Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: See PDF for abstract. / AFRIKKANSE OPSOMMING: Sien PDF vir die opsomming.

Thesis (MScEng)--Stellenbosch University, 2012 / ENGLISH ABSTRACT: A technology that has advanced immeasurably as a result of the necessity for green energy production is the harnessing of wind energy. One of the most important aspects of a wind turbine is its supporting structure. The tower of a wind turbine needs to be sufficiently reliable and structurally sound to ensure that the design life of the wind turbine machine is unaffected. The tower also needs to be of the correct height to ensure that the full potential of energy capture is realised. The supporting structure of a wind turbine constitutes up to as much as 30% of the total costs of a wind turbine. The most common wind turbine supporting structures seen worldwide today are Steel Monopole Towers. The large cost proportion of the tower compels the industry to investigate the most feasible alternative supporting tower structures and thus prompted the research developed in this thesis. In this thesis the focus is on small scale wind turbines (<50kW), more specifically, a 3kW Wind Turbine. The proposed alternative design the support structures of small scale wind turbines to the presently used Steel Monopole tower was a Steel Lattice tower. Both a Steel Lattice and Steel Monopole Tower was designed for a 3kW Wind Turbine using rational design methods determined from pertinent sections of the South African design codes. The Tower designs needed to incorporate the details of the element connections, so as to encompass all of the cost parameters accurately. The foundation design of each of the towers was also required from the point of view of cost analysis completeness, and ended up playing a critical role in the feasibility analysis. To validate the design methods, the two towers were modelled in the finite element package Strand7 and a number of different analyses were performed on the two towers. The analyses included linear static, nonlinear static, natural frequency and harmonic frequency analyses. The towers were assessed for a number of different load case combinations and were examined in terms of stress states, mass participation factors and deflections, to mention a few, for the worst loading combination cases that were encountered. Once a final design was reached for both the Steel Lattice and Steel Monopole Towers, each element from which they were made was assessed from a structural viewpoint to determine manufacturing and construction costs. The cost analysis was conducted by means of asking a number of leading construction companies for unit prices for each of the identified elements to be assessed. The fabrication and construction of each of the Towers was then compared to determine which one was more feasible, in terms of each design aspect considered as well as looking at the complete end product. It was found that the Steel Lattice Tower was more feasible from the points of view of fabrication, and construction, as well as having a far more cost effective foundation. This was a positive conclusion from the perspective of the proposal for a more feasible alternative to the presently used Steel Monopole Towers. The outcome of the research conducted here could certainly prove to be worth considering from a wind farm development perspective, with particular focus on the up and coming Wind Industry developments in South Africa. / AFRIKAANSE OPSOMMING: As gevolg van die noodsaaklikheid vir die produksie van volhoubare energie is ʼn tegnologie wat met rasse skrede vooruitgegaan het die vir die benutting van windenergie. Een van die belangrikste aspekte van 'n windturbine is die ondersteunende struktuur. Die toring van 'n windturbine moet funksioneel en struktureel betroubaar wees om te verseker dat die ontwerpleeftyd van die windturbine masjien nie nadelig beïnvloed word nie. Die toring moet ook die regte hoogte wees om te verseker dat die volle potensiaal van die wind energie in meganiese energie omgesit word. Die koste van die ondersteunende struktuur van 'n windturbine verteenwoordig tot 30% van die totale koste van 'n windturbine. Die mees algemene vorm van ondersteunende strukture vir windturbines wat vandag wêreldwyd teëgekom word, is die van 'n enkel staal buisvormige toring. Die groot koste‐komponent van die toring dwing die industrie om ondersoek in te stel na die mees koste effektiewe prakties uitvoerbare alternatief vir die ondersteunende toring struktuur. Hierdie aspek van die struktuur