Tesi sul tema "Concentrated solar plant"

Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.
Cataloged from PDF version of thesis.
Concentrating solar power (CSP) stands as a promising renewable energy technology with the ability to contribute towards global reduction of carbon emissions. A major obstacle to increased adoption of CSP plants has to do with their high initial investment cost; consequently, there is a powerful desire to find improvements that decrease the initial capital investment for a CSP plant. One such improvement involves connecting modularized parabolic trough segments, each with the same dimensions, decreasing the overall amount of actuators required along with greatly simplifying system control architecture. This thesis is concerned with the extent to which parabolic solar trough modules can be connected together while still being able to operate to desired accuracy under expected load. Accuracy requirements are calculated, along with expected loads resulting in frictional torque on the trough. These expected loads are combined with a model for the effect of connecting multiple trough modules to generate a relationship between number of chained modules and required torsional stiffness. To verify said model, an experimental setup was designed and constructed to simulate loads due to both trough weight and wind loads.
by Kabir Abiose.
S.B.

The majority of the power generated today is produced using fossil fuels,emitting carbon dioxide and other pollutants every second. Also, fossil fuels will eventually run out. For the increasing worldwide energy demand, the use f reliable and environmentally beneficial natural energy sources is one of the biggest challenges. Alongside wind and water, the solar energy which is clean, CO2-neutral and limitless, is our most valuable resource. Concentrated solar power (CSP) is becoming one of the excellent alternative sources for the power industry. The successful implementation of this technology requires the efficient design of tracking and operation system of the CSP solar plants. A detailed analysis of components needed for the design of cost-effective and optimum tracker for CSP solar systems is required for the power plant modeling, which is the primary subject of this thesis. A comprehensive tracking and operating system of a parabolic trough solar power plant was developed focusing primarily on obtaining optimum and cost effective design through the simplified methodology of this work. This new model was implemented for a 50 kWe parabolic trough solar power plant at University of South Florida, Tampa.

This thesis is an investigation of critical failure modes of solar tower power system in concentrated solar power (CSP) technology. The thesis evaluated the causes and impacts of failure on the major components and apply the failure Mode and Effect Analysis (FMEA) to CSP solar tower system. This research proposed an alternative method to overcome the limitations of Risk Priority Number (RPN) from traditional FMEA. A case study applies the proposed approach to CSP solar tower system for a better prioritization of failure mode in order to reduce the risk of failures.

One of the most relevant problems to solve at a planetary scale is the access to an affordable clean source of energy as CO2 equivalent emissions should be reduced significantly. Some authors aim for a zero emissions target for 2050. Renewable energies will play a leading role in this energy transition, and solar energy with storage is a promising technology exploring a renewable and worldwide available resource. Within the present thesis component development like a new thermal storage thermocline tank design or having latent heat storage capability are technological developments that have been pursued and analyzed on a system perspective basis, focusing on reducing the LCOE value of a commercial STE plant using TRNSYS software. Material research with molten salts mixtures and cement based materials has been performed at lab scale. A fully validation should occur through a 13 partners pan-European H2020 project called NEWSOL which has been developed supported on the laboratory data obtained. Moreover, incorporation of local available material, “modern slag” from an old mine of Alentejo region, was also studied. The material could be used as an aggregate incorporated into calcium aluminate cement (CAC) or as filler. This would help to solve a local environmental complex problem related to soil, air and water pollution due to heavy metals and mining activity in Mina de São Domingos, Southeast of Portugal. The integration of these results underlies a broad energy transition model, a proposal is presented in this thesis, with the aim to foster development towards a sustainable usage of resources and promote clean technologies especially in the energy sector. This model can be locally adapted depending on the pattern of existing industries. The goal is to achieve a smooth transition into a clean tech energy society in line with the target of achieving zero emissions for 2050; Optimização Energética de uma Central de Concentração Solar com Armazenamento de Energia Resumo: Um dos problemas mais relevantes a resolver a uma escala planetária é o acesso, com um custo moderado, a fontes limpas de energia considerando que as emissões equivalentes de CO2 derão ser reduzidas drasticamente. Alguns autores ambicionam mesmo um objetivo de zero emissões em 2050. As energias renováveis irão desempenhar um papel preponderante nesta transição energética, sendo que a energia solar com armazenamento é uma tecnologia promissora que aproveita um recurso renovável e disponível em boa parte do Planeta. Na presente tese foi realizado o desenvolvimento de componentes nomeadamente o design que um novo tanque do tipo termocline, ou de novos elementos recorrendo ao calor latente, desenvolvimentos tecnológicos que foram analizados de uma perspectiva de sistema, dando o enfoque na redução do custo nivelado da electricidade (LCOE) para uma planta Termosolar usando o software TRNSYS. Foi também realizada investigação em laboratório ao nível dos materiais com várias misturas de sais fundidos inclusivé em contacto directo com materiais de base cimenticia. Uma validação completa deverá ocorrer no projeto NEWSOL do programa H2020 que reúne um consórcio de 13 parceiros europeus e que foi preparado e submetido tendo por base os resultados laboratoriais obtidos. Adicionalmente, incorporação de material disponível (escória de minério) de uma mina abandonada da região do Alentejo foi outro dos aspectos estudados. Verificou-se que este material poderá ser utilizado como agregado num ligante do tipo cimento de aluminato de cálcio (CAC) ou como “filler”. Este re-aproveitamento resolveria um problema ambiental complexo derivado do elevado conteúdo de metais pesados resultantes da actividade de mineração e que actualamente provocam poluição do solo, água e ar na área da Mina de São Domingos, Sudeste de Portugal. Estes progressos deverão ser integrados num modelo de transição energética mais amplo. Na presente tese, uma proposta concreta é apresentada, com o objectivo de incentivar o desenvolvimento na direção de uma utilização sustentável dos recursos e a promoção de tecnologias limpas nomeadamente no sector da energia. Este modelo poderá ser adaptado localmente dependendo do padrão de indústrias existente. O objectivo é atingir uma transição suave para uma sociedade de energias limpas em linha com o objectivo de atingir zero emissões de CO2 equivalente em 2050.

Solar Tower Power Plants with thermal energy storage are a promising technology for dispatchable renewable energy in the near future. Storage integration makes possible to shift the electricity production to more profitable peak hours. Usually two tanks are used to store cold and hot fluids, but this means both higher related investment costs and difficulties during the operation of the variable volume tanks. Another solution can be a single tank thermocline storage in a multi-layered configuration. In such tank both latent and sensible fillers are employed to decrease the related cost by up to 30% and maintain high efficiencies.  The Master thesis hereby presented describes the modelling and implementation of a thermocline-like multi-layered single tank storage in a STPP. The research work presents a comprehensive methodology to determine under which market structures such devices can outperform the more conventional two tank storage systems. As a first step the single tank is modelled by means of differential energy conservation equations. Secondly the tank geometrical design parameters and materials are taken accordingly with the applications taken into consideration. Both the steady state and dynamic models have been implemented in an existing techno-economic tool developed in KTH, in the CSP division (DYESOPT). The results show that under current cost estimates and technical limitations the multi-layered solid PCM storage concept is a better solution when peaking operating strategies are desired, as it is the case for the two-tier South African tariff scheme. In this case the IRR of an optimal designed power plant can be decreased by 2.1%. However, if a continuous operation is considered, the technology is not always preferred over the two tank solution, yet is a cheaper alternative with optimized power plants. As a result the obtained LCOE can be decreased by 2.4%.

