems applications: A contributed review

Wireless sensor nodes (WSNs) and embedded microsystems have recently gained tremendous traction from researchers due to their vast sensing and monitoring applications in various fields including healthcare, academic, finance, environment, military, agriculture, retail, and consumer electronics. An essential requirement for the sustainable operation of WSN is the presence of an uninterrupted power supply; which is currently obtained from electrochemical batteries that suffer from limited life cycles and are associated with serious environmental hazards. An alternative to replacing batteries of WSNs; either the direct replacement or to facilitate battery regular recharging, is by looking into energy harvesting for its sustainable drive. Energy harvesting is a technique by which ambient energy can be converted into useful electricity, particularly for low‐power WSNs and consumer electronics. In particular, vibration‐based energy harvesting has been a key focus area, due to the abundant availability of vibration‐based energy sources that can be easily harvested. In vibration‐based energy harvesters (VEHs), different optimization techniques and design considerations are taken in order to broaden the operation frequency range through multi‐resonant states, increase multi‐degree‐of‐freedom, provide nonlinear characteristics, and implement the hybrid conversion. This comprehensive review summarizes recent developments in VEHs with a focus on piezoelectric, electromagnetic, and hybrid piezoelectric‐electromagnetic energy harvesters. Various vibration and motion‐induced energy harvesting prototypes have been reviewed and discussed in detail with respect to device architecture, conversion mechanism, performance parameters, and implementation. Overall sizes of most of the reported piezoelectric energy harvesters are in the millimeter to centimeter scales, with resonant frequencies in the range of 2‐13 900 Hz. Maximum energy conversion for electromagnetic energy harvesters can potentially reach up to 778.01 μW/cm³. The power produced by the reported hybrid energy harvesters (HEHs) is in the range of 35.43‐4900 μW. Due to the combined piezoelectric‐electromagnetic energy conversion in HEHs, these systems are capable of producing the highest power densities.     

Piezoelectric cable macro‐fiber composites for use in energy harvesting

Piezoelectric cable is a commercial electronic sensor that incorporates the piezoelectric polymer polyvinylidene fluoride. This paper investigated a potential application of piezoelectric cable for energy harvesting. A method for testing the electrical output using the tensile load was developed and used to determine the output properties of the cable. A design for a piezoelectric cable fiber composite is presented, along with recommendations for potential applications and further research. Copyright © 2014 John Wiley & Sons, Ltd.     

Optimal sizing of autonomous hybrid energy system using supply‐demand‐based optimization algorithm

Hybrid energy systems (HESs) comprising photovoltaic (PV) arrays and wind turbines (WTs) are remarkable solutions for electrifying remote areas. These areas commonly fulfil their energy demands by means of a diesel genset (DGS). In the present study, a novel computational intelligence algorithm called supply‐demand‐based optimization (SDO) is applied to the HES sizing problem based on long‐term cost analysis. The effectiveness of SDO is investigated, and its performance is compared with that of the genetic algorithm (GA), particle swarm optimization (PSO), gray wolf optimizer (GWO), grasshopper optimization algorithm (GOA), flower pollination algorithm (FPA), and big‐bang‐big‐crunch (BBBC) algorithm. Three HES scenarios are implemented using measured solar radiation, wind speed, and load profile data to electrify an isolated village located in the northern region of Saudi Arabia. The optimal design is evaluated on the basis of technical (loss of power supply probability [LPSP]) and economic (annualized system cost [ASC]) criteria. The evaluation addresses two performance indicators: surplus energy and the renewable energy fraction (REF). The results reveal the validity and superiority of SDO in determining the optimal sizing of an HES with a higher convergence rate, lower ASC, lower LPSP, and higher REF than that of the GA, PSO, GWO, GOA, FPA, and BBBC algorithms. The performance analysis also reveals that an HES comprising PV arrays, WTs, battery banks, and DGS provides the best results: 238.7 kW from PV arrays, 231.6 kW from WTs, 192.5 kWh from battery banks, and 267.6 kW from the DGS. The optimal HES exhibits a high REF (66.4%) and is economically feasible ($104 323.10/year) and environmentally friendly. The entire load demand of the area under study is met without power loss (LPSP = 0%).     

