A flexible cooking zone composed of partially overlapped inductors

Domestic induction cookers are evolving from fixed cooking areas to flexible surfaces in such a way that the pot can be placed at any position. This implies the use of a larger number of reduced-sized inductors, which present a lower efficiency. As a solution to increase the efficiency while maintaining the flexibility, we propose the use of partially overlapped inductors of a larger size. This concept is currently in use in wireless power transfer systems, where the transmitter arrangement consists of several overlapped coils. The aim of this paper is to evaluate this concept applied to domestic induction heating appliances, with special emphasis in analyzing the effects of introducing the multicoil system with dissipative media. Moreover, the losses in the winding will be studied in detail. The system will be prototyped and tested, delivering up to 3.7 kW

EMI Reduction Via Resonator Coils in Glassless Integrated Domestic Induction Systems

This paper explores the magnetic flux emissions of induction heating systems compared with inductively coupled heating systems. Inductively coupled heating uses a resonator coil attached to the ferromagnetic load in order to improve energy transfer from the appliance to the load. The magnetic flux emissions of both kinds of systems are simulated, and their dependence on coil current and turn number is outlined. The paper focuses on emitted near field, whose measurement and limits are determined by norm. Several prototypes are developed and tested to verify the simulation

Printed circuit board coils of multi-track litz structure for 3.3 kW inductive power transfer system

This paper presents the optimization procedure of an inductive power transmission (IPT) system which utilizes large size spiral printed circuit board (PCB) coils for high- power transfer. Printed circuit boards for coil assembly provides advantages in the manufacturing process through the use of cost- effective flexible fabrication techniques. Furthermore, this kind of construction offers a low profile device, which is of great interest for applications with space constraints. PCB-based IPT system coils can achieve high energy efficiency by applying litz-structure braiding techniques, as investigated in this work, where the objective was to obtain an optimized balance between the conduc- tion losses and proximity losses associated with the number and dimensions of the traces. Considering the geometrical dimensions and manufacturing constraints, we will proceed to obtain the characteristics of the coil to achieve optimal performance. The estimation of coil losses were in part based on finite element simulations, and the results were conveniently processed with the appropriate mathematical methods. Numerical simulation and experimental results were conducted for validation on a prototype suitable to transfer up to 3.3 kW for a transmitter- receiver distance of 10 cm. In the experimental arrangement, a maximum efficiency in the coils of 93% has been measured, and the overall efficiency of 88% has been reached for the entire IPT system

Adapting of Non-Metallic Cookware for Induction Heating Technology via Thin-Layer Non-Magnetic Conductive Coatings

We analyze the feasibility of heating non-metallic cookware, unappropriate for heating by means of induced currents, with the purpose of extending the applicability range of the current induction heating cooktops. In order to turn materials as glass, ceramic, wood or plastic into suitable for the induction heating technology, we propose the use of thin layers of a metal (not necessarily a ferromagnetic material) which can be deposited on a surface by means of a thin or thick layer technology. For this purpose, the inductive performance of these layers is investigated by means of an analytical electromagnetic model, finite element simulations and experimental measurements. Calculations point out that for a specific induction arrangement working at a fixed frequency, it exists a thickness which maximizes the induction efficiency for each layer material. The suitability of this result is tested by means of a set of samples with copper thin layers whose thicknesses range from one hundred of nanometers to tens of micrometers, which are implemented using a phase vapor deposition (PVD) technology. The obtained induction efficiency and equivalent resistance are compared with those obtained with conventional ferromagnetic materials. As a proof of concept, the inner and outer bottoms of two glass pots are covered with a copper layer of 2µm, and 1.5µm , respectively, and 1 kW is inductively supplied by means of a series resonant inverter, reaching the boiling water conditions

Energy Management

Forecasts point to a huge increase in energy demand over the next 25 years, with a direct and immediate impact on the exhaustion of fossil fuels, the increase in pollution levels and the global warming that will have significant consequences for all sectors of society. Irrespective of the likelihood of these predictions or what researchers in different scientific disciplines may believe or publicly say about how critical the energy situation may be on a world level, it is without doubt one of the great debates that has stirred up public interest in modern times. We should probably already be thinking about the design of a worldwide strategic plan for energy management across the planet. It would include measures to raise awareness, educate the different actors involved, develop policies, provide resources, prioritise actions and establish contingency plans. This process is complex and depends on political, social, economic and technological factors that are hard to take into account simultaneously. Then, before such a plan is formulated, studies such as those described in this book can serve to illustrate what Information and Communication Technologies have to offer in this sphere and, with luck, to create a reference to encourage investigators in the pursuit of new and better solutions

