This thesis explores how an Android application that is used in combination with tangible appcessories is capable of facilitating a learning experience for visually impaired students within the specific domain of geometry. This study’s approach illustrates how using an application in combination with a physical appcessory can provide information concerning geometry to the visually impaired. An application, called Invisible Tangible Geometry (ITG), was programmed using Android in conjunction with a 3D printed model. This thesis describes the application, the physical appcessory, as well as early stage user studies. The application enables visually impaired users to explore simple geometric forms displayed on a tablet through sound and vibrotactile feedback. A physical appcessory, that can be manipulated to adopt several forms and is dynamic, is used in addition. Its shape is sensed by the tablet adds an additional tactile layer to the application and experience. Within the thesis a methodological framework, as well as a user-centered design approach was applied. An expert interview and three user engagements with visually impaired individuals serve as early validations of the project and ideas and provide feedback that directs design and development of future work. Current avenues for the future work will include additional interaction modes in the application. For example, the ability to digitize real world forms, and improving the robustness of the tangible appcessory. The plan, for future development, is to establish an autonomous functioning application that enables the visually impaired to be able to explore, participate and interact with geometry smoothly and without the need of aid from others. The correlation of application and appcessory will allow for anything between a quick glance, through feeling the model, and gaining detailed information, by using the application. The application enhances provided information through the use of a model and enriched digital feedback.

This Master’s Degree project has been performed on behalf of Vanuatu Renewable Energy and Power Association. The purpose of the project was to suggest the design of stand-alone renewable power supply systems on Futuna Island in the Republic of Vanuatu. Futuna is the easternmost island in Vanuatu with a population of about 400 people. The island covers an area of just 13 km2. The proposed sites for power production were the villages of Mission Bay, Matangi, Herald Bay and Iahsoa. In Mission Bay and Matangi the power should be produced by wind turbines and in Herald Bay and Iahsoa, solar modules are proposed. The results of the study showed that some parts of Futuna Island can be suitable for wind power production and wind speeds in the order of 5-7 m/s are suggested. However, wind monitoring on the sites are required to estimate the exact potential. Furthermore, the study showed that there is less uncertainty involved with estimating the power output from the solar modules. In addition, solar power proved to be more reliable and less vulnerable to local variations in weather and topography. Solar modules are therefore considered more appropriate for small scale power production on the island, at least until the wind climate is better known. The results of the study also showed that proper sizing of battery banks and cables are essential to increase the efficiency and lifetime of the systems. If there are insufficient financial resources in the project, it is therefore recommended in the report to use all resources available to properly size the systems in 1-2 villages rather than to inadequately size the systems in all the villages. / Ögruppen Vanuatu är en självständig nation som består av mer än 83 bebodda öar av varierande storlek. Landet ligger mellan Fiji och Australien i Stilla havet och tillhör enligt FN världens fattigaste länder. Av landets befolkning på ungefär 200 000 människor är minst 80 procent självförsörjande bönder. Förutom på några av de större öarna där man byggt ut elnät till viss del finns det i princip ingen produktion av elektrisk energi i landet. Undantaget är några enstaka dieselaggregatsystem och solcellssystem som installerats med hjälp av privata medel och bistånd. Dock är många av dessa mikrosystem beroende av fossilt bränsle som måste importeras och därför är både dyrt och ofta en bristvara då transporten mellan öarna kan vara oberäknelig. Öarnas geografiska isolation och bristen på infrastruktur hindrar utvecklingen av storskalig energiproduktion i landet. För att förbättra denna situation initierade frivilligorganisationen Vanuatu Renewable Energy and Power Association (VANREPA) år 2005 ett projekt med syftet att producera elektrisk energi på öarna Futuna och Aneityum med hjälp av förnybara energikällor. Landet har gott om förnybara energiresurser i form av hög solinstrålning, passadvindar, biobränslen och höga vulkanberg som även möjliggör produktion av vattenkraft. Landet har därför potential att producera relativt billig och miljövänlig energi med hjälp av lokala resurser. Projektet leds av VANREPA’s grundare David Stein, ursprungligen från USA, och finansieras med hjälp av bidrag från EU. Det här examensarbetet har utförts