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Potential and Kinetic Potential: stored energy –It has the potential to do work, but it is not in the action of doing any work. Examples of Mechanical Energy : Sound – molecules of air hitting your ear drum causing it to vibrate.
Endothermic and Exothermic Reactions Breaking bonds between atoms uses energy– this is an Endothermic process Making bonds between atoms releases energy– this is an Exothermic process. Energy Transfer Law of Conservation of Energy: Energy is neither created nor destroyed – it is converted.
Here electrical energy is being converted to: ____________ But what other conversions are happening? Here electrical energy is being converted to: ________________ But what other conversions are happening? Heat & Energy Transfer Reassessment Review Directions To start click “Slide Show” and “From Beginning” As you go through the PowerPoint, take DETAILED. The Nature of Energy An unbalanced force must be applied to an object to change its motion. Potential and Kinetic Energy doesn’t just “appear” it comes from something or some other form. Warm Up How do the arrangement and behavior of particles of matter differ in solids, liquids, and gases?
Practice You are provided with a glass of milk and a swimming pool of milk ?Which will have the higher heat capacity? Practice When 600g of water in an electric kettle is heated from 20 o C to 85 o C to make a cup of tea, how much heat flows into the water? Molar Heat of Fusion (?H fus ) The amount of heat necessary to melt 1.0 mole of a substance at its melting point. Molar Heat of Vaporization(?H vap ) The amount of heat necessary to boil 1.0 mole of a substance at its boiling point.
Question: How much energy is required to raise the temperature of 45 g of H 2 O from 30 °C to 150 °C? Science, Technology and Medicine open access publisher.Publish, read and share novel research.
Kinetic Energy HarvestingHelios Vocca1 and Francesco Cottone2[1] NiPS Laboratory, Department of Physics, University of Perugia, Perugia, INFN Perugia and Wisepower srl, Italy[2] ESIEE Paris, University of Paris Est, Paris, France1. Kinetic theory and phases of matter Kinetic theory – all matter is made up of tiny particles that are constantly in motion. Temperature Temperature is related to the random motion of atoms & molecules in a substance. Heat and temperature Heat- the thermal energy transferred from one substance to another due to a temperature difference (Av.
Ionic bonds Ionic compounds are not arranged in molecules, but instead form large crystals held together by ionic bonds.
Hydrogen bonds Covalent molecules form solids when intermolecular forces are great enough to hold molecules together, usually as a crystal.
Van der waals forces Other molecules are attracted by weaker dipole and London dispersion forces. Liquids Intermolecular forces hold particles together, but particles are not locked in place.
Liquids and Kinetic Theory Liquids have three properties that relate to the Kinetic Theory: 1.
Vapor pressure The vapor pressure is a measure of how much gas there is at a given temperature.
Heat of vaporization Energy required to go from a liquid to a solid at the same temperature.
Heat of vaporization How many Joules are required to convert 150 g of water at 100°C to steam? Hydroelectric – Water pressure causing a turbine to spin Friction – rubbing objects together creating heat. Energy is the ability of things to change or to cause change in other things Work takes place when energy is transferred to an object. Energy Potential Kinetic Electrical Nuclear Chemical Gravitational Elastic Mechanical Sound Thermal Radiant -- Light WORK Cover. The Flow of Energy Thermochemistry - concerned with heat changes that occur during chemical reactions. Energy is the ability to do work Potential energy The energy stored in objects because of their position Gravitational Potential Energy.
Energy is the ability to do work It allows us to change or move matter We have learned to utilize energy to make life more.
Ability to do work or cause change Produces Warmth Produces Light Produces Sound Produces Movement Produces Growth Powers Technology.
Comparison between cantilever and buckled beam response as a function of the noise intensity (source: Vocca et al.
IntroductionThe recovery of wasted energy present in the ambient that is a reject of artificial or natural processes to power wireless electronics is paving the way for enabling a huge number of applications.