konseptualisering het gelei tot die navorsing wat in hierdie tesis onderneem is. Die fokus van die navorsing is op klein skaal windturbines (<50kW), en meer spesifiek op 'n 3kW windturbine model. Die alternatiewe ontwerp wat ontwikkel is vir klein skaal wind turbines se ondersteunende structure, is 'n staal vakwerk toring as alternatief vir die staal buisvormige toring. Beide 'n staal vakwerk en staal buisvormige toring vir 'n 3kW wind turbine is ontwerp deur rasionele ontwerp metodes. Die toepaslike gedeeltes van die Suid‐Afrikaanse ontwerp kodes is hiervoor gebruik. Die ontwerp vir die toring moet die besonderhede van die element verbindings in ag neem en die nodige koste parameters moet akkuraat bepaal word. Die ontwerp van die fondament van elke toring is ook noodsaaklik vir die volledigheid van die koste‐ontleding en dit speel ook 'n kritieke rol in die gangbaarheid analise. Om die ontwerp metodes te bevestig, is die twee tipes torings in die eindige element pakket, Strand7, gemodelleer en 'n aantal verskillende ontledings vir die twee torings is uitgevoer. Die ontledings sluit lineêr en nie‐lineêr statiese ontledings asook natuurlike frekwensie en dinamiese ontledings onder harmoniese belastings in. Die torings is vir 'n aantal verskillende lasgevalkombinasies ondersoek en in die spannings toestande, massadeelname faktore en defleksies vir die ergste laskombinasie gevalle wat ondervind is, is geassesseer. Sodra 'n finale ontwerp vir beide die staal vakwerk en staal buisvormige toring voltooi is, is elke element beoordeel uit 'n strukturele en materiaal oogpunt om die kostes daarvan te bepaal. Die koste‐analise is baseer op data wat voorsien is deur 'n aantal vooraanstaande konstruksiemaatskappye op 'n prys per eenheid basis vir elk van die geïdentifiseerde elemente wat geassesseer moes word. Die vervaardiging en konstruksie van elke toring is dan vergelyk om te bepaal watter een die mees haalbaar is, in terme van elke toepaslike ontwerpsaspek en deur ook die volledige eindproduk te evalueer. Daar is bevind dat die staal vakwerk toring uit die oogpunt van vervaardiging en konstruksie, asook as gevolg van 'n meer koste‐effektiewe fondament, die voorkeur alternatief verteenwoordig het. Dit was 'n positiewe gevolgtrekking uit die oogpunt van die soeke na 'n ander alternatief as die buisvormige staal torings wat tans algemeen in gebruik is. Die uitkoms van hierdie navorsing verdien oorweging uit ʼn windplaas ontwikkelingsperspektief, met ʼn spesifieke fokus op die opkomende ontwikkelinge in die wind energie industrie in Suid‐Afrika.

The research describes an optimized waste-to-energy technology that utilizes agricultural residues for renewable energy, while reducing global methane emissions and maintaining food security. Laboratory-, pilot- and farm-scale anaerobic batch digesters were evaluated to enhance methane production from the anaerobic digestion of untreated rice straw in dry conditions using a novel co-digestion approach. An existing farm-scale biogas plant loaded with rice straw and piggery wastewater produced 295 MWh in a 422-day digestion cycle. The long acclimation period (approximately 200 days) and low biogas yield (181 LCH4/kgVS) could be enhanced by adding anaerobic sludge from the pulp and paper mill treatment process. In a laboratory setting, the addition of the sludge resulted in a specific methane yield of 335 LCH4/kgVS within 92 days. Hydrolysis of the straw was accelerated, and stable conditions were observed in terms of pH, alkalinity and nutrients. Similar improvements were demonstrated in pilot-scale digesters (1 m3) - a specific methane yield of 231 LCH4/kgVS was achieved in a 93-day digestion cycle with the sludge compared to 189 days without the sludge. Insufficient mixing within the pilot-scale system caused lower overall methane yields than those obtained in the laboratory-scale digesters. If sufficient mixing and mesophilic conditions are maintained within the farm-scale system, the co-digestion of rice straw with pig wastewater and paper mill sludge (wet weight ratio of 1:1.25:0.5) has the potential to reduce the retention time to three months (versus 422 days) and increase methane yields to over 300 LCH4/kgVS

<p style="text-align: justify;">Rad se bavi problemom smanjenja proizvodnje<br />električne energije fotonaponske elektrane u<br />uslovima promenljivog zračenja. Predlaže se novi<br />metod analize rada u uslovima senčenja putem makro- i<br />mikrorekonfiguracije FN polja, koja povećava<br />proizvodnju električne energije.</p> / <p>The paper presents the problem of reducing electricity<br />production of PV power plant under variation of solar<br />radiation conditions. The author proposed a new method of<br />analysis PV power plant works under partial shading<br />condition trough micro- and macroconfiguration of PV array.</p>