i samarbete med VANREPA, och med David Stein som handledare. Ämnesgranskare på Uppsala universitet har varit Marcus Berg och examinator har varit Kjell Pernestål. Examensarbetet har även utförts som en Minor Field Study i samarbete med Arbetsgruppen för tropisk ekologi (ATE) på Uppsala universitet och med stipendium från Styrelsen för internationellt utvecklingssamarbete (Sida). I tillägg har examensarbetet finansierats med hjälp av ett resestipendium ur Jacob A. Letterstedts resestipendiefond som förvaltas av Kungl. Vetenskapsakademien (KVA). Syftet med examensarbetet har varit att föreslå lämplig design av de fyra förnybara kraftproduktionssystem som planeras i byarna Mission Bay, Matangi, Herald Bay och Iahsoa på Futuna. Den totala befolkningen på ön består av ungefär 400 människor. Det var önskvärt att kraftproduktionssystemen utformades så enkelt som möjligt. Detta för att underlätta att drift och underhåll ska kunna skötas av den lokala befolkningen på ön men även för att minimera projektets kostnader. Eftersom både efterfrågan och produktion av energi kommer att vara relativt låga var det även önskvärt att minimera alla förluster så mycket som möjligt. Dessutom var det önskvärt att systemen designades med möjlighet för expansion då detta endast anses vara ett första steg i att försörja Futuna med elektrisk energi. Komponenter som inkluderades i designen var vindturbiner, solpaneler, batterier och kablar. Ett antal givna förutsättningar begränsade utförandet av examensarbetet. Dels var vindturbinerna och solpanelerna redan införskaffade vid den tidpunkt då författaren påbörjade examensarbetet. Detta innebar att det inte fanns möjlighet att påverka vare sig val av produktionsmetod eller antal produktionsenheter. Dessutom hade byggnaderna för batteribankerna i de fyra byarna redan byggts. Eftersom det var viktigt att hålla förlusterna och kostnaderna på en minimal nivå kunde därför inte heller placeringen av solpanelerna eller vindturbinerna påverkas, då dessa måste placeras så nära batteribankerna och konsumenterna som möjligt. Utförandet av examensarbetet delades in i tre delar. I den första delen gjordes förberedande litteraturstudier i Sverige om småskaliga energisystem i allmänhet och förutsättningarna i Vanuatu i synnerhet. I den andra delen utfördes under sex veckor fältstudier på plats i Vanuatu. Under denna period genomfördes bland annat en fältresa till Futuna, där de fyra platserna föreslagna för kraftproduktion besöktes. Under fältresan samlades relevanta data in, såsom koordinater för platserna i behov av elektrisk energi och topografiska förutsättningarna för sol- och vindkraft på de fyra platserna. Dessutom intervjuades representanter för de fyra byarna för att kartlägga var och till vad elektrisk energi var önskvärd. Under den sista delen av examensarbetet analyserades materialet som samlats in under fältstudierna tillsammans med ämnesgranskaren på Uppsala universitet. Den förväntade kraftproduktionen från solpanelen och vindturbinerna uppskattades med hjälp av data från NASA, då inga vind- eller solmätningar gjorts på plats per idag. På grund av den stora osäkerheten med att använda dessa data är den beräknade kraftproduktionen inte lika exakt som den annars kunnat vara. När den förväntade kraftproduktionen uppskattats beräknades den nödvändiga storleken på batteribankar och kablar. För att inte underdimensionera systemen inkluderades ett visst antal dagar som batteribanken skulle kunna försörja den givna lasten med elektrisk energi om vind eller sol skulle utebli. Dessutom dimensionerades batteribankerna för ett maximalt urladdningsdjup, detta för att förlänga batteriernas liv. Kablarna dimensionerades för att minimera spänningsfall och i gränsfall valdes därför alltid den större kabelstorleken. Både batteribankarna och kablarna dimensionerades även med hänsyn till övriga förluster i systemet. Studien visade att vissa områden på Futuna kan vara lämpade för vindkraftsproduktion. Dock krävs vindmätningar på plats för att kunna uppskatta den exakta potentialen. Osäkerheten med kraftproduktion från solceller är mindre än för vindturbiner. Denna energikälla är också mindre känslig för lokala variationer och kräver mindre kunskap hos lokalbefolkningen för drift och underhåll. Solenergi anses därför vara en bättre lämpad energikälla för småskalig kraftproduktion på ön, åtminstone tills man fått en bättre uppfattning om det rådande vindklimatet. Kostnaden för batterier är en känslig del av energisystemen som tyvärr inte går att komma undan, då kraftproduktionen är för instabil för att försörja lasten direkt. Det är mycket viktigt att batteribankernas kapacitet dimensioneras korrekt, för att undvika kortlivade system. Underdimensionerade batteribanker leder även till mindre effektiva system då en mindre andel av den producerade energin kan användas. Detsamma gäller för dimensioneringen av kablar, eftersom för högt spänningsfall kan leda till att den producerade energin inte når fram till konsumenten. Om tillräckliga finansiella resurser saknas för att slutföra projektet är det därför rekommenderat att snarare satsa på korrekt dimensionerade system i 1-2 byar än ofullständigt dimensionerade system i alla fyra byarna.

