Browsing by Subject "Energy harvesting"
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Item Acknowledgment Strategies for Efficient Asymmetric Routing in Energy Harvesting Wireless Sensor Networks(2013-05) Gade, Tejaswi; Lim, Sunho; Youn, EunseogEnergy conservation has been a primary concern in wireless sensor networks (WSNs), where long-term operations are often required in hard-reach environments. Due to unavoidable batteries replacement or replenishment, diverse energy harvesting techniques have been integrated with WSNs to overcome limited battery power and extend the network lifetime. However, variable transmission power levels caused by non-uniform energy harvesting rates can lead to asymmetric links. In this document, we propose weighted and lazy acknowledgment schemes and their combination to efficiently route sensory data to a sink over asymmetric links. The weighted acknowledgment (WACK) can differentiate multiple paths between data source and the sink by assigning multiplicative weights on the paths. The lazy acknowledgment (LACK) can assure reverse path by waiting for extended communication range. An asymmetric link aware backoff mechanism is also proposed to avoid data contention and collision. We compare the proposed schemes through extensive simulation experiments and their results indicate that the proposed acknowledgment strategies can be a viable approach in energy harvesting WSNs.Item An energy harvesting aware data dissemination strategy for energy rechargeable wireless sensor networks(2012-08) Gosavi, Amit; Lim, Sunho; Lakhani, GopalA wireless sensor network (WSN) is often deployed in a harsh or hard-reach area and is required to operate for a long period time to collect and route sensed information. Since each sensor node (later node) is battery-powered, prudent energy-efficient mechanisms have been proposed to extend the network life-time. However, recharging (or replacing) battery is ultimately unavoidable. In this thesis, we consider energy harvesting (or scavenging) with environmental energy sources, such as solar, wind, or vibration. Then we extend the original sensor protocols for information via negotiation (SPIN) and propose an energy harvesting aware data dissemination strategy for energy rechargeable wireless sensor networks, called Green-SPIN. In Green-SPIN, each node intermittently harvests energy and judiciously changes its communication range. We compare the performance of three data dissemination schemes as a function of number of nodes and the communication range through extensive simulation: Flooding, SPIN with broadcast (SPIN-BC), SPIN with reliability (SPIN-RL), and Green-SPIN. Our simulation results indicate that the proposed scheme achieves more data dissemination rate than the SPIN-RL in the low node density and short communication range. Compared to Flooding and SPIN-BC, both proposed scheme and SPIN-RL show two times higher data dissemination rate. The proposed scheme also shows competitive performance with SPIN-RL in high node density and extended communication range. In addition, the proposed scheme transmits similar number of data packets with the SPIN-RL.Item Analysis and design of 3 stage voltage rectifier multiplier and 2 stage multi-phase voltage doubler for and energy harvesting system(2012-08) Shrivastava, Ravindranath; Gale, Richard O.; Li, ChangzhiThe reliability and the efficiency of the wireless link between the TX/RX for wireless sensors devices depends on the environmental conditions such as change in the physical distance or changes in the orientation between transmitter and receiver. So the need arises to monitor and the ability to adjust the wireless link between TX/RX without interrupting the operation of the wireless sensor. Also the ambient wireless energy can also be harvested to power the wireless sensor circuitry. We propose an N-Stage Voltage Multiplier/Rectifier built in AMI06 process using a Schottky diode to convert the ambient RF Energy into DC voltage which can be measured to evaluate the strength of the Wireless link. The proposed system can be used to monitoring and vary the wireless link parameters such as the resonant matching condition between TX/RX antenna coil and physical alignment without interrupting the operation of the wireless sensor. Also the DC energy harvested can be boosted further by our proposed multiphase charge pump to a higher DC Level which can be used by the wireless sensor circuitry. The DC power harvested can also be used alongside the on board battery which will lead to increase in battery efficiency. The voltage multiplier/rectifier and charge pump involving the power stage and the feedback circuitry can be built on the same die as the wireless sensor circuitry which can lead to less bulky system.Item Design and production of an energy harvesting wireless sensor(2013-05) Bar, Farris Ahmad; Abraham, Jacob A.The widespread deployment of wireless sensors in our homes, offices, factories