The number of IoT (Internet of Things) devices available on the market has been growing rapidly in the past few years and is expected to grow even more in the years to come. These IoT devices are predominantly in the form of very small wireless peripherals with low power consumption making them suitable for running over extended periods of time using only coin cell batteries. In this degree project, conducted at Shortcut Labs AB, we investigate whether or not some of these devises could be suitable for being powered exclusively by kinetic energy without the need for any long term interim power storage, such as batteries or super capacitors. If this is possible it would not only remove the hassle of having to replace batteries at regular intervals, which is important if the devices are positioned at remote locations, but it could also help to reduce the amount of battery waste in the long run. For the sake of this project we have designed a hardware circuit that is able to communicate with other devices using a custom built protocol running on top of the Bluetooth Low Energy standard. This circuit does not require a battery and could potentially be used for many years without the need for any maintenance. To demonstrate this, the technology has successfully been applied to a concept product in the form of a dimmer wheel that can be used to change the brightness or color of Smart Home light bulbs. This is achieved by using a small electric motor as a generator in combination with an energy harvesting circuit in order to generate a stable voltage suitable for use with a wireless module. / Antalet uppkopplade IoT-enheter har ökat drastiskt de senaste åren och väntas fortsätta öka framöver. IoT, eller Sakernas Internet som det kallas på svenska, består övervägande av små trådlösa enheter med så pass låg strömförbrukning att de ofta kan drivas enbart av knappcellsbatterier. I detta examensarbete, utfört på Shortcut Labs AB, undersöker vi huruvida några av dessa enheter med fördel skulle kunna drivas uteslutande av rörelseenergi utan att kräva någon form av långtidsmellanlalgring av denna energi, så som exempelvis i ett batteri eller en kondensator. Om detta var möjligt så skulle det innebära att man slipper byta batterier vid jämna mellanrum, vilket kan vara viktigt om enheten i fråga är otillgänglig placerat. Givetvis kan också onödigt batteriavfall undvikas, något som alltid är eftertraktat i branschen. I detta projekt så har vi designat och konstruerat en elektronikkrets som trådlöst kan kommunicera med andra enheter via ett skräddarsytt protokoll som är implementerat ovanpå Bluetooth Low Energstandarden. Denna krets kräver inget batteri och skulle potentiellt sett kunna operera under många år utan behov av underhåll. För att demonstrera detta så har tekniken applicerats på en konceptprodukt i form av en dimmer som kan användas för att ändra antingen ljusstyrkan eller färgen hos så kallade smarta lampor. Detta uppnås genom att använda en liten DC-motor kombinerad med en energiskördande krets som genererar en lämplig stabil spänning, vilket krävs för att kretsen skall kunna operera.

Piezoelectric-based energy harvesting devices provide an attractive approach to powering remote devices as ambient mechanical energy from vibrations is converted to electrical energy. These devices have numerous potential applications, including actuation, sensing, structural health monitoring, and vibration control -- the latter of which is of particular interest here. This work seeks to develop an understanding of energy harvesting behavior within the framework of a semi-active technique for reducing turbomachinery blade vibrations, namely resonance frequency detuning. In contrast with the bulk of energy harvesting research, this effort is not focused on maximizing the power output of the system, but rather providing the low power levels required by resonance frequency detuning. The demands of this technique dictate that harvesting conditions will be far from optimal, requiring that many common assumptions in conventional energy harvesting research be relaxed. Resonance frequency detuning has been proposed as a result of recent advances in turbomachinery blade design that have, while improving their overall efficiency, led to significantly reduced damping and thus large vibratory stresses. This technique uses piezoelectric materials to control the stiffness, and thus resonance frequency, of a blade as the excitation frequency sweeps through resonance. By detuning a structure*s resonance frequency from that of the excitation, the overall peak response can be reduced, delaying high cycle fatigue and extending the lifetime of a blade. Additional benefits include reduced weight, drag, and noise levels as reduced vibratory stresses allow for increasingly light blade construction. As resonance frequency detuning is most effective when the stiffness states are well separated, it is necessary to harvested at nominally open- and short-circuit states, corresponding to the largest separation in stiffness states. This presents a problem from a harvesting standpoint however, as open- and short-circuit correspond to zero charge displacement and zero voltage, respectively, and thus there is no energy flow. It is, then, desirable to operate as near these conditions as possible while still harvesting sufficient energy to provide the power for state-switching. In this research a metric is developed to study the relationship between harvested power and structural stiffness, and a key result is that appreciable energy can be harvested far from the usual optimal conditions in a typical energy harvesting approach. Indeed, sufficient energy is available to power the on-blade control while essentially maintaining the desired stiffness states for detuning. Furthermore, it is shown that the optimal switch in the control law for resonance frequency detuning may be triggered by a threshold harvested power, requiring minimal on-blade processing. This is an attractive idea for implementing a vibration control system on-blade, as size limitations encourage removing the need for additional sensing and signal processing hardware.