In response to the extensive energy demands on national and global levels, concentrated solar power (CSP) plants are designed to harness and convert solar energy to electricity. For such green energy application, robust, reliable and durable materials for CSP constructions are required. The corrosion resistance is among many parameters to consider in these thermal-electrical stations such as for pipes and storage tanks in CSP. In this investigation, the corrosion behavior of AISI 304 stainless steel (18 wt. % Cr, 8 wt. % Ni) with the heat transfer fluid, also known as solar salt, has been examined. The ternary eutectic salt mixture with the composition, 53 wt. % KNO3, 40 wt. % NaNO2, and 7 wt. % NaNO3, that melts at 142°C, has a potential use in CSP as a heat transfer fluid. The solar salt was prepared for this corrosion study from reagent grades of high purity nitrites and nitrates. Samples of AISI 304 stainless steel were sectioned from a sheet stock of the alloy and exposed to solar salt at 530°C in air at 1 atmospheric pressure. After test intervals of 250, 500, and 750 hours in total immersion condition, AISI 304 stainless steel samples have developed a scale of corrosion products made up of multiple oxides. X-ray diffraction and scanning electron microscopy with X-ray energy-dispersive spectroscopy were employed to examine the extent of corrosion and identify the corrosion products. Transmission electron microscopy was used to verify the corrosion products identity via electron diffraction patterns. Oxides of iron were found to be the primary corrosion products in the presence of the molten alkali nitrates-nitrite salt mixture because of the dissolution of the protective chromium oxide (Cr2O3) scale formed on AISI 304 stainless steel coupons. The corrosion scale was uniform in thickness and made up of sodium iron oxide (NaFeO2), iron oxide, hematite (Fe2O3), and chromium-iron oxide (Cr,Fe)2O3 solid solution. The latter was found near the AISI 304 stainless steel. This indicates that the scale formed, particularly on the upper layers with presence of sodium iron oxide and iron oxide, hematite, is protective, and forms an effective barrier against penetration of fused solar salt. At the alloy interface with the bulk corrosion scale, the corrosion process induced a compositional modification in the grains located at the interface. There are iron rich and iron depleted grains at the interface if compared to the nominal iron content of the alloy. The mode of attack is identified as uniform at the test temperature of 530°C, showing a parabolic behavior with a parabolic rate constant (Kp) equals to 1.08&"215;10^(-17)(m2/sec). By extrapolation, annual corrosion rate is estimated to reach 0.784 mils per year. Corrosion behavior of AISI 304 stainless steel is discussed in terms of thermodynamics and reaction paths.
M.S.M.S.E.
Masters
Materials Science Engineering
Engineering and Computer Science
Materials Science and Engineering

Concentrated Solar Thermal technology (CST) is a very promising renewable energy technology and has a broad range of use. Conventionally, CST systems are mostly used for power generation according to the Rankine cycle and thus often referred to as Concentrated Solar Power (CSP). In this present study, the solar heat is utilized to drive a thermochemical redox cycle of a metal-oxide in order to produce synthetic gas, a combination of hydrogen and carbon monoxide. Later, the synthetic gas is converted into usable liquid fuel whereas the production pathway is CO2 free. This thesis focuses on the process modeling and economic evaluation of solar-driven future fuels production plants. Four future fuels have been selected and modeled using commercial simulation software Aspen Plus®. These 4 future fuels are syngasoline, syndiesel, ethanol and methanol where they can be seen as a very good substitute for current transportation fuels. The heat required at high temperature is delivered using concentrated solar thermal technology with tower configuration for which the heliostat field is designed using in-house software HFLCAL developed by DLR. Syngas is converted into aforementioned fuels using either Fischer-Tropsch or plug-flow reactor. The reactor is modeled taking into account the kinetic of reaction for each fuel, while in case of the absence of kinetic, a stoichiometric approach is implemented. To analyze the hourly plant’s performance, a quasi-steady state analysis is done within MATLAB® environment. The metric used to evaluate the plants are production cost in €/L and overall thermal efficiency. The results show that aforementioned conversion pathway yields higher production costs compared to current market while the lowest production cost is obtained for Methanol at 1.42 €/L. It is shown that solid to solid heat exchanger (STS) efficiency plays a major role in order to make the plant more economically viable. Combining electricity supply of Photovoltaic (PV) and CSP is also shown to be one way to reduce the production cost. If the plant combines PV-CSP is used as the electricity source, syngasoline emerges to be the closest proposed plant to current market fuel production cost with a production cost of 5.99 €/L at the base case scenario which corresponds to 622% relative difference with current market’s production cost and 2.87 €/L at the best case scenario which corresponds to 245% relative difference with current market’s production cost. At the base case scenario, the highest overall thermal efficiency is obtained for the syngasoline plant (4.05%) and at the best case scenario for the ethanol plant (9.2%).

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CAPEs
Notadamente nos últimos anos, a geração de eletricidade a partir de fontes renováveis de energia tem mostrado contínuo aumento que está relacionado, sobretudo, às preocupações com as variações climáticas, à dependência dos combustíveis fósseis e à necessidade de suprir a geração de energia elétrica com recursos que produzam menos impactos ao meio ambiente. A capacidade instalada da energia renovável no mundo, que foi de 800GW em 2004, alcançou 1.712GW em 2014 e a participação na matriz energética global também aumentou, atingindo o percentual de 22,8% em 2014. O Brasil possui uma matriz energética predominantemente renovável. Somente em 2014, aproximadamente 74,6% da eletricidade gerada procedeu das fontes renováveis de energia. O percentual restante (25,4%) proveio dos combustíveis fósseis e das fontes nucleares. Mas, muito embora o País possua uma matriz energética tipicamente renovável, nota-se que o principal sistema de geração é o aproveitamento hidráulico, que é bem vulnerável às variações climáticas globais e pode apresentar, em função disso, redução de sua capacidade instalada em longo prazo. Visando contribuir para a diversificação da matriz energética brasileira, esta pesquisa apresenta dois métodos distintos e macroespaciais para auxiliar a seleção de áreas potenciais para a inserção de usinas solares termoelétricas: o Método baseado no Processo Analítico Hierárquico, que trata o problema da localização sob uma organização hierárquica de critérios, como pressupõe os axiomas do Método AHP; e o Método do Custo de Produção de Eletricidade, que define os locais aptos em função do custo nivelado da eletricidade (LCOE – Levelised Cost of Electricity). Ambas as metodologias foram aplicadas para Pernambuco, localizado na região Nordeste do Brasil, e considerou a implantação de usinas de coletores parabólicos de 80MWe, tipo SEGS, operando somente em modo solar, sem armazenadores térmicos. Com base nas análises realizadas, confirmou-se que Pernambuco apresenta grande potencial para a implantação de usinas solares, principalmente no Sertão Pernambucano, onde foram encontrados os ambientes mais favoráveis à instalação. Na aplicação do Método AHP, por exemplo, o Sertão apresentou alto potencial de instalação em todos os cenários avaliados, inclusive no cenário Ponto de Partida, onde os pesos não foram considerados. No Método do Custo de Produção de Eletricidade, o Sertão também mostrou alto potencial de instalação uma vez que os custos de geração de energia elétrica encontrados foram os menores do estado (da ordem de R$ 337,16/MWh). Este custo é elevado quando comparado com o preço da eletricidade gerada pela fonte hidráulica no país (R$ 182,09/MWh), por exemplo, mas estão em conformidade quanto ao esperado para sua inserção no mercado brasileiro. De modo geral, as abordagens apresentadas se mostraram muito consistentes e revelaram um potencial bastante promissor para o desenvolvimento da tecnologia em Pernambuco. Este potencial deverá ser avaliado detalhadamente e incluir a medição local da radiação solar por pelo menos cinco anos.
Notably in recent years, the generation of electricity using energy from renewable resources has presented continuous increase, which is due to, especially, the concerns about climate changes, the dependency in fossil fuel and the necessity of production of electric energy with resources to decrease the negative impacts in the environmental. The global renewable power generation capacity, which presented 800GW on the beginning of 2004, reaching an estimated 1,712GW at year’s end 2014, and the renewable electricity global production in 2014 presented 22.8%. Brazil has a mainly renewable energy matrix. In 2014, 74.6% of the electricity produced came from renewable sources of energy. The remaining percentage comes from fossil fuels and nuclear sources (25.4%). Although it shows a remarkably renewable character, it is notable that the main source of generation of electricity is the water source, which is susceptible the climate changes, and should present the reduction in your capacity installed in a long term. As a way of contributing to diversify the energy matrix Brazilian, this work presents two different methodologies macro spatial for the selection of the best sites for insertion of solar thermal power plants: the methodologies based on analytic hierarchy process (AHP) where the selection the best site was based on means of the hierarchical organization of criteria according to axioms of the AHP method; and the method based on cost of electricity generation where the best site were selected according to Levelised Cost of Electricity (LCOE). Both studies were made in Pernambuco, located in Northeastern Region of Brazil and considered the implementation of a parabolic trough solar power plant, of 80MWe, operating exclusively in solar mode, without thermal stores. The analyzes performed confirmed that the Pernambuco presents great potential for the installation of solar thermal power plants, especially, in the Sertão Pernambucano where the best sites were located. In the methodologies AHP, for example, this region presented great potential for the installation in all scenarios analyzed, including the Ponto de Partida scenarios where weights are not used. In the method based on cost of electricity, the Sertão presented great potential also. In this region it is possible to find electric energy generation costs by MWh of the order of R$ 337.16. This costs are still high when comparing the cost of generation of the hydraulic source (R$ 182.09/MWh) in Brazil, although, they comply as to expected for its insertion in the Brazilian Market. The methodologies used demonstrated very consistent and identified a promising potential for solar thermal power generation in Pernambuco. This potential should be analyzed in details and include the local measurement of the incident direct normal solar irradiation for at least five years.

