Showing papers on "Energy harvesting published in 2005"
TL;DR: A whirlwind survey of energy harvesting can be found in this article, where the authors present a survey of recent advances in energy harvesting, spanning historic and current developments in sensor networks and mobile devices.
Abstract: Energy harvesting has grown from long-established concepts into devices for powering ubiquitously deployed sensor networks and mobile electronics. Systems can scavenge power from human activity or derive limited energy from ambient heat, light, radio, or vibrations. Ongoing power management developments enable battery-powered electronics to live longer. Such advances include dynamic optimization of voltage and clock rate, hybrid analog-digital designs, and clever wake-up procedures that keep the electronics mostly inactive. Exploiting renewable energy resources in the device's environment, however, offers a power source limited by the device's physical survival rather than an adjunct energy store. Energy harvesting's true legacy dates to the water wheel and windmill, and credible approaches that scavenge energy from waste heat or vibration have been around for many decades. Nonetheless, the field has encountered renewed interest as low-power electronics, wireless standards, and miniaturization conspire to populate the world with sensor networks and mobile devices. This article presents a whirlwind survey through energy harvesting, spanning historic and current developments.
2,497 citations
Journal Article•
TL;DR: In this article, the authors describe key issues and tradeoffs which arise in the design of solar energy harvesting, wireless embedded systems and present the design, implementation, and performance evaluation of Heliomote, their prototype that addresses several of these issues.
Abstract: Sustainable operation of battery powered wireless embedded systems (such as sensor nodes) is a key challenge, and considerable research effort has been devoted to energy optimization of such systems. Environmental energy harvesting, in particular solar based, has emerged as a viable technique to supplement battery supplies. However, designing an efficient solar harvesting system to realize the potential benefits of energy harvesting requires an in-depth understanding of several factors. For example, solar energy supply is highly time varying and may not always be sufficient to power the embedded system. Harvesting components, such as solar panels, and energy storage elements, such as batteries or ultracapacitors, have different voltage-current characteristics, which must be matched to each other as well as the energy requirements of the system to maximize harvesting efficiency. Further, battery nonidealities, such as self-discharge and round trip efficiency, directly affect energy usage and storage decisions. The ability of the system to modulate its power consumption by selectively deactivating its sub-components also impacts the overall power management architecture. This paper describes key issues and tradeoffs which arise in the design of solar energy harvesting, wireless embedded systems and presents the design, implementation, and performance evaluation of Heliomote, our prototype that addresses several of these issues. Experimental results demonstrate that Heliomote, which behaves as a plug-in to the Berkeley/Crossbow motes and autonomously manages energy harvesting and storage, enables near-perpetual, harvesting aware operation of the sensor node.
1,063 citations
TL;DR: This paper modeled, designed, and built small cantilever-based devices using piezoelectric materials that can scavenge power from low-level ambient vibration sources, and presents some new designs that can be tuned to the frequency of the host surface, thereby expanding the method's flexibility.
Abstract: Pervasive networks of wireless sensor and communication nodes have the potential to significantly impact society and create large market opportunities. For such networks to achieve their full potential, however, we must develop practical solutions for self-powering these autonomous electronic devices. We've modeled, designed, and built small cantilever-based devices using piezoelectric materials that can scavenge power from low-level ambient vibration sources. Given appropriate power conditioning and capacitive storage, the resulting power source is sufficient to support networks of ultra-low-power, peer-to-peer wireless nodes. These devices have a fixed geometry and - to maximize power output - we've individually designed them to operate as close as possible to the frequency of the driving surface on which they're mounted. In this paper, we describe these devices and present some new designs that can be tuned to the frequency of the host surface, thereby expanding the method's flexibility. We also discuss piezoelectric designs that use new geometries, some of which are microscale (approximately hundreds of microns).
1,036 citations
TL;DR: This technique, called synchronized switch harvesting (SSH), is derived from the synchronized switch damping (SSD), which is a nonlinear technique previously developed to address the problem of vibration damping on mechanical structures, results in a significant increase of the electromechanical conversion capability of piezoelectric materials.