Volume Graph Ranking Task: Rank the states on the basis of the average kinetic energy of the atoms in the gas sample at each state. Do Now: Sketch a graph showing the relationship between Temperature and Kinetic Energy of Particles.
Strongest intermolecular force is hydrogen bonding, between the H of one molecule, and an N, O or F of another.
These forces are also between positive and negative ends of a molecule, but the charges are usually much smaller than in hydrogen bonds.
The ability to do work or cause change It occurs in different forms: –Electrical, chemical, light, mechanical Energy comes in. One of the main targeted technologies that meets the levels of harvestable power, typically few hundreds of microwatts, is represented by wireless sensor networks (WSNs) [1]. Multimodal energy harvestingThe multimodal approach consists in a multi-vibration harvester, designed to be excited when the natural driving frequency approaches one natural frequency of the harvester. What do you think this did to the temperature needed to turn from a solid liquid or liquid gas? Energy ? The ability to cause change ? Can take many different forms ? Kinetic - moving ? Potential - positional.
This technology consists of a grid of spatially-distributed wireless nodes that sense and communicate information like acceleration, temperature, pressure, toxicity of the air, biological parameters, magnetic field, light intensity and so on, among each other and up to the end user through a fixed server.
In this case useful power can be harvested over multiple frequency spectra, increasing the bandwidth that can be covered for efficient energy harvesting.One way to design a multimodal VEH consists in the combination of more transduction mechanisms together.
In the next years, WSNs will be massively employed in a wide range of applications such as structural monitoring, industrial sensing, remote healthcare, military equipment, surveillance, logistic tracking and automotive monitoring. In fact, harvesting energy directly from the ambient not only represents a realistic mean to integrate or substitute batteries, but is the sole way for enabling many contemporary and future wireless applications that will be all integrated in the so called “internet of things” [2]. Actually, WSNs already have the characteristics of ubiquity, self-organizing and self-healing but they would not be deployable unless they will also be self-powering.


The harvester consists of a cantilever beam with piezoelectric crystal plates bonded on it at a fixed distance each other; a permanent magnet is attached at the cantilever tip oscillating within a coil fixed to the housing structure. As a matter of fact, it is very expensive and impractical to change batteries in most of the anticipated potential applications. It this configuration the electromagnetic transducer generates high output power at the cantilever first mode (at 20 Hz), while the piezoelectric transducer generates higher power at the cantilever second mode (at 300 Hz).
For long-term operation in inaccessible or harsh locations, energy harvesting is a key solution.
The combination of the two schemes in one device is able to improve significantly the harvester response covering two frequency ranges. For example, long-term environmental, structural health of buildings or bridge monitoring and control would require many thousands of integrated sensors impossible to be replaced or maintained. The drawback of this solution is the difficulty in combining the output power from two different mechanisms, thus requiring two separate converting circuits.A different approach rather than exploiting the energy present at different modes of a single oscillator is to design a cantilever array integrated in one single device. The possibility for chronically ill patients to be continuously monitored without changing batteries would represent a significant improvement in their life quality. If the geometric parameters of the harvester are appropriately selected, a wide vibration bandwidth can be exploited. Among various renewable energy present in the environment such as solar, radio frequency RF, temperature difference and biochemical, kinetic energy in the form of mechanical vibrations is deemed to be the most attractive, in the low-power electronic domain, for its power density, versatility and abundance [3]. This type of energy source is located in buildings, vibrating machineries, transportations, ocean waves and human beings, and it can be converted to power mobile devices.
The power consumption of wireless sensors has been largely reduced in the last years thanks to the Ultra-Low-Power electronics [4]. Typical power needs of mobile devices can range from few microwatts for wristwatches, RFID, MEMS sensors and actuators up to hundreds of milliwatts for MP3, mobile phone and GPS applications. They are usually in a sleep state for the 99.9% of their operation time, waking up for a few milliseconds only to communicate data. 2008 [29]).In the first design, (b), various cantilevers with different lengths and tip masses attached to a common base compose a piezoelectric cantilever array.