Concentrating solar power (CSP) plant is a promising technology that exploits direct normal irradiation (DNI) from the sun to be converted into thermal energy in the solar field. One of the advantages of CSP technology is the possibility to store thermal energy in thermal energy storage (TES) for later production of electricity. The integration of thermal storage allows the CSP plant to be a dispatchable system which is defined as having a capability to schedule its operation using an innovative dispatch planning tool. Considering weather forecast and electricity price profile in the market, dispatch planning tool uses an optimization algorithm. It aims to shift the schedule of electricity delivery to the hours with high electricity price. These hours are usually reflected by the high demand periods. The implementation of dispatch optimizer can benefit the CSP plants economically from the received financial revenues. This study proposes an optimization of dispatch planning strategies for the parabolic trough CSP plant under two dispatch approaches: solar driven and storage driven. The performed simulation improves the generation of electricity which reflects to the increase of financial revenue from the electricity sale in both solar and storage driven approaches. Moreover, the optimization also proves to reduce the amount of dumped thermal energy from the solar field.

Dans ce travail de thèse, nous développons et appliquons des techniques d'optimisation dans la conception et la gestion de l'énergie. Tout d'abord, nous nous concentrons sur l'optimisation bi-niveaux et développons une nouvelle analyse théorique pour les jeux à un seul meneur et plusieurs suiveurs avec des contraintes de cardinalité. Cette analyse est ensuite appliquée à la localisation optimale des stations de recharge pour véhicules électriques. La deuxième partie est consacrée à l'optimisation économique, à long terme et à court terme, des centrales solaires à concentration. Une approche innovante d'optimisation globale combinant la conception optimale du stockage et l'exploitation optimale dans un contexte de marché est développée. Ensuite, dans un perspective à court terme, le contrôle optimal de la production d'énergie d'une centrale solaire est analysé
In this thesis work, we develop and apply optimization techniques in energy design and management. First we focus on bilevel optimization and developed new theoretical analysis for single-leader-multi-follower games with cardinality constraints. It is then applied to optimal location of charging stations for electric vehicles. The second part is dedicated to economic optimization of solar power plants from a long term as well as from a short term perspective. Innovating global optimization approach mixing optimal design of storage and optimal operation in a market context is developed. Then at a short term scale, the optimal control of energy production of a solar power plant is analysed
En este trabajo de tesis, desarrollamos y aplicamos técnicas de optimización en el dise˜no y gestión de energía. En primer lugar, nos enfocamos en la optimización binivel y desarrollamos nuevo análisis teórico para single-leader-multi-follower games con restricciones de cardinalidad. Luego, se aplica a la localización óptima de estaciones de carga por vehículos eléctricos. La segunda parte está dedicada a la optimización económica de plantas solares desde una perspectiva a largo plazo, así como desde una perspectiva a corto plazo. Se desarrolla un enfoque innovador de optimización global que combina el dise˜no óptimo de almacenamiento y la operación óptima en un contexto de mercado. Luego, a escala a corto plazo, se analiza el control óptimo de la producción de energía de una planta solar

The research focused on renewable energy storage using hydrogen-rich materials. These materials can store thermochemical heat energy used as thermal batteries in concentrated solar power plants. High-temperature metal hydrides have been identified as the next-generation thermal batteries for concentrated solar power plants. They have higher energy densities than conventional energy storage materials such as molten salts. I believe our research's innovative and multifaceted approach can provide enhanced green energy production and hence reduce CO2 emissions.