Abstract: This paper presents a new technique of electrical energy generation using mechanically excited piezoelectric materials and a nonlinear process. This technique, called synchronized switch harvesting (SSH), is derived from the synchronized switch damping (SSD), which is a nonlinear technique previously developed to address the problem of vibration damping on mechanical structures. This technique results in a significant increase of the electromechanical conversion capability of piezoelectric materials. Comparatively with standard technique, the electrical harvested power may be increased above 900%. The performance of the nonlinear processing is demonstrated on structures excited at their resonance frequency as well as out of resonance.
949 citations
TL;DR: In this paper, a non-optimized prototype low-level ambient MEMS harvester producing 30 μW/cm3 is designed and modeled, and a MEMS fabrication process for the prototype device is presented based on past work.
Abstract: Design considerations for piezoelectric-based energy harvesters for MEMS-scale sensors are presented, including a review of past work. Harvested ambient vibration energy can satisfy power needs of advanced MEMS-scale autonomous sensors for numerous applications, e.g., structural health monitoring. Coupled 1-D and modal (beam structure) electromechanical models are presented to predict performance, especially power, from measured low-level ambient vibration sources. Models are validated by comparison to prior published results and tests of a MEMS-scale device. A non-optimized prototype low-level ambient MEMS harvester producing 30 μW/cm3 is designed and modeled. A MEMS fabrication process for the prototype device is presented based on past work.
740 citations
TL;DR: In this article, three types of piezoelectric devices are investigated and experimentally tested to deter deterministic power harvesting from the vibration of a discharged nickel metal hydride battery.
Abstract: Piezoelectric materials can be used as a means of transforming ambient vibrations into electrical energy that can then be stored and used to power other devices. With the recent surge of microscale devices, piezoelectric power generation can provide a convenient alternative to traditional power sources used to operate certain types of sensors/actuators, telemetry, and MEMS devices. However, the energy produced by these materials is in many cases far too small to directly power an electrical device. Therefore, much of the research into power harvesting has focused on methods of accumulating the energy until a sufficient amount is present, allowing the intended electronics to be powered. In a recent study by Sodano et al. (2004a) the ability to take the energy generated through the vibration of a piezoelectric material was shown to be capable of recharging a discharged nickel metal hydride battery. In the present study, three types of piezoelectric devices are investigated and experimentally tested to deter...
673 citations
TL;DR: In this article, a nonlinear approach to optimize the power flow of vibration-based piezoelectric energy-harvesting devices is presented, which maximizes the mechanical to electrical energy conversion.
Abstract: This article presents a nonlinear approach to optimize the power flow of vibration-based piezoelectric energy-harvesting devices. This self-adaptive principle is based on a particular synchronization between extraction of the electric charge produced by the piezoelectric element and the system vibrations, which maximizes the mechanical to electrical energy conversion. An analytical expression of the optimal power flow is derived from a simple electromechanical model. An electronic circuit designed to perform the synchronous charge extraction is proposed. Theoretical predictions confirmed by experimental results show that the new principle increases the harvested power by 400% as compared with a quasilinear impedance adaptation optimization method.
562 citations
24 Apr 2005
TL;DR: Experimental results demonstrate that Heliomote, which behaves as a plug-in to the Berkeley/Crossbow motes and autonomously manages energy harvesting and storage, enables near-perpetual, harvesting aware operation of the sensor node.
Abstract: Sustainable operation of battery powered wireless embedded systems (such as sensor nodes) is a key challenge, and considerable research effort has been devoted to energy optimization of such systems. Environmental energy harvesting, in particular solar based, has emerged as a viable technique to supplement battery supplies. However, designing an efficient solar harvesting system to realize the potential benefits of energy harvesting requires an in-depth understanding of several factors. For example, solar energy supply is highly time varying and may not always be sufficient to power the embedded system. Harvesting components, such as solar panels, and energy storage elements, such as batteries or ultracapacitors, have different voltage-current characteristics, which must be matched to each other as well as the energy requirements of the system to maximize harvesting efficiency. Further, battery non-idealities, such as self-discharge and round trip efficiency, directly affect energy usage and storage decisions. The ability of the system to modulate its power consumption by selectively deactivating its sub-components also impacts the overall power management architecture. This paper describes key issues and tradeoffs which arise in the design of solar energy harvesting, wireless embedded systems and presents the design, implementation, and performance evaluation of Heliomote, our prototype that addresses several of these issues. Experimental results demonstrate that Heliomote, which behaves as a plug-in to the Berkeley/Crossbow motes and autonomously manages energy harvesting and storage, enables near-perpetual, harvesting aware operation of the sensor node.
