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Esta dissertação oferece contribuições para o campo da energia eólica, e fornece um roteiro claro para a tomada de decisão baseada em dados, bem como orientações práticas para otimizar a operação e manutenção. No contexto atual da transformação digital e crescente demanda energética surge a necessidade de soluções inovadores e sustentáveis em larga escala, como a energia eólica offshore. A energia eólica é uma fonte de energia renovável que tem o potencial de contribuir significativamente para a matriz energética global. A implementação e operação de projetos eólicos offshore são desafiadores devido aos custos elevados e à natureza intrínseca dos riscos no ambiente marítimo, por isso necessitam operar em sua máxima eficiência e desempenho, tendo em vista a viabilidade económica. Este trabalho tem como objetivo a compreensão dos fatores principais que influenciam o desempenho energético dos aerogeradores através dos dados que revelam as interrupções e falhas de sistemas. Os resultados obtidos nesta pesquisa destacam a necessidade de uma abordagem integrada, buscando o conhecimento técnico especializado com a aplicação de tecnologias de monitoramento em tempo real e análise de dados. Ao reconhecer os padrões de falhas e as lacunas de eficiência, os gestores podem direcionar seus esforços para aprimorar a fiabilidade, a disponibilidade e a performance geral dessas unidades geradoras de energia elétrica. Através da implementação das recomendações resultantes deste estudo, espera-se que as instituições possam alcançar uma expressiva rentabilidade e sustentabilidade, alinhando-se de forma eficaz com as demandas atuais, garantindo uma posição sólida no ambiente empresarial e contribuindo para um futuro energético mais equilibrado.

THE EFFECT OF ADDITIVES ON THE FUSION TEMPERATURES OF COALS SUMMARY In coal processing, coal ash may cause serious problems such as clinker trouble in fluidized bed gasifiers, sintering in stoker combustors, agglomeration in fluidized bed combustors, fouling of heating surface in combustors, vaporization of harmful elements from the ash. Therefore, prediction of ash behavior is of vital importance, particularly for combustion systems In fluidized bed combustion systems, agglomeration (sintering) of ash (coal) and bed material particles can cause severe problems. As a result of agglomeration, deposition can form on heat transfer surfaces and bed walls. Accumulation of sticky ashes on surfaces can cause substantial decrease in heat transfer coefficient, disturb air distribution and consequently fluidization in the bed. In the most serious cases, sintering of particles can lead to heavy agglomerate mass which finally disturb fluidization and combustion completely. In these cases the system has to be dismantled in order to remove agglomerates and restore the normal operation. The measurement of so called characteristic ash temperatures, namely initial deformation temperature (IT), softening temperature (ST), hemispherical temperature (HT) and fusion temperature (FT) is considered to be one of the best methods to estimate the behavior of coal ash in coal combustors in practice. The agglomeration is a process which describes formation of agglomerates from particles under heating. The earlier works suggest that, in fluidized bed combustors, agglomeration can occur as a result of partial melting and stickiness of bed particles due to the operating of fluidized bed at temperatures higher than the melting point of coal. But later research indicate that agglomeration can occur at temperatures much lower than the ash fusion temperature. The temperature at which agglomeration starts is called first sintering temperature. The properties and behavior of ashes are remarkably different among coals and since coal ash is extremely complex mixture of minerals it is not possible to predict the fusion behavior of such mixture from its chemical composition with a reasonable accuracy. Many correlations have been developed to estimate the softening and fusion behavior of ashes from their chemical composition, in general, all of them suggest that the softening and fusion temperatutes increase as the amounts of asidic oxides (SİO2, AI2O3) in the ash increase. Therefore, it is essential to study the individual coal deposit in order to see how they exactly behave in practical combustion. The objectives of this work is to determine the