Showing papers on "Energy harvesting published in 2004"

A Review of Power Harvesting from Vibration using

Abstract: The process of acquiring the energy surround- ing a system and converting it into usable electrical energy is termed power harvesting. In the last few years, there has been a surge of research in the area of power harvesting. This increase in research has been brought on by the mod- ern advances in wireless technology and low-power electron- ics such as microelectromechanical systems. The advances have allowed numerous doors to open for power harvesting systems in practical real-world applications. The use of pie- zoelectric materials to capitalize on the ambient vibrations surrounding a system is one method that has seen a dramat- ic rise in use for power harvesting. Piezoelectric materials have a crystalline structure that provides them with the ability to transform mechanical strain energy into electrical charge and, vice versa, to convert an applied electrical potential into mechanical strain. This property provides these materials with the ability to absorb mechanical energy from their surround- ings, usually ambient vibration, and transform it into electrical energy that can be used to power other devices. While piezo- electric materials are the major method of harvesting energy, other methods do exist; for example, one of the conventional methods is the use of electromagnetic devices. In this paper we discuss the research that has been performed in the area of power harvesting and the future goals that must be achieved for power harvesting systems to find their way into everyday use. and replacement of the battery can become a tedious task. In the case of wireless sensors, these devices can be placed in very remote locations such as structural sensors on a bridge or global positioning system (GPS) tracking devices on ani- mals in the wild. When the battery is extinguished of all its power, the sensor must be retrieved and the battery re- placed. Because of the remote placement of these devices, obtaining the sensor simply to replace the battery can be- come a very expensive task or even impossible. For in- stance, in civil infrastructure applications it is often desirable to embed the sensor, making battery replacement unfeasible. If ambient energy in the surrounding medium could be ob- tained, then it could be used to replace or charge the battery. One method is to use piezoelectric materials to obtain ener- gy lost due to vibrations of the host structure. This captured energy could then be used to prolong the life of the power supply or in the ideal case provide endless energy for the electronic devices lifespan. For these reasons, the amount of research devoted to power harvesting has been rapidly in- creasing. In this paper we review and detail some of the top- ics in power harvesting that have been receiving the most research, including energy harvesting from mechanical vi- bration, biological systems, and the effects of power har- vesting on the vibration of a structure.

A Review of Power Harvesting from Vibration using Piezoelectric Materials

Abstract: The process of acquiring the energy surrounding a system and converting it into usable electrical energy is termed power harvesting. In the last few years, there has been a surge of research in the area of power harvesting. This increase in research has been brought on by the modern advances in wireless technology and low-power electronics such as microelectromechanical systems. The advances have allowed numerous doors to open for power harvesting systems in practical real-world applications. The use of piezoelectric materials to capitalize on the ambient vibrations surrounding a system is one method that has seen a dramatic rise in use for power harvesting. Piezoelectric materials have a crystalline structure that provides them with the ability to transform mechanical strain energy into electrical charge and, vice versa, to convert an applied electrical potential into mechanical strain. This property provides these materials with the ability to absorb mechanical energy from their surroundings, usually ambient vibration, and transform it into electrical energy that can be used to power other devices. While piezoelectric materials are the major method of harvesting energy, other methods do exist; for example, one of the conventional methods is the use of electromagnetic devices. In this paper we discuss the research that has been performed in the area of power harvesting, and the future goals that must be achieved for power harvesting systems to find their way into everyday use.

An electromagnetic, vibration-powered generator for intelligent sensor systems

Abstract: This paper describes the design of miniature generators capable of converting ambient vibration energy into electrical energy for use in powering intelligent sensor systems. Such a device acts as the power supply of a microsystem which can be used in inaccessible areas where wires can not be practically attached to provide power or transmit sensor data. Two prototypes of miniature generator are described and experimental results presented. Prototype A is based around two magnets coupled to a coil attached to a cantilever; prototype B is based around four magnets. For prototype A, experimental results are given for its resonant frequency and its open circuit and loaded output as a function of vibration amplitude. For prototype B, experimental results are given for the generator's Q factor in air and vacuum, its output voltage as a function of vibration amplitude as well as its magnetic field strength. This generator has been tested on a car engine and shown to produce a peak power of 3.9 mW with an average power of 157 micro watts.