506 citations
TL;DR: In this paper, a self-powered piezoelectric sensor is studied, in which one piece of a PEG element is simultaneously used as a sensor and a power generator under vibration environment.
Abstract: Sensors play a crucial role in structural systems with concern over 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 for 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 article, a self-powered piezoelectric sensor is studied, in which one piece of piezoelectric element is simultaneously used as a sensor and a power generator under vibration environment. Concurrent design with piezoelectric materials in sensor and power generator is inte...
313 citations
TL;DR: This tutorial paper examines architectural and circuit design techniques for a microsensor node operating at power levels low enough to enable the use of an energy harvesting source and proposes architecture for achieving the required ultra-low energy operation.
Abstract: This tutorial paper examines architectural and circuit design techniques for a microsensor node operating at power levels low enough to enable the use of an energy harvesting source. These requirements place demands on all levels of the design. We propose architecture for achieving the required ultra-low energy operation and discuss the circuit techniques necessary to implement the system. Dedicated hardware implementations improve the efficiency for specific functionality, and modular partitioning permits fine-grained optimization and power-gating. We describe modeling and operating at the minimum energy point in the subthreshold region for digital circuits. We also examine approaches for improving the energy efficiency of analog components like the transmitter and the ADC. A microsensor node using the techniques we describe can function in an energy-harvesting scenario.
293 citations
TL;DR: In this article, the authors quantified the amount of energy generated by a piezoelectric plate and investigated two methods of accumulating the energy thus produced, one using a capacitor and the other using rechargeable nickel metal hydride batteries.
Abstract: The concept of capturing the normally lost energy surrounding a system and converting it into electrical energy that can be used to extend the lifetime of that system's power supply or possibly provide an endless supply of energy to an electronic device has captivated many researchers and has brought forth a growing amount of attention to power harvesting. One of the most common methods of obtaining the energy surrounding a system is to use piezoelectric materials. Piezoelectric materials have a crystalline structure that provides a unique ability to convert an applied electrical potential into a mechanical strain or vice versa, or convert an applied strain into an electrical current. The latter of these two properties allows the material to function as a power harvesting medium. In most cases the piezoelectric material is strained through the ambient vibration around the structure, thus allowing a frequently unused energy source to be utilized for the purpose of powering small electronic systems. However, the amount of energy generated by these piezoelectric materials is far smaller than that needed by most electronic devices. For this reason, the methods of accumulating and storing the energy generated, until sufficient power has been captured, is the key to developing completely self-powered systems. This article quantifies the amount of energy generated by a piezoelectric plate and investigates two methods of accumulating the energy thus produced. The first method uses a capacitor, which in early research has been the most common method of storing the energy generated and the second utilizes rechargeable nickel metal hydride batteries. The advantages of each method are discussed and the rechargeable battery is found to have more desirable qualities for power harvesting than the capacitor. Additionally, this manuscript represents, for the first time, the fact that the power output by a piezoelectric material is capable of recharging a discharged battery. Through the excitation of a piezoelectric plate, it is demonstrated that a 40 mAh battery can be charged in less than half an hour at resonance and in only a few hours with a random signal similar to that of a typical vibrating piece of machinery.
Abstract: The small amount of power demanded by many present-day electronic devices opens up the possibility to convert part of the energy present in the environment into electrical energy, using several methods. One such method is to use piezoelectric film-bending beams inside a shoe, and use part of the mechanical energy employed during normal walking activity. This study analyzes several bending beam structures suitable for the intended application (shoe inserts and walking-type excitation) and obtains the resulting strain for each type as a function of their geometrical parameters and material properties. As a result, the optimum configuration can be selected.
