Power and selection of contract terms: The case from the Brazilian orange juice sector

ABSTRACT We propose a model to explain how contract terms are selected in the presence of a form of economic power: contract power. The orange juice sector is used to illustrate an analysis that demonstrates the effects of contract power on the economic organization of the sector. We define contract power as the ability to exploit contractual gaps or failures of contractual provisions, which are strategically left incomplete. Empirical evidence from content analysis of antitrust documents supports the logic of contract power in the orange juice sector in three forms: avoiding changes to payment methods from weight to solid contents (quality); using information asymmetries to manipulate indexes that calculate the formula of orange prices; and deliberately harvesting oranges late in order to dehydrate the fruit, which consequently reduces weight and price. The paper contributes to understanding the selection of contract terms and the debate about how antitrust offices can deal with this issue.

Energy harvesting methods for wireless sensor nodes in heavy-duty vehicles

The number of autonomous wireless sensor and control nodes has been increasing rapidly during the last decade. Until recently, these wireless nodes have been powered with batteries, which have lead to a short life cycle and high maintenance need. Due to these battery-related problems, new energy sources have been studied to power wireless nodes. One solution is energy harvesting, i.e. extracting energy from the ambient environment. Energy harvesting can provide a long-lasting power source for sensor nodes, with no need for maintenance. In this thesis, various energy harvesting technologies are studied whilst focusing on the theory of each technology and the state-of-the-art solutions of published studies and commercial solutions. In addition to energy harvesting, energy storage and energy management solutions are also studied as a subsystem of a whole energy source solution. Wireless nodes are also used in heavy-duty vehicles. Therefore a reliable, long-lasting and maintenance-free power source is also needed in this kind of environment. A forestry harvester has been used as a case study to study the feasibility of energy harvesting in a forestry harvester’s sliding boom. The energy harvester should be able to produce few milliwatts to power the target system, an independent limit switch.

Hay strewing, brush harvesting of seed and soil disturbance as tools for the enhancement of botanical diversity in grasslands

Since the middle of the last century agricultural intensification within Europe has led to a drastic decline in the extent of botanically diverse grasslands. Whilst measures to enhance the diversity of agriculturally-improved grasslands are in place, success has often been limited. One of the primary factors limiting success is the paucity of sources of propagules of desirable species in the surrounding landscape. The restoration of two contrasting grassland types lowland hay meadow and chalk grassland) was examined using a replicated block experiment to assess the effectiveness of two methods of seed application (hay strewing and brush harvesting) and two methods of pre-treatment disturbance (power harrowing and turf stripping). The resulting changes in botanical composition were monitored for 4 years. Seed addition by both methods resulted in significant temporal trends in plant species composition and increases in plant species richness, which were further enhanced by disturbance. Power harrowing increased the effectiveness of the seed addition treatments at the lowland hay meadow site. At the chalk grassland site a more severe disturbance created by turf stripping was used and shown to be preferable. Whilst both hay strewing and brush harvesting increased plant species richness, hay strewing was more effective at creating a sward similar to that of the donor site. Soil disturbance and seed application rate at the recipient site and timing of the hay cut at the donor site are all factors to be considered prior to the commencement of restoration management. (c) 2006 Elsevier Ltd. All rights reserved.

On the performance of a dual-mode non-linear vibration energy harvesting device

The research trend for harvesting energy from the ambient vibration sources has moved from using a linear resonant generator to a non-linear generator in order to improve on the performance of a linear generator; for example, the relatively small bandwidth, intolerance to mistune and the suitability of the device for low-frequency applications. This article presents experimental results to illustrate the dynamic behaviour of a dual-mode non-linear energy-harvesting device operating in hardening and bi-stable modes under harmonic excitation. The device is able to change from one mode to another by altering the negative magnetic stiffness by adjusting the separation gap between the magnets and the iron core. Results for the device operating in both modes are presented. They show that there is a larger bandwidth for the device operating in the hardening mode compared to the equivalent linear device. However, the maximum power transfer theory is less applicable for the hardening mode due to occurrence of the maximum power at different frequencies, which depends on the non-linearity and the damping in the system. The results for the bi-stable mode show that the device is insensitive to a range of excitation frequencies depending upon the input level, damping and non-linearity.