Characterization of metals and salts‐based thermal energy storage materials using energy balance method

Thermal energy storage technologies minimize the imbalance between energy production and demand. In this context, latent heat storage materials are of great importance as they have a higher density of energy storage as compared with the sensible heat storage materials. The present study involves the characterization of energy storage materials using an energy balance cooling curve analysis method. The method estimates the convective heat transfer coefficient in the solidification range to characterize the phase change materials for applications in energy storage. The method is more beneficial than the Computer Aided Cooling Curve analysis methods as it eliminates baseline calculations and the associated fitting errors. Metals (Sn) and salts (KNO₃ and NaNO ₃) were used in the present work. Phase change characteristics like the rate of cooling, liquidus and solidus temperatures, time for solidification, and enthalpy of phase change were estimated for both metals and salts. It was observed that the energy balance cooling curve analysis method worked very well for metals but not well suited for low conductivity salts. Salts could not be characterized since the thermal gradient existing within the salt sample was not considered in this method.     

Power reclamation efficiency of a miniature energy‐harvesting device using external fluid flows

This study represents experimental results related to the energy‐harvesting capability of a miniature power reclamation device based on external liquid flows. The device's reclamation principle depends on the conversion of mechanical energy into electrical energy. The mechanical energy in the device was generated by capturing vibrations caused by external liquid flows via the device's tails, which were designed by taking inspiration from the body shape of the black ghost knife fish, Apteronotus albifrons. The reclaimed power was obtained through magnetic polarization, which was generated by rotating circular waterproof magnet structures as a result of rotating movements of the mentioned tails and is transferred to 3.76 V (Ni‐Mg) batteries. Power reclamation was also simulated using COMSOL 4.2a software in order to compare the maximum reclaimable theoretical energy‐harvesting capacity with the experimental results. Experimental tests were performed within a range of flow velocities (1.0 ~ 5.0 m/s) for various fluid densities (plain water, low‐salt water and high‐salt water) in order to obtain extensive experimental data related to the device in response to external fluid flows. According to experimental results, the device could generate powers up to 17.2 W. On the other hand, the maximum reclaimable power was obtained at 25.7 W from COMSOL Multiphysics 4.2a simulations. Promising energy harvesting results imply that the output from this device could be used as a power source in many applications such as in lighting and global positioning system (GPS) devices. Copyright © 2014 John Wiley & Sons, Ltd.     

A new modeling and solution method for optimal energy flow in electricity‐gas integrated energy system

With the increasing interdependency of electricity and gas, it is necessary to simultaneously investigate electric power system and natural gas system from the perspective of an electricity‐gas integrated energy system (EGIES). As an extension and integration of both optimal power flow (OPF) and optimal gas flow (OGF), optimal energy flow (OEF) is regarded as the cornerstone of the EGIES and lays an essential foundation for further research on the EGIES's operation and analysis considering stochastic conditions and contingency states. The objective of this paper is to develop a generalized mathematical model and a universally applicable simulation tool for the OEF problem. First, natural gas system is modeled in a way similar to electric power system according to electricity‐gas analogy analysis, where gas admittance, gas nodal admittance matrix, and the nodal equation of gas flow conservation are derived. Then, a generalized accurate OEF model is formulated by simultaneously integrating the OPF model and the OGF model as well as their coupling constraints in a unified modeling framework. Furthermore, an available hybrid optimization approach consisting of whale optimization algorithm, MATPOWER, hydraulic calculation iterative program, and nonstationary penalty function method is put forward to solve the OEF problem. The accuracy, feasibility, and applicability of the proposed modeling and solution method is finally demonstrated by analyzing Belgian 20‐node gas system combined with IEEE 30‐bus test system.     

Graphene‐based materials for flexible electrochemical energy storage

Sustainable development of renewable energy sources is one of the most important themes that humanity faces in this century. Wide use of renewable energy sources will require a drastically increased ability to store electrical energy. Electrochemical energy storage devices are expected to play a key role. With the increased demand in flexible energy resource for wearable electronic devices, great efforts have been devoted to developing high‐quality flexible electrodes for advanced energy storage and conversion systems. Because of its high specific surface area, good chemical stability, high mechanical flexibility, and outstanding electrical properties, graphene, a special allotrope of carbon with two‐dimensional mono‐layered network of sp² hybridized carbon, have been showing great potential in next‐generation energy conversion and storage devices. This review presents the latest advances on the flexible graphene‐based materials for the most vigorous electrochemical energy storage devices, that is, supercapacitors and lithium‐ion batteries. Copyright © 2014 John Wiley & Sons, Ltd.     