TL;DR: In this paper, a piezoelectric windmill with 12 bimorph actuators was demonstrated for the remote powering of sensors and communication devices, achieving a power of 10.2 mW across a load of 4.6 kΩ after rectification.
Abstract: This study demonstrates a technology, "Piezoelectric Windmill", for generating the electrical power from wind energy. The electric power-generation from wind energy is based on piezoelectric effect and utilizes the bimorph actuators. Piezoelectric Windmill consists of piezoelectric actuators arranged along the circumference of the mill in the cantilever form. Using the camshaft gear mechanism an oscillating torque is generated through the flowing wind and applied on the actuators. A working prototype was fabricated utilizing 12 bimorphs (60 ×20 ×0.5 mm3) having a preload of 23.5 gm. Under a nominal torque level corresponding to normal wind flow and oscillating frequency of 6 Hz, a power of 10.2 mW was successfully measured across a load of 4.6 kΩ after rectification. Combined with the wireless transmission, this technology provides a practical solution to the remote powering of sensors and communication devices.
TL;DR: In this paper, two clamped circular plate structures, a fully electroded unimorph and a so-called regrouped electrode unimorph, are modeled and then used to calculate energy generation with varying thickness ratios.
Abstract: Energy harvesting using piezoelectric materials 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, increased interest in wearable computer concepts and remote electrical devices has provided motivation for more extensive study of piezoelectric energy harvesting. The theory behind cantilever-type piezoelectric elements is well known, but the transverse moving plate elements, which can be used in energy generation from pressure sources is not yet fully developed. The power generation in a pressure-loaded plate depends on several factors. Among them, the thickness of each layer is important, as is the electrode pattern used. In this article, two clamped circular plate structures, a fully electroded unimorph, and a so-called regrouped electrode unimorph, are modeled. These models are then used to calculate energy generation with varying thickness ratios. The results of this analysi...
16 May 2005
TL;DR: In this paper, the authors demonstrate smart wireless sensing nodes capable of operation at extremely low power levels using piezoelectric materials and/or solar cells, and demonstrate extremely low average power consumption.
Abstract: The objective of this work was to demonstrate smart wireless sensing nodes capable of operation at extremely low power levels. These systems were designed to be compatible with energy harvesting systems using piezoelectric materials and/or solar cells. The wireless sensing nodes included a microprocessor, on-board memory, sensing means (1000 ohm foil strain gauge), sensor signal conditioning, 2.4 GHz IEEE 802.15.4 radio transceiver, and rechargeable battery. Extremely low power consumption sleep currents combined with periodic, timed wake-up was used to minimize the average power consumption. Furthermore, we deployed pulsed sensor excitation and microprocessor power control of the signal conditioning elements to minimize the sensors’ average contribution to power draw. By sleeping in between samples, we were able to demonstrate extremely low average power consumption. At 10 Hz, current consumption was 300 microamps at 3 VDC (900 microwatts); at 5 Hz: 400 microwatts, at 1 Hz: 90 microwatts. When the RF stage was not used, but data were logged to memory, consumption was further reduced. Piezoelectric strain energy harvesting systems delivered ~2000 microwatts under low level vibration conditions. Output power levels were also measured from two miniature solar cells; which provided a wide range of output power (~100 to 1400 microwatts), depending on the light type & distance from the source. In summary, system power consumption may be reduced by: 1) removing the load from the energy harvesting & storage elements while charging, 2) by using sleep modes in between samples, 3) pulsing excitation to the sensing and signal conditioning elements in between samples, and 4) by recording and/or averaging, rather than frequently transmitting, sensor data.
15 Aug 2005
TL;DR: In this paper, a harmonically matched trapezoidal geometry was used to solve the problem of uneven strain distribution in a cantilevered rectangular piezoelectric beam, increasing the power per unit volume.