In recent years the number of bicycles with e-motors has been increased steadily. Within the pedelec – bikes where an e-motor supports the pedaling – a special group of transportation bikes has developed. These bikes have storage boxes in addition to the basic parts of a bike. Due to the space available on top of those boxes it is possible to install a PV system to generate electricity which could be used to recharge the battery of the pedelec. Such a system would lead to grid independent charging of the battery and to the possibility of an increased range of motor support. The feasibility of such a PV system is investigated for a three wheeled pedelec delivered by the company BABBOE NORDIC.The measured data of the electricity generation of this mobile system is compared to the possible electricity generation of a stationary system.To measure the consumption of the pedelec different tracks are covered, and the energy which is necessary to recharge the bike battery is measured using an energy logger. This recharge energy is used as an indirect measure of the electricity consumption. A PV prototype system is installed on the bike. It is a simple PV stand alone system consisting of PV panel, charge controller with MPP tracker and a solar battery. This system has the task to generate as much electricity as possible. The produced PV current and voltage aremeasured and documented using a data logger. Afterwards the average PV power is calculated. To compare the produced electricity of the on-bike system to that of a stationary system, the irradiance on the latter is measured simultaneously. Due to partial shadings on the on-bike PV panel, which are caused by the driver and some other bike parts, the average power output during riding the bike is very low. It is too low to support the motor directly. In case of a similar installation as the PV prototype system and the intention always to park the bike on a sunny spot an on-bike system could generate electricity to at least partly recharge a bike battery during one day. The stationary PV system using the same PV panel could have produced between 1.25 and 8.1 times as much as the on-bike PV system. Even though the investigation is done for a very specific case it can be concluded that anon-bike PV system, using similar components as in the investigation, is not feasible to recharge the battery of a pedelec in an appropriate manner. The biggest barrier is that partial shadings on the PV panel, which can be hardly avoided during operation and parking, result in a significant reduction of generated electricity. Also the installation of the on-bike PV system would lead to increased weight of the whole bike and the need for space which is reducing the storage capacity. To use solar energy for recharging a bike battery an indirect way is giving better results. In this case a stationary PV stand alone system is used which is located in a sunny spot without shadings and adjusted to use the maximum available solar energy. The battery of the bike is charged using the corresponding charger and an inverter which provides AC power using the captured solar energy.

No description available.