Submitted by Silvana Teresinha Dornelles Studzinski (sstudzinski) on 2017-03-16T13:43:10Z No. of bitstreams: 1 Gleiton Ariel Guedes Pires_.pdf: 999723 bytes, checksum: c4e2ac031c9624b170d72249a1b0512d (MD5) / Made available in DSpace on 2017-03-16T13:43:10Z (GMT). No. of bitstreams: 1 Gleiton Ariel Guedes Pires_.pdf: 999723 bytes, checksum: c4e2ac031c9624b170d72249a1b0512d (MD5) Previous issue date: 2016-10-25 / FINEP - Financiadora de Estudos e Projetos / itt Chip - Instituto Tecnológico de Semicondutores da Unisinos / O Brasil apresenta grande potencial de geração de energia solar fotovoltaica, em um contexto de crescente demanda de energia. Em vista disso, torna-se necessária a correta e eficaz caracterização elétrica dos módulos fotovoltaicos. Esta caracterização é importante tanto na determinação da curva I-V (corrente – tensão), quanto em outros parâmetros (produtividade fotovoltaica 𝑌�������𝑓�������, perdas de captura Lc e desempenho global PR) de estimativa de produtividade energética. Este trabalho descreve a metodologia utilizada para a caracterização de quatro tecnologias de módulos fotovoltaicos (monocristalino, policristalino, CIGS e silício amorfo) e uma análise de produtividade energética para a cidade Porto Alegre – RS. Para tanto, foi estipulado um gerador fotovoltaico de 1kW pico, considerando um sistema conectado à rede com Fator de Dimensionamento (FDI) igual a 1,0. Utilizando-se o software PVsyst, foram quantificadas as produtividades energéticas devido à inclinação de instalação e à variação azimutal. A análise dos resultados levou em conta três parâmetros: a produtividade dos módulos, as perdas de captura e o desempenho global do sistema PR. Foram analisadas diversas configurações de posicionamento e de inclinação de instalação dos módulos e, posteriormente, foi realizado um comparativo entre os resultados obtidos em relação à produtividade energética na posição de referência, que consiste em instalar os módulos para o norte geográfico com inclinação próxima à latitude do local. A pesquisa indica que os módulos monocristalino e policristalino apresentam bons desempenhos orientados entre leste e oeste com ângulos de inclinação de até 40°. Os módulos CIGS e a-Si apresentam bons índices desempenho orientados a norte e oeste com ângulos de inclinação de até 30°. / The fat the Brazil presents a major photovoltaic solar energy generation, allied to the increasing energy demand, it makes necessary the correct and efficient photovoltaic modules electric characterization. This characterization is important to the determination of the I-V curve (current-tension), as well as in other parameters (Yield Factor Yf, capture losses Lc and performance ratio PR) for the estimate energy productivity. This study describes the methodology utilized for the characterization of four photovoltaic modules technologies (monocrystalline, polycrystalline, CIGS and amorphous silicon) and an energy productivity analysis for the city of Porto Alegre – RS. For that, was stipulated a 1kW peak photovoltaic generator, considering a grid-connected system with a Sizing Factor (FDI) equal to 1,0. Using the PVsyst software, Power productivity was quantified due to the installation inclination and the azimuthal variation. The results analysis took in account three parameters: module productivity, capture losses, performance ratio of the system. Several positioning configurations and modules installation inclination were analyzed. Posteriorly, a comparison was made between the results gathered according to the power productivity in the reference position, which consists in installing the modules to the geographic north with inclination close to the local latitude. The research indicates that the monocrystalline e polycrystalline modules present good performance when oriented between east and west with inclination angles up to 40º. The CIGS and a-Si modules present good ratio when oriented north and west with inclination angles up to 30º

