Energy harvesting in cellular networks is an emerging technique to enhance the sus- tainability of power-constrained wireless devices. In this thesis, I consider the co- channel deployment of a macrocell overlaid with several small cells. In our model, the small cell base stations (SBSs) harvest their energy from environment sources (e.g., solar, wind, thermal) whereas the macrocell base station (MBS) uses conven- tional power supply. Given a stochastic energy arrival process, a power control policy for the downlink transmission of both MBS and SBSs is derived such that they can obtain their own objectives on a long-term basis (e.g., maintain the target signal-to- interference-plus-noise ratio [SINR] on a given transmission channel). To this end, I propose to use two di erent forms of stochastic game for the cases when the number of SBSs is small and when it becomes very large i.e. a very dense network. Numerical results demonstrate the signi cance of the developed optimal power control policy in both cases over the conventional methods.

Wireless micro-sensors can enjoy popularity in biomedical drug-delivery treatments and tire-pressure monitoring systems because they offer in-situ, real-time, non-intrusive processing capabilities. However, miniaturized platforms severely limit the energy of onboard batteries and shorten the lifespan of electronic systems. Ambient energy is an attractive alternative because the energy from light, heat, radio-frequency (RF) radiation, and motion can potentially be used to continuously replenish an exhaustible reservoir. Of these sources, solar light produces the highest power density, except when supplied from indoor lighting, under which conditions the available power decreases drastically. Harnessing thermal energy is viable, but micro-scale dimensions severely limit temperature gradients, the fundamental mechanism from which thermo piles draw power. Mobile electronic devices today radiate plenty of RF energy, but still, the available power rapidly drops with distance. Harvesting kinetic energy may not compete with solar power, but in contrast to indoor lighting, thermal, and RF sources, moderate and consistent vibration power across a vast range of applications is typical. Although operating conditions ultimately determine which kinetic energy-harvesting method is optimal, piezoelectric transducers are relatively mature and produce comparatively more power than their counterparts such as electrostatic and electromagnetic kinetic energy transducers. The presented research objective is to develop, design, simulate, fabricate, prototype, test, and evaluate CMOS ICs that harvest ambient kinetic energy in periodic and non-periodic vibrations using a small piezoelectric transducer to continually replenish an energy-storage device like a capacitor or a rechargeable battery. Although vibrations in surrounding environment produce abundant energy over time, tiny transducers can harness only limited power from the energy sources, especially when mechanical stimulation is weak. To overcome this challenge, the presented piezoelectric harvesters eliminate the need for a rectifier which necessarily imposes threshold limits and additional losses in the system. More fundamentally, the presented harvesting circuits condition the transducer to convert more electrical energy for a given mechanical input by increasing the electromechanical damping force of the piezoelectric transducer. The overall aim is to acquire more power by widening the input range and improving the efficiency of the IC as well as the transducer. The presented technique in essence augments the energy density of micro-scale electronic systems by scavenging the ambient kinetic energy and extends their operational lifetime. This dissertation reports the findings acquired throughout the investigation. The first chapter introduces the applications and challenges of micro-scale energy harvesting and also reviews the fundamental mechanisms and recent developments of various energy-converting transducers that can harness ambient energy in light, heat, RF radiation, and vibrations. Chapter 2 examines various existing piezoelectric harvesting circuits, which mostly adopt bridge rectifiers as their core. Chapter 3 then introduces a bridge-free piezoelectric harvester circuit that employs a switched-inductor power stage to eliminate the need for a bridge rectifier and its drawbacks. More importantly, the harvester strengthens the electrical damping force of the piezoelectric device and increases the output power of the harvester. The chapter also presents the details of the integrated-circuit (IC) implementation and the experimental results of the prototyped harvester to corroborate and clarify the bridge-free harvester operation. One of the major discoveries from the first harvester prototype is the fact that the harvester circuit can condition the piezoelectric transducer to strengthen its electrical damping force and increase the output power of the harvester. As such, Chapter 4 discusses various energy-investment strategies that increase the electrical damping force of the transducer. The chapter presents, evaluates, and compares several switched-inductor harvester circuits against each other. Based on the investigation in Chapter 4, an energy-investing piezoelectric harvester was designed and experimentally evaluated to confirm the effectiveness of the investing scheme. Chapter 5 explains the details of the IC design and the measurement results of the prototyped energy-investing piezoelectric harvester. Finally, Chapter 6 concludes the dissertation by revisiting the challenges of miniaturized piezoelectric energy harvesters and by summarizing the fundamental contributions of the research. With the same importance as with the achievements of the investigation, the last chapter lists the technological limits that bound the performance of the proposed harvesters and briefly presents perspectives from the other side of the research boundary for future investigations of micro-scale piezoelectric energy harvesting.