Doutoramento em Engenharia Mecânica
The PhD project addresses the potential of using concentrating solar power (CSP) plants as a viable alternative energy producing system in Libya. Exergetic, energetic, economic and environmental analyses are carried out for a particular type of CSP plants. The study, although it aims a particular type of CSP plant – 50 MW parabolic trough-CSP plant, it is sufficiently general to be applied to other configurations. The novelty of the study, in addition to modeling and analyzing the selected configuration, lies in the use of a state-of-the-art exergetic analysis combined with the Life Cycle Assessment (LCA). The modeling and simulation of the plant is carried out in chapter three and they are conducted into two parts, namely: power cycle and solar field. The computer model developed for the analysis of the plant is based on algebraic equations describing the power cycle and the solar field. The model was solved using the Engineering Equation Solver (EES) software; and is designed to define the properties at each state point of the plant and then, sequentially, to determine energy, efficiency and irreversibility for each component. The developed model has the potential of using in the preliminary design of CSPs and, in particular, for the configuration of the solar field based on existing commercial plants. Moreover, it has the ability of analyzing the energetic, economic and environmental feasibility of using CSPs in different regions of the world, which is illustrated for the Libyan region in this study. The overall feasibility scenario is completed through an hourly analysis on an annual basis in chapter Four. This analysis allows the comparison of different systems and, eventually, a particular selection, and it includes both the economic and energetic components using the “greenius” software. The analysis also examined the impact of project financing and incentives on the cost of energy. The main technological finding of this analysis is higher performance and lower levelized cost of electricity (LCE) for Libya as compared to Southern Europe (Spain). Therefore, Libya has the potential of becoming attractive for the establishment of CSPs in its territory and, in this way, to facilitate the target of several European initiatives that aim to import electricity generated by renewable sources from North African and Middle East countries. The analysis is presented a brief review of the current cost of energy and the potential of reducing the cost from parabolic trough- CSP plant. Exergetic and environmental life cycle assessment analyses are conducted for the selected plant in chapter Five; the objectives are 1) to assess the environmental impact and cost, in terms of exergy of the life cycle of the plant; 2) to find out the points of weakness in terms of irreversibility of the process; and 3) to verify whether solar power plants can reduce environmental impact and the cost of electricity generation by comparing them with fossil fuel plants, in particular, Natural Gas Combined Cycle (NGCC) plant and oil thermal power plant. The analysis also targets a thermoeconomic analysis using the specific exergy costing (SPECO) method to evaluate the level of the cost caused by exergy destruction. The main technological findings are that the most important contribution impact lies with the solar field, which reports a value of 79%; and the materials with the vi highest impact are: steel (47%), molten salt (25%) and synthetic oil (21%). The “Human Health” damage category presents the highest impact (69%) followed by the “Resource” damage category (24%). In addition, the highest exergy demand is linked to the steel (47%); and there is a considerable exergetic demand related to the molten salt and synthetic oil with values of 25% and 19%, respectively. Finally, in the comparison with fossil fuel power plants (NGCC and Oil), the CSP plant presents the lowest environmental impact, while the worst environmental performance is reported to the oil power plant followed by NGCC plant. The solar field presents the largest value of cost rate, where the boiler is a component with the highest cost rate among the power cycle components. The thermal storage allows the CSP plants to overcome solar irradiation transients, to respond to electricity demand independent of weather conditions, and to extend electricity production beyond the availability of daylight. Numerical analysis of the thermal transient response of a thermocline storage tank is carried out for the charging phase. The system of equations describing the numerical model is solved by using time-implicit and space-backward finite differences and which encoded within the Matlab environment. The analysis presented the following findings: the predictions agree well with the experiments for the time evolution of the thermocline region, particularly for the regions away from the top-inlet. The deviations observed in the near-region of the inlet are most likely due to the high-level of turbulence in this region due to the localized level of mixing resulting; a simple analytical model to take into consideration this increased turbulence level was developed and it leads to some improvement of the predictions; this approach requires practically no additional computational effort and it relates the effective thermal diffusivity to the mean effective velocity of the fluid at each particular height of the system. Altogether the study indicates that the selected parabolic trough-CSP plant has the edge over alternative competing technologies for locations where DNI is high and where land usage is not an issue, such as the shoreline of Libya.
O projeto de Doutoramento aborda o potencial de usar centrais de energia solar concentrada (CSP) como um sistema de produção de energia alternativa disponível na Líbia. Uma análise nas vertentes exergética, energética, económica e ambiental foi realizada para um tipo particular destas centrais – um sistema de 50 MW com receção parabólica, porém ela é suficientemente geral para ser aplicada a outras configurações. A originalidade do estudo, para além da modelação e análise da configuração selecionada encontra-se na utilização do estado da arte em termos da análise exergética combinada com a avaliação do ciclo de vida (LCA). A modelação e simulação da central CSP selecionada são efetuadas no terceiro capítulo tendo em consideração as duas componentes: ciclo de potência e campo de coletores solar. O modelo computacional para a análise do sistema foi desenvolvido com base em equações algébricas que descrevem o sistema, e que são resolvidas usando o software EES. Deste modo, são definidas as propriedades em cada ponto de interesse para os diferentes elementos do sistema, o que assim permite determinar as energias, eficiências e irreversibilidades desses elementos. O modelo desenvolvido tem o potencial de se tornar uma ferramenta de grande utilidade para o projeto preliminar de engenharia de centrais CSP, e também para a avaliação da eventual reconfiguração de centrais elétricas solares comerciais em operação. Além disso, o modelo pode ser utilizado no estudo de viabilidade da operação de centrais CSP, através da análise energética, económica e ambiental, para regiões diferentes da que foi escolhida no presente estudo -Trípoli (Líbia). O cenário total da viabilidade da operação da central CSP é completado através da análise horária com base anual apresentada no quarto capítulo. Esta análise permite a comparação de diferentes sistemas e, eventualmente permite fazer a seleção com base nas componentes económicas e energéticas, que são determinadas dentro do contexto do software greenius. A análise também toma em conta o impacto de financiamento e incentivos dados aos projetos no custo da produção de energia. O principal resultado desta análise é a verificação que o desempenho é mais elevado, com o consequente menor custo nivelado da eletricidade, para a Líbia em comparação com o Sul da Europa (Espanha). Assim a Líbia tem o potencial de se tornar um candidato atrativo para o estabelecimento de centrais CSP com o objetivo, como foi considerado em várias iniciativas europeias, de exportar eletricidade gerada através de fontes de energia renováveis de países do Norte de África e Médio Oriente para a Europa. A análise apresenta uma breve revisão do custo corrente da eletricidade e o potencial para reduzir o custo da energia a partir da tecnologia de receção parabólica de centrais CSP. A avaliação do ciclo de vida com base exergética (ELCA) e a avaliação do ciclo de vida convencional são realizadas para a centrais CSP específicas no quinto capítulo. Os objetivos são 1) avaliar o impacto ambiental e custo, em termos de do ciclo iv de vida exergético do sistema; 2) identificar pontos fracos em termos da irreversibilidade dos processos; e 3) verificar se as centrais CSP podem reduzir o impacto ambiental e o custo de geração de eletricidade em comparação com centrais que consomem combustível fóssil. O capítulo ainda apresenta uma análise termoeconómica com base na metodologia do custo específico da exergia (SPECO), que avalia o custo relacionado com a destruição de exergia. A análise verificou que o impacto mais importante é a contribuição apresentada pelo campo solar (79%), e os materiais com maior impacto são: aço (47%), sal fundido (25%) e óleo sintético (21%). A análise ELCA mostra que a maior demanda de exergia é devida ao aço (47%); a análise existe uma considerável demanda de exergia relacionada com o sal fundido e ainda o óleo sintético. Em comparação com as centrais que consomem combustível fóssil (NGCC e óleo) a central sistema CSP apresenta menor impacto ambiental, enquanto o pior desempenho ambiental é o da central com queima de óleo seguida pela central a gás natural (NGCC). Na central CSP, o campo solar apresenta o custo mais elevado, enquanto o gerador de vapor, entre os componentes do ciclo de potência, apresenta o maior custo. O armazenamento de energia térmica permite que as centrais CSP superem a intermitência de radiação solar para responder à procura de energia elétrica independentemente das condições climáticas, e também possam estender a produção de eletricidade para além da disponibilidade da radiação solar diária. A análise numérica do transiente térmico de um sistema de armazenamento de gradiente térmico é realizada durante a fase de carregamento. O sistema de equações que descreve o modelo numérico é resolvido através da utilização de diferenças finitas implícitas no tempo usando o software Matlab. Os resultados da análise indicam que as previsões estão em boa concordância com os dados experimentais para a evolução no tempo da região de gradiente térmico, em particular para regiões mais afastadas da entrada. Nesta região os desvios observados são provavelmente causados pelo alto nível de turbulência devido à penetração do jato no seio do tanque de armazenamento. O modelo analítico simples para simular a turbulência que foi desenvolvido melhora os resultados. Esta abordagem não requer esforço computacional adicional e determina a difusidade térmica efetiva ao longo do tanque.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 140-148).
The main drawback to renewable energy systems is the higher cost of production compared to competitors such as fossil fuels. Thus, there is a need to increase the efficiency of renewable energy systems in an effort to make them more cost competitive. In this study, the use of nanosurfaces is evaluated for its benefits in improving the efficiency of a concentrated solar tower power system by increasing the energy retained by the receiver surface, and for reducing the fouling on geothermal heat exchangers. The samples tested for the solar receiver application were Inconel 617, Inconel 617 with a 150 nm layer of platinum, Inconel 617 with a 150 nm layer of platinum and a 550 nm layer of nickel oxide, oxidized nickel, and silicon carbide. The experimental results indicated that the platinum was an ineffective diffusion barrier, nickel oxide displays solar selective properties, and silicon carbide would be the best choice for a surface among the samples tested. This indicates that at the operating temperatures for this receiver at 700 °C, a black body surface is more effective than a practical solar selective surface. The nanosurfaces tested for the antifouling application in geothermal systems were subjected to chemistry conditions similar to that in a Dry Cooling Tower at a geothermal plant in Larderello, Italy. Each sample's performance was measured by determining each samples weight change and surface characterization after exposure in an experimental loop. The best performing coatings, all of which showed negligible weight gain, were the Curran 1000 coating from Curran International, the Curran 1000 coating with nanographene, and the Curralon coating with PTFE. Upon further analysis, the Curran 1000 with nanographene was identified as the most promising coating option.
by Alexander W. Rehn.
S.M.