Ce travail de thèse présente l'optimisation d'une technologie de valorisation énergétique qui utilise des résidus agricoles pour la production d'énergies renouvelables, tout en réduisant les émissions mondiales de méthane et en garantissant la sécurité alimentaire. Des digesteurs anaérobies à l'échelle laboratoire, pilote et industrielle ont été évalués afin d'améliorer la production de méthane à partir de la digestion anaérobie de la paille de riz non traitée dans des conditions sèches en utilisant une approche nouvelle de co-digestion. Une installation de production biogaz à l'échelle d'une ferme chargée de paille de riz et d'eaux usées produites par une porcherie génère 295 MWh dans un cycle de digestion 422 jours. La période d'acclimatation relativement longue (environ 200 jours) et le faible rendement en biogaz (181 LCH4/kg MVS) pourraient être améliorées en ajoutant des boues anaérobies issues d'un procédé de traitement d'effluents de l'industrie papetière. Au laboratoire, l'ajout de la boue conduit à un rendement de méthane spécifique de 335 LCH4/kgMVS dans les 92 jours. L'hydrolyse de la paille a été accélérée, et des conditions stables ont été observées en termes de pH, d'alcalinité et de nutriments. Des améliorations similaires ont été démontrés dans des digesteurs à l'échelle pilote (1 m3) - un rendement de méthane spécifique de 231 LCH4/kgMVS a été obtenu dans un cycle de digestion à 93 jours avec de la boue comparativement à 189 jours sans la boue. Un mélange insuffisant dans le système à l'échelle pilote a causé des rendements de production de méthane inférieurs à ceux obtenus dans les digesteurs l'échelle du laboratoire. Si les conditions mésophiles et de mélange suffisantes sont maintenues dans le système à l'échelle industrielle, la co-digestion de la paille de riz avec des eaux usées produites par une porcherie et des boues issues d'un procédé de traitement d'effluent de l'industrie papetière (rapport poids humide de 1:1.25:0.5) a le potentiel de réduire le temps de rétention à trois mois (contre 422 jours) et d'augmenter les rendements de production de méthane à plus de 300 LCH4/kgMVS / The research describes an optimized waste-to-energy technology that utilizes agricultural residues for renewable energy, while reducing global methane emissions and maintaining food security. Laboratory-, pilot- and farm-scale anaerobic batch digesters were evaluated to enhance methane production from the anaerobic digestion of untreated rice straw in dry conditions using a novel co-digestion approach. An existing farm-scale biogas plant loaded with rice straw and piggery wastewater produced 295 MWh in a 422-day digestion cycle. The long acclimation period (approximately 200 days) and low biogas yield (181 LCH4/kgVS) could be enhanced by adding anaerobic sludge from the pulp and paper mill treatment process. In a laboratory setting, the addition of the sludge resulted in a specific methane yield of 335 LCH4/kgVS within 92 days. Hydrolysis of the straw was accelerated, and stable conditions were observed in terms of pH, alkalinity and nutrients. Similar improvements were demonstrated in pilot-scale digesters (1 m3) – a specific methane yield of 231 LCH4/kgVS was achieved in a 93-day digestion cycle with the sludge compared to 189 days without the sludge. Insufficient mixing within the pilot-scale system caused lower overall methane yields than those obtained in the laboratory-scale digesters. If sufficient mixing and mesophilic conditions are maintained within the farm-scale system, the co-digestion of rice straw with pig wastewater and paper mill sludge (wet weight ratio of 1:1.25:0.5) has the potential to reduce the retention time to three months (versus 422 days) and increase methane yields to over 300 LCH4/kgVS

Urban microgrids are smart and complex energy systems that help integrate renewables into our cities, turning our neighborhoods into partly energy self-sufficient hubs. Moreover, they create the space for electricity transactions between neighbors, transforming the former consumers into prosumers. The following work proposes the implementation of an urban microgrid to a neighborhood in Lisbon, Portugal. This dissertation’s objective is designing and discovering the optimal photovoltaic and storage capacity, optimal electricity dispatch, effects of distributed energy production in grid voltage and economic viability of such a system. With this purpose, a comprehensive model was elaborated, considering specific site weather data, electric loads, grid topology and utility tariffs. The self-sufficiency of Arco do Cego was found to be 66% in this study, reducing its carbon footprint by 61%. A detailed map of where to place each PV system and battery bank was generated, with specific electricity dispatch strategies. Moreover, the system was designed under real grid voltage, current and power flow constraints.