Estimation of Electric Charge Output for Piezoelectric Energy Harvesting

Abstract: Piezoelectric materials (PZT) can be used as mechanisms to transfer mechanical energy, usually ambient vibration, into electrical energy that can be stored and used to power other devices. With the recent advances in wireless and micro-electro-mechanical-systems (MEMS) technology, sensors can be placed in exotic and remote locations. As these devices are wireless it becomes necessary that they have their own power supply. The power supply in most cases is the conventional battery; however, problems can occur when using batteries because of their finite life span. Because most sensors are being developed so that they can be placed in remote locations such as structural sensors on a bridge or global positioning service (GPS) tracking devices on animals in the wild, obtaining the sensor simply to replace the battery can become a very expensive task. Fur- thermore, in the case of sensors located on civil structures, it is often advantageous to embed them, making access impossible. Therefore, if a method of obtaining the untapped energy surrounding these sensors was implemented, significant life could be added to the power supply. One method is to use PZT materials to obtain ambient energy surrounding the test specimen. This captured energy could then be used to prolong the power supply or in the ideal case provide endless energy for the sensors lifespan. The goal of this study is to develop a model of the PZT power harvesting device. This model would simplify the design procedure necessary for determining the appropriate size and vibration levels necessary for sufficient energy to be produced and supplied to the electronic devices. An experimental verification of the model is also performed to ensure its accuracy.

Power Sources for Wireless Sensor Networks

Abstract: Wireless sensor networks are poised to become a very significant enabling technology in many sectors. Already a few very low power wireless sensor platforms have entered the marketplace. Almost all of these platforms are designed to run on batteries that have a very limited lifetime. In order for wireless sensor networks to become a ubiquitous part of our environment, alternative power sources must be employed. This paper reviews many potential power sources for wireless sensor nodes. Well established power sources, such as batteries, are reviewed along with emerging technologies and currently untapped sources. Power sources are classified as energy reservoirs, power distribution methods, or power scavenging methods, which enable wireless nodes to be completely self-sustaining. Several sources capable of providing power on the order of 100 μW/cm3 for very long lifetimes are feasible. It is the authors’ opinion that no single power source will suffice for all applications, and that the choice of a power source needs to be considered on an application-by-application basis.

Energy harvesting for wireless sensor operation and data transmission

Abstract: A device for powering a load from an ambient source of energy is provided. The device includes an energy harvesting device for harvesting energy from the ambient source of energy wherein the rate energy is harvested from the ambient source of energy is below that required for directly powering the load. A storage device is connected to the energy harvesting device. The storage device receives electrical energy from the energy harvesting device and is for storing the electrical energy. A controller is connected to the storage device for monitoring the amount of electrical energy stored in the storage device and for switchably connecting the storage device to the load when the stored energy exceeds a first threshold. The system can be used for powering a sensor and for transmitting sensor data, such as tire pressure.

Shaft mounted energy harvesting for wireless sensor operation and data transmission

Abstract: A device for monitoring a rotating shaft is provided. The device measures strain in the shaft and provides angular velocity and torque in the shaft. The device includes a sensor, sensor conditioning circuitry, a microprocessor, and a transmitter, all located on a rotating shaft. The device obtains power by harvesting mechanical energy of the rotating shaft itself. Coils are provided rotating with the shaft and permanent magnets are mounted adjacent the rotating shaft so electrical energy is induced in the coils as they rotate through the magnetic field of the permanent magnets. A battery or capacitor is connected to the coils for storing energy. A microprocessor is connected to the sensors, the storage device, and the transmitter for managing power consumption and for monitoring the amount of electrical energy stored in the storage device and for switchably connecting the storage device to the transmitter when the stored energy exceeds a threshold.