characteristic ash temperatures of some major Turkish lignites, to investigate the relationship between their temperatures and inorganic compositions and relationship between ash fusiontemperatures and inorganic compositions and relationship between ash fusion temperature and agglomeration temperature of some selected coals. The effect of addition of some metal oxides which are the major component of ashes of coals on the characteristic temperatures is also investigated. Ten coal samples studied were taken from the major lignite deposits in various districts of Turkey. One sample out of ten is oil shale. The samples are ; 1 ) Beypazarı - Ankara 2 ) Çan - Çanakkale 3 ) Elmalı ( Soma ) - Manisa 4 ) Eynez - Manisa 5 ) Deniş ( Soma ) - Manisa 6 ) Göynük - Bolu 7 ) Göynük Oil shale - Bolu 8 ) Kısrakdere - Manisa 9 ) Tunçbilek - Kütahya 10) Yatağan - Muğla The following analyses were carried out in order to characterize coal samples and ashes : Proximate analysis, elemental analysis, measurement of characteristic temperatures and chemical analysis of ashes. Coal samples were crushed and sieved to - 200 mesh and ashes were prepared using the TS 330 procedures. Ash compositions were determined according to ASTM procedure D 2795 - 86. Ash fusion measurements were made by using a LECO AF - 500 type ash fusion furnace with digital read - out, sensivity of 5K and a maximum temperature of 1844 K according to the ASTM procedure D 1857 - 68. Ash cones were prepared and put into the furnace and were heated to the fusion temperature with a heating rate of 8 K/ min. under oxidizing gas atmosphere. The results are presented as the an average values of repeated measurements. The results of chemical analysis of ashes and ash fusion measurements are presented in Table 1 and Table 2 respectively. As seen from Table 2, initial deformation temperatures and fusion temperatures of lignites change between 1377 - 1573 K and 1482 - 1844 K, respectively. The fusion temperature of Eynez lignite was out of the temperature range of ash fusion furnace and it could not be measured exactly. Comparison of Table 1 and Table 2 indicated that, in general, coals with higher Si02 and lower Fe203 contents such as Eynez, Elmalı, Kısrakdere, Tunçbilek and Yatağan lignites have higher initial deformation and fusion temperatures while coals with higher Na20 percentages have lower fusion temperatures. However, no regular relationship is seen between chemical composition and critical temperatures of ashes. For example, in spite of their high Na20 percentages, Eynez, Kısrakdere and Tunçbilek lignites have fusion temperatures higher than that those with lower Na20 percentages. In Figure 1, the initial deformation temperatures are given as a function of total percentage of (Na20 + K20 + CaO + MgO). These oxides are called basic oxides which are considered, chemically, to be the most active components and have the leading role in agglomeration (sintering) behavior of ash. It is clear from figure that no regular relationship between composition and deformation temperature can bedescibed for original coal ashes. The initial deformation temperature differs widely even for ashes having nearly the same total basic oxide percentage. A set of experiments was carried out by using of Na2C03, K2CO3, CaO and MgO as additives to ashes in order to investigate the relationship between the X U.m&<*J..lIX-/.CA,I1^-TVJX^VS^IT : Initial deformation temperature, ST : Softening temperature, HT temperature, FT :Fusion temperature. Hemispherical composition and fusion charteristics for the individual ashes. In these experiments, CaO and Na20 contents of all ashes were increased by adding of CaO and Na2C03. K2C03 and MgO were added only to Beypazarı lignite ash. The characteristic temperatures of Beypazarı Elmah, Eynez, Tunçbilek and Yatağan lignites and Göynük oil shale decreased regularly with increasing CaO content while no considerable changes was observed for other lignites. A maximum decrease of 130 K was determined in fusion temperature with an increase of 9% in CaO for Eynez and Yatağan lignites. The Na20 content of ashes was increasd by using Na2CÛ3. Increasing of the amount of Na20 lowered the characteristic temperatures of Beypazarı, Çan, Eynez, Kısrakdere, Tunçbilek and Yatağan lignite ashes. Temperature profiles of Elmah XIlignite ash had a minimun around 8% Na20 below which temperatures decreased while above which increased slightly with increase in Na20 contest. Increasing of Na20 content by 10%, caused a 120 K and 180 K reduction in fusion temperatures of Beypazarı and Eynez lignite, respectively, which were the highest reductions determined. Other ashes were not affected significantly by the Na20. 