A microgripper for single cell manipulation

This thesis presents the development of an electrothermally actuated microgripper for the manipulation of cells and other biological particles. The microgripper has been fabricated using a combination of surface and bulk micromachining techniques in a three mask process. All of the fabrication details have been chosen to enable a tri-layer, polymer (SU8) - metal (Au) - polymer (SU8), membrane to be released from the substrate stress free and without the need for sacrificial layers. An actuator design, which completely eliminates the parasitic resistance of the cold arm, is presented. When compared to standard U-shaped actuators, it improves the thermal efficiency threefold. This enables larger displacements at lower voltages and temperatures. The microgripper is demonstrated in three different configurations: normally open mode, normally closed mode, and normally open/closed mode. It has-been modelled using two coupled analytical models - electrothermal and thermomechanical - which have been custom developed for this application. Unlike previously reported models, the electrothermal model presented here includes the heat exchange between hot and cold arms of the actuators that are separated by a small air gap. A detailed electrothermomechanical characterisation of selected devices has permitted the validation of the models (also performed using finite element analysis) and the assessment of device performance. The device testing includes electrical, deflection, and temperature measurements using infrared (IR) thermography, its use in polymeric actuators reported here for the first time. Successful manipulation experiments have been conducted in both air and liquid environments. Manipulation of live cells (mice oocytes) in a standard biomanipulation station has validated the microgripper as a complementary and unique tool for the single cell experiments that are to be conducted by future generations of biologists in the areas of human reproduction and stem cell research

Renewable Energy

Renewable Energy is energy generated from natural resources - such as sunlight, wind, rain, tides and geothermal heat - which are naturally replenished. In 2008, about 18% of global final energy consumption came from renewables, with 13% coming from traditional biomass, such as wood burning. Hydroelectricity was the next largest renewable source, providing 3% (15% of global electricity generation), followed by solar hot water/heating, which contributed with 1.3%. Modern technologies, such as geothermal energy, wind power, solar power, and ocean energy together provided some 0.8% of final energy consumption. The book provides a forum for dissemination and exchange of up - to - date scientific information on theoretical, generic and applied areas of knowledge. The topics deal with new devices and circuits for energy systems, photovoltaic and solar thermal, wind energy systems, tidal and wave energy, fuel cell systems, bio energy and geo-energy, sustainable energy resources and systems, energy storage systems, energy market management and economics, off-grid isolated energy systems, energy in transportation systems, energy resources for portable electronics, intelligent energy power transmission, distribution and inter - connectors, energy efficient utilization, environmental issues, energy harvesting, nanotechnology in energy, policy issues on renewable energy, building design, power electronics in energy conversion, new materials for energy resources, and RF and magnetic field energy devices

QU Research and COVID-19 Pandemic

The launch of "Qatar University Research Magazine" marks the university's numerous achievements in the field of scientific research. It will also serve as a platform to highlight all our research related initiatives and activities carried out by the various research centers and colleges within the university