Performance aware tasking for environmentally powered sensor networks

Abstract: The use of environmental energy is now emerging as a feasible energy source for embedded and wireless computing systems such as sensor networks where manual recharging or replacement of batteries is not practical. However, energy supply from environmental sources is highly variable with time. Further, for a distributed system, the energy available at its various locations will be different. These variations strongly influence the way in which environmental energy is used. We present a harvesting theory for determining performance in such systems. First we present a model for characterizing environmental sources. Second, we state and prove two harvesting theorems that help determine the sustainable performance level from a particular source. This theory leads to practical techniques for scheduling processes in energy harvesting systems. Third, we present our implementation of a real embedded system that runs on solar energy and uses our harvesting techniques. The system adjusts its performance level in response to available resources. Fourth, we propose a localized algorithm for increasing the performance of a distributed system by adapting the process scheduling to the spatio-temporal characteristics of the environmental energy in the distributed system. While our theoretical intuition is based on certain abstractions, all the scheduling methods we present are motivated solely from the experimental behavior and resource constraints of practical sensor networking systems.

Energy harvesting circuit

Abstract: A station having a means for receipt of ambient energy from the environment and energizing power storage devices of objects of interest comprising one or more antennae and circuitry for converting said ambient energy into DC power for energizing said power storage devices. The circuitry for converting the ambient energy into DC power may include a rectifier/charge pump. The antenna of the station is tuned to maximize DC energy at the output of the rectifier/charge pump. The station can be used to energize power storage devices including capacitors and batteries that are used in electronic devices, such as cell phones, cameras, PDAs. Various antenna constructions may be employed.

Evaluation of motions and actuation methods for biomechanical energy harvesting

Abstract: This paper addresses energy harvesting from biomechanical motions. Such a technique is useful for powering small portable devices, such as wireless phones, music players, and digital assistants. For very low power devices, biomechanical energy may be enough to provide baseload power. In others, such as cell phones (which typically requires up to 3 W), biomechanical energy would recharge batteries for extended use between line charges, or allow for peak just-in-time power. In this paper, we consider several biomechanical motions for power generation. We evaluate actuation methods, including magnetic, piezoelectric, electrostatic, and electrical polymers for various motions in terms of energy, power, mass, and cost. We also discuss the practical issues associated with each, especially in terms of the power electronics required to connect the biomechanical sources to useful loads.

Energy harvester with adjustable resonant frequency

Abstract: The present subject matter discloses devices, systems, and methodologies for harvesting power from environmentally induced vibrations. Piezoelectric devices (24) and structures are disclosed that may be employed in combination with electromagnetic (100) or capacitive (92, 94) elements to enhance the power harvesting capabilities of the piezoelectric devices (24). The electromagnetic (100) and capacitive (92, 94) elements may be used to assist in maintaining system mechanical resonance in order to maximize energy harvesting capabilities. Power harvesting devices and systems in accordance with the subject technology may concurrently operate as sensors in motion sensitive applications thus providing self-powered monitoring capabilities.

System for optimal energy harvesting and storage from an electromechanical transducer

Abstract: A device for collection of energy from mechanical disturbances and distribution of that energy to an electrical load. A transducer converts mechanical energy in the form of forces and displacements into electrical energy in the form of charge pulses. The charge pulses are rectified into a Direct Current (DC) power signal and accumulated and stored in an input storage element. A controlled conversion circuit assures that the voltage on the storage element is maintained within a predetermined optimal range for energy harvesting from the transducer, avoiding the application of peak voltages. The controlled conversion circuit can be hard wired and/or controllably adjustable to match a given disturbance characteristic. Only when the voltage is within the optimal range for a given type of disturbance will the controlled conversion circuit enable a DC/DC converter to further convert the stored energy to a voltage that is coupled to an output storage element. This technique optimizes power conversion by controlling the high voltage to low version conversion process by, for example, sensing the disturbance with external sensor or internal voltage of the system, and then using this information about the disturbance to control how and when the electrical conversion process will occur.

High-performance piezoelectric vibration energy reclamation

Abstract: A new approach of energy reclamation from mechanical vibrations is presented in this paper. The conversion from mechanical energy into electrical energy is achieved using piezoelectric materials. The originality of the proposed approach is based on a nonlinear treatment of the voltage delivered by a piezoelectric insert embedded in a vibrating structure. This nonlinear processing induces a strong increase of the power conversion capability of the piezoelectric insert. The theoretical principle of the nonlinear treatment is exposed, and the analytical model of an electrical generator is developed. The results given by the model are compared to those of an experimental set-up. Experimental results show that the extracted electrical energy may be increased beyond 400%.