10 15 20 25 30 %{CaO+ MgO+ Na20+ K20} 35 40 Figure 1. Change of fusion temperature of oginal coal ashes with (Na20 + K20 + CaO + MgO) % Another topic studied in this work is the relationship between the agglomeration and characteristic temperatures of lignites. For this purpose, a set of experiments was performed in which the agglomeration temperatures (Tag) of Beypazarı, Çan, Eynez, Kisrakdere, Göynük and Yatağan lignites were determined in a 10 cm id fluidized bed combustor. Results of agglomeration measurements are compiled in Table 3. The difference between agglomeration temperature and characteristic temperatures are also included in the Table. The differences described as AT, = IT - Tag, AT2 = ST - TAG, AT3= HT - TAG, AT4 = FT - TAG Agglomeration tempertures listed in Table 3 are lowest temperatures where first agglomerates formed. Data in the table indicate that agglomeration of lignite can occur at temperatures several hundred degrees below fusion temperature for a lignite in a fluidized bed coal combustor. Values of ATi, AT2, AT3 > AT4 show that the agglomeration behavior of lignites with different ash compositions vary widely and can not be explained on the basis of ash fusion temperature. XIITable 3. Agglomeration Temperature of Some Lignites. X1U ÖZET Kömür yakma sistemlerinde karşılaşılan sinterlesme ve aglomerasyon olayları, yanmanın sürekliliği açısından problem yaratmakta ve sistemin verimim olumsuz yönde etkilemektedir. Aglomerasyon, kül taneciklerinin birbirine yapışıp, katı bir kütle haline gelmesi olayıdır ve özellikle akışkan yataklı yakma sistemlerinde karşılaşılan önemli bir. problemdir. Temel olarak kömürün anorganik yapı özelliklerinden kaynaklanmaktadır. Bu nedenle JmL ergime sıcakhldarı ve aglomerasyon özellikleri arasında bir etkileşim olduğu sarınmaktadır. Bu çalışmada, 9 linyit ile bir bitümlü şistin küllerinin anorganik yapılan ile özgül sıcaklıkları olarak bilinen, başlangıç deformasyon (İT), yumuşama (ST), yan küreselleşme (HT) ve akma {FT) sıcaklıkları arasındaki ilişki incelenmiştir. Çalışmada, hem orjinal, hem de belirli oranlarda, Na2C03, K2C03, CaO ve MgO katılarak bileşimleri değiştirilmiş olan `katkılı küller` göz önüne alınmıştır. Küllerin anorganik yapılan, standart yöntemler kullanılarak belirlenmiştir. Özgül sıcaklıkları LECO AF 500 model bir cihaz kullanılarak, ASTM D 1857 ' ye göre oksitleyici atmosferde ölçülmüştür. Aglomerasyon sıcaklıkları ise 10 cm çapında bir akışkan yatakta ölçülmüştür. Orjinal küllerin İT değerleri 1377-1576 K, ST değerleri 1414-1801 K, HT değerleri 1460-1814 K, FT değerleri 1482- 1844 K arasında değişmektedir. Özgül sıcaklıkları en yüksek olan kömü Eynez linyiti, en düşük olan ise Göynük bitümlü şisti olmuştur. Orjinal küllerin anorganik yapılan ile özgül sıcaklıklan arasında sistematik herhangibir ilişki görülmemiştir. Genel olarak, Na20 içerikleri yüksek olan kömürlerin çoğunlukla daha düşük sıcaklıklarda, buna karşın SİO2 oranlan yüksek ve Fe203 oranlan düşük kömürler ise daha yüksek sıcaklıklarda ergimiştir. Ancak bu durum incelene bütün kömürler için, geçerli değildir. Aynı tür küllerin yapısal değişimlerini özgül sıcaklıklara etkisini görmek amacıyla, bazı küllere değişik oranlarda Na2C03, K2CO3, CaO ve MgO katılarak hazırlanan katkılı küllerle yapılan ölçümlerin sonuçlan, sıcaklıklan en fazla etkileyen katkının Na2C030İduğunu göstermiştir. Toplam Na20 içeriğine bağlı olarak, özgül sıcaklıklarda genelde bir düşme eğilimi gözlenmiştir. Na20 katkısı bazı kömürlerin ergime sıcaklıklarını 120 K kada^düşürmüştür. Kömürlerin aglomerasyon sıcaklıkları, deformasyon sıcaklıklarına (IT) allında kalmaktadır. Aglomerasyon sıcaklıkları İT değerlerinden 175-346 K, ergime sıcaklıklarından ise, yaklaşık olarak 346-551 K daha düşük olmuştur. Akışkan yataklarda yanan kömür taneciklerinin sıcaklığının ölçülen ortalama yatak sıcaklığından yaklaşık olarak, 100-150 K daha yüksek olduğu göz önüne alındığında, aglomerasyonun deformasyon sıcaklığında veya ona çok yalan sıcaklık seviyelerinde başladığı anlaşılmaktadır. 79