A wireless imaging system for monitoring strawberry fields provides enough quality image data for computer vision algorithms to make meaningful yield predictions. This report contains a design for a wireless sensor network modified with mesh networking techniques to extend coverage range and a solar energy harvesting system to improve sensor node lifetime. A two hop system with six nodes is implemented in a laboratory environment validating the communication systems integrity over an 800’ range. Moving from a primary battery system to solar energy harvesting increases the module lifetime indefinitely.

Converting vibrations to a usable form of energy has been the topic of many recent investigations. The ultimate goal is to convert ambient or aeroelastic vibrations to operate low-power consumption devices, such as microelectromechanical systems, heath monitoring sensors, wireless sensors or replacing small batteries that have a nite life span or would require hard and expensive maintenance. The transduction mechanisms used for transforming vibrations to electric power include: electromagnetic, electrostatic, and piezoelectric mechanisms. Because it can be used to harvest energy over a wide range of frequencies and because of its ease of application, the piezoelectric option has attracted significant interest. In this work, we investigate the performance of different types of piezoelectric energy harvesters. The objective is to design and enhance the performance of these harvesters. To this end, distributed-parameter and phenomenological models of these harvesters are developed. Global analysis of these models is then performed using modern methods of nonlinear dynamics. In the first part of this Dissertation, global nonlinear distributed-parameter models for piezoelectric energy harvesters under direct and parametric excitations are developed. The method of multiple scales is then used to derive nonlinear forms of the governing equations and associated boundary conditions, which are used to evaluate their performance and determine the effects of the nonlinear piezoelectric coefficients on their behavior in terms of softening or hardening. In the second part, we assess the influence of the linear and nonlinear parameters on the dynamic behavior of a wing-based piezoaeroelastic energy harvester. The system is composed of a rigid airfoil that is constrained to pitch and plunge and supported by linear and nonlinear torsional and flexural springs with a piezoelectric coupling attached to the plunge degree of freedom. Linear analysis is performed to determine the effects of the linear spring coefficients and electrical load resistance on the flutter speed. Then, the normal form of the Hopf bifurcation (flutter) is derived to characterize the type of instability and determine the effects of the aerodynamic nonlinearities and the nonlinear coefficients of the springs on the system's stability near the bifurcation. This is useful to characterize the effects of different parameters on the system's output and ensure that subcritical or "catastrophic" bifurcation does not take place. Both linear and nonlinear analyses are then used to design and enhance the performance of these harvesters. In the last part, the concept of energy harvesting from vortex-induced vibrations of a circular cylinder is investigated. The power levels that can be generated from these vibrations and the variations of these levels with the freestream velocity are determined. A mathematical model that accounts for the coupled lift force, cylinder motion and generated voltage is presented. Linear analysis of the electromechanical model is performed to determine the effects of the electrical load resistance on the natural frequency of the rigid cylinder and the onset of the synchronization region. The impacts of the nonlinearities on the cylinder's response and energy harvesting are then investigated. / Ph. D.

Consider a bottom-hinged Oscillating Wave Surge Converter (OWSC): This device oscillates due to the hydrodynamic forces applied on it by the action of ocean waves. The focus of this thesis is to build upon the in-house multi-block generalized coordinate finite volume solver GenIDLEST using a collocated grid arrangement within the framework of the fractional-step method to make it compatible to simulate such systems. The first step in this process is to deploy a convection scheme which differentiates between air and water. This process is further complicated by the 1:1000 density and 1:100 viscosity ratio between the two fluids. For this purpose, a phase field method is chosen for its ease of implementation and proven boundedness and conservativeness properties. Extensive validation and verification using standard test cases, such as droplet in shear flow, Rayleigh Taylor instability, and the Dam Break Problem is carried out. This development is then coupled with the present Immersed Boundary Module which is used to simulate the presence of moving bodies and again verified against test cases, such as the Dam Break problem with a vertical obstacle and heave decay of a partially submerged buoyant cylinder. Finally, a relaxation zone technique is used to generate waves and a numerical beach technique is used to absorb them. These are then used to simulate the Oscillating Surge Wave Converter. / Master of Science / An Oscillating Wave Surge Converter can be best described as a rectangular flap, hinged at the bottom, rotating under the influence of ocean waves from which energy is harvested. The singular aim of this thesis is to model this device using Computational Fluid Dynamics (CFD). More specifically, the aim is to model this dynamic device with the full Navier Stokes Equations, which include inertial forces, arising due to the motion of the fluid, viscous forces which dissipate energy, and body forces such as gravity. This involves three key steps: 1. Modelling the air-water interface using a convection scheme. A phase field method is used to differentiate between the two fluids. This task is made more challenging because of the very large density and viscosity differences between air and water. 2. Model dynamic moving geometries in a time-dependent framework. For this, we rely on the Immersed Boundary Method. 3. Develop a numerical apparatus to generate and absorb ocean waves. For this, we rely on the Relaxation Zone and Numerical Beach Method. These developments are validated in different canonical problems and finally applied to a two-dimensional oscillating surge wave energy converter.