In this thesis, the possibility of harvesting energy from a multicore power cableconnected to a power outlet is presented and evaluated. By surrounding a powercable with a conductive material connected to ground, it is shown that the dif-ference in potential between the power cable and the conductive material causesa capacitance which can charge a capacitor that in combination with an energymanagement circuit can be used to wirelessly transmit data with an interval de-pending on factors like the length of the surrounding material and the type ofcable it is placed around. In addition to this, a technique to, in a non-invasiveway, sense whether there is alternating current flowing in a multicore power ca-ble is brought up. The results show that this technique can be used to detectalternating current without having a device connected between the power cableand the power outlet. These two sections combined are used to design a surveil-lance system that should monitor consumer electronics in the home environmentwhere there is a fire hazard. The system should send out a warning signal thatis visible for the homeowner to remind the user to switch off the power of theelectronic devices before leaving home.

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. / text

Colloidal quantum dot photovoltaics (CQDPV) offer a big potential to be a renewable energy source due to low cost and tunable band-gap. Currently, the certified power conversion efficiency of CQDPV has reached 9.2%. Compared to the 31% theoretical efficiency limit of single junction solar cells, device performances have still have a large potential to be improved. For photovoltaic devices, a classical way to enhance absorption is to increase the thickness of the active layers. Although this approach can improve absorption, it reduces the charge carriers extraction efficiency. Photo-generated carriers, in fact, are prone to recombine within the defects inside CQD active layers. In an effort to solve this problem, we proposed to increase light absorption from a given thickness of colloidal quantum dot layers with the assistance of disorder. Our approach is to develop new types of electrodes with multi-scale disordered features, which localize energy into the active layer through plasmonic effects. We fabricated nanostructured gold substrates by electrochemical methods, which allow to control surface disorder as a function of deposition conditions. We demonstrated that the light absorption from 600 nm to 800 nm is impressively enhanced, when the disorder of the nanostructured surface increases. Compared to the planar case, the most disorder case increased 65% light absorption at the wavelength of λ = 700nm in the 100 nm PbS film. The average absorption enhancement across visible and infrared region in 100 nm PbS film is 49.94%. By developing a photovoltaic module, we measured a dramatic 34% improvement in the short-circuit current density of the device. The power conversion efficiency of the tested device in top-illumination configuration showed 25% enhancement.

No description available.

As the world endures and approaches a string of energy crises, both financially and environmentally, this project aims to critique and challenge society's relationship with energy by provoking individuals to examine their current habits of energy consumption, consider the future implications of these actions, and question their willingness to make sacrifices for a cleaner environment. This is accomplished through the development of a fictional society in the near future in which individuals are required to produce all the electrical energy that they need or desire to consume. Within the daily narrative of a fictional family of five, the details and events of their everyday lives have been extrapolated to create a liminal world where mundane, yet peculiar diegetic prototypes create tense situations, uncomfortable behaviors, and unforeseen consequences. Plot devices manifested include distributed government information in the form of an energy harvesting catalog, product infomercial, energy bill, and a home monitoring brochure. The narrative emphasis and human driven context aspires to foster a new lens of speculation, imagination, and discovery regarding the production and consumption of energy. What if you were required to produce all the energy you desire to consume?

As sources of energy are becoming more scarce and expensive, energy harvesting is receiving more global interest and is currently a growing field. Energy harvesting is the process of converting ambient energy, such as vibration, to electrical energy that can power a multitude of applications. Vibration energy is the by-product of everyday life; it is generated from any perceivable activity. While typically viewed as noise, there is a strong potential for harvesting this energy and deploying it to useful applications. The focus of this thesis will be using vibration as the ambient source of energy. Hybrid energy harvesters employ more than one of the harvesting technologies. In this thesis, two hybrid harvesters that utilize piezoelectric, magnetostrictive, and electromagnetic technologies are designed, modelled, and tested. Both of these harvesters have beams that are spiral in shape. The use of the spiral geometry allows the system to have a lower natural frequency as opposed to the traditional cantilever beam, while still maintaining a high volume of active material. The first harvester that is discussed is the P-MSM harvester. It utilizes piezoelectric and magnetostrictive material. Both materials are configured in a spiral beam geometry and allowed to resonate independently. The resonance frequency of these two materials is designed to create wideband energy harvesting. This allows the harvester to be operating efficiently even if the ambient vibration shifts a small amount. The second harvester that is discussed is the P-MAG harvester. It utilizes piezoelectric and electromagnetic technologies. It also incorporates a spiral geometry for the piezoelectric layers and includes a magnet attached at the centre. The magnet is placed in the centre of the spiral to reduce the natural frequency of the system and to also actively contribute to the harvesting. This harvester has two sources operating at the same resonant frequency, which allows it to have a larger power output than if the sources were separated. Finally, finite element analysis was used to model both harvesters. ANSYS was used for the piezoelectric material and COMSOL was used for the electromagnetic material. The results are compared to the experimental and are in good agreement.