Abstract Turkey is currently in the middle of its sixth attempt over the last 60 years to introduce nuclear power. This paper analyzes Turkey’s past and present motivation, capacity and strategies to identify the factors which influence deployment of nuclear power and draw lessons for other nuclear newcomer countries. While existing literature points to a correlation between nuclear power, strong state involvement, centralized energy planning and the rhetoric linking energy to national prestige and security, we show that these factors are not sufficient for a successful nuclear program. We also show that autocratic rule and nuclear weapons aspirations can undermine rather than support the development of civilian nuclear power as it is often presumed in the literature. Turkey’s current strategy based on intergovernmental agreements with Russia and Japan is laced with irony since it is motivated by energy security considerations and yet relies on foreign entities for construction, ownership and operation of nuclear power plants as well as the development of human capacity. Although Ankara intends to build the third nuclear power plant with own resources this seems unlikely based on the South Korean and Japanese experience, both of which needed much more time and effort to localize the industry.

Modelling the economics of climate change is daunting. Many existing methodologies from social and physical sciences need to be deployed, and new modelling techniques and ideas still need to be developed. Existing bread-and-butter micro- and macroeconomic tools, such as the expected utility framework, market equilibrium concepts and representative agent assumptions, are far from adequate. Four key issues—along with several others—remain inadequately addressed by economic models of climate change, namely: (1) uncertainty, (2) aggregation, heterogeneity and distributional implications (3) technological change, and most of all, (4) realistic damage functions for the economic impact of the physical consequences of climate change. This paper assesses the main shortcomings of two generations of climate-energy-economic models and proposes that a new wave of models need to be developed to tackle these four challenges. This paper then examines two potential candidate approaches—dynamic stochastic general equilibrium (DSGE) models and agent-based models (ABM). The successful use of agent-based models in other areas, such as in modelling the financial system, housing markets and technological progress suggests its potential applicability to better modelling the economics of climate change.

Extreme summer droughts are expected to occur more often in the future in NW Europe due to climate change. These droughts might accelerate the rate of peat oxidation in drained peat areas, with impacts on soil subsidence, GHG emission and water quality. This study aimed at providing more insight in the oxidation of deep peat layers that had not previously been exposed to air, the so-called secondary decomposition. We incubated two types of peat (eutrophic and oligotrophic), sampled from permanently anoxic peat layers from nature reserves and agricultural peat meadows. Peat samples were incubated for thirteen weeks under anoxic conditions, but were exposed to air for one to eight weeks. The production of CO2 and CH4 was quantified as a proxy for decomposition; concentrations of soluble nutrients and phenolic compounds were also measured. The results showed that oxygenation led to a steep increase in the rate of decomposition, indicated by higher carbon loss rates during and after oxygenation compared to non-oxygenated samples. Carbon loss rates increased more for eutrophic peat (agricultural area: 352%, nature reserve: 182%) than for oligotrophic peat (83% and 159% respectively). Most peat samples investigated showed higher post-oxygenation CO2 and/or CH4 production compared to the anoxic pre-oxygenation period. This indicates that oxygenation stimulates decomposition, even after anoxic conditions have returned. Contrary to the enzymic latch theory, no effects of oxygenation on the concentrations of soluble or condensed phenolic compounds were detected. Soluble nutrient concentrations did not change due to oxygenation either. Noteworthy is the occurrence of pyrite mineralization and associated acidification in eutrophic peat. Thus, low summer water levels, for example due to climate change, should be avoided in order to limit exceptionally high decomposition rates and associated problems such as increasing subsidence rates, greenhouse gas emission, sulfate release and acidification.