Thesis (MEng)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Most rural African villages enjoy high levels of sunlight, but rolling out solar power generation technology to tap into this renewable energy resource at remote rural sites in Africa pose a number of design challenges. To meet these challenges, a project has been initiated to design, build and test/evaluate a knock down 3 kW peak electrical stand-alone self-tracking dual-axis concentrating solar power system. This study focusses on the mechatronic engineering aspects in the design and development of a dynamic mechatronic platform and digital electronic control system for the stand-alone concentrating solar power system. Design specifications require an accurate automatic positioner and control system for a motorized parabolic solar reflector with an optical solar harnessing capacity of 12 kWt at solar noon. It must be suitable for stand-alone rural power generation. This study presents a conceptual design and engineering prototype of a balanced cantilever tilt-and-swing dual-axis slew drive actuation means as mechatronic solar tracking mobility platform for a ∼12 m2 lightweight parabolic solar concentrator. Digital automation of the concentrated solar platform is implemented using an industrial Siemens S7-1200 programmable logic controller (PLC) with digital remote control interfacing, pulse width modulated direct current driving, and electronic open loop/closed loop solar tracking control. The design and prototype incorporates off-the-shelf components to support local manufacturing at reduced cost and generally meets the goal of delivering a dynamic mechatronic platform for a concentrating solar power system that is easy to transport, assemble and install at remote rural sites in Africa. Real-time experiments, conducted in the summer of South Africa, validated and established the accuracy of the engineering prototype positioning system. It shows that the as-designed and -built continuous solar tracking performs to an optical accuracy of better than 1.0◦ on both the azimuth and elevation tracking axes; and which is also in compliance with the pre-defined design specifications. Structural aspects of the prototype parabolic dish are evaluated and optimized by other researchers while the Stirling and power handling units are under development in parallel projects. Ultimately, these joint research projects aim to produce a locally manufactured knock down do-it-yourself concentrated solar power generation kit, suitable for deployment into Africa.
AFRIKAANSE OPSOMMING: Landelike gebiede in Afrika geniet hoë vlakke van sonskyn, maar die ontwerp van betroubare sonkrag tegnologie vir die benutting van hierdie hernubare energie hulpbron by afgeleë gebiede in Afrika bied verskeie uitdagings. Om hierdie uitdagings te oorkom, is ’n projek van stapel gestuur om ’n afbreekbare 3 kW piek elektriese alleenstaande selfaangedrewe dubbel-as son-konsentreeder te ontwerp, bou en te toets. Hierdie studies fokus op die megatroniese ingenieurs-aspekte in die ontwerp en ontwikkeling van ’n dinamiese megatroniese platform en ’n digitale elektroniese beheerstelsel vir die alleenstaande gekonsentreerde sonkrag stelsel. Ontwerp spesifikasies vereis ’n akkurate outomatiese posisionering en beheer stelsel vir ’n motor aangedrewe paraboliese son reflekteerder met ’n optiesekollekteer- kapasiteit van 12 kWt by maksimum sonhoogte, en veral geskik wees vir afgeleë sonkrag opwekking. Hierdie studie lewer ’n konsepsuele ontwerp en ingenieurs-prototipe van ’n gebalanseerde dubbelas swaai-en-kantel swenkrat aandrywingsmeganisme as megatroniese sonvolg platform vir ’n ∼12 m2 liggewig paraboliese son konsentreerder. Digitale outomatisering van die son konsentreerder platform is geimplementeer op ’n industriële Siemens S7-1200 programmeerbare logiese beheerder (PLB) met ’n digitale afstandbeheer koppelvlak, puls-wydte-gemoduleerde gelykstroom aandrywing en elektroniese ooplus en geslote-lus sonvolg beheer. Die ontwerp en prototipe maak gebruik van beskikbare komponente om lae-koste plaaslike vervaardiging te ondersteun en slaag in die algemeen in die doel om ’n dinamiese megatroniese platform vir ’n gekonsentreerde sonkrag stelsel te lewer wat maklik vervoer, gebou en opgerig kan word op afgeleë persele in Afrika. Intydse eksperimente is gedurende die somer uitgevoer om die akkuraatheid van die prototipe posisionering sisteem te evalueer. Dit toon dat die sisteem die son deurlopend volg met ’n akkuraatheid beter as 1.0◦ op beide die azimut en elevasie sonvolg asse, wat voldoen aan die ontwerp spesifikasies. Strukturele aspekte van die prototipe paraboliese skottel word deur ander navorsers geëvalueer en verbeter terwyl die Stirling-eenheid en elektriese sisteme in parallelle projekte ontwikkel word. Die uiteindelike doel met hierdie groepnavorsing is om ’n plaaslik vervaardigde doen-dit-self sonkrag eenheid te ontwikkel wat in Afrika ontplooi kan word.

El protagonisme creixent de la tecnologia solar termoelèctrica entre el ventall de les energies renovables es centra en la seva capacitat d’adaptar la seva producció a la demanda energètica exigida. La gestionabilitat d’aquest tipus de centrals s’ha aconseguit amb la integració de sistemes d’emmagatzematge tèrmic en les mateixes. La major part dels sistemes d’emmagatzematge tèrmic, ja sigui els que s’utilitzen a nivell comercial com aquells que es troben en fase de desenvolupament proposen l’ús de sals inorgàniques foses com a medi d’emmagatzematge. Aquestes sals presenten l’inconvenient de la seva alta corrosivitat a altes temperatures. Per un costat, s’han analitzat els fenòmens de corrosió associats a les sals solars utilitzades a la planta pilot TES-PS10 mitjançant la instal·lació de racks de testimonis de corrosió als tancs de sals. A més, al finalitzar l’operació de la instal·lació pilot s’ha dut a terme un estudi post-mortem dels seus. Finalment, amb l’objectiu d’abaratir el cost de l’inventari de sals, s’ha analitzat a nivell de laboratori la corrosivitat de diferents mescles de nitrats de baixa puresa. El segon bloc de la tesi es centra en els sistemes d’emmagatzematge tèrmic en calor latent. Concretament, s’analitza la corrosió associada a la mescla peritèctica 46% LiOH-54% KOH proposta com a material de canvi de fase en un mòdul d’evaporació d’instal·lacions termoelèctriques de generació directa de vapor. D’aquesta forma, s’han dut a terme una sèrie d’assajos a nivell de laboratori amb l’objectiu d’avaluar el comportament envers la corrosió de diferents materials en contacte amb aquests hidròxids.
El creciente protagonismo de la tecnología solar se centra en su capacidad para adaptar su producción a la demanda energética exigida. La gestionabilidad de este tipo de centrales se ha conseguido mediante la integración de sistemas de almacenamiento térmico en sales fundidas. El uso de sales fundidas en sistemas de almacenamiento térmico presenta el hándicap de su corrosividad a alta temperatura. El primer bloque de la Tesis analiza los fenómenos de corrosión asociados a las sales solares en la planta piloto TES-PS10 mediante la instalación de racks de corrosión en los tanques de sales. Además, se ha llevado a cabo un estudio post-mortem de componentes de la instalación. Finalmente, se ha analizado a nivel de laboratorio la corrosividad de distintas mezclas de nitrato de baja pureza. El segundo bloque de la tesis se centra en los sistemas de almacenamiento en calor latente. En concreto, se analiza la corrosión asociada a la mezcla peritéctica 46% LiOH-54% KOH propuesta como material de cambio de fase en el módulo de evaporación en plantas de generación directa de vapor. De este modo, se han llevado a cabo ensayos de corrosión a nivel de laboratorio para evaluar el comportamiento a corrosión de distintos materiales en contacto con los hidróxidos.
The growing of concentrated solar power (CSP) within the different renewable energies is due to its ability to adapt the production to the required energy demand. The dispatchability of this type of plants has been achieved through the integration of molten salts thermal storage systems (TES). Molten salts have a handicap associated to their corrosiveness at high temperature. First block of this Thesis analyzes the corrosion phenomena associated with solar salts used in TES-PS10 pilot plant by installing corrosion racks in the salt tanks. Moreover, a postmortem study of different components was performed after facility shut down. Finally, in order to reduce the cost of the salt inventory in TES systems, the corrosivity of different low purity nitrates mixtures has been analyzed at laboratory scale. The second block of the Thesis focuses on latent heat storage systems. Specifically, it has been analyzed the corrosion associated with the proposed 46% LiOH-54% KOH peritectic mixture as a phase change material in the evaporation module of direct steam generation (DSG) CSP plants. Thus, corrosion tests have been performed at laboratory level to evaluate the corrosion performance of several materials in contact with such hydroxides.