In recent years, energy harvesting has been generating great interests among researchers, scientists and engineers alike. One of the major reasons for this increased interest sterns from the desire to have autonomous perpetual power supplies for remote monitoring sensor nodes utilizing some of the already available and otherwise wasted energy in the environment in a very innovative and useful way (and at the same time, maintaining a green environment). Scientists and engineers are constantly looking for ways of obtaining continuous and uninterrupted data from several points of interests especially remote or dangerous locations, using sensors coupled with RF transceivers, without the need of ever replacing or recharging the batteries that power these devices. This is now made possible through energy harvesting technologies which serve as suitable power supply substitutes, in many cases, for low power devices. With the proliferation of wireless energy in the environment through different radio frequency bands as well as natural sources like solar, wind and heat energy, it has become a desirable thing to take advantage of their availability by harvesting and converting them to useful electrical energy forms. The energy so harnessed or harvested could then be utilized in sensor nodes. Now, since these energy sources fluctuate from time to time, and from place to place, there is the need to have a form of energy accumulation, conversion, conditioning and storage. The stored energy would then be reconverted and used by the sensors nodes and/or RF transceivers when needed. The process through which this is done is referred to as energy management. In this research work, many types of energy harvesting transducers were explored including – solar, thermal, electromagnetic and piezo/vibration. A proof of concept approach for an on-demand electromagnetic power generator is then presented towards the end. While most, if not all, of the energy harvesting techniques discussed needed some time to accumulate enough charge to operate their respective systems, the on-demand energy harvester makes energy available as at and when needed. In summary, a system level design is presented with suggested future research works.

Ocean Data Acquisition System (ODAS) buoys are deployed in many seas around the world, a subset of these are wave monitoring buoys. Most are powered by solar panels. Many of these buoys are subjected to movement from waves, and could benefit from a wave energy converter specifically designed for ODAS buoys (WECO). A particular buoy that could benefit from this technology is the TriAXYS wave buoy [1]. This thesis discusses the development of a self-contained WECO that would replace one of the buoys four on board batteries, and harvest energy from the buoy motion to charge the remaining three batteries. A major constraint on the WECO is that it can’t affect buoy motion and jeopardize wave data that is derived from the motion. Rather than follow a traditional approach to simulating the motion of the buoy / WECO system, using hydrodynamic modelling and theoretical wave profiles, existing motion data from a buoy installation was analyzed to find the loads that were applied to the buoy to cause the motion. The complete set of mass properties of the TriAXYS buoy were derived from the 3D model provided by AXYS Technologies. These mass properties were compared to the linear and rotational accelerations to find the loads that were applied at the buoy center of gravity (CG) to cause the recorded motion. An installation off the coast of Ucluelet, BC was selected for this investigation because it is subjected to open ocean swells, and data from the winter months of November to March of 2014 to 2016 is available. Winter data was used since there is more wave action to power the WECO during the winter months, and there is sufficient solar irradiation to power the buoy in summer months. Accurate buoy motion data at a 4 Hz sampling rate was available from three rotational rate gyros and three linear accelerometers installed in the buoy. Each dataset of samples represented a 20 minute window that was recorded once every hour. Five conceptual WECO designs were developed, each of which focused on the extraction of power from a different degree of freedom (DOF) of buoy motion (surge, sway, heave, roll, and iv pitch). Three designs used a sliding (linear) oscillating mass, and one was aligned with each of the surge, sway, and heave axis of the buoy. Two designs used a rotating oscillating mass, and the axis of rotation of each device was aligned with either the roll or pitch axis of the buoy. All proposed WECO configurations were modeled as articulated mass, spring, and damper systems in MATLAB using the Lagrange method. Each WECO/buoy assembly formed an articulated body. Mass properties for each configuration were derived from the 3D models. The equations of motion for the original buoy no longer applied, but the environmental forces applied to the hull would still be valid as long as the WECO didn’t alter motion significantly. The power take off (PTO) was modeled following standard convention as a viscous dashpot. The damping effect of the dashpot was included in the models using Rayleigh’s dissipation function that estimated the energy dissipated by the PTO. A subset of load datasets was selected for evaluating the maximum power potential of each WECO. Each WECO was tuned to each dataset of loads using the spring rate, and the damping coefficient was optimized to find the maximum power while avoiding end stop collisions. A second subset of data was selected to evaluate the average power that would be generated throughout the winter months for the two most promising designs. This evaluation was performed for static spring and damping coefficients, and the coefficients that resulted in the highest power output were discovered. The motion of the WECO oscillating mass with respect to the buoy was used in conjunction with the damping ratio to form an estimate of the ideal (i.e. with no mechanical or electrical losses) power generation potential of each WECO configuration during the winter months. The two leading WECO designs both had sliding (linear) oscillating masses, one was aligned with the surge axis and produced theoretical average of just over 0.5 W, the other was aligned with the heave axis and produced theoretical average of just under 0.5 W. / Graduate