Abstract: Vibration energy scavenging with piezoelectric material can currently generate up to 300 microwatts per cubic centimeter, making it a viable method of powering low-power electronics. Given the growing interest in small-scale devices, particularly wireless sensor networks, concerns over how to indefinitely power them have become extremely relevant. Current limiting factors in the field of piezoelectric vibration energy scavenging include: coupling coefficients, strain distribution, and frequency matching. This paper addresses each of these three factors with a novel design and a corresponding analysis of its performance. For example, the power output of a cantilevered rectangular piezoelectric beam is limited by its uneven strain distribution under load. A prototype scavenger using a harmonically matched trapezoidal geometry solves this problem by evening the strain distribution throughout the beam, increasing by 30% the output power per unit volume. Another design is created which softens the frequency response of the generator, relaxing the constraint of frequency matching. The paper concludes that each of the three challenges to vibration energy scavenging can be met through creativity in mechanism design, making higher power densities possible and broader applications more feasible.
01 Jan 2005
TL;DR: In this article, the authors present several methods to design an energy harvesting device depending on the type of energy avaliable, which can be used to either recharge a battery, or even to directly power the electronic device.
Abstract: The trends in technology allow the decrease in both size and power consumption of complex digital systems. This decrease in size and power gives rise to new paradigms of computing and use of electronics, with many small devices working collaboratively or at least with strong communication capabilities. Examples of these new paradigms are wearable devices and wireless sensor networks. Currently, these devices are powered by batteries. However, batteries present several disadvantages: the need to either replace or recharge them periodically and their big size and weight compared to high technology electronics. One possibility to overcome these power limitations is to extract (harvest) energy from the environment to either recharge a battery, or even to directly power the electronic device. This paper presents several methods to design an energy harvesting device depending on the type of energy avaliable.
TL;DR: In this paper, the authors presented a new application of the synchronized switch harvesting on inductors (SSHI) which results in a significant increase of the electromechanical conversion capability of piezoelectric materials.
Abstract: This paper presents a new application of the ‘Synchronized Switch Harvesting on Inductor’ (SSHI). This nonlinear technique results in a significant increase of the electromechanical conversion capability of piezoelectric materials. Previous studies have shown the interest of this technique on steady state excited structures equipped with piezoelectric elements where the harvested power may be increased nearly tenfold compared to the standard technique. It is herein demonstrated that this technique is also very effective for pulsed excitation. It is shown that the SSHI technique increases the harvesting process efficiency between 250 and 450%, depending on the electromechanical coupling coefficient of the structure.
TL;DR: This paper presents several methods to design an energy harvesting device depending on the type of energy avaliable, which could be used to recharge a battery, or even to directly power the electronic device.
Abstract: The trends in technology allow the decrease in both size and power consumption of complex digital systems. This decrease in size and power gives rise to new paradigms of computing and use of electronics, with many small devices working collaboratively or at least with strong communication capabilities. Examples of these new paradigms are wearable devices and wireless sensor networks. Currently, these devices are powered by batteries. However, batteries present several disadvantages: the need to either replace or recharge them periodically and their big size and weight compared to high technology electronics. One possibility to overcome these power limitations is to extract (harvest) energy from the environment to either recharge a battery, or even to directly power the electronic device. This paper presents several methods to design an energy harvesting device depending on the type of energy avaliable.
TL;DR: In this paper, a model for a clamped circular unimorph piezoelectric plate has been developed for the purpose of analyzing the influence of geometric design parameters and electrode configuration on the amount of electrical energy that can be harvested from an applied pressure source.
Abstract: In a companion article, a model for a clamped circular unimorph piezoelectric plate has been developed for the purpose of analyzing the influence of geometric design parameters and electrode configuration on the amount of electrical energy that can be harvested from an applied pressure source. It has been shown that the ratio of layer thickness (piezoelectric layer to substrate layer) and electrode pattern have a significant effect on energy conversion for harvesting. Specifically, the theoretical analysis shows that regrouping of the electrodes (i.e., segmenting the electrode into a specific pattern) can lead to optimized energy harvesting in a clamped circular plate structure. This article provides experimental validation of these results. In this article, three circular plate piezoelectric energy generators (PEGs), one unmodified and two regrouped unimorph PEGs, were used to support the analysis.