Allocation to private infrastructure debt investments has increased in the recent years [15]. For managers of multi-asset portfolios, it is important to be able to assess the risk of the total portfolio and the contribution to risk of the various holdings in the portfolio. This includes being able to explain the risk of having private infrastructure debt investments in the portfolio. The modelling of private infrastructure debt face many challenges, such as the lack of private data and public indices for private infrastructure debt. In this thesis, two approaches for modelling private infrastructure debt in a parametric risk factor model are proposed. Both approaches aim to incorporate revenue risk, which is the risk occurring from the type of revenue model in the infrastructure project or company. Revenue risk is categorised into three revenue models; merchant, contracted and regulated, as spread level differences can be distinguished for private infrastructure debt investments using this categorisation. The difference in spread levels between the categories are used to estimate β coefficients for the two modelling approaches. The spread levels are obtained from a data set and from a previous study. In the first modelling approach, the systematic risk factor approach, three systematic risk factors are introduced where each factor represent infrastructure debt investments with a certain revenue model. The risk or the volatility for each of these factors is the volatility of a general infrastructure debt index adjusted with one of the β coefficients. In the second modelling approach, the idiosyncratic risk term approach, three constant risk terms for the revenue models are added in order to capture the revenue risk for private infrastructure debt investments. These constant risk terms are estimated with the β coefficients and the historical volatility of a infrastructure debt index. For each modelling approach, the commonly used risk measures standalone risk and risk contribution are presented for the entire block of the infrastructure debt specific factors and for each of the individual factors within this block. Both modelling approaches should enable for better explanation of risk in private infrastructure debt investments by introducing revenue risk. However, the modelling approaches have not been backtested and therefore no conclusion can be made in regards to whether one of the proposed modelling approaches actually is better than current modelling approaches for private infrastructure debt. / Investeringar i privat infrastrukturskuld har ökat de senaste åren [15]. För βägare av portföljer med investeringar i samtliga tillgångsslag är det viktigt att kunna urskilja risken från de olika innehaven i portföljen. Det finns många utmaningar vad gäller modellering av privat infrastrukturskuld, så som den begränsade mängden privat data och publika index för privat infrastrukturskuld. I denna uppsats föreslås två tillvägagångssätt för att modellera privat infrastrukturskuld i en parametrisk riskfaktormodell. Båda tillvägagångssätten eftersträvar att inkorporera intäktsrisk, vilket är risken som beror på den underliggande intäktsmodellen i ett infrastrukturprojekt eller företag. Intäksrisk delas in i intäksmodellerna "merchant", "contracted" och "regulated", då en skillnad i spreadnivå mellan privata infrastrukturskuldinvesteringar kan urskiljas med denna kategorisering. Skillnaden i spreadnivå mellan de olika kategorierna används för att estimera β -koefficienter som används i båda tillvägagångssätten. Spreadnivåerna erhålls från ett dataset och från en tidigare studie. I det första tillvägagångssättet, den systematiska riskfaktor-ansatsen, introduceras tre systematiska riskfaktorer som representerar infrastrukturskuldinvesteringar med en viss intäktsmodell. Risken eller volatiliten för dessa faktorer är densamma som volatiliteten för ett index för infrastrukturskuld justerat med en av β -koefficienterna. I det andra tillvägagångssättet, den idriosynktratiska riskterm-ansatsen, adderas tre konstanta risktermer för intäktsmodellerna för att fånga upp intäktsrisken i de privata infrastrukturinvesteringarna. De konstanta risktermerna är estimerade med β -koefficienterna och en historisk volatilitet för ett index för infrastrukturskuld. För båda tillvägagångssätten presenteras riskmåtten stand-alone risk1 och risk contribution2. Riskmåtten ges för ett block av samtliga faktorer för infrastrukturskuld och för varje enskild faktor inom detta block. Båda tillvägagångssätten borde möjliggöra bättre förklaring av risken för privata infrastrukturskuldinvesteringar i en större portfölj genom att ta hänsyn till intäktsrisken. De två tillvägagångssätten för modelleringen har dock ej testats. Därför kan ingen slutsats dras med hänsyn till huruvida ett av tillvägagångssätten är bättre än de som används för närvärande för modellering av privat infrastrukturskuld.

A novel probabilistic method has been developed for modelling the operation of energy storage in electricity systems with significant amounts of wind and solar powered generation. This method is based on a spectral analysis of the variations of wind speed and solar irradiance together with profiles of electrical demand. The method has been embodied in two Matlab computer programs: Wind power only: This program models wind power on any time scale from seconds to years, with limited modelling of demand profiles. This program is only capable of modelling stand-alone systems, or systems in which the electrical demand is replaced by a weak grid connection with limited export capacity. 24-hours: This program models wind power, solar PV power and electrical demand, including seasonal and diurnal effects of each. However, this program only models store cycle times (variations within a time scale) of 24 hours. This program is capable of modelling local electrical demand at the same time as a grid connection with import or export capacity and a backup generator. Each of these programs has been validated by comparing its results with those from a time step program, making four Matlab programs in total. All four programs calculate the power flows to and from the store, satisfied demand, unsatisfied demand and curtailed power. The programs also predict the fractions of time that the store spends full, empty, filling or emptying. The results obtained are promising. Probabilistic program results agree well with time step results over a wide range of input data and time scales. The probabilistic method needs further refinement, but can be used to perform initial modelling and feasibility studies for renewable energy systems. The probabilistic method has the advantage that the required input data is less, and the computer run time is reduced, compared to the time step method.