Electromagnetic generators for power harvesting

Abstract: The design of electromagnetic generators that can be integrated within shoe soles is described. In this way, parasitic energy expended by a person when walking can be tapped and used to power portable electronic equipment. Designs are based on discrete permanent magnets and copper wire coils, and it is intended to improve performance by applying micro-fabrication technologies. Detailed descriptions of design and measurements of initial prototype structures are presented, with which RMS voltage levels of over 500 mV have been achieved. Predicted power levels are comparable to those achieved with integrated piezoelectric generators. The design of a second generator structure is introduced. A comparison of the two types of electromagnetic generator structures is presented.

Energy harvesting system, apparatus and method

Abstract: An energy harvesting device, system and method are described. The energy harvester collects acoustic energy and transforms it into electrical energy for use by a sensor. The energy harvester utilizes a piezoelectric device, which may be encased, either wholly or partially, within an acoustic chamber. Alternatively, the piezoelectric device may be entirely exterior to the acoustic chamber, which acts to amplify the collected acoustic energy.

Power conversion from piezoelectric source with multi-stage storage

Abstract: A system and corresponding method for generating electric power from a rotating tire's mechanical energy concerns a piezoelectric power generation device associated with a power harvesting and conditioning module. The piezoelectric structure is preferably mounted within a tire structure such that electric charge is generated therein as the wheel assembly moves along a ground surface. The electrodes of the piezoelectric structure are coupled to a power harvesting and conditioning module that rectifies the resultant electric current from the piezoelectric structure, conditions and stores it in a multi-stage energy storage device, preferably a plurality of capacitors. A regulated voltage source is provided from the energy stored in the power generation device and can be used to selectively power various electronics systems integrated within a tire or wheel assembly. An example of an integrated tire electronics system for use with the disclosed power generation device corresponds to a tire monitoring system that wirelessly transmits such information as tire pressure, temperature and identification variables to a remote receiver location.

Feasibility study of a self-powered piezoelectric sensor

Abstract: Sensors play a crucial role in structural systems with the concern of reliability/failure issues. The development of wireless monitoring systems has been of great interest because wireless transmission has been proven as a convenient means to transmit signals while minimizing the use of many long wires. However, the wireless transmission systems need sufficient power to function properly. Conventionally, batteries are used as the power sources of the remote sensing systems. However, due to their limited lifetime, replacement of batteries has to be carried out periodically, which is inconvenient. In recent years, piezoelectric materials have been developed as sensing and actuating devices mostly, and power generators in some cases. In this paper, a self-powered piezoelectric sensor is studied, in which one piece of piezoelectric material will be simultaneously used as a sensor and a power generator under vibration environment. Concurrent design with piezoelectric materials in sensor and power generator is integrated with energy storage device. We evaluate sensing and power generating abilities individually, and then their concurrent sensing and energy harvesting performances. The possibilities of the piezoelectric sensor to power wireless transmission systems are discussed. Experimental efforts are carried out to study the feasibility of the self-powered piezoelectric sensor system.

Electrostrictive polymers for mechanical energy harvesting

Abstract: Recent advances in electroactive polymers including high field induced strain, high elastic energy density (~1 J/cm3), and relatively high energy conversion efficiency, approaching those of natural muscles, create new opportunities for many applications. Harvesting electric energy from mechanical sources such as a soldier during walking is one such example. Several electroactive polymers developed recently are briefly reviewed. The paper further presents analysis on the key steps in achieving energy harvesting effectively. It is shown that one may make use of smart electronics to modify the electric boundary conditions in the electroactive polymers during the energy harvesting cycle to realize higher energy conversion efficiency in the systems compared with the efficiency of the material itself. Due to the fact that the energy density of the electromagnetic based energy harvesting devices scales with the square root of the device volume, the paper shows that the electroactive polymers based energy harvesting devices exhibit higher energy density and therefore are more suitable for this application.