Superconducting wireless power transfer for electric vehicles

Electric vehicles (EVs) are an important pillar for the transition towards a cleaner and more sustainable future as renewable energy can penetrate into the transportation section and act as energy storage to cope with the intermittent supply of such energy sources. EVs have recently been significantly developed in terms of both performance and drive range. Various models are already commercially available, and the number of EVs on roads increases rapidly. Rather than being limited by physical cable connections, the wireless (inductive) link creates the opportunity of dynamic charging – charging while driving. Once realised, EVs will no longer be limited by their achievable range and the requirement for battery capacity will be greatly reduced. However, wireless charging systems are limited in their transfer distance and power density. Such drawbacks can be alleviated through high-temperature superconductors (HTS) and their increased current carrying capacity, which can substitute conventionally used copper coils in the charging pads. This thesis investigates the effectiveness of wireless power transfer (WPT) systems as a whole and when HTS coils are used as well as HTS performance at operating frequencies commonly used in WPT-systems. Initially, the fundamentals of superconductivity are outlined to give some background on how such conductors can help tackle problems occurring in WPT-systems and how their behaviour can be simulated. Subsequently, key technical components of wireless charging are summarised and compared, such as compensation topologies, coil design and communication. In addition, health and safety concerns regarding wireless charging are addressed, as well as their relevant standards. Economically, the costs of a wide range of wireless charging systems has also been summarised and compared. To explore the benefits of WPT-system for EVs, a force-based vehicle model is coupled with an extended battery model to simulate the impact of wireless charging on the state of charge of the accumulator sub-system. In total, three different scenarios, i.e. urban, highway and combined driving are presented. The trade-off between having a standalone charging option versus combined dynamic (or on-road charging) and quasi-dynamic (stationary charging in a dynamic environment) wireless charging is outlined and minimum system requirements, such as charging power levels and road coverage, for unlimited range are established. Furthermore, the effects of external factors such as ambient temperature, battery age and wireless transfer efficiency are investigated. It is shown that employing combined charging at medium power levels is sufficient to achieve unlimited range compared to high power requirements for standalone charging. HTS coils show great potential to enhance the WPT-system performance with high current-carrying capability and extremely low losses under certain conditions. However, HTS coils exhibit highly nonlinear loss characteristics, especially at high frequencies (above 1 kHz), which negatively influence the overall system performance. To investigate the improvements, copper, HTS and hybrid wireless charging systems in the frequency range of 11-85 kHz are experimentally tested. Results are compared with finite element analysis (FEA) simulations, which have been combined with electrical circuit models for performance analysis. The measurements and modelling results show good agreement for the WPT-system and HTS charging systems have a much higher transfer efficiency than copper at frequencies below 50 kHz. As the operating frequency increases towards 100 kHz, the performance of HTS systems deteriorates and becomes comparable to copper systems. Similar results are obtained from hybrid systems with a mixture of HTS and copper coils, either as transmitting or receiving coils. Nevertheless, it has been demonstrated that HTS significantly improves the transfer efficiency of wireless charging within a certain range of frequencies. The AC losses occurring in HTS coils, particularly transport current loss, magnetisation loss and combined loss, at high frequencies are studied further. A multilayer 2D axisymmetric coil model based on H-formulation is proposed and validated by experimental results as the HTS film layer is inapplicable at such frequencies. Three of the most commonly employed coil configurations, namely: double pancake, solenoid and circular spiral are examined. While spiral coils experience the highest transport current loss, solenoid coils are subject to the highest magnetisation loss due to the overall distribution of the turns. Furthermore, a transition frequency is defined for each coil when losses in the copper layer exceed the HTS losses. It is much lower for coils due to the interactions between the different turns compared to single HTS tapes. At higher frequencies, the range of magnetic field densities, causing a shift where the highest losses occur, decreases until losses in the copper stabilisers always dominate. In addition, case studies investigating the suitability of HTS-WPT are proposed. Lastly, methods to reduce AC losses of HTS coils are investigated with particular focus on flux diverters, which have been used for low frequency superconducting applications but their effectiveness at high frequencies is unexplored. Therefore, the impact of flux diverters on HTS double pancake coils operating at high frequencies up to 85 kHz is researched. Various geometric characteristics of the flux diverter are investigated such as air gap between diverter and coil, width and thickness. An FEA-model was used to examine the coil and diverter losses at such frequencies and different load factors between 0.1 and 0.8. It is demonstrated that flux diverters are a viable option to reduce the coil losses even at high frequencies and the width of the coil has the biggest impact on the loss reduction. In general, flux diverters are more suitable for applications using high load factors. Lastly, the impact of the diverter in terms of magnetic field distribution above the coil and overall loss distribution in the HTS coil was examined