Renewable energy for energy production, like Solar, is turning out to be very pertinent in today's world [1]. It is very clear that Solar Energy is going to emerge as one of the key sources of energy in future. Moreover, the storage option is going to play an essential role to the future deployment of solar power plants. Concentrated solar power plants with thermal storage, photovoltaic plants integrated with battery energy storage, and hybrid plants are attractive solutions to obtain a stable and dispatchable energy production. Investors or policymakers usually find it challenging to come up with the most feasible solar storage technology because they need to consider techno-economic feasibility, and at the same time, from a market or administrative perspective as well. So, this thesis study will address the key problem which is aimed at investors or policymakers since there is a need to choose the best solar storage technology at a utility level in future based on so many attributes. The thesis project was carried out in two phases which includes forecast modelling & estimations and techno-economic assessment of virtual plants. These two phases helped to address various questions in relation to the problem statement of this study. The entire thesis study broadly covered seven countries spanning across four major regions around the world. The first phase of the thesis, forecast modelling estimations shows how the seven countries will look in future (2020 – 2050) with respect to installed capacity and costs for PV, CSP, and BESS technologies. Some major results from phase 1 include, in low-cost estimates, China will remain to be the market leader in PV & CSP by 2050. In U.S.A and India, the installed costs of PV are projected to decline by 70% by 2050. By 2050, the installed costs of Solar Tower technology are estimated to drop by about 65% in China and Spain. In U.S.A, the prices of BESS technology are likely to fall by around 58 – 60 % by 2050. In the second phase of thesis study, a techno-economic evaluation of virtual plants addressed the aspects which are to be considered for a solar project if it is deployed in future across seven specific countries. Results from this analysis helps investors or policymakers to choose the cheapest solar storage technology at a utility level across seven specific countries in future (2020 – 2050). Key results from this analysis show that, in the U.S.A, by 2050, PV+BESS will be the cheapest storage technology for 4 – 10 storage hours. Addition of another renewable technology will add up more viability to the comparison. In China, Hybrid will be the cheapest storage technology for 4 – 8 hrs by 2050. There is huge potential for deployment of CSP & hybrid plants in future than PV. In South Africa, CSP will be the cheapest storage technology by 2050 for 4 – 10 hours of storage. It is assumed that deployment of BESS projects at utility level starts from 2025 in South Africa. Beyond this, market forces analysis was carried out which offers insights especially for the policymakers of how various drivers and constraints are influencing each solar technology across the specific countries in future. Overall, the entire thesis study provides guidelines/insights to investors or policy makers for choosing the best solar storage technology in future at a utility scale for a particular country.
Förnybar energi för energiproduktion, liksom Solar, visar sig vara mycket relevant i dagens värld [1]. Det är mycket tydligt att solenergi kommer att framstå som en av de viktigaste energikällorna i framtiden. Dessutom kommer lagringsalternativet att spela en väsentlig roll för den framtida distributionen av solkraftverk. Koncentrerade solkraftverk med värmelagring, solcellsanläggningar integrerade med batterilagring och hybridanläggningar är attraktiva lösningar för att få en stabil och skickbar energiproduktion. Investerare eller beslutsfattare brukar tycka att det är utmanande att komma på den mest genomförbara solcellstekniken eftersom de måste överväga teknikekonomisk genomförbarhet, och samtidigt, ur ett marknads- eller administrativt perspektiv också. Så denna avhandlingsstudie kommer att ta itu med nyckelproblemet som riktar sig till investerare eller beslutsfattare eftersom det finns ett behov av att välja den bästa solenergilagringstekniken på en användningsnivå i framtiden baserat på så många attribut. Avhandlingsprojektet genomfördes i två faser som inkluderar prognosmodellering och uppskattningar och teknikekonomisk bedömning av virtuella anläggningar. Dessa två faser hjälpte till att ta itu med olika frågor i samband med problemstudien i denna studie. Hela avhandlingsstudien omfattade i stort sju länder som sträcker sig över fyra stora regioner runt om i världen. Den första fasen i avhandlingen, prognosmodelleringsuppskattningar visar hur de sju länderna kommer att se ut i framtiden (2020 - 2050) med avseende på installerad kapacitet och kostnader för PV-, CSP- och BESS -teknik. Några viktiga resultat från fas 1 inkluderar, i lågkostnadsuppskattningar, att Kina kommer att vara marknadsledande inom PV och CSP år 2050. I USA och Indien beräknas de installerade kostnaderna för PV minska med 70% år 2050. Av 2050 beräknas de installerade kostnaderna för Solar Tower -teknik sjunka med cirka 65% i Kina och Spanien. I USA kommer priserna på BESS -teknik sannolikt att sjunka med cirka 58 - 60 % år 2050. I den andra fasen av avhandlingsstudien behandlade en teknikekonomisk utvärdering av virtuella anläggningar de aspekter som ska övervägas för ett solprojekt om det används i framtiden i sju specifika länder. Resultaten från denna analys hjälper investerare eller beslutsfattare att välja den billigaste solenergilagringstekniken på en användningsnivå i sju specifika länder i framtiden (2020 - 2050). Viktiga resultat från denna analys visar att i USA, år 2050, kommer PV+BESS att vara den billigaste lagringstekniken på 4 - 10 lagringstimmar. Tillägg av en annan förnybar teknik kommer att öka jämförbarheten. I Kina kommer Hybrid att vara den billigaste lagringstekniken i 4-8 timmar fram till 2050. Det finns en enorm potential för distribution av CSP & hybridanläggningar i framtiden än PV. I Sydafrika kommer CSP att vara den billigaste lagringstekniken år 2050 för 4 - 10 timmars lagring. Det antas att distributionen av BESS -projekt på verktygsnivå börjar från 2025 i Sydafrika. Utöver detta genomfördes marknadskravsanalys som ger insikter speciellt för beslutsfattarna om hur olika drivkrafter och begränsningar påverkar varje solteknik i de specifika länderna i framtiden. Sammantaget ger hela avhandlingsstudien riktlinjer/insikter till investerare eller beslutsfattare för att välja den bästa solenergitekniken i framtiden i en nyttoskala för ett visst land.