and infrastructure has opened the door for system designers to create novel approaches for powering wireless sensor nodes. In recent years, energy harvesting has emerged as the power supply of choice for embedded system designers, enabling wireless sensors to be used in applications that previously were not feasible with conventional battery-powered designs. This report details the design and development of an energy harvesting wireless sensor from concept to production. Design constraints included the requirement to operate reliably in a wide variety of environments, the use of commercially available components, and a visually appealing form factor. The result is a very power-efficient, solar-powered wireless sensor that measures temperature, voltage, and illumination level at the solar cell and has an ultra slim form factor.Item Design of a solar energy harvesting system for structural health monitoring systems(2012-08) Inamdar, Sumedh Anand; Crawford, Richard H.; Wood, Kristin L.The work described in this thesis discusses the design of a solar energy harvesting system to support a structural health monitoring system. The objective was to design a photovoltaic system capable of powering a wireless gateway and cellular modem, a static DC 14W load, while meeting certain functional and energy requirements for deployment on a bridge. A literature review of the application, technologies, components, and latest innovations in solar energy technology was completed. A methodology for designing a system for attaching energy harvesting systems onto bridges while meeting design requirements is presented as a tool for engineers and students. The use of the tool was demonstrated through a study which revealed that the methodology aided in producing concepts that were higher in quality, quantity, and better met design requirements. A PV array performance model was used to determine the proper PV module size, battery bank size, panel orientation, the usefulness of a solar tracker and MPPT charge controller, and whether the use of two separate PV modules with independent geometric orientations provide better performance as compared to a single larger panel. It was found from the study that the optimal PV system design specifications were a 120W Polycrystalline PV panel, a 120 A-hr LiFePO4 battery bank, a 45 degree tilt and 0 degrees solar azimuth angle (south), and an MPPT controller. The results from the analytical model also showed that the maximum energy produced with two independent panels would be at a solar azimuth angle of 0 degrees (south) and tilt angles of 45 and 50 degrees respectively. However, these energy gains were insignificant compared to simply increasing the size of the PV module. This result was verified by physical experiments. The physical embodiment of the solar energy harvester with these characteristics, including the mount to the bridge and the panel, was conceptualized, refined, analyzed for structural integrity, and prototyped.Item Design of an electromagnetic vibration energy harvester for structural health monitoring of bridges employing wireless sensor networks(2011-08) Dierks, Eric Carl; Wood, Kristin L.; Crawford, Richard H.Energy harvesting is playing an increasingly important role in supplying power to monitoring and automation systems such as structural health monitoring using wireless sensor networks. This importance is most notable when the structures to be monitored are in rural, hazardous, or limited access environments such as busy highway bridges where traffic would be greatly disrupted during maintenance, inspection, or battery replacement. This thesis provides an overview of energy harvesting technologies and details the design, prototyping, testing, and simulation of an energy harvester which converts the vibrations of steel highway bridges into stored electrical energy through the use of a translational electromagnetic generator, to power a wireless sensor network for bridge structural health monitoring. An analysis of bridge vibrations, the use of nonlinear and linear harvester compliance, resonant frequency tuning, and bandwidth widening to maximize the energy harvested is presented. The design approach follows broad and focused background research, functional analysis, broad and focused concept generation and selection, early prototyping, parametric modeling and simulation, rapid prototyping with selective laser sintering, and laboratory testing with replicated bridge vibration. The key outcomes of the work are: a breadth of conceptual designs, extensive literature review, a prototype which harvests an average of 80µW under bridge vibration, a prototype which provides quick assembly, mounting and tuning, and the conclusion that a linear harvester out performs a nonlinear harvester with stiffening magnetic compliance for aperiodic vibrations such as those from highway bridges.Item Design of vibrational and solar energy harvesting systems for powering wireless