TL;DR: In this article, the use of auxiliary structures, consisting of a mechanical fixture and a lead zirconate/lead titanate (PZT) piezoelectric element, which can be attached to any vibrating system, was examined.
Abstract: Future, self-contained sensors and processing units will need onboard, renewable power supplies to be truly autonomous. One way of supplying such power is through energy harvesting, a process by which ambient forms of energy are converted into electricity. One energy harvesting technique involves converting kinetic energy, in the form of vibrations, into electrical energy through the use of piezoelectric materials. This study examines the use of auxiliary structures, consisting of a mechanical fixture and a lead zirconate/lead titanate (PZT) piezoelectric element, which can be attached to any vibrating system. Adjusting various parameters of these structures can maximize the strain induced in the attached PZT element and improve power output.
TL;DR: Comparison with a magnetic-based energy harvesting system suggests that electrostrictive energy harvesting systems are preferable for "small" energy harvesting applications with low-frequency excitation.
Abstract: The recent development of electrostrictive polymers has generated new opportunities for high-strain actuators. At the current time, the investigation of using electrostrictive polymer for energy harvesting, or mechanical to electrical energy conversion, is beginning to show its potential for this application. In this paper we discuss the mechanical and electrical boundary conditions for maximizing the energy harvesting density and mechanical-to-electrical coupling of electrostrictive materials. Mathematical models for different energy harvesting approaches were developed under quasistatic assumptions. Energy harvesting densities then are determined for representative electrostrictive material properties using these models. Comparison with a magnetic-based energy harvesting system suggests that electrostrictive energy harvesting systems are preferable for "small" energy harvesting applications with low-frequency excitation.
TL;DR: In this paper, a new approach of the piezoelectric power conversion based on a non linear voltage processing is presented, leading to three novel high-performance techniques, theoretical predictions and experimental results show that the novel techniques may increase the power harvested above 800% compared to standard techniques.
Abstract: This paper compares the performances of vibration-powered electrical generators using a piezoelectric ceramic and a piezoelectric single crystal associated to several power conditioning interfaces. A new approach of the piezoelectric power conversion based on a non linear voltage processing is presented, leading to three novel high-performance techniques. Theoretical predictions and experimental results show that the novel techniques may increase the power harvested above 800% compared to standard techniques.
01 Apr 2005
TL;DR: In this article, the feasibility of using piezoelectric materials in a power source for micro-electro-mechanical systems (MEMS) devices was presented. But the authors only evaluated the power generation of two different shapes of the piezofilms: square and circle.
Abstract: This paper presents the feasibility of using piezoelectric materials in a power source for micro-electro-mechanical systems (MEMS) devices. The finite element method (FEM) is adopted to evaluate the power generations of commercially available piezofilms that are subjected to a fluctuating pressure source (blood pressure). The accuracy of the results obtained from the FEM is verified by comparing with the corresponding results obtained from a theoretical analysis. In addition, an experiment is undertaken in order to evaluate the power generation of two different shapes of the piezofilms: square and circle. Finally, a brief discussion is made on the storage of experimentally harvested power and use of the MEMS applications.
Patent•
27 Jul 2005TL;DR: In this article, the present subject matter discloses apparatus and methodologies for fabricating apparatus for harvesting power from environmentally induced vibrations Piezoelectric devices and structures (1600) are disclosed that employ constant force spring or flexure arrangements (1512) in balanced opposition configurations (1510, 1534) to enhance the power harvesting capabilities of the piezoeelectric devices.
Abstract: The present subject matter discloses apparatus and methodologies for fabricating apparatus for harvesting power from environmentally induced vibrations Piezoelectric devices and structures (1600) are disclosed that employ constant force spring or flexure arrangements (1512) in balanced opposition configurations (1510, 1534) to enhance the power harvesting capabilities of the piezoelectric devices (1600) 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
01 May 2005
TL;DR: It is demonstrated that subthreshold-voltage circuit design (400 mV and below) lends itself well to the performance and energy demands of sensor network processors, and it is shown that the landscape for microarchitectural energy optimization dramatically changes in the subth threshold domain.
