Electromagnetic finite element design of axial flux permanent magnet machines for low speed applications

© 2014 IEEE. The higher torque to volume ratio of Axial Flux Permanent Magnet (AFPM) machines, when compared with their radial flux counterparts, is enhanced in multi pole design, making them suitable for low speed applications. This paper presents a comprehensive approach to the finite element-aided electromagnetic design of a double-sided AFPM machine with internal rotor. The Finite Element (FE) model is included in a coupled electromagnetic-thermal design procedure. Special attention is given to leakage fluxes, synchronous and armature reaction inductances and no-load electromotive force computation. The evaluation of the FE model routine of the design procedure is performed through experimental validation of a prototype machine.info:eu-repo/semantics/publishedVersio

Adsorption cooler design, modeling, and dynamics and performance analyses

This paper presents an adsorption cooler (AC) driven by the surplus heat of a solar thermal domestic hot water system to provide cooling to residential buildings. A cylindrical tube adsorber using granular silica gel as adsorbent and water as adsorbate is considered. The AC is modelled using a two-dimensional distributed parameter model that was implemented in previous adsorption heating and cooling studies. The performance coefficients of the resultant thermally driven colling system are obtained for a broad range of working conditions. The thermally driven AC has a coefficient of performance (COP) of 0.5 and a specific cooling power (SCP) of 44 W.kg--1, considering condenser, evaporator, and regeneration temperatures of 15 oC, 18 oC, and 70 oC, respectively. Moreover, results show that the AC can be used for refrigeration purposes at temperatures as low as 2 oC, and that it can also operate during hotter days under temperatures of 42 oC.This work was supported by the grant SFRH/BD/145124/2019 and the projects UIDB/00481/2020 and UIDP/00481/2020 - FCT - Fundação para a Ciência e a Tecnologia; and CENTRO-01-0145-FEDER-022083 - Centro Portugal Regional Operational Programme (Centro2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund. The present study was developed in the scope of the Smart Green Homes Project [POCI-01- 0247-FEDER- 007678], a co-promotion between Bosch Termotecnologia S.A. and the University of Aveiro. It is financed by Portugal 2020 under the Competitiveness and Internationalization Operational Program, and by the European Regional Development Fund

Membrane interactions of S100A12 (Calgranulin C)

S100A12 (Calgranulin C) is a small acidic calcium-binding peripheral membrane protein with two EF-hand structural motifs. It is expressed in macrophages and lymphocytes and highly up-regulated in several human inflammatory diseases. In pigs, S100A12 is abundant in the cytosol of granulocytes, where it is believed to be involved in signal modulation of inflammatory process. In this study, we investigated the interaction of the porcine S100A12 with phospholipid bilayers and the effect that ions (Ca2+, Zn2+ or both together) have in modifying protein-lipid interactions. More specifically, we intended to address issues such as: (1) is the protein-membrane interaction modulated by the presence of ions? (2) is the protein overall structure affected by the presence of the ions and membrane models simultaneously? (3) what are the specific conformational changes taking place when ions and membranes are both present? (4) does the protein have any kind of molecular preferences for a specific lipid component? To provide insight into membrane interactions and answer those questions, synchrotron radiation circular dichroism spectroscopy, fluorescence spectroscopy, and surface plasmon resonance were used. The use of these combined techniques demonstrated that this protein was capable of interacting both with lipids and with ions in solution, and enabled examination of changes that occur at different levels of structure organization. The presence of both Ca2+ and Zn2+ ions modify the binding, conformation and thermal stability of the protein in the presence of lipids. Hence, these studies examining molecular interactions of porcine S100A12 in solution complement the previously determined crystal structure information on this family of proteins, enhancing our understanding of its dynamics of interaction with membranes

The role of the compressor isentropic efficiency on non-intrusive refrigerant side characterization of transcritical CO2 heat pump water heaters

Characterizing the refrigerant side of heat pump water heaters (HPWHs) can be intrusive and expensive. On the other hand, direct external measurement techniques can be unfeasible, particularly in commercial HPWHs for residential applications. Non-intrusive in-situ characterization methods have already been successfully implemented in subcritical heat pumps, providing the refrigerant mass flowrate and the equipment energy performance, by using contact temperature sensors and electric power meters. Subcritical suction and discharge specific enthalpies necessary to apply the method can be obtained from the measured temperatures and their corresponding saturation pressures. Nevertheless, this approach does not apply to the transcritical CO2 HPWHs. In the supercritical region, temperature and pressure are independent variables, and an iterative process regarding the compressor isentropic efficiency has to be considered. However, when isentropic efficiency data is not available, an additional procedure is required, using a validated gas cooler model to verify the physical reliability of the numerical solutions.The present study was developed in the scope of the Smart Green Homes Project [POCI-01- 0247-FEDER- 007678], a co-promotion between Bosch Termotecnologia S.A. and the University of Aveiro. It is financed by Portugal 2020 under the Competitiveness and Internationalization OP, and by the European Regional Development Fund (ERDF). This work was funded by the grant SFRH/BD/148378/2019 and the projects UIDB/00481/2020 and UIDP/00481/2020 – FCT-Fundação para a Ciência e Tecnologia; and CENTRO-01- 0145-FEDER-022083 – Centro2020, under the PORTUGAL 2020 Partnership Agreement, through the ERDF

Comprehensive analysis and evaluation of cogging torque in Axial Flux Permanent Magnet machines