Consequently, their average power consumption has been reduced below 10µW in order to match the power density capability of current generators (100-300 microwatts per cubic centimeter). In the second, (c), the cantilevers are the same but the first mode response is changed varying the tip masses. Each cantilever presents a unique resonant frequency, the combination of which into a single device creates a sort of mechanical band-pass filter. By properly selecting the different parameters, the device can be designed to provide a voltage response on a wide frequency range.It has been demonstrated by [30] that the improved bandwidth and performance were worth the modest increase in size of the proposed array device.
A cantilever array configuration in respect to the hybrid solution, doesn’t present the difficulty in combining the output power from the different mechanisms, but requires one rectifier for each cantilever to avoid output cancellation due to the phase difference between the cantilevers.As a matter of fact, the multimodal approach increases the bandwidth increasing the volume or the weight of the harvester, thus reducing the energy density.
Capacitors are usually preferred as temporary storage systems for their longer lifetime, higher power density and fast recharging.
Specifically for the cantilever array, only one cantilever or a subset of them are active at the same time generating a certain amount of power while the others are at off-resonance.
Up-conversion energy harvestingIn many practical situations, the ambient vibrations suitable for energy harvesting including human vibrations, natural events (i.e. Main conversion techniquesThere are three main categories of kinetic-to-electrical energy conversion systems: piezoelectric, electrostatic and electromagnetic. In addition, there is the magnetostrictive branch as a variant of piezoelectric except for the use of magnetically polarized materials [6].
The direct piezoelectric effect used for energy harvesting was early discovered by French physicists Jacques and Pierre Curie in 1880.
It occurs when an electric charge is generated within a material in response to applied mechanical stress (Figure 2).
Hence, another frequency-robust solution for VEH is to ‘transfer’ the source vibration frequency to the harvester resonance frequency so that useful power can be harnessed in low frequency excitation scenarios.A typical up-conversion schematic is presented in Figure 11, where the basic principle of such a device is evident [30].
The strain and coupling coefficients in the fundamental piezoelectric equations are in general much higher in 33 mode than in 31 [7].
The oscillator with elastic constant k has a resonant frequency in a lower region respect to the resonant frequencies of the piezoelectric beams. However the 33 mode of bulk crystal corresponds to very high natural frequencies (~1 to 100 kHz), while longitudinal strain is easily produced within a cantilever beam that resonates at lower frequencies (~100 Hz) (Figure 2c). When the tooth passes and hits the cantilever tips, the cantilevers start oscillating at their natural frequency. However, piezoelectric coupling decreases very fast at micrometric scale and relatively large load impedances are required to reach the optimal working point [8].
2006 [31]).This frequency up-conversion technique was further pursued in few applications like the generators for low and variable speed rotary machineries [31].
For low frequency applications, like those related to wearable sensors, polymer-based materials (e.g.
It can be implemented combining different oscillators and interaction mechanisms, like magnetic or electrostatic, maintaining its basic principle.This technique is a way to decouple the exciting frequency and the harvester vibration one, thus the performances are insensitive to the excitation frequency as long as it is less than the resonant frequency of the harvester. The drawback is that the ‘first unit’ resonance frequency needs to be tuned to the main frequency of the vibration source. Electromagnetic technique is simply realized, according to Faraday’s law, by coupling a static magnetic field produced by a permanent magnet and a solenoid in relative motion – one of which usually acts as a stator; the other as a mover. In case the exciting vibrations are spread in a wide frequency range, the advantages of this method lose efficiency.5.
These systems show complementary behaviour in terms of frequency bandwidth and optimal load in relation to piezoelectric techniques. Non-linear techniquesAll the above-mentioned strategies to harvest energy from the environment belong to the entire category of linear (or resonant) harvesting techniques.