sensor networks in bridge structural health monitoring applications(2014-12) Adams, Jacob Allan; Crawford, Richard H.Structural health monitoring systems provide a promising route to real-time data for analyzing the current state of large structures. In the wake of two high-profile bridge collapses due to an aging highway infrastructure, the interest in implementing such systems into fracture-critical and structurally deficient bridges is greater now than at any point in history. Traditionally, these technologies have not been cost-effective as bridges lack existing wiring architecture and the addition of this is cost prohibitive. Modern wireless sensor networks (WSN) now present a viable alternative to traditional networking; however, these systems must incorporate localized power sources capable of decade-long operation with minimal maintenance. To this end, this thesis explores the development of two energy harvesting systems capable of long-term bridge deployment with minimal maintenance. First, an electromagnetic, linear, vibrational energy harvester is explored that utilizes the excitations from passing traffic to induce motion in a translating permanent magnet mass. This motion is then converted to electrical energy using Faraday’s law of induction. This thesis presents a review of vibrational energy harvesting literature before detailing the process of designing, simulating, prototyping, and testing a selected design. Included is an analysis of the effects of frequency, excitation amplitude, load, and damping on the power production potential of the harvester. Second, a solar energy harvester using photovoltaic (PV) panels is explored for powering the critical gateway component of the WSN responsible for data aggregation. As solar energy harvesting is a more mature technology, this thesis focuses on the methodologies for properly sizing a solar harvesting system and experimentally validating the selected design. Fabrication of the prototype system was completed and field testing was performed in Austin, TX. The results validate the selected system’s ability to power the necessary 14 W DC load with a 0° panel azimuth angle (facing direct south) and 45° tilt.Item EtherLux, a low power wireless display(2009-12) Hocker, Andrew Edward; Aziz, Adnan; McDermott, MarkReal time information is essential in many businesses and as a method to inform employees and consumers, so that they can make informed decisions. In offices, warehouse and stores it can be advantageous to have tens to hundreds of smaller displays to deliver a variety of information. This paper details the design, implementation and testing of a wireless low power solar powered display system as a solution to deliver real time information. The system uses an Organic LCD to maintain an image for years on no power and uses very little power to update and refresh the display. The system uses off- the-shelf components to achieve multiple updates per day and, with the right lighting conditions, can perform up to one refresh per minute. The system is entirely powered by incandescent light, has a built in radio, and utilizes capacitors to store charge and deliver power, removing the need for rechargeable batteries. The wireless signal works at 2.4GHz and uses the low power 802.15.4 protocol to send and receive data at a range of 75 feet. It has no observable issue operating in environments with 2.4GHz wireless signals, such as 802.11g. The whole system can be built for under $75.00, and takes up an area of 6" x 8" including the photovoltaic cells.Item Evaluating vehicular-induced vibrations of typical highway bridges for energy harvesting applications(2012-05) Reichenbach, Matthew Craig; Wood, Sharon L.; Helwig, Todd A.Highway bridges are vital links in any transportation network. Identifying the possible safety problems in the approximately 600,000 bridges across the U.S. is generally accomplished through labor-intensive, visual inspections. Wireless monitoring technology seeks to improve current practices by supplementing the visual inspections with real-time evaluation of bridges. To be economically feasible, wireless sensor networks should be able to (a) operate independent of the power grid, and (b) achieve a service life of at least ten years. Novel energy harvesting approaches have been investigated to fulfill these two criteria. In particular, the feasibility of a vibration energy harvester as a long-term power source was assessed. The goal of the research was to process measured acceleration data and analyze the vibrational response of typical highway bridges under truck loads. The effects of ambient temperature, truck traffic patterns, and harvester position on the power content of the vibrations were explored, as well as the effects of linear and nonlinear harvesters. This thesis presents the results of evaluating the response of five steel bridges in Texas and Oregon for energy harvesting applications.Item Fundamentals of