Submitted by Irene Nascimento (irene.kessia@ufpe.br) on 2017-04-10T17:20:12Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO -DAVI CAVALCANTI certa.pdf: 1682949 bytes, checksum: e88ff7ec323c0df6eb4f0102509ba5b3 (MD5) / Made available in DSpace on 2017-04-10T17:20:12Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) DISSERTAÇÃO -DAVI CAVALCANTI certa.pdf: 1682949 bytes, checksum: e88ff7ec323c0df6eb4f0102509ba5b3 (MD5) Previous issue date: 2016-02-23 / Capes / O crescimento da população mundial vem causando um aumento substancial na demanda por energia o que poderá causar em curto prazo uma crise energética, pois grande parte da energia consumida em todo mundo é proveniente de fontes não renováveis como o petróleo, já que sua prospecção e utilização tem causado grandes danos a natureza, impactando vários ecossistemas e colaborando com o aquecimento global. Por estes motivos, novas tecnologias para geração de energia limpa vêm sendo criadas. Um exemplo destas são as células a combustível, que são dispositivos que convertem energia química em elétrica. Porém esta tecnologia apresenta algumas limitações, como deficiências na transferência de elétrons, baixa geração de potência e altos custos associados a utilização de catalizadores metálicos, os quais aumentam os custos de implantação e dificultam sua utilização em larga escala. Visando superar estas limitações uma variação desta tecnologia foi desenvolvida, a chamada célula a combustível fotossintética. Neste tipo de célula a combustível, microalgas como a Chlorella vulgaris são utilizadas no compartimento catódico substituindo catalizadores químicos melhorando sua sustentabilidade e reduzindo os custos de implantação. As utilizações de cátodos de microalgas também colaboram com o sequestro de carbono da atmosfera, o convertendo em oxigênio e biomassa rica em metabolitos de grande valor comercial como amido e lipídios. No presente estudo a microalga C. vulgaris foi utilizada no compartimento catódico de uma célula a combustível fotossintética a fim de se analisar sua eficiência na produção de energia, sua capacidade de sequestrar o dióxido de carbono da atmosfera e seu acúmulo de materiais de reserva como amido e lipídios totais. Na primeira parte deste estudo a microalga C. vulgaris foi utilizada como aceptora de elétrons em um compartimento catódico, onde durante 10 dias de experimento foram avaliados a quantidade de CO2 capturada pelas células de algas (7mg/L de CO2), a composição da biomassa, Amido (3%) e Lipídios (70%) e parâmetros eletroquímicos como a Eficiência Coulômbica (CE = 33,1%) e densidade de corrente máxima (Idmax = 147 mA cm²). Em seguida esta condição foi submetida a um planejamento fatorial completo 2², onde as variáveis independentes, tempo de iluminação e a concentração de nitrogênio foram testadas sobre a produção de eletricidade e acúmulo de amido e lipídios. Durante os experimentos foi constatado que a iluminação é o fator que mais influi na geração de energia, onde foram obtidos valores de densidade de corrente máxima Idmax = 178 mA/cm² com uma eficiência coulômbica de 42,5%, além de uma acumulação máxima de amido de 38% e 77% de lipídios, demonstrando que a utilização de um cátodo fotossintético para produção de energia é viável e eficiente na produção de metabólitos com elevado valor comercial. / The global population growth has caused a substantial increase in demand for energy, which in short-term may cause an energy crisis, since much of the energy consumed throughout the world comes from non-renewable sources like oil. Besides its exploration and use cause great damage to the environment, affecting diverse ecosystems and contributing to global warming. For those reasons, are being created new technologies for clean energy generation. An example of these technologies is Fuel Cells, which are devices that convert chemical energy into electric. However, this technology has some limitations, such as defects in electron transfer, low power output and high costs associated with the use of metal catalysts, which increase deployment costs and hamper its use on a large scale. Aiming to overcome these limitations, a variation of this technology was developed, the so-called photosynthetic fuel cell. In this type of fuel cell, microalgae such as Chlorella vulgaris are used in the cathode compartment replacing chemical catalysts improving their sustainability and reducing deployment costs. The uses of microalgae cathodes also collaborate with carbon capture from the atmosphere, turning it into oxygen and biomass rich in metabolites of great commercial value as starch and lipids. In the current study the microalgae C. vulgaris was used in the cathode compartment of a photosynthetic fuel cell in order to analyze its energy production efficiency, their ability to sequester atmospheric carbon dioxide and its accumulation of reserve materials such as starch and total lipids. The first part of this study microalga C. vulgaris was utilized as an electron acceptor in a cathode compartment, which were analyzed during 10 days of experiment the amount of CO2 captured by the algae cells (7mg/L-1 of CO2), the composition of the biomass starch (3%) and lipids (70%) and electrochemical parameter as coulombic efficiency (CE = 33.1%) and the maximum current density (mA Idmax = 147 cm²). Then this condition was subjected to a complete factorial design 2² where the independent variables, illumination time and the concentration of nitrogen were tested on the production of electricity and accumulation of starch and lipids. During the experiments it was evidenced that enlightenment is the factor that most affects the power generation, which were obtained maximum current density values Idmax = 178 mA/cm² with a coulombic efficiency of 42.5%, and a maximum accumulation of 38% of starch and 77% of lipid, demonstrating that the use of a photosynthetic cathode for energy generation is feasible, and also in the production of metabolites with a high commercial value.