They are recommended for lower frequencies (2-20 Hz), small impedance and medium size [10]. In general, for a generic linear system, even more complicated than a simple cantilever, the transfer function presents one or more peeks corresponding to the resonance frequencies and thus it is effective mainly when the incoming energy is abundant in that frequency region.
Unfortunately this is a serious limitation when it is required to build a vibration energy harvester of small dimension, for at least two main reasons, the first is that, as discussed above, the frequency spectrum of available vibrations instead of being sharply peaked at some frequency is usually very broad. Most of the commercial solutions are available at centimetre scales because they exhibit higher power density than piezoelectric devices. The second reason is that the frequency spectrum of available vibrations is particularly rich in energy in the low frequency range, and it is very difficult, if not impossible, to build small, low-frequency resonant systems. On the other hand, the integration of electromagnetic harvesters into micro-electro-mechanical-systems (MEMS) results difficult. In fact a resonant oscillator is capable of harvesting energy only in a very narrow band, around its resonant frequency. Figure 3.(a) Simple architecture of em-VEH where a moving magnet (mover) oscillates with respect to a fixed coil (stator). Non-resonant oscillators have to be taken into account.Increase the capability of harvesting energy at low frequency (below few hundred Hz) because this is where most of the ambient energy is available. Due to geometrical constraints a small dimension linear harvester in not feasible.No need for frequency tuning after the initial set-up of the harvester.


Frequency tuning is a feature of resonant systems, thus if we move to non-resonant systems this requirement will be automatically satisfied.As we have seen before the search for the best solution in terms of non-resonant systems should start from the potential energy function U(z).
When a force is applied to the mass either the dielectric gap or the overlap surface of electrodes varies depending on the moving direction: the first case being referred to as an in-plane gap-closing converter (Figure 4a), while the second case as an overlap varying converter (Figure 4b). In fact U(z) plays the role of dynamical energy storage facility (before transduction) for our mechanical oscillator and thus it is here that we should focus our attention.The best solution in terms of non-resonant systems should start from the potential energy function U(z). As a consequence, the capacitance changes and additional charges occur at the electrodes in order to balance the bias voltage.
Hence, during the movement of the proof mass, a current flows through a load shunted to plates. A similar method of fixed bias voltage is that of charge constrained where a constant charge is held into the plates by means of a battery or another capacitor. One of the main disadvantages of electrostatic vibration harvesters is the need of an external voltage source in order to be pre-charged. This fact seems to contrast with the goal of energy recycling from the ambient, but makes sense if the source comes from the energy storage associated to the harvester [12].
In that case the generator only needs to be kick-started at the beginning of the conversion process.
Moreover, the silicon based MEMS do not have problems of aging as for piezoelectric materials. However the generated power is pretty much small compared to piezoelectric and electromagnetic [16].Nowadays, vibration energy harvesters are delivered on the real market by some leading companies such as Perpetuum Ltd, Ferro Solution and Mide Volture although they have quite bulky size. Prototypes of MEMS-based harvesters have been demonstrated by universities and private teams, though they are still at experimental stage. Miao implemented a parametric generator for biomedical applications [17] and examples of piezoelectric nano-mechanical generators are also emerging [18]. Linear spring-mass-damper models of VEHs Kinetic energy harvesters are divided into two categories: those that utilize direct application of force and those that make use of the inertial force associated to a moving mass m. Inertial generators, are preferred to direct-force devices for vibration energy harvesting as they only need one point of attachment to a vibrating structure, thus allowing a simpler miniaturization.Figure 6 illustrates basic models of (a) direct and (b) inertial force vibration-based generators independent from the conversion technology. In the second case, the driving force F(t) is equal to ?my, where the base vibrations are represented as y(t) and dot stands for the derivative with respect to time. Finally, the electrical part includes the resistive load RL through which flows the generated current i. Figure 6.Models of non-technology specific (a) direct-force and (b) inertial-force generators.
The electrical force fe can be in general a complicated function of displacement, velocity or acceleration.Williams and Yates early defined a basic technology independent model of micro-electric generator for vibration energy harvesting [16]. In that case the conversion force fe being considered as an electrical damping force proportional to the velocity fe = ?dez.