M.S. / Electronics, wearable devices are important in nowadays informationalized lifestyle. One prominent problem with those electronic devices is that almost all of them depend on batteries as power sources, which has become a bottleneck due to the limited life span. Constantly replacing or recharging batteries is inconvenient, burdensome, and sometimes even impossible. This problem is more intractable when the power cannot be accessed conveniently (such as during fieldwork, hiking, and military missions). What’s more, no matter how much energy the battery stores, it will drain eventually. In addition, large battery will add extra weight and occupy space. Substitute power supply that conquer these aforementioned dilemmas are thus highly desirable. Energy harvesting by its nature could be an inexhaustible replacement for batteries. This insight inspires so many energy harvesting researchers tirelessly working and trying to make it happen. Suspended backpack is an effective way to harvest energy from human motions.This study evaluates different energy harvesting backpack configurations and comprehensively assessed the power generation, dynamic interaction and human comfort. Dynamic modelling considering the dynamic interaction between human body and backpack is established to optimize the design. Bench tests and treadmill tests are carried out to evaluate the real performance. Experimental results show that the harvesting energy from human motion via a suspended energy-harvesting backpack could incessantly generate considerable electricity applicable for charging carry-on electronic devices. The potential application scenarios of this technology include solders, field-workers as well as outdoor adventure.

In the current pursuit of sustainable energy, biofuel cells are attracting considerable attention. Within biomedical engineering, the concept of harnessing energy from biological fluids, such as blood, holds significant promise, enabling both full autonomy and miniaturization. In this context, this study aims to identify the most efficient biofuel cells for miniaturised implantable biosensors and design a prototype based on the obtained results. To achieve this goal, a systematic literature review was conducted, comparing biofuel cells based on relevant parameters for powering devices, including power density and operative voltages. This categorization guided material selection, considering a cost-performance trade-off. Carbon nanotubes and Laccase were chosen to facilitate oxygen reduction at the cathode, while carbon nanotubes with Glucose Oxidase (with and without ferrocenemethanol) played a similar role at the anode—where glucose proved to be the most advantageous fuel. Electrode functionalization and assessment involved electrochemical and morphological analyses, culminating in the recording of initial results for the biofuel cell prototype. The analysis of scientific literature revealed that under physiological conditions, including pH, glucose concentration, and single-chamber biofuel cells, the maximum power density obtained was 1 mW/cm$^2$ at 0.65 V. The use of nanomaterials, such as carbon nanotubes, and enzymes proved crucial for achieving this performance by enhancing electron transfer, increasing the effective area, and introducing specificity to each electrode, enabling the biofuel cell to operate without the need for a membrane. During the design phase, the functionalisation of the cathode highlighted the critical role of oxygen, which has a limited concentration in the solution. At the anode, the attempt to achieve mediated electron transfer proved successful, in contrast to the method of direct electron transfer. Finally, the characterisation of the biofuel cell demonstrated a preliminary power generation of 0.38 $\micro$W/cm$^2$ at 0.2 V in 500 mM glucose. The preliminary development of the prototype confirms the feasibility of generating energy with the selected materials and highlights its limitations, laying the foundation for its optimization—such as through a more robust stabilization method. Furthermore, the project proves valuable in the context of active medical device development, enabling a comparison between the requirements of a hypothetical implantable sensors and cutting-edge technology.