Towards Wearable Autonomous Microsystems

Abstract: This paper presents our work towards a wearable autonomous microsystem for context recognition. The design process needs to take into account the properties of a wearable environment in terms of sensor placement for data extraction, energy harvesting, comfort and easy integration into clothes and accessories. We suggest to encapsulate the system in an embroidery or a button. The study of a microsystem consisting of a light sensor, a microphone, an accelerometer, a microprocessor and a RF transceiver shows that it is feasible to integrate such a system in a button-like form of 12 mm diameter and 4 mm thickness. We discuss packaging and assembly aspects of such a system. Additionally, we argue that a solar cell on top of the button – together with a lithium polymer battery as energy storage – is capable to power the system even for a user who works predominantly indoors.

Power harvesting sensor for monitoring and control

Abstract: A sensor system (20) includes a power harvesting subsystem (22), a control subsystem (24), a sensor subsystem (26), and a communication subsystem (28). Electromechanical systems generate and dissipate multiple forms of waste energy as a by-product of system operation. Waste energy in the system may lead to destructive side effects which adversely affect the life of system elements. The sensor system (20) is powered above a predetermined level and communicates the sensed information to a remote processor for system diagnosis.

Exploitation of the thermotunnel effect for energy scavenging

Abstract: Over the past few years, MEMS and smart material technologies improvements have allowed autonomous sensor devices to become more and more widespread. As batteries are not always appropriate to power these systems, energy scavenging solutions from ambient power are currently being developed. In particular, many researches have been carried out to improve thermal to electrical energy conversion in ambient temperature gradients. Until now, thermoelectric materials are still the most employed for this application. However, the recent developments in nanoscale device structures open different perspectives. In these nanoscale systems, the heat transport is achieved between two electrodes thanks to electron tunneling. The thermotunnel effect is currently widely studied in the cooling configuration where it has already been shown that it is more efficient than the Peltier effect. We have decided to evaluate this effect in the reciprocal way of work with the objective of being able to power a small sensor node. Considering a device with a simplicial geometrical structure, a modeling has been developed in order to evaluate the feasibility of conversion of a thermal flow into an electrical power based on thermotunneling effect. Comparisons with thermoelectric performances at ambient temperature have been performed.

Active automatic tuning for a recharging circuit

Abstract: An energy harvesting circuit (6) has an active automatic tuning circuit to search for broadcast frequency in a band of interest and selecting only those broadcast signals received with sufficient RF strength to be used in energy harvesting. This circuit would provide power storage devices with a circuit that has a means to select the ambient RF that can maximize or enhance the performance of an RFID circuit by increasing the amount of energy for harvesting. This automatic tuning would enable a power storage devices charger circuit to move from location to location without manual tuning of the circuit and increase the effective range of an RFID circuit.

Energy harvesting concepts for small electric unmanned systems

Abstract: In this study, we identify and survey energy harvesting technologies for small electrically powered unmanned systems designed for long-term (>1 day) time-on-station missions. An environmental energy harvesting scheme will provide long-term, energy additions to the on-board energy source. We have identified four technologies that cover a broad array of available energy sources: solar, kinetic (wind) flow, autophagous structure-power (both combustible and metal air-battery systems) and electromagnetic (EM) energy scavenging. We present existing conceptual designs, critical system components, performance, constraints and state-of-readiness for each technology. We have concluded that the solar and autophagous technologies are relatively matured for small-scale applications and are capable of moderate power output levels (>1 W). We have identified key components and possible multifunctionalities in each technology. The kinetic flow and EM energy scavenging technologies will require more in-depth study before they can be considered for implementation. We have also realized that all of the harvesting systems require design and integration of various electrical, mechanical and chemical components, which will require modeling and optimization using hybrid mechatronics-circuit simulation tools. This study provides a starting point for detailed investigation into the proposed technologies for unmanned system applications under current development.