Il y a un intérêt croissant pour les systèmes d'énergie solaire concentrée (CSP) qui peuvent fonctionner à des températures supérieures à 1000 °C afin d'optimiser leur efficacité. L'un des défis consiste à définir un matériau récepteur qui sera soumis à un chauffage à haute température dans l'air. Contrairement aux revêtements utilisés dans les turbines à gaz, le ou les systèmes revêtement(s)/substrat doivent avoir une conductivité thermique élevée pour assurer un transfert thermique optimal vers le fluide. Les revêtements de nitrure d'aluminium (AlN), déposés par dépôt chimique en phase vapeur à 1100-1200 °C à une vitesse de croissance de 10-50 µm·h-1, sont choisis pour leur conductivité thermique élevée, leur faible coefficient de dilatation thermique, leur stabilité thermique élevée et leur capacité à développer des couches stables d'alumine au-dessus de 1000 °C. Les alliages à base de molybdène sont choisis comme substrat pour leurs excellentes propriétés thermiques et mécaniques. Les alliages à base de fer formant des couches d'alumine sont également choisis comme substrats modèles pour étudier le potentiel de ces revêtements et réduire le nombre de paramètres lors de l'oxydation. Des tests accélérés d'oxydation cyclique et des mesures d'émissivité permettent d'évaluer les revêtements AlN comme matériaux pour les récepteurs CSP haute température. Les systèmes multicouches présentent une faible dégradation après des centaines de cycles thermiques à 800 °C dans l'air et peuvent supporter des températures plus élevées (1100 °C) pendant 100 à 500 h selon l'épaisseur du revêtement. Néanmoins, l'oxydation cyclique rapide dans les fours solaires conduit à des fissures dans les revêtements. Un modèle analytique est développé pour étudier l'évolution des contraintes dans le(s) système(s) revêtement(s)/substrat. Les résultats calculés sont en bon accord avec les données expérimentales. Les mesures des propriétés optiques révèlent une diminution de l'absorptivité après oxydation pour les revêtements AlN, mais une augmentation significative de l'absorptivité lorsque un revêtement de SiC est ajouté comme couche de finition
There is an increasing interest for concentrated solar power (CSP) systems which can work at temperatures higher than 1000 °C to optimize efficiency. One of the challenges is to design the receiver that will be heated at high temperature in air. Compared to coatings in gas turbine engine, the coating(s)/substrate system must have a high thermal conductivity to ensure a good heat transfer to the fluid. Aluminum nitride (AlN) coating, deposited by chemical vapor deposition at 1100-1200 °C at a growth rate of 10-50 µm·h-1, is selected for its high thermal conductivity, low thermal expansion coefficient, high temperature stability and its ability to develop stable alumina scales above 1000 °C. Molybdenum-based alloys are selected as substrate materials for their excellent thermal and mechanical properties. The alumina-forming iron-based alloys are also chosen as model substrates to reduce the influencing parameters in real-life receivers and to study the potential of these coatings. Accelerated cyclic oxidation tests and emissivity measurements allow the evaluation of AlN coatings as materials for high temperature CSP receivers. The multilayered systems exhibit low degradation after hundreds of thermal cycles at 800 °C in air and can support higher temperatures (1100 °C) for 100 to 500 h depending on the coating thickness. Nevertheless, the fast cyclic oxidation in solar furnace leads to cracks through the coatings. An analytical model is developed to study the stress evolution within the coating(s)/substrate system. Calculated results are in good agreement with experimental data. The measurements of the optical properties reveal a decrease of absorptivity after oxidation for AlN coatings, but a significant increase of absorptivity when SiC coating is added as a top layer

The United Nations (UN) project "Sustainable energy for all" sets three ambitious objectives to favor a sustainable development and to limit climate change: - Universal access to modern energy services. Electricity is currently not available for 1.3 billion people and the global energy demand is expected to grow of about 35% within 2040, due to the increasing world population and the expanding economies - Double the global rate of improvement in energy efficiency - Double the share of renewable energy sources (RESs) in the global energy mix In addition, according to the climate scenario assessed in the fifth assessment report (AR5) of the International Panel on Climate Change (IPCC), the prevention of undesirable climate effects requires a 40-70% reduction of greenhouse gas (GHG) emissions, compared with 2010 levels, by mid-century, and to near-zero by the end of this century (IPCC, 2014). The achievement of such objectives requires and encourages the spread of RESs in the global energy mix, gradually replacing depleting and polluting energy sources based on fossil fuels, which still have the main incidence on the energy sector. RESs already play a major role in several countries, due to the technological development and the increasing market competitiveness, and the world renewable power capacity reached 22.1% in 2013, showing an increasing trend in 2014 (REN, 2014). However, supporting policies, robust investments from the private sector and efforts from the scientific community are still crucial to demonstrate the technical and economic sustainability and effectiveness of RESs, helping their large-scale diffusion. Starting from such a background, this Ph.D dissertation focuses on the study, design and development of methods and tools for the optimization and enhancement of renewable energy technologies and their effective integration with energy storage solutions and traditional energy sources powered by fossil fuels (hybrid energy systems). The analysis of the major literature and the different scenarios and perspectives of RESs in the national and international contexts have shown that their economic sustainability, and then their diffusion, is closely connected to a number of technical, economic/financial and geographical parameters. Such parameters are the input of the analytic models developed for the techno-economic design of photovoltaic (PV) plants and small wind turbines (SWTs) and applied to the economic feasibility study, through multi-scenario analysis, of such systems in some of the main European Union (EU) Countries. Among the obtained results, the self-consumption of the produced energy plays a crucial role in the economic viability of SWTs and PV plants and, particularly, after the partial or total cut of incentives and uncertainties related to supporting policies within the EU context. The study of the energy demand profile of a specific user and the adoption of battery energy storage (BES) systems have been identified as effective strategies to increase the energy self-consumption contribution. Such aspects have led to the development of an analytic model for the techno-economic design of a grid connected hybrid energy system (HES), integrating a PV plant and a BES system (grid connected PV-BES HES). The economic profitability of the grid connected PV-BES HES, evaluated for a real case study, is comparable with PV plants without storage in case of a significant gap between the cost of energy purchased from the grid and the price of energy sold to the grid, but high BES system costs due to the initial investment and the maintenance activities and the eventual presence of incentives for the energy sold to the grid can make the investment not particularly attractive. Thus, the focus has shifted to the techno-economic analysis of off-grid HES to meet the energy demand of users in remote areas. In this context, BES systems have a significant role in the operation and management of the system, in addition to the storage of exceeding energy produced by the intermittent and variable RESs. The analysis has also been strengthened by an industrial application with the aim to configure, test and install two off-grid HESs to meet the energy demand of a remote village and a telecommunication system. In parallel, two experimental activities in the context of solar concentrating technology, a promising and not fully developed technology, have been carried out. The former activity deals with the design, development and field test of a Fresnel lens pilot-scale solar concentrating prototype for the PV energy distributed generation, through multi-junction solar cells, and the parallel low temperature heat recovery (micro-cogeneration CPV/T system). The latter activity deals with the development of a low cost thermal energy (TES) storage prototype for concentrating solar power (CSP) plants. TES systems show a great potential in the CSP plants profitability since they can overcome the intermittent nature of sunlight and increase the capacity factor of the solar thermal power plant. Concluding, the present Ph.D dissertation describes effective methods and tools for the optimization and enhancement of RESs. The obtained results, showing their critical issues and potential, aim to contribute to their diffusion and favor a sustainable development
Il progetto delle Nazioni Unite "Sustainable energy for all" ha fissato tre obiettivi ambiziosi per favorire uno sviluppo sostenibile e limitare l'impatto del cambiamento climatico: - Accesso universale a moderni servizi elettrici. Tali servizi sono attualmente indisponibili per circa 1.3 miliardi di persone ed è previsto un aumento del 40% della domanda globale di energia elettrica entro il 2040, a causa dell'incremento della popolazione mondiale e delle economie in crescita nei paesi in via di sviluppo - Raddoppio del tasso globale di miglioramento dell'efficienza energetica - Raddoppio del contributo di fonti di tipo rinnovabile nel mix energetico globale Inoltre, lo scenario climatico proposto nel "fifth assessment report (AR5)" redatto da "International Panel on Climate Change (IPCC)" stabilisce la necessità di ridurre l'emissione di gas ad effetto serra del 40-70%, rispetto ai valori registrati nel 2010, entro il 2050 ed eliminarli in modo quasi definitivo entro la fine del secolo con lo scopo di evitare effetti climatici indesiderati. Il raggiungimento di tali obiettivi richiede e incoraggia la diffusione di fonti energetiche rinnovabili (FER) all'interno del mix energetico globale, rimpiazzando gradualmente le fonti di energia convenzionali basate su combustibili fossili, inquinanti e in via di esaurimento, che hanno ancora l'incidenza principale nel settore energetico. A seguito nel loro sviluppo tecnologico e la crescente competitività nel mercato, le FER rivestono già un ruolo fondamentale nel mix energetico di numerose Nazioni ricoprendo il 22.1% del fabbisogno globale di energia nel 2013 e mostrando un andamento in rialzo nel 2014 (REN, 2014). Tuttavia, sono ancora cruciali politiche di supporto, ingenti investimenti privati e contributi della comunità scientifica per dimostrare l'efficacia e la sostenibilità tecnica ed economica delle FER e favorire, quindi, una loro diffusione in larga scala. In questo contesto, la seguente tesi di dottorato è rivolta allo studio, progettazione e sviluppo di metodi e strumenti per l'ottimizzazione e la valorizzazione di tecnologie energetiche rinnovabili e la loro integrazione efficace con fonti di produzione di energia convenzionali alimentate da combustibili fossili e sistemi di accumulo di energia (Sistemi energetici di tipo ibrido). I contributi scientifici disponibili in letteratura e l'analisi dei diversi scenari e delle prospettive delle FER nei vari contesti nazionali ed internazionali hanno dimostrato che la loro sostenibilità economica, e quindi la loro diffusione, è strettamente legata ad una serie di parametri tecnici, economico / finanziari e geografici. Tali parametri sono stati impiegati come input in due modelli analitici sviluppati per la progettazione tecnico-economica di impianti fotovoltaici (FV) e micro turbine eoliche e applicati per lo studio della loro fattibilità economica, attraverso analisi multi-scenario, in alcuni dei maggiori Paesi Europei. I risultati ottenuti hanno mostrato come l'autoconsumo dell'energia prodotta rivesta un ruolo fondamentale nella redditività economica dei citati impianti ed, in particolare, a seguito del taglio parziale o totale dei sistemi di incentivazione e l'incertezza attorno alle politiche di supporto all'interno del panorama Europeo. Lo studio specifico del profilo di domanda elettrica delle utenze e l'impiego di sistemi di accumulo di energia sono stati identificati come strategie efficaci al fine di incrementare la quota di autoconsumo. Tali considerazioni hanno portato allo sviluppo di un modello analitico utile alla progettazione tecnico-economica un sistema energetico ibrido connesso alla rete Nazionale integrante un impianto FV e un sistema di accumulo a batterie. La redditività del sistema, valutata su un caso reale, risulta comparabile a un impianto fotovoltaico privo di batterie in caso di un gap significativo tra il costo dell'energia elettrica acquistata dalla rete e il prezzo di vendita dell'energia elettrica ceduta in rete. Tuttavia, gli elevati costi dovuti all'acquisto iniziale e alle attività di manutenzione, e l'eventuale incentivazione sulla vendita dell'energia in rete, non rendono l'investimento particolarmente attrattivo per impianti connessi alla rete. L'attenzione si è quindi rivolta all'analisi tecnico-economica di sistemi energetici ibridi non connessi alla rete, comunemente definiti in isola o off-grid, per soddisfare il fabbisogno energetico di utenti in area remote e quindi prive di allaccio a una rete elettrica. In tali sistemi, i sistemi di accumulo a batterie, oltre alla capacità di accumulo dell'energia prodotta in eccesso variabili e intermittenti FER, hanno funzioni fondamentali nella gestione del sistema stesso. L'attività è stata anche rafforzata da un'applicazione industriale per la configurazione, test e installazione di due sistemi energetici ibridi in isola impiegati per soddisfare il fabbisogno energetico di un villaggio e di un sistema di telecomunicazione situati in aree remote. In parallelo, sono state svolte due attività sperimentali applicate alla promettente, ma non ancora completamente sviluppata a livello industriale, tecnologia solare a concentrazione. La prima attività riguarda la progettazione, sviluppo e test sperimentali di un prototipo in scala ridotta di concentratore solare a lenti di Fresnel per la produzione distribuita di energia elettrica, mediante l'uso di celle fotovoltaiche multi giunzione, ed energia termica a bassa temperatura, tramite un sistema di recupero termico. La seconda attività concerne lo sviluppo e test sperimentali di un prototipo di sistema di accumulo termico per impianti termodinamici alimentati da sistemi a concentrazione solare. Il sistema di accumulo consente di compensare la natura intermittente e variabile della fonte solare incrementando le ore di funzionamento dell'impianto termodinamico con i conseguenti benefici economici. Concludendo, la presente tesi di dottorato include la descrizione di metodi e strumenti per l'ottimizzazione e valorizzazione delle FER. I risultati evidenziano le criticità e potenzialità dei sistemi studiati con lo scopo di contribuire a una loro diffusione e favorire uno sviluppo sostenibile