Internet of Things (IoT) is a revolutionary paradigm approaching both industries and consumers everyday life. It refers to a network of addressable physical objects that contain embedded sensing, communication and actuating technologies, to sense and interact with the environment where being deployed. It can be considered as a modern expression of Mark Weiser's vision of ubiquitous computing where tiny networked computers become part of everyday objects, fusing together the virtual world and the physical word. Recent advances in hardware solutions have led to the emergence of powerful wireless IoT systems that are entirely energy-autonomous. These systems extract energy from their environment and operate intermittently, only as power is available. Battery-less sensors present an opportunity for the pervasive wide-spread of remote sensor deployments that require little maintenance and have low cost. As the number of IoT endpoint grows -- industry forecast trillions of connected smart devices in the next few years -- new challenges to program, manage and maintain such a huge number of connected devices are emerging. Web technologies can significantly ease this process by providing well-known patterns and tools - like cloud computing - for developers and users. However, the existing solutions are often too heavyweight or unfeasible for highly resource-constrained IoT devices. This dissertation presents a comprehensive analysis of two of the biggest problems that the IoT is currently facing: R1) How are we going to provide connectivity to all these devices? R2) How can we improve the quality of service provided by these tiny autonomous motes that rely only on limited energy scavenged from the environment? The first contribution is the study and deployment of a Low-Power Wide-Area-Network as a feasible solution to provide connectivity to all the expected IoT devices to be deployed in the following years. The proposed technology offers a novel communication paradigm to address discrete IoT applications, like long-range (i.e., kilometers) at low-power (i.e., tens of mW). Moreover, results highlight the effectiveness of the technology also in the industrial environment thanks to the high immunity to external noises. In the second contribution, we focus on smart metering presenting the design of three smart energy meters targeted to different scenarios. The first design presents an innovative, cost-effective smart meter with embedded non-intrusive load monitoring capabilities intended for the domestic sector. This system shows an innovative approach to provide useful feedback to reduce and optimize household energy consumption. We then present a battery-free non-intrusive power meter targeted for low-cost energy monitoring applications that lower both installation cost due to the non-intrusive approach and maintenance costs associated to battery replacement. Finally, we present an energy autonomous smart sensor with load recognition capability that dynamically adapts and reconfigures its processing pipeline to the sensed energy consumption. This enables the sensor to be energy neutral, while still providing power consumption information every 5 minutes. In the third contribution, we focus on the study of low-power visual edge processing and edge machine learning for the IoT. Two different implementations are presented. The first one discusses an energy-neutral IoT device for precision agriculture, while the second one presents a battery-less long-range visual IoT system, both leveraging on deep learning algorithms to avoid unnecessary wireless data communication. We show that there is a clear benefit from implementing a first layer of data processing directly in-situ where the data is acquired, providing a higher quality of service to the implemented application.

This work presents an investigation of a piezoelectric sensor based energy harvesting system, which collects energy from the surrounding environment. Increasing costs and scarcity of fossil fuels is a great concern today for supplying power to electronic devices. Furthermore, generating electricity by ordinary methods is a complicated process. Disposal of chemical batteries and cables is polluting the nature every day. Due to these reasons, research on energy harvesting from renewable resources has become mandatory in order to achieve improved methods and strategies of generating and storing electricity. Many low power devices being used in everyday life can be powered by harvesting energy from natural energy resources. Power overhead and power energy efficiency is of prime concern in electronic circuits. In this work, an energy harvester is modeled and simulated in Simscape™ for the functional analysis and comparison of achieved outcomes with previous work. Results demonstrate that the harvester produces power in the 0 μW to 100 μW range, which is an adequate amount to provide supply to low power devices. Power efficiency calculations also demonstrate that the implemented harvester is capable of generating and storing power for low power pervasive applications.

Embedding small wireless sensors into the environment allows for monitoring physical processes with high spatio-temporal resolutions. Today, these devices are equipped with a battery to supply them with power. Despite technological advances, the high maintenance cost and environmental impact of batteries prevent the widespread adoption of wireless sensors. Battery-free devices that store energy harvested from light, vibrations, and other ambient sources in a capacitor promise to overcome the drawbacks of (rechargeable) batteries, such as bulkiness, wear-out and toxicity. Because of low energy input and low storage capacity, battery-free devices operate intermittently; they are forced to remain inactive for most of the time charging their capacitor before being able to operate for a short time. While it is known how to deal with intermittency on a single device, the coordination and communication among groups of multiple battery-free devices remain largely unexplored. For the first time, the present thesis addresses this problem by proposing new methods and tools to investigate and overcome several fundamental challenges.