Evaluation and minimization of cogging torque in Axial Flux Permanent Magnet (AFPM) machines become essential specially in direct drives for low speed applications. This paper presents a comprehensive analysis of the cogging torque in AFPM machines designed for low speed applications and mitigation methods are proposed. Evaluation methodologies of the cogging torque based on Finite Element Analysis (FEA) computations are discussed and applied to a double-sided, internal rotor, AFPM reference machine. From the performance comparison of Maxwell stress tensor and virtual work methods on the evaluation of cogging torque, it is possible to conclude that the latter overestimates the amplitude of the cogging torque into a considerable extent.info:eu-repo/semantics/publishedVersio

Prototype of an axial flux permanent magnet generator for wind energy systems applications

Small scale wind power applications require a cost effective and mechanically simple generator in order to be a reliable energy source. The use of direct driven generators, instead of geared machines, reduces the number of drive components, which offers the opportunity to reduce costs and increases system reliability and efficiency. For such applications, characterized by low speed of rotation, the axial flux permanent magnet generator is particularly suited, since it can be designed with a large pole number and high torque density. This paper presents a double-sided axial flux permanent magnet low-speed generator, with internal rotor and slotted stators. Such a structure gives a good compromise between performance characteristics and feasibility of construction. Test results obtained from the prototype are reported.FC

An axial flux permanent magnet synchronous generator for a gearless wind energy system

In low speed applications such as wind energy conversion systems, the use of direct driven generators, instead of geared machines, reduces the number of drive components, which offers the opportunity to reduce costs and increases system reliability and efficiency. The Axial Flux Permanent Magnet (AFPM) generator is particularly suited for such application, since it can be designed with a large pole number and a high torque density. This paper presents the design, construction and experimental validation of a double-sided AFPM synchronous generator prototype, with internal rotor and slotted stators. Design objectives embrace achieving a good compromise between performance characteristics and feasibility of construction, which results in a cost competitive machine

Baobab: uma fonte natural de vitamina C

Introdução: As vitaminas distinguem-se de outros constituintes dietéticos por, em quantidades mínimas, beneficiarem diversos processos metabólicos. A vitamina C (ácido L-ascórbico), presente em frutas e legumes, é fundamental para a nutrição humana, por ser um antioxidante natural. No entanto, os teores do ácido L-ascórbico, principal forma biologicamente ativa desta vitamina, decrescem significativamente ao longo do amadurecimento dos alimentos. O conhecimento da composição nutricional e fitoquímica de frutos exóticos, caso da múcua (Baobab), pode dar a conhecer novas fontes de bioativos e permitir a sua valorização, contribuindo para a sustentabilidade social e económica da região de origem. Objetivos: Análise quantitativa do teor total de vitamina C da polpa do fruto da Adansonia digitata L., conhecida Baobab, espécie nativa de África. Métodos: O teor de ácido ascórbico foi determinado por HPLC-DAD, segundo um método previamente validado. 2 g de amostra foram adicionados a 12 mL de solução estabilizadora (ácido perclórico 10%, v/v) + ácido metafosfórico 1%, p/v). Para a determinação do teor de vitamina C total, utilizou-se tris(2-carboxietil) fosfina (5 mM). O teor de ácido desidroascórbico (forma biologicamente menos ativa) foi determinado por diferença. Resultados: O teor total de vitamina C foi de 26,1 mg/100 g, sendo 22,8 mg/100 g de ácido L-ascórbico e 3,33 mg/100 g de ácido desidroascórbico. Embora estes valores sejam significativamente inferiores aos descritos na laranja (49,1 mg/100 g) e no kiwi (55,2 mg/100 g), este fruto tem um período de conservação substancialmente maior. Atendendo aos seus teores reduzidos de humidade, o Baobab pode ser uma alternativa natural rica em antioxidantes. Conclusões: Este estudo salienta o potencial efeito antioxidante de uma fruta tropical pouco estudada e apenas consumida pela população local. A estabilidade do teor de ácido L-ascórbico observada no Baobab promove novas perspetivas de exploração e utilização de recursos naturais, no âmbito das ciências da nutrição

A New Age for Quercus spp. Fruits: Review on Nutritional and Phytochemical Composition and Related Biological Activities of Acorns

The current global food system must adapt to the expected growth of world population (about 9 billion individuals by 2050). This adaptation will probably include an increased consumption of edible wild foods, due to their richness in micronutrients and bioactive compounds, besides providing a cost-effective and sustainable way of improving caloric food security. A striking example of such natural matrices is the Quercus genus, which has the additional advantage of being widespread throughout the Northern Hemisphere. In a traditional sense, Quercus fruits (acorns) were mainly used in animal feeding, despite their potentially important role on the rural economy. But this preconception is changing. In fact, their nutritional value, high contents in phytochemical compounds, biological activity (such as antioxidant, anticarcinogenic, and cardioprotective properties) and use in the treatment of specific diseases (such as atherosclerosis, diabetes, or Alzheimer's disease) have raised the interest in integrating acorns into the human diet. Accordingly, this comprehensive overview was designed to provide an evidence-based review of the literature, with the objective to achieve useful conclusions regarding the nutritional properties, methodologies of extraction, identification, and characterization of a wide variety of bioactive compounds and scientifically validated bioactivities in Quercus species worldwide. The industrial by-products from acorn oil extraction or flour production are also included. Data regarding the analytical techniques, individual compounds, and their bioactivities, are organized in tables. The reported data are discussed and directions for further investigations are suggested, highlighting the use of acorns in food, nutraceutical, and pharmaceutical applications.The authors are grateful for the financial support (UID/QUI/ 50006/2013-POCI/01/0145/FEDER/007265) from FCT/ MEC through national funds and cofinanced by FEDER, under the Partnership Agreement PT2020. J.C.M. Barreira thanks FCT, POPH-QREN, and FSE for his grant (SFRH/BPD/72802/ 2010). The authors thank Telma Oliveira for drawing the acorn sketch depicted in Figure 1.info:eu-repo/semantics/publishedVersio