In industrialized countries, large amounts of mineral wastes are produced. They are re-used in various ways, particularly in road and earth constructions, substituting primary resources such as gravel. However, they may also contain pollutants, such as heavy metals, which may be leached to the groundwater. The toxic impacts of these emissions are so far often neglected within Life Cycle Assessments (LCA) of products or waste treatment services and thus, potentially large environmental impacts are currently missed. This study aims at closing this gap by assessing the ecotoxic impacts of heavy metal leaching from industrial mineral wastes in road and earth constructions. The flows of metals such as Sb, As, Pb, Cd, Cr, Cu, Mo, Ni, V and Zn originating from three typical constructions to the environment are quantified, their fate in the environment is assessed and potential ecotoxic effects evaluated. For our reference country, Germany, the industrial wastes that are applied as Granular Secondary Construction Material (GSCM) carry more than 45,000 t of diverse heavy metals per year. Depending on the material quality and construction type applied, up to 150 t of heavy metals may leach to the environment within the first 100 years after construction. Heavy metal retardation in subsoil can potentially reduce the fate to groundwater by up to 100%. One major challenge of integrating leaching from constructions into macro-scale LCA frameworks is the high variability in micro-scale technical and geographical factors, such as material qualities, construction types and soil types. In our work, we consider a broad range of parameter values in the modeling of leaching and fate. This allows distinguishing between the impacts of various road constructions, as well as sites with different soil properties. The findings of this study promote the quantitative consideration of environmental impacts of long-term leaching in Life Cycle Assessment, complementing site-specific risk assessment, for the design of waste management strategies, particularly in the construction sector.

II ABSTRACT Climate change is expected due to the increasing atmospheric concentrations of carbondioxide and other trace gasses, which lead to changes in the radioactive balance of the atmosphere. Such changes propagate further to those in temperature i and other climatic variables. Hydrologic systems and water resources are likely to be seriously impacted by global climate change. Such processes as surface runoff, precipitation, soil moisture, groundwater, water quality, and sea levels will be significantly exposed to effects of climate change. Eventually, these effects will have to be considered in water resources planning and management. The study presented stems from the above needs and addresses the problem of climate change-water resources interactions. It is intended here to investigate the possible effects of climate change on watershed scale hydrologic processes and water demand. Within this context, the current methods used in developed countries are applied to the case of the Gediz River Basin, and possible impacts of changes in climatic variables, i.e., precipitation and temperature, are investigated as they relate to runoff The results of the study should not considered as exact values to represent the effects of climate change. They are essentially `estimates` on `likely` effects of an expected climate change. However, the results also show that, if the prescribed climate change scenarios do occur in the future, they will have significant effects on the hydrology of the basin which, in turn, affects water demand for various water resources development plans. Accordingly, the study presented should be considered as an initial step towards assessment of climate change impacts and should be reaccomplished in future attempts towards any planning or management activity in the basin. ÖZET İklim değişikliği, atmosferdeki karbondioksit (CO2) ve diğer antropojen sera gazı konsantrasyonlarının giderek artması sonucu beklenmektedir. İklim değişikliğinin sonucunda beklenen en önemli olgu, sıcaklık, yağış, evapotranspirasyon, akış gibi temel iklimsel ve hidrolojik değişkenlerdeki muhtemel değişimlerdir. Bu etkilerin su kaynakları planlama ve yönetiminde değerlendirilmesi gerekmektedir. Sunulan çalışma, iklim değişikliğinin su kaynakları ile olan ilişkisini incelemektedir. Bu değişimlerden hidrolojik çevrimin ve su kaynaklarının gerek miktarı ve gerekse kalitesinin de etkilenmesi beklenmektedir. Dolayısıyla, küresel iklim değişikliğinin havza su dengesine ve su kaynaklarının planlama ve yönetimine de yansıması söz konusudur. Bu kapsamda sunulan çalışmada alt havza bazında sıcaklık ve yağış gibi iklim parametrelerinin, akıma olan etkileri incelenmiş ve duyarlılık analizi ile sonuçlar değerlendirilmiştir. 75