Many parameters used for Wind Resource Assessment (WRA) have uncertainty and variability, yet are input into the process as single values. The extent of the uncertainty or variance may not be known, and may or may not be significant enough to affect output. This Thesis focused on the energy calculation element of WRA, to assess the affect that errors (uncertainty) in three key user inputs had on the energy results. A parameter was chosen from each of the main groups influencing the energy calculation: wind speed (atmosphere), surface roughness (site conditions), and power curve (turbine technology). Reasonable variation due to uncertainty for wind speed and power curve were taken from other studies and their application simplified. Roughness change was assessed over the 5 classes (Class 0 (water) to 4 (dense forest/city)). WindPRO software was used to calculate the Annual Energy Production (AEP) and applied to three different wind turbine generators at the same coordinate. A sensitivity analysis was done on the AEP results using a hybrid One-At-a-Time Local Sensitivity Analysis by determining percentage changes from baselines and an overall rate of change for those key input parameters. The results showed that roughness class change effect was not linear. Changing from Class 0 to 1, AEP was on average -8±1%. Class 1 to 2 change was on average ‑12±1%. Class 2 to 3 change was on average -20±2%. Class 3 to 4 change was on average -29±2%. The wind speed change effect was found to be roughly linear. If mean wind speed has an error of ±10%, the AEP could be expected to be out by approximately +18/‑17% with a standard deviation of +4/-3%. The power curve change effect was also roughly linear. A PC±9% error leads to an approximate +6/-7% AEP error with a standard deviation of ±1%. Roughness class change was the most sensitive parameter to AEP with a 14.5 average rate of change, followed by wind speed at 1.8, then power curve with a 0.8 rate. Results compared reasonably well with other relevant studies.

The 34 silos at Jarlaberg today contain crude oil but after the lease of land expires at 2036 are refurbished and remade to hold 2 500 000 m3 of water from Stockholm archipelago. Sharing the industrial plot of the reworked silos are 13 buildings with 2000 households between them. At the shores of the rocky hills is a new landmark with two swirling metal structures reflecting daylight and the shining light from the structure bellow. The building contains two hydro turbines, with the glass roofs and metal vortexes above, a landmark to be seen from both the built plateaus above and the opposite side shores as a celebration of the renewable energy progress of 2030-2050.  The project started as a look at industrial architecture and its relation to city spaces. Specifically the implementation of a stored capacity hydropower solution if placed close to major city centers which demanding more, renewable energy. At first the ambition was to integrate a series of turbines to the new Slussen water outlet from Mälaren to Saltsjön but after further readings the theme of letting the industries society’s development  is dependent upon be a part in planning the cities expansion. To join a industrial function to a housing plan would make a large impact on the urban space in-between the two. To both make a bond but also show the story of the production of energy the project provides. The sides of the silos have been fitted with a series of stepped gradients for seating and to access the top of the water reservoirs. The bottom of the gradients connect to the urban spaces such as parks and squares. Providing both a sun step for seating and meeting spaces close to areas of activity.