Heterogeneous Cellular Networks(2013-12) Dhillon, Harpreet Singh; Andrews, Jeffrey G.The increasing complexity of heterogeneous cellular networks (HetNets) due to the irregular deployment of small cells demands significant rethinking in the way cellular networks are perceived, modeled and analyzed. In addition to threatening the relevance of classical models, this new network paradigm also raises questions regarding the feasibility of state-of-the-art simulation-based approach for system design. This dissertation proposes a fundamentally new approach based on random spatial models that is not only tractable but also captures current deployment trends fairly accurately. First, this dissertation presents a general baseline model for HetNets consisting of K different types of base stations (BSs) that may differ in terms of transmit power, deployment density and target rate. Modeling the locations of each class of BSs as an independent Poisson Point Process (PPP) allows the derivation of surprisingly simple expressions for coverage probability and average rate. One interpretation of these results is that adding more BSs or tiers does not necessarily change the coverage probability, which indicates that fears of "interference overload" in HetNets are probably overblown. Second, a flexible notion of BS load is incorporated by introducing a new idea of conditionally thinning the interference field. For this generalized model, the coverage probability is shown to increase when lightly loaded small cells are added to the existing macrocellular networks. This is due to the fact that owing to the smaller loads, small cells typically transmit less often than macrocells, thus contributing less to the interference power. The same idea of conditional thinning is also shown to be useful in modeling the non-uniform user distributions, especially when the users lie closer to the BSs. Third, the baseline model is extended to study multi-antenna HetNets, where BSs across tiers may additionally differ in terms of the number of transmit antennas, number of users served and the multi-antenna transmission strategy. Using novel tools from stochastic orders, a tractable framework is developed to compare the performance of various multi-antenna transmission strategies for a fairly general spatial model, where the BSs may follow any general stationary distribution. The analysis shows that for a given total number of transmit antennas in the network, it is preferable to spread them across many single-antenna BSs vs. fewer multi-antenna BSs. Fourth, accounting for the load on the serving BS, downlink rate distribution is derived for a generalized cell selection model, where shadowing, following any general distribution, impacts cell selection while fading does not. This generalizes the baseline model and all its extensions, which either ignore the impact of channel randomness on cell selection or lumps all the sources of randomness into a single random variable. As an application of these results, it is shown that in certain regimes, shadowing naturally balances load across various tiers and hence reduces the need for artificial cell selection bias. Fifth and last, a slightly futuristic scenario of self-powered HetNets is considered, where each BS is powered solely by a self-contained energy harvesting module that may differ across tiers in terms of the energy harvesting rate and energy storage capacity. Since a BS may not always have sufficient energy, it may not always be available to serve users. This leads to a notion of availability region, which characterizes the fraction of time each type of BS can be made available under variety of strategies. One interpretation of this result is that the self-powered BSs do not suffer performance degradation due to the unreliability associated with energy harvesting if the availability vector corresponding to the optimal system performance lies in the availability region.Item Harvesting wind energy using a galloping piezoelectric beam(2011-05) Mahadik, Rohan Ram; Sirohi, Jayant; Bennighof, JeffreyGalloping of structures such as transmission lines and bridges is a classical aeroelastic instability that has been considered as harmful and destructive. However, there exists potential to harness useful energy from this phenomenon. The study presented in this paper focuses on harvesting wind energy that is being transferred to a galloping beam. The beam has a rigid prismatic tip body. Triangular and D-section are the two kinds of cross section of the tip body that are studied, developed and tested. Piezoelectric sheets are bonded on the top and bottom surface of elastic portion of the beam. During galloping, vibrational motion is input to the system due to aerodynamic forces acting on the tip body. This motion is converted into electrical energy by the piezoelectric (PZT) sheets. A potential application for this device is to power wireless sensor networks on outdoor structures such as