In this thesis, solar-hydrogen Stand-Alone Power System (SAPS) which is planned to be built for the emergency room of a hospital is designed. The system provides continuous, off-grid electricity during the whole period of a year without any external electrical power supply. The system consists of Photovoltaic (PV) panels, Proton Exchange Membrane (PEM) based electrolyzers, PEM based fuel cells, hydrogen tanks, batteries, a control mechanism and auxiliary equipments such as DC/AC converters, water pump, pipes and hydrogen dryers. The aim of this work is to investigate the optimal system configuration and component sizing which yield to high performance and low cost for different user needs and control strategies. TRNSYS commercial software is used for the overall system design and simulations. Numerical models of the PV panels, the control mechanism and the PEM electrolyzers are developed by using theoretical and experimental data and the models are integrated into TRNSYS. Overall system models include user-defined components as well as the default software components. The electricity need of the emergency room without any shortage is supplied directly from the PV panels or by the help of the batteries and the fuel cells when the solar energy is not enough. The pressure level in the hydrogen tanks and the overall system efficiency are selected as the key design parameters. The major component parameters and various control strategies affecting the hydrogen tank pressure and the system efficiency are analyzed and the results are presented.

Made available in DSpace on 2014-06-11T19:30:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-03-01Bitstream added on 2014-06-13T21:01:25Z : No. of bitstreams: 1 godoy_rb_dr_ilha.pdf: 3494392 bytes, checksum: 572327823a0ebf4a37a2c4352c009edc (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Uma das importantes aplicações dos sistemas inversores está associada ao fornecimento de energia elétrica. Com este foco destacam-se o fornecimento para cargas críticas, o fornecimento em áreas desprovidas dos usuais sistemas de transmissão e distribuição e aplicações com multi-fontes primárias de energia, incluindo-se neste caso, as aplicações para geração distribuída, com possibilidade de conectividade com a rede elétrica de distribuição ou, com o paralelismo entre estruturas isoladas. Atualmente, topologias e filosofias de controle que atendam as características das aplicações supracitadas são de interesse técnico e científico. Neste sentido, a possibilidade de paralelismo entre inversores sem interconexão do controle tem se mostrado atrativa à medida que se exigem sistemas distribuídos e adaptáveis às variações paramétricas do circuito. Entretanto, problemas de estabilidade e resposta dinâmica devem ser solucionados para garantir a confiabilidade de tais sistemas. Sendo assim, neste trabalho inicialmente é realizada a modelação em espaço de estados de sistemas compostos por inversores cuja filosofia de controle esteja embasada nas curvas P- e Q-V. Com esta modelação, tornam-se possíveis avaliações de estabilidade e resposta dinâmica através dos autovalores da matriz de estados. Propõe-se assim a busca da estabilidade dos sistemas com melhores respostas dinâmicas através de alterações nos valores da matriz de estados, resultando-se em autovalores que representem parâmetros de desempenho otimizados. Obviamente que alterações na matriz de estados estão associadas a alterações na planta, contudo, alterações em parâmetros físicos não são interessantes, uma vez que não são simples de serem obtidas na prática. Sendo assim, são propostas alterações nas constantes que definem as inclinações das curvas de controle P- e Q-V... / One of main applications of inverter systems is associated to electrical energy supply. With this focus it emphasizes the supply of energy to critical loads, the supply of energy to areas devoid of the usual transmission and distribution systems of energy and the use of primary energy in multi-fonts applications, including in this case, distributed generation applications with grid connectivity or, parallelism in stand alone applications. Currently, topologies and control philosophies capable to assure the applications characteristics above mentioned are in technical and scientific interests. In this way, the possibility of inverter parallelism with no control interconnection has showed attractive, since distributed systems and adaptable systems to parametric variations are mandatory nowadays. However, stability troubles and inadequate dynamic responses must be solved to ensure reliability of these systems. So, in this work is performed the state space modeling of systems set by inverters whose