Development of organogels for chocolate spreads application

Orientador: Ana Paula Badan RibeiroTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de AlimentosResumo: Nos últimos anos, alguns avanços na estruturação das bases lipídicas permitiram uma influência direta na modificação de propriedades de óleos e gorduras para aplicação em produtos alimentícios. Os mecanismos estruturantes das bases lipídicas podem ser classificados como convencionais ou não convencionais. Mecanismos não convencionais trazem a tecnologia de organogéis como uma tendência, que consiste no uso de agentes de auto-montagem para reter o óleo líquido, resultando em uma rede de gel estruturada. Questões controversas sobre o papel dos ácidos graxos trans e saturados nos alimentos levaram a mudanças progressivas na legislação de vários países para incluir mais informações para os consumidores. Neste contexto, os organogéis têm sido indicados como uma alternativa viável para a obtenção de gorduras semi-sólidas com reduzido teor de ácidos graxos saturados (AGS) e propriedades compatíveis para aplicação em alimentos. O objetivo desta tese de doutorado foi apresentar os estudos que abordam os organogéis lipídicos como uma alternativa para a aplicação de alimentos, caracterizar os spreads de chocolate comerciais e suas respectivas fases lipídicas, visando estratégias de reformulação dessa categoria de produto, além da caracterização físico-química de estruturantes de grau alimentício com potencial uso no desenvolvimento de organogéis, avaliar o efeito de estruturantes de grau alimentício isoladamente, em misturas binárias, ternárias ou mais, em diferentes concentrações, sobre a formação de organogéis de óleo de girassol alto oleico e produzir spreads de chocolate com redução do teor de AGS. Os spreads de chocolate comerciais analisados neste estudo mostraram estabilidade, uma vez que não houve exsudação de óleo líquido durante o período de estabilização, no entanto, eles poderiam apresentar menores níveis de AGS para atender a demanda de consumidores que buscam alimentos mais saudáveis. Todos os estruturantes apresentaram propriedades semelhantes, como alta concentração de ácidos graxos saturados, alto teor de sólidos na temperatura analisada, baixo tempo de indução de cristalização, alta resistência térmica, bem como parâmetros uniformes quanto à morfologia e dimensões cristalinas. Os organogéis analisados são bases lipídicas com potencial para serem usados como substitutos de gordura em processos industriais, para atender uma demanda de consumidores que buscam por alimentos mais saudáveis. Os spreads de chocolate com organogel mostraram alta estabilidade, indicando que o uso de organogéis como substituto de bases lipídicas convencionais em spreads de chocolate foi eficiente, uma vez que apresentaram comportamento similar ao padrão produzido com óleo de palma e redução de AGS variando entre 69,79 a 76,04%. Dessa forma, é possível produzir um produto de qualidade utilizando baixa concentração de estruturante e reduzindo o teor de AGSAbstract: In recent years, some advances in the structuring of lipid bases have allowed a direct influence on the modification of properties of oils and fats for application in food products. The structuring mechanisms of the lipid bases can be classified as conventional or unconventional. Unconventional mechanisms bring organogel technology as a trend, which is the use of self-assembling agents to retain liquid oil, resulting in a structured gel network. Controversial questions about the role of trans and saturated fatty acids in food have led to progressive changes in legislation in several countries to include more information for consumers. In this context, organogels have been indicated as a viable alternative to obtain low saturated fatty acid (SFA) semisolid fats and compatible properties for food application. The aim of this doctoral dissertation was to present the studies that approach lipid organogels as an alternative for food application, to characterize the commercial chocolate spreads and their respective lipid phases, aiming at strategies of reformulation of this product category, besides the physical-characterization. Chemistry of food grade structurants with potential use in organogel development, to evaluate the effect of food grade structurants alone, in binary, ternary or more mixtures, at different concentrations, on the formation of high oleic sunflower oil organogels and produce chocolate spreads with reduced SFA content. The commercial chocolate spreads analyzed in this study showed stability as there was no liquid oil exudation during the stabilization period; however, they could have lower levels of SFA to meet the demand of consumers seeking healthier foods. All structurants had similar properties, such as high concentration of saturated fatty acids, high solids content at the analyzed temperature, short crystallization induction time, high thermal resistance, as well as uniform morphological parameters and crystalline dimensions. The analyzed organogels are lipid bases with potential to be used as fat substitutes in industrial processes, to meet a demand of consumers who are looking for healthier foods. The organogel chocolate spreads showed high stability, indicating that the use of organogels as a substitute for conventional lipid bases in chocolate spreads was efficient, since they presented similar behavior to the palm oil pattern and reduction of SFA ranging from 69.79 to 76.04%. Thus, it is possible to produce a quality product using low concentration of structurant and reducing the SFA contentDoutoradoTecnologia de AlimentosDoutora em Tecnologia de AlimentosCAPE