On the optimum parameters of a device for harvesting energy from running and walking

This paper investigates the feasibility of using an energy harvesting device tuned such that its natural frequency coincides with higher harmonics of the input to capture energy from walking or running human motion more efficiently. The paper starts by reviewing the concept of a linear resonant generator for a tonal frequency input and then derives an expression for the power harvested for an input with several harmonics. The amount of power harvested is estimated numerically using measured data from human subjects. Assuming that the input is periodic, the signal is reconstructed using a Fourier series before being used in the simulation. It is found that although the power output depends on the input frequency, the choice of tuning the natural frequency of the device to coincide with a particular higher harmonic is restricted by the amount of damping that is needed to maximize the amount of power harvested, as well as to comply with the size limit of the device. It is also found that it is not feasible to tune the device to match the first few harmonics when the size of the device is small, because a large amount of damping is required to limit the motion of the mass.

Modeling of piezoelectric energy harvesting considering the dependence of the rectifier circuit

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of railway track vibration induced by passing trains on an energy harvesting device

Pós-graduação em Engenharia Mecânica - FEIS

On energy harvesting form time-limited excitations: simulations and case study

Linear resonant harvesters have been the most common type of generators used to scavenge energy from mechanical vibrations. When subject to harmonic excitation, good performance is achieved once the device is tuned so that its natural frequency coincides with the excitation frequency. In such a situation, the average power harvested in a cycle is proportional to the cube of the excitation frequency and inversely proportional to the suspension damping, which is sought to be very low. However, a very low damping involves a relatively long transient in the system response, where the classical formulation adopted for steady-state regimes do not hold. This paper presents an investigation into the design of a linear resonant harvester to scavenge energy from time-limited harmonic excitations involving a transient response, which could be more likely in some practical situations. An application is presented considering train-induced vibrations.

Influence of pattern gradation on the design of piezocomposite energy harvesting devices using topology optimization

Piezoelectric materials can be used to convert oscillatory mechanical energy into electrical energy. Energy harvesting devices are designed to capture the ambient energy surrounding the electronics and convert it into usable electrical energy. The design of energy harvesting devices is not obvious, requiring optimization procedures. This paper investigates the influence of pattern gradation using topology optimization on the design of piezocomposite energy harvesting devices based on bending behavior. The objective function consists of maximizing the electric power generated in a load resistor. A projection scheme is employed to compute the element densities from design variables and control the length scale of the material density. Examples of two-dimensional piezocomposite energy harvesting devices are presented and discussed using the proposed method. The numerical results illustrate that pattern gradation constraints help to increase the electric power generated in a load resistor and guides the problem toward a more stable solution. (C) 2012 Elsevier Ltd. All rights reserved.

Convertitori di potenza multi-sorgente per applicazioni di energy harvesting

L’obiettivo di questa tesi è stato lo svilippo di un convertitore di potenza per applicazioni di energy harvesting in grado di convogliare l’energia estratta da diversi tipi di trasduttori di grandezze ambientali in un unico dispositivo di storage, ad es. un condensatore, utilizzabile per alimentare circuiti a basso consumo. L’idea di base è stata quella di ottimizzare il trasferimento di energia, attraverso una rete logica in grado di gestire le priorità di conversione dalle diverse tipologie di sorgenti e grazie ad una implementazione di un algoritmo di Maximum Power Point Tracking. In base alle specifiche di progetto, in una prima fase è stata sviluppata la rete a livello funzionale, poi sono stati scelti i componenti più opportuni ed infine si è verificato il funzionamento attraverso simulazioni circuitali.

Ultra-Low Power and Non-intrusive Wireless Monitoring for Smart Buildings

Wireless Sensor Networks (WSNs) offer a new solution for distributed monitoring, processing and communication. First of all, the stringent energy constraints to which sensing nodes are typically subjected. WSNs are often battery powered and placed where it is not possible to recharge or replace batteries. Energy can be harvested from the external environment but it is a limited resource that must be used efficiently. Energy efficiency is a key requirement for a credible WSNs design. From the power source's perspective, aggressive energy management techniques remain the most effective way to prolong the lifetime of a WSN. A new adaptive algorithm will be presented, which minimizes the consumption of wireless sensor nodes in sleep mode, when the power source has to be regulated using DC-DC converters. Another important aspect addressed is the time synchronisation in WSNs. WSNs are used for real-world applications where physical time plays an important role. An innovative low-overhead synchronisation approach will be presented, based on a Temperature Compensation Algorithm (TCA). The last aspect addressed is related to self-powered WSNs with Energy Harvesting (EH) solutions. Wireless sensor nodes with EH require some form of energy storage, which enables systems to continue operating during periods of insufficient environmental energy. However, the size of the energy storage strongly restricts the use of WSNs with EH in real-world applications. A new approach will be presented, which enables computation to be sustained during intermittent power supply. The discussed approaches will be used for real-world WSN applications. The first presented scenario is related to the experience gathered during an European Project (3ENCULT Project), regarding the design and implementation of an innovative network for monitoring heritage buildings. The second scenario is related to the experience with Telecom Italia, regarding the design of smart energy meters for monitoring the usage of household's appliances.