control philosophy is based on P- and Q-V curves. With this modeling it becomes possible evaluations of stability and dynamic response through state matrix eigenvalues. Thus, it proposes to assure the systems stability and better dynamic responses through changes on state matrix values, resulting in eigenvalues that represent optimized performance parameters. Obviously those variations in state matrix are associated with plant variations, however, physical parameters variations are not interesting, seeing that it is not simple to be obtained in practical situations. In face of this are proposed variations in constants that define the slopes of P- and Q-V curves. These slopes intervene directly on state matrix values and consequently in systems eigenvalues. The variations on constants are not performed randomly, nevertheless based on evolutionary algorithm capable to search values that represent...(Complete abstract click electronic access below)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The continuous economic development of many countries and the emerging environmental issues (gas emissions and the greenhouse effect) observed in the last decades forced an intense research in renewable energy sources. Hydro, photovoltaic (PV) and wind energy conversion are the most explored technologies due to their considerable advantages, such as reliability, low environmental impact and capability to support microgrid systems or to connect to the electric grid. Among these energy sources the PV is pointed out as one of the most modular and environmentally friendly technologies. Furthermore, this technology enabled, by means of stand-alone or off-grid systems, the access of electricity in many communities distant form the grid, and even in difficult access remote applications. However, the PV panel still represents low efficiency and high cost, making imperative the use of efficient and reliable energy processing stages. Therefore, this work proposes a stand-alone photovoltaic system with decentralized configuration, aiming a high energy yield. For the output stage, a multilevel inverter was chosen, aggregating the intrinsic advantages that these converters present. The analysis of each energy processing stage is presented, as well as the modeling and control of the employed converters. Due to the requirement of a backup system (in stand-alone systems), a decentralized configuration of the battery bank is proposed. Moreover, aiming to optimize the backup system lifetime and reduce the maintenance costs, a controlled charge/discharge process on the batteries is implemented. Simulation and experimental results are presented, verifying the functionality of the proposed structure. / O contínuo desenvolvimento econômico de diversos países e as emergentes questões ambientais (emissão de gases e efeito estufa), observados nas últimas décadas, forçaram uma intensa pesquisa em fontes renováveis de energia. Hidro, fotovoltaica (PV Photovoltaic) e eólica são as tecnologias mais exploradas devido as suas vantagens consideráveis, como confiabilidade, reduzidos impactos ambientais e capacidade de suprir pequenas redes ou conexão com a rede elétrica de distribuição. Entre estas fontes de energia, a fotovoltaica destaca-se por ser uma das tecnologias mais modulares, apresentando os menores índices de impactos ambientais. Ainda, esta tecnologia possibilitou, através dos sistemas autônomos (off-grid), o acesso de energia elétrica a diversas comunidades distantes da rede de distribuição, e também em aplicações remotas de difícil acesso. Entretanto, o painel PV ainda apresenta reduzido rendimento e elevado custo, tornando indispensável o uso de estágios de processamento de energia eficientes e confiáveis. Nesse sentido, este trabalho propõe um sistema fotovoltaico autônomo que utiliza uma configuração descentralizada, visando um melhor aproveitamento de energia gerada. Para o estágio de saída, optou-se pela utilização de um inversor multinível, agregando as vantagens intrínsecas que este tipo de conversor apresenta. São apresentadas as análises de cada estágio de processamento de energia, bem como a modelagem e controle de cada conversor empregado. É proposta uma configuração descentralizada para o banco de baterias, visto que se faz necessário um sistema de armazenamento para sistemas autônomos. Ainda, o controle empregado para o sistema de armazenamento de energia implementa um processo de carga/descarga controlado no banco de baterias, visando o aumento da vida útil destas e a redução dos custos por manutenção. São apresentados resultados de simulação e experimentais, comprovando a funcionalidade da estrutura.

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