High efficiency passive piezo energy harvesting circuit

Abstract: A circuit (10) passively discharges energy from a piezoelectric device (12) and stores the energy in a power storage element (14) The circuit has two parallel flow paths each including a diode set (20, 22, 24; 26, 28, 30) and an inductor (16, 18) electrically connected to opposite sides of a piezoelectric device A power storage element is connected to both inductors The diode sets are alternately forward biased, and energy from the piezoelectric device discharges through the inductor(s) A portion of the energy is stored in the inductor(s) and the remaining portion is stored in the power storage element The benefits achieved include passive switching between the parallel circuit paths through diodes in place of traditional switches, and the additional energy stored by the inductors which is also transferred to the power storage element Passive switching conserves additional energy

An experimental comparison between several active composite actuators for power generation

Abstract: The use of piezoelectric materials for power harvesting has gained significant interest over the past few years. The majority of research on this subject has sought to quantify the amount of energy generated in power harvesting applications, or to develop methods of improving the amount of energy generated. Usually, a monolithic PZT material with a traditional electrode pattern and poled through its thickness is used in power harvesting research projects. In recent years, however, several companies and research institutions have begun to develop and market a broad range of piezoelectric composite sensor/actuator packages, each conceived for specific operational advantages and characteristics. Commonly, these devices are employed in control and vibration suppression applications, and their potential for use in power harvesting systems remains largely unknown. Two frequently implemented design techniques for improving the performance of such actuators are the use of interdigitated electrodes and piezofibers. This paper seeks to experimentally quantify the differences in power harvesting application performance between several of these new actuators and to identify the reasons for their relative performance characteristics. A special focus on the structural and compositional differences between each actuator is incorporated in the discussion of the effectiveness of each actuator as power harvesting devices.

Piezoelectric Non-linear Systems for Standalone Vibration Con- trol and Energy Reclamation

Abstract: The technique proposed here addresses the problem of optimizing the electrical energy generated by a piezoelectric element attached on a vibrating structure. It could be applied either for resonance damping, in the field of vibration limitation or acoustic comfort (echo-control) but also for stand-alone microgenerator using the vibration energy for supplying an electronic board (energy harvesting). The proposed solution takes advantage of an original non-linear processing of the voltage generated by piezoelements. This processing is named as SSD for Synchronized Switch Damping and is based on simple commutations. It has the advantage of a very low power requirement as well as a simple electronic processing. It has both advantages of a large bandwidth as well as being a stand-alone system using the vibration as a source of energy. Moreover, no sensor is required, the piezoelement acting both as a sensor and as an actuator. The technique can work at any frequency without the need for a large tuning inductor, especially for low frequency applications. There is no need for external power supply unless for the low power circuitry of the switch device which could easily be self-powered.

Device for electro-magnetohydrodynamic (EMHD) energy harvesting

Abstract: This paper describes a device that uses flow-induced electromagnetic induction as a source of continuous electrical power. The target application is energy harvesting (auxiliary power) for unmanned undersea vehicle (UUV) intelligence, reconnaissance, surveillance (ISR) operations to extend mission duration (trickle charging) or to power supplementary sensor systems. Other military/commercial applications can be envisioned as well for any system that involves the flow of low conductivity fluids and a need for low-level continuous electrical power. The basic device consists of orthogonal pairs of electrodes and a permanent magnet mounted flush with the vehicle surface. When a conducting fluid (e.g., seawater) flows over the device, an electric field is established in the fluid resulting from the motion of the conducting fluid through the magnetic field. The mean flow induced electric field in the fluid is mapped to a DC voltage across the electrode pairs by the same physical process exploited in electromagnetic flow meters. The theoretical basis for the device operation is developed here and used to determine the optimum device/array configuration and to provide numerical estimates of the available DC power. For a UUV at an operating speed of 10 knots, it is estimated that a continuous DC power level of 10mW can be obtained by a relatively compact array of these devices. Laboratory experiments and a more complete analytical model are required to develop an operational system for a full-scale UUV.

Harvesting energy from a cantilever piezoelectric beam

Abstract: Energy harvesting using piezoelectric material is not a new concept, but its small generation capability has not been attractive for mass energy generation. For this reason, little research has been done on the topic. Recently, wearable computer concepts, as well as small portable electrical devices, are a few motivations that have ignited the study of piezoelectric energy harvesting. The theory behind cantilever type piezoelectric elements is well known, as is the suppression of beam vibrations, but not from the context of extracting energy for later use. In this paper we analyze the governing equations of a unimorph beam in terms of the electrical energy that can be generated from base excitations with an eye toward developing design tools for energy harvesting hardware.