Progetto di un circuito convertitore di potenza per applicazioni di energy harvesting a bassissime tensioni

In questo lavoro si vuole mostrare come sia possibile realizzare un circuito per energy harvesting totalmente autonomo, quindi senza l’ausilio di batterie, per sorgenti ultra-low voltage, in particolare per sorgenti termoelettriche sottoposte a piccoli gradienti di temperatura ed in grado di erogare tensioni di qualche decina di millivolt. Si esporrà come il circuito sia capace di avviarsi, autosostenersi ed alimentare un piccolo carico. Si è scelta una architettura basata su componenti discreti suddivisa in due macro blocchi: un circuito di startup implementato attraverso un’architettura a trasformatore piezoelettrico e un boost converter pilotato in catena aperta da un oscillatore ultra-low power.

Progetto di un nodo sensore wireless ultra low-power per rilevazione del movimento

Negli ultimi anni il tema del risparmio energetico nei sistemi elettronici ha suscitato sempre maggiore interesse, poiché grazie allo sviluppo tecnologico è stato possibile creare dispositivi in grado di operare a bassa potenza. Sempre più applicazioni elettroniche richiedono di funzionare tramite fonti di energia limitata, come per esempio le batterie, con un’autonomia in alcuni casi anche di 15-20 anni, questo è il motivo per il quale è diventato fondamentale riuscire a progettare sistemi elettronici in grado di gestire in modo intelligente l’energia a disposizione. L’utilizzo di batterie però spesso richiede costi aggiuntivi, come per esempio il semplice cambio, che in alcune situazioni potrebbe essere difficoltoso poiché il sistema elettronico si potrebbe trovare in luoghi difficilmente raggiungibili dall’uomo; ecco perché negli ultimi anni il tema della raccolta di energia o anche chiamato Energy Harvesting, sta suscitando sempre più interesse. Con l’Energy Harvesting si possono catturare ed accumulare per poi riutilizzare, piccole quantità di energia presenti nell’ambiente. Attraverso sistemi di Energy Harvesting è quindi diventato possibile trasformare energia cinetica, differenze di temperatura, effetto piezoelettrico, energia solare ecc.. in energia elettrica che può essere utilizzata per alimentare semplici applicazioni elettroniche, nel caso di questa tesi un nodo sensore wireless. I vantaggi dei sistemi di Energy Harvesting rispetto a sistemi alimentati a batteria sono i seguenti: - Costi di manutenzione ridotti; - Fonte di energia idealmente inesauribile e con un impatto ambientale negativo nullo. La potenza fornita da sistemi di Energy Harvesting si aggira intorno a qualche centinaia di uW, perciò è chiaro che il sistema da alimentare deve essere ottimizzato il più possibile dal punto di vista energetico, per questo motivo il progettista si deve impegnare per evitare qualsiasi spreco energetico e dovrà utilizzare dispositivi che permettono una gestione intelligente dell’energia a disposizione, al fine di ottenere la migliore efficienza possibile.

Progetto di una scheda PCB per applicazioni di Energy Harvesting a bassissime tensioni

Progetto di una scheda PCB per applicazioni di Energy Harvesting a bassissime tensioni. Il circuito è in grado di avviarsi, autosostenersi e alimentare un piccolo carico.

Energy harvesting from piezoelectric devices embedded in a 3D printed wing

This thesis work has been carried out at Clarkson University in Potsdam NY, USA and involved the design of a low elongation wing, consisting of parts made by polylactide (PLA) using the fused deposition model (FDM) technology of Rapid Prototyping, then assembled together in a thin aluminum spar. The aim of the research is to evaluate the feasibility of collecting electrical energy by converting mechanical energy from the vibration of the wing flutter. With this aim piezoelectric stripes were glued in the inner part of the wing, as well as on the aluminum spar, as monomorphic configuration. During the phases of the project, particular attention was given to the geometry and the materials used, in order to trigger the flutter for low flow velocity. The CAD software SolidWorks® was used for the design of the wing and then the drawings were sent to the Clarkson machine shop in order to to produce the parts required by the wing assembly. FEM simulations were performed, using software MSC NASTRAN/PATRAN®, to evaluate the stiffness of the whole wing as well as the natural vibration modes of the structure. These data, in a first approximation, were used to predict the flutter speed. Finally, experimental tests in the Clarkson wind tunnel facility were carried out in order to validate the results obtained from FEM analysis. The power collected by the piezoelectrics under flutter condition was addressed by tuning the resistors downstream the electronic circuit of the piezoelectrics.