bridges and buildings. The relative importance of various parameters of the system such as wind speed, material properties of the beam, electrical load, beam natural frequency and aerodynamic geometry of the tip body is discussed. A model is developed to predict the dynamic response, voltage and power results. Experimental investigations are performed on a representative device in order to verify the accuracy of the model as well as to study the feasibility of the device. A maximum output power of 1.14 mW was measured at a wind velocity of 10.5 mph.Item Innovative energy harvesting technology for wireless bridge monitoring systems(2011-08) Weaver, Jason Michael; Wood, Kristin L.; Crawford, Richard H.; Seepersad, Carolyn C.; Wilson, Preston; Wood, SharonEnergy harvesting is a promising and evolving field of research capable of supplying power to systems in a broad range of applications. In particular, the ability to gather energy directly from the environment without human intervention makes energy harvesting an excellent option for powering autonomous sensors in remote or hazardous locations. This dissertation examines the possibility of using energy harvesting in new and innovative ways to power wireless sensor nodes placed in the substructures of highway bridges for structural health monitoring. Estimates for power requirements are established, using a wireless sensor node from National Instruments as an example system. Available power in a bridge environment is calculated for different energy sources, including solar radiation, wind, and vibration from traffic. Feasibility of using energy harvesting in such an application is addressed for both power availability and cost as compared with grid power or primary batteries. An in-depth functional analysis of existing energy-harvesting systems is also presented, with insights into where innovation would be most beneficial in future systems. Finally, the development of a suite of complementary energy-harvesting devices is described. Because conditions on bridges may vary, multiple solutions involving different energy domains are desired, with the end user able to select the harvester most appropriate for the specific installation. Concept generation techniques such as mind-mapping and 6-3-5 (C-Sketch) are used to produce a wide variety of concepts, from which several promising concept variants are selected. The continued development for one concept, which harvests vibration using piezoelectric materials, is described. Analytical modeling is presented for static and dynamic loading, as well as predicted power generation. Two proof-of-concept prototypes are built and tested in laboratory conditions. Through the development of this prototype, it is shown that the example wireless sensor node can successfully be powered through energy harvesting, and insights are shared concerning the situations where this and other energy harvesters would be most appropriate.Item New architecture development for energy harvesting(2011-08) Reddy, Divya; Bayne, Stephen B.This research presents the design of an ultra-low power energy scavenging system capable of collecting and managing energy from ambient vibrations and RF electromagnetic waves. The main motive is to develop a self-powered system which is a substitute for remotely placed low power batteries with rare human interaction. Firstly, the energy transducers, commercial piezoelectric generators with a wide frequency range of 26 – 205Hz and the antenna with a center frequency of 916MHz are evaluated and characterized to maximize the efficiency. Both antenna and piezoelectric generator can form an array of each type to increase the energy being harvested. Secondly, the power electronic circuits involved in the energy harvesting are designed in 0.6um CMOS technology and the simulation results are presented. Charge pumps and rectifier were optimized to operate with low voltage ranges since the energy produced by the piezoelectric generator and the whip antenna is found to be in microwatts and less from the test results. The AC output from the piezoelectric generator is rectified and boosted to required output level using an AC-DC charge pump. A rectifier and DC-DC charge pump are adopted for the efficient conversion of voltage from the antenna. A back-up battery will be provided for the start-up of DC-DC charge pump at low input conditions. An LDO is designed to provide regulated output of 4.1 V to the battery. Finally, the collected energy will be stored in a 50uAh capacity thin film battery which is intended for low-voltage and low-power applications.Item Next generation wind energy harvesting to power bridge health monitoring systems(2012-05) Zimowski, Krystian Amadeusz; Crawford, Richard H.; Wood, Kristin L.The research reported in this thesis is part of a project to develop a remote wireless sensing network for monitoring the health of highway bridges. Remote health monitoring that does not require direct