However, the electrical restoring force can in general be a complex function of the mass displacement, velocity and acceleration. In addition, such an approximation does not take into account of the effect of the electrical branch coupled to the mechanical system.In the following we describe the lumped parameters model of the VEH by including the electrical domain as sketched in Figure 6b. The first equation describes the dynamics of the inertial mass while the second equation accounts for the coupled electrical circuit. V is the produced voltage across the electrical resistance and ? is the electromechanical coupling factor; ?c represents the characteristic cut-off frequencies of the electrical circuit of the system operating as high-pass filter due to the specific transduction technique.
These characteristic parameters are derived from the harvester design depending on the specific conversion method and architecture as explained in the following examples. Usually, the internal resistance Ri of a piezoelectric crystal is very high, hence ?i is negligible.
Case 2: electromagnetic generator Let consider a simple “magnet in-line coil” electromagnetic generator as schematized in Figure 3a. Actually, the above fundamental parameters are also valid for other systems such as “magnet across coil” arrangement depicted in Figure 3b.In both cases the governing equations are the same, and they can be also rewritten in a more convenient nondimensional form similar to [22]. Transfer functionsLet now consider the simple case of harmonic excitation y(t) = Y0ej?t as input. We can transform the motion equations(1) and (2) into the Laplace domain, with s=j? as the Laplace variable (where j stands for the imaginary unit). The function Y(s), Z(s), and V(s) are the acceleration amplitude, mass displacement and output voltage delivered to the resistive load respectively. In any case, for applications and environments that feature a vibration source consistent in frequency and time, linear systems can still represent an optimal choice. Beyond linear energy harvestingIn most of the reported studies, the energy harvesters are designed as linear oscillators that match their resonant frequencies to the excitation frequencies of the environment to achieve the maximum output power.This condition can be easily performed when the excitation frequency is well known and stable in time.
It is in fact possible to choose the correct geometry and harvester dimension for frequency matching.
However, when the ambient excitation frequency is unknown or varies in time, the previous conditions are not guaranteed. Therefore a harvester with a fixed resonant frequency is not able to achieve an optimal output power.Various strategies have been investigated to overcome this practical inconvenient and increase the bandwidth of vibration-based harvesters.
In the following the state-of-the-art techniques are summarised in three main categories: resonance frequency tuning, multimodal oscillators and frequency up-conversion.
Frequency tuningIn some cases it has been demonstrated [24] that the resonance frequency of an oscillator can be tuned to the main exciting frequency in two different ways: passive and active. The passive mode requires an intermittent power input (manual or automatic) to check and tune the system until the frequency match is complete, then the power requirement is zero since the excitation frequency varies again.
The three harvesters are realized with a piezoelectric beam, in which the tuning mechanism is purely mechanical in the first case by [25], magnetic in the second by [26], and piezoelectric in the third by [27].The solution (a) is realized with a proof mass consisting in a fixed part combined with a movable part. The fixed part of the mass is made with a relatively small density material and the tuning mass with a higher density one.
In this way the frequency tunability is increased by moving the distance of the centre of gravity of the proof mass. In this prototype, the frequency range can be manually varied in the 130-180 Hz range moving the tip mass up to 21 mm.The solution (b) of Figure 8 is realized by coupling two magnets fixed to the free end of the cantilever beam to two other magnets fixed to the top and bottom sides of the enclosure device. All the magnets have a vertical magnetization in such a way to perform an attractive and repulsive force on each side of the beam. Manually tuning the distance between the magnets using a screw, the magnetic force can be changed inducing a change in the cantilever stiffness.
The resonant frequency can be varied in the 22-32 Hz range.The latter case (c), of Figure 8, presented by Roundy and Zhang [25], is an active tuning mechanism. They analytically demonstrated that an active tuning actuator never resulted in a net increase in power output.




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