Concentrated solar power (CSP) is an efficient means of renewable energy that makes use of solar radiation to produce electricity instead of making use of conventional fossil fuel techniques such as burning coal. The aim of this study is the simulation and characterisation of a CSP plant in order to gain a better understanding of the dominant plant dynamics. Due to the nature of the study, the dissertation is divided into two main parts namely the simulation of a CSP plant model and the characterisation of the plant model. Modelling the CSP plant takes the form of developing an accurate Flownex® model of a 40 MW combined cycle CSP plant. The model includes thermal energy storage as well as making use of a duct burner. The Flownex® model is based on an existing TRNSYS model of the same plant. The Flownex® model is verified and validated, by making use of a bottom-up approach, to ensure that the developed model is in fact correct. The characterisation part of this dissertation involves evaluating the dynamic responses unique to that of a CSP plant as stated in the literature. This involves evaluating the dominant dynamic behaviour, the presence of resonant and anti-resonant modes found within the control bandwidth, and the change in the dynamics of the plant as the plants’ operating points change throughout the day. Once the developed model is validated, characterisation in the form of evaluating the open loop local linear models of the plant is implemented. In order to do so, these models are developed based on model identification processes, which include the use of system identification software such as Matlab® SID Toolbox®. The dominant dynamic behaviour of the plant model, obtained from the developed local linear models, represents that of an over damped second order system that changes as the operating points of the plant change; with the models’ time responses and the bandwidth decreasing and increasing respectively as the thermal energy inputs to the plant increases. The frequency response of the developed local linear models also illustrates the presence of resonant and antiresonant modes found within the control bandwidth of the solar collector field’s temperature response. These modes however are not found to be present in the mechanical power output response of the plant. The use of adaptive control, such as feedforward and gain-scheduled controllers, for the plant should be developed to compensate for the dynamic behaviours associated with that of a CSP plant.
MIng (Computer and Electronic Engineering), North-West University, Potchefstroom Campus, 2015

M.Ing.
The necessity for deployment of Concentrated Solar Power (CSP) technology in the South African energy sector is examined in this dissertation. A background is given on the different technologies that exist in the solar power sector with specific reference to Concentrated Solar Thermal Power (CSTP). The economic, social and environmental benefits that this technology embodies in the near-, medium-, and long-term is discussed in detail. It highlights the local market potential for the establishment and large-scale roll out of CSP technology in a South African context and the economic value-chain that could subsequently be created...

碩士
國立高雄第一科技大學
光電工程研究所
98
The main purpose of the present research is to develop a sun-tracking system for concentrated photovoltaic system. Use two linear image CCD sensors to design a Light Direction Sensor, and then use this sensor with the method of vector operation in 3-D space helps system to find the position of the sun. The two-axis mechanism helps the plants to face the sun accurately. This system using AVR® 8-bit RISC microcontroller ATmega16 to built the system platform. ATmega16 is a cheap and powerful single-chip, that can helps us to reduce the production cost.Finally, the result of tracking accuracy test: the error is less than 0.12°, it’s better than the previous generation (0.9°), and the resolution of Light Direction Sensor is 0.04°.