human observation has many advantages in terms of cost and increased productivity. However, bridges that cannot be easily connected to the power grid require alternative means of acquiring power. This thesis describes the design of a wind energy harvester to power a particular component in the sensor network, the wireless router. The work discussed in this thesis provides a review of relevant literature and development of a detailed analytical modeling of wind turbine behavior. The analytical model provides key information on sizing generators and choosing appropriate wind turbine dimensions to provide the required amount of power. The analytical model also distinguishes the performance of vertical and horizontal axis wind turbines. The model is verified through design and testing of a first generation prototype and benchmarking of a commercially available turbine. Based on these results, the design of the next generation wind harvesting system is described. A new methodology to design non-destructive attachment systems is also discussed.Item Photovoltaic (PV) and fully-integrated implantable CMOS ICs(2012-05) Ayazianmavi, Sahar; Hassibi, Arjang; Pearce, John A.; Banerjee, Sanjay K.; Aziz, Adnan; Soenen, EricToday, there is an ever-growing demand for compact, and energy autonomous, implantable biomedical sensors. These devices, which continuously collect in vivo physiological data, are imperative in the next generation patient monitoring systems. One of the fundamental challenges in their implementation, besides the obvious size constraints and the tissue-to-electronics biocompatibility impediments, is the efficient means to wirelessly deliver power to them. This work addresses this challenge by demonstrating an energy-autonomous and fully-integrated implantable sensor chip which takes advantage of the existing on-chip photodiodes of a standard CMOS process as photovoltaic (PV) energy-harvesting cells. This 2.5 mm × 2.5 mm chip is capable of harvesting [mu]W’s of power from the ambient light passing through the tissue and performing real-time sensing. This system is also MRI compatible as it includes no magnetic material and requires no RF coil or antennae. In this dissertation, the optical properties of tissue and the capabilities of the CMOS integrated PV cells are studied first. Next, the implementation of an implantable sensor using such PV devices is discussed. The sensor characterizing and the in vitro measurement results using this system, demonstrate the feasibility of monolithically integrated CMOS PV-driven implantable sensors. In addition, they offer an alternative method to create low-cost and mass-deployable energy autonomous ICs in biomedical applications and beyond.Item A stochastic geometry analysis of cooperative wireless networks powered by energy harvesting(2015-05) Khan, Talha Ahmed; Heath, Robert W., Ph. D.; Orlik, Philip VEnergy harvesting technology is essential for enabling green, sustainable and autonomous wireless networks. In this report, a large-scale wireless network with energy harvesting transmitters is considered, where a group of transmitters forms a cluster to cooperatively serve a desired user in the presence of co-channel interference and noise. Using stochastic geometry, simple closed-form expressions are derived to characterize the outage performance at the user as a function of important parameters such as the energy harvesting rate, the energy buffer size and the cluster size for a given cluster geometry. The analysis is further extended to characterize the delay due to transmission failure. The developed framework is flexible in that it allows the in-cluster transmitters to have possibly different energy harvesting capabilities. The analytical expressions are first validated using simulations and then used for investigating the impact of different parameters such as cluster and buffer size on outage performance. The results suggest that substantial outage performance can in fact be extracted with a relatively small energy buffer. Moreover, the utility of having a large energy buffer increases with the cluster size as well as with the energy harvesting rate.Item Wind energy harvesting for bridge health monitoring(2011-05) McEvoy, Travis Kyle; Wood, Kristin L.The work discussed in this thesis provides a review of pertinent literature, a design methodology, analytical model, concept generation and development, and conclusions about energy harvesting to provide long-term power for bridge health monitoring. The methodology gives structure for acquiring information and parameters to create effective energy harvesters. The methodology is used to create a wind energy harvester to provide long-term power to a wireless communication network. An analytical model is developed so the system can be scaled for different aspects of the network. A proof of concept is constructed to test the methodology's effectiveness, and validate the feasibility and analytical model.