Devido à crescente preocupação com as alterações climáticas e à consequente mudança de paradigma, gradualmente são utilizados mais veículos elétricos e híbridos, como é o caso dos FCHEV (Fuel cell Hybrid Electric Vehicle). Como é característico nos veículos híbridos, a existência de duas fontes de energia faz com que seja crucial otimizar a distribuição de potência, sendo esta a chave para melhorar o desempenho do veículo. Assim, definiu-se como medida principal de desempenho o consumo equivalente em Gasoline Gallon Equivalent, que efetua um tradeoff entre o consumo de hidrogénio e o consumo ponderado de energia da bateria, em função do seu estado de carga. Tendo como principais objetivos o aumento do tempo de vida dos componentes e a redução do consumo do veículo, construiu-se uma estratégia de gestão energética em tempo real, baseada em programação dinâmica, com extração de regras de controlo pela response surface methodology e implementação de machine learning para a identificação dos tipos de ciclo de condução. A estratégia foi construída e simulada em Matlab, partindo da modelação do sistema e da implementação da função DPM (Dynamic Programming Matrix), desenvolvida pelo instituto ETH Zurich para efetuar a programação dinâmica. Seguidamente, foi utilizada a função stepwiselm e a app Regression Learner para extrair as regras de controlo e, finalmente, recorreu-se à app Classification Learner para identificar os ciclos de condução. Toda a estratégia foi complementada com o Matlab Coder, para fazer a transição do algoritmo para linguagem C, suportada pela ECU. Os resultados foram analisados no final de cada fase de implementação, validando a metodologia proposta. Assim, na fase de otimização demonstrou-se que é possível melhorar o consumo equivalente, relativamente ao algoritmo implementado no veículo, obtendo-se uma redução média superior a 15%, sem se demonstrarem alterações significativas no consumo de H2. A partir destes resultados, efetuou-se a extração de regras de controlo, utilizando duas estratégias distintas: regressões não lineares e árvores de decisão. No caso da primeira, não foi possível demonstrar que efetivamente o consumo equivalente é menor, apesar da percentagem de redução desse consumo ser em média superior a zero. No caso da segunda, a robustez do modelo de machine learning demonstrou que em média o consumo equivalente é menor do que no algoritmo atualmente presente no autocarro, sendo que a percentagem de redução em média ultrapassa os 10%. Com ambas as estratégias, as alterações no consumo de H2 não se mostraram significativas. Na fase de reconhecimento do ciclo de condução, utilizou-se uma árvore de decisão que foi analisada para diferentes tempos de decisão, demonstrando-se que com 600 e 300 segundos a identificação apresentou os melhores resultados de accuracy, sendo percetível que para 300 segundos será reduzido o espaço em memória na ECU para armazenamento dos parâmetros de condução, mostrando-se também ser mais preciso em cenários mais semelhantes com a realidade. Finalmente os testes de estrada demonstraram melhorias de 15.7% no consumo equivalente, 24.4% no consumo de H2 e 6.8% no rendimento, com a estratégia que utiliza regressões não lineares. No entanto, o algoritmo mais adequado seria o construído com árvores de decisão, que devido à sua complexidade não foi possível de implementar na ECU.

Organic solar cells utilize an energy-level offset to generate free charge carriers. Although a very small energy-level offset increases the open-circuit voltage, it remains unclear how exactly charge generation is affected. Here we investigate organic solar cell blends with highest occupied molecular orbital energy-level offsets (∆EHOMO) between the donor and acceptor that range from 0 to 300 meV. We demonstrate that exciton quenching at a negligible ∆EHOMO takes place on timescales that approach the exciton lifetime of the pristine materials, which drastically limits the external quantum efficiency. We quantitatively describe this finding via the Boltzmann stationary-state equilibrium between charge-transfer states and excitons and further reveal a long exciton lifetime to be decisive in maintaining an efficient charge generation at a negligible ∆EHOMO. Moreover, the Boltzmann equilibrium quantitatively describes the major reduction in non-radiative voltage losses at a very small ∆EHOMO. Ultimately, highly luminescent near-infrared emitters with very long exciton lifetimes are suggested to enable highly efficient organic solar cells. Donor–acceptor systems with low energy-level offset enable high power efficiency in organic solar cells yet it is unclear what drives charge generation. Classen et al. show that long exciton lifetimes enable efficient exciton splitting and thus generation of free charges while also suppressing voltage losses.