Abstract: Sensor network processors and their applications are a growing area of focus in computer system research and design. Inherent to this design space is a reduced processing performance requirement and extremely high energy constraints, such that sensor network processors must execute low-performance tasks for long durations on small energy supplies. In this paper, we demonstrate that subthreshold-voltage circuit design (400 mV and below) lends itself well to the performance and energy demands of sensor network processors. Moreover, we show that the landscape for microarchitectural energy optimization dramatically changes in the subthreshold domain. The dominance of leakage power in the subthreshold regime demands architectures that i) reduce overall area, ii) increase the utility of transistors, while iii) maintaining acceptable CPI efficiency. We confirm these observations by performing SPICE-level analysis of 21 sensor network processors and memory architectures. Our best sensor platform, implemented in 130nm CMOS and operating at 235 mV, only consumes 1.38 pJ/instruction, nearly an order of magnitude less energy than previously published sensor network processor results. This design, accompanied by bulk-silicon solar cells for energy scavenging, has been manufactured by IBM and is currently being tested.
TL;DR: How harvesting environmental energy in sensor networks changes the way an application developer views energy management is examined, and devices that combine energy harvesting and data acquisition are proposed, and prototype devices are discussed.
Abstract: This article examines how harvesting environmental energy in sensor networks changes the way an application developer views energy management, and discusses prototype devices. Then it proposes devices that combine energy harvesting and data acquisition. Then it explores novel approaches for optimizing the power extracted using piezoelectric materials. The final one explores kinetic and thermal energy harvesting from human users' activities. We usually use energy harvesting systems to convert and collect the environment's energy flows. A new wearable computing concept is considering these energy flows to be data flows as well. Current piezoelectric energy harvesting research falls into two key areas: developing optimal energy harvesting structures and highly efficient electrical circuits to store the generated charge or present it to the load circuit. Our research focuses primarily on the first area, in which the goal is to create small, lightweight structures that couple very well to mechanical excitation and converts the most usable electrical energy.
TL;DR: In this article, the capability of harvesting the electric energy from mechanical vibrations in a dynamic environment through a unimorph piezoelectric membrane transducer was investigated, and a power of 1.8 mW was generated at resonance frequency (2.58 kHz) across a 56 kQ optimal resistor and for a 2 g acceleration.
Abstract: In this paper we investigate the capability of harvesting the electric energy from mechanical vibrations in a dynamic environment through a unimorph piezoelectric membrane transducer. Due to the impedance matrices connecting the efforts and flows of the membrane, we have established the dynamic electric equivalent circuit of the transducer. In a first study and in order to validate theoretical results, we performed experiments with a vibrating machine moving a macroscopic 25 mm diameter piezoelectric membrane. A power of 1.8 mW was generated at the resonance frequency (2.58 kHz) across a 56 kQ optimal resistor and for a 2 g acceleration.
Patent•
19 Jul 2005
TL;DR: An article of footwear having a piezoelectric energy harvesting apparatus in the sole member walking or running applies a first force deforming a PEC actuator, thereby generating electrical energy.
Abstract: An article of footwear having a piezoelectric energy harvesting apparatus in the sole member Walking or running applies a first force deforming a piezoelectric actuator, thereby generating electrical energy An energy storage circuit stores electrical energy generated by the piezoelectric actuator for later application to electrical devices
Patent•
20 Apr 2005TL;DR: In this paper, a high-efficiency power converter converts the unregulated AC electrical energy generated by an energy harvesting device to regulated quasi-continuous DC or AC power delivered to a load.
Abstract: A high-efficiency power converter converts the unregulated AC electrical energy generated by an energy harvesting device to regulated quasi-continuous DC or AC power delivered to a load. A DC link capacitor stores energy from the AC input. Control electronics alternately transfers regulated power to the load and recharges the capacitor in accordance with a hysteresis window in the capacitor energy. The control electronics terminates transfer of regulated power to the load and initiates recharging of the capacitor when the capacitor voltage, hence energy falls below a lower threshold and terminates capacitor charging and initiates power transfer when the capacitor voltage, hence energy exceeds an upper threshold.