A new thinking for renewable energy model: Remote sensing‐based renewable energy model

This paper mainly focuses on the two issues through remote sensing: assessment of the renewable energy potential and integration of the renewable energy model. Three methods for assessing the renewable energy potential with remote sensing (RS) are proposed. The methods can provide more precise evaluation of renewable energy potential, which is the first vital step to develop renewable energy model. The paper then first presents three integrations of the renewable energy model with RS and points out that with respect to the problems one of them is employed. The assessment methods based on RS and the integrations with RS are illustrated by a simple example with Europe solar energy data set. The results show that Germany is the optimal country to install photovoltaic with a capacity of 137 125 GW. Copyright © 2009 John Wiley & Sons, Ltd.     

Development of an ocean wave energy harvester with a built‐in frequency conversion function

The research develops a novel harvester associated with a built‐in frequency conversion device to harness energy from ocean waves based on the piezoelectric effect. The developed harvester consists of 2 generators driven by rotational motions converted from vertical motions by a rack and pinion actuator. The generator has a rotator with a magnetic bar attached to its blade tips and a stator. By this innovative design, the harvester is capable of converting ocean waves with low frequencies to mechanical vibrations with higher excitation frequencies of the piezoelectric transducer for increasing its energy conversion efficiency. A corresponding mathematical model for the harvester is developed to evaluate the generated power. The simulation results show that the generated power increases with increases in the ocean wave height, number of magnetic bars and decreases in the wave period, the distance between 2 opposite magnetic bars, and harvester's submerged part height. The power output is realized up to 260 W with the height, length, and width of the harvester being 1m × 1m × 1m, at the ocean wave height and period being 2 m and 7 seconds, respectively.     

Techno‐economic assessment for energy generation using bagasse: case study

Bagasse is selected as the biomass source that is studied because of its annual significant rate production in Iran and potential for energy generation. Bagasse has been as an energy source for the production of energy required to run the sugar factory. The energy needed by factories was supplied by burning bagasse directly inside furnaces, which had an exceptionally low output. To this end, today, a secondary use for this waste product is in combined heat and power plants where its use as a fuel source provides both heat and power. In addition, low efficiency of traditional methods was caused to increase the use of modern methods such as anaerobic digestion, gasification and pyrolysis for the production of bio‐fuels. In this paper, the energy conversion technologies are compared and ranked for the first time in Iran. Therefore, the most fundamental innovation of this research is the choice of the best energy conversion technology for the fuel production with a higher efficiency. To assess the feasibility application and economic benefit of biogas CHP plant, a design for a typical biogas unit is programmed. The results show the acceptable payback period; therefore, economically and technically, biogas CHP plant appears to be an attractive proposition in Iran. Copyright © 2012 John Wiley & Sons, Ltd.     

Multi‐criteria algorithm‐based methodology used to select suitable domes for compressed air energy storage

Storing energy allows both the efficiency and availability of renewable energy to be increased, thus dissociating actual from expected generation and from consumption demands. Compressed air energy storage (hereinafter ‘CAES’) enables the efficient and cost‐effective storage of large amounts of energy, achieving a capacity of over 100 MWh. There are several geological structures that can be used as CAES, among which the use and construction of salt domes are particularly noteworthy. However, there is a high exploration risk associated with subsurface exploration. To this end, it is advisable to establish a detailed schedule to select and characterize structures, with the purpose of minimizing the aforementioned risk. Multi‐criteria algorithms can be used to establish a hierarchy of the alternatives and to identify the structures with the greatest potential with an objective approach. The analytic hierarchy process method is used in this paper as the selection algorithm, which is based on identifying and assessing criteria and weighting each criterion. In accordance with the analytic hierarchy process method, the goal was divided into a series of different level criteria, defining a breakdown structure of the problem to select salt domes. This paper defines a structure hierarchization method that allows the objective establishment of the areas with the highest potential for CAES, considering both technical and socioeconomic factors. Therefore, a supporting decision‐making method may be established to reduce the exploration risk associated with underground structures. Copyright © 2017 John Wiley & Sons, Ltd.