• Energy Research
• Embargo close
• 15. Life on land close
• 9. Industry and infrastructure close
• SDSN Greece close

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.

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.

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

Due to climate change, the frequency and intensity of droughts are expected to increase. To improve resilience to droughts, proactive drought management is essential. Economic assessments are typically included to decide on the drought risk-reducing investments to make. The choice of both methods and scope of economic assessments influences the outcome, and thus the investment choice. This paper aims to identify how comprehensively economic assessments are applied in practice. Through a systematic literature review, 14 actual economic assessments are identified and their methods are evaluated based on seven criteria for economic assessments as derived from the United Nations Framework Convention on Climate Change (UNFCCC). The results show that in practice, economic assessments rarely address all criteria. Applying a limited number of criteria reduces the scope and narrows the approach, possibly leading to the underestimation of drought risk reduction approaches' related benefits. Applying the seven criteria in practice will improve the results of economic assessments of drought risk reduction measures, allowing for optimal investment selection. Based on the different criteria, a Framework for Economic Assessments of Drought Risk-Reducing Applications (FEADRRA) is proposed. Applying the criteria of the framework can support decision-makers in drought risk management and in carrying out the most fitting drought interventions.

SUMMARY SOLAR CELL POWER PLANTS Extensive research and development activities are currently being conducted ali över the world in the area of utilizing renewable energy resources. The interest of the utilization of local renewable energy resources for devoloping countries has been enhanced by the dramatic increase of oil prices in the early seventies. Öne of the most promising renewable resources is the solar energy. The recent developments in the solid state industry accompanied by a parallel increase in energy prices and the environmental restrictions as well as the need for reliable sources of energy lead to the consideration and assessment of new sources of energy which can secure the needs of public with a minimum impact on the environment. An important candidate is the photovoltaic (PV) source of energy, where the solar radiation is directly converted into electricity that can either be residentially used as a local self-sufficient source such as telecommunication, vaccine refrigeration, lighting, battery charging and water pumping applications ör interconnected to available AÇ public grid. in this work about the photovoltaic systems that are connected to the grid, the voltage obtained from the array is converted to three phase sinusoidal voltage by a static inverter vvhich supplies the public grid and the system is simulated. A utility - interactive PV system (Figüre 1) consists of a variety of subsystems: a PV array subsystem, a power conditioning subsystem, a utility interconnection subsystem, and control subsystem. The PV array subsystem converts solar energy into direct current (DC) electrical povver and delivers it to the power conditioning subsystem (PCS) through the DC interface. The array subsystem also provides protection and necessary electrical isolation between the PCS and the array, and may include experimental instrumentation for monitoring the performance of the array. The utility interconnection subsystem, through the alternating current (AÇ) interface with the PCS, provides synchronization with the utility and, if necessary, acts to electrically isolate the PV system from the utility. The control subsystem, operating through the PCS, oversees the performance of the entire PV system. it also enables overall coordination of the system protection, communicates status information to the utility dispatch center, and, if desired, provides an information and tracking VIIfeedback loop with the PV array. in central PV stations, the PCS may also processes operational commands from the utility dispatch center. in operation, the PCS converts DC power from the array into AÇ povver, provides optimum amount of power to be extracted from the PV array for any given insolation and environmental conditions, matches frequency and phase of the voltage desired by the utility, and provides. protection not only for its internal components but also for the equipment external to the PCS..i, UTILITYCONTROL AND rı^MTi,TINFORMATION SIGNALS CONTKOL ^ SUBSYSTEM rJ^IS PVPOWER CON-UTILITY^- ARRAY-*- DITIONING -+.INTERCON.*~ SOLAR l SUBSYSTEMSUBSYSTEM SUBSYSTEM UTILITY ENERGY4 4 Figüre 1. Block Diagram of a Utility-Interactive Photovoltaic System To achieve a compatible integration of the PV system with the utility, it is essential that the design of the PCS accommodate the dynamic range of interactions between the PV system and the utility grid. These arise from changes in both grid conditions and the output of the PV array. The proper and safe interconnections of PV subsystems require not only the identifications of their mutual functional constraints, but also a knovvledge of how to select ör design the PV subsystems vvithin such constraints. These constraints, therefore, are important in the selection ör evaluation of a PCS that is suitable for central station PV systems. A solar celi (SC) generator possesses a line of maximum povver, and it is most desirable that the operation of the load line should be close to the maximum povver line of the generator. in such a case, good matching exists between the generator and the load for the best performance of the system and maximum utilization of the solar cells. The VIII-Toperating points of the photovoltaic system can generally be accomplished by either carefully selecting the I-V characteristics of the load to be connected to the SC generator, ör incorporating an electronic control device (a maximum-power- point-tracker (MPPT)), which provides the necessary impedance matching the SC generator and the inclusion of a MPPT in PV systems depends on several factors: load type and profile; climatic conditions; the fractional cost of the MPPT and its efficiency; and the gain in energy. An electrical circuit design can be simulated before it is actually built, and necessary changes may be done without touching any hardvvare. Any design that is thought to be complete can be checked easily. Building an electrical circuit is the most practical way to check it, but it is expensive and time consuming. it is useful to simulate the design carefully by using a computer program. Figüre 2 shows the PV system simulated by using PSpice which is a member of the Spice (Simulation Program with Integrated Circuit Emphasis) family of circuit simulators. The solar celi is a semiconductor device that converts the solar radiation directly to electrical energy. The celi is a nonlinear device and can be represented by the I-V terminal characteristics, Figüre 3, ör by an approximate electrical equivalent circuit as shown in Figüre 4. The solar celi is an electrical celi of low level voltage and power, therefore the cells are in series and in parallel combinations in order to form an array of the desired voltage and power levels. The I-V equation of a single celi is given by: I = İL - Is [exp[(q/nkT). (V + RsI) - l] ] where İL is the light generated current, Is is the saturation current, kT/q is the thermal voltage, n is the perfection factor, Rs is the series resistance of the celi. For each characteristic curve there is an optimum operating point with respect to the power. Proper load selection allows the maximum power to be transferred. in this work, to convert the DC voltage into three phase sinusoidal voltage, a three-phase bridge inverter is used. The power circuit of a three-phase bridge inverter using thyristors is shown in Figüre 5, where commutation and snubber circuits are omitted for simplicity. The inverter consists of three half bridge units where the upper and lower thyristors of each unit are switched on and off alternately for 180° intervals. The three half-bridges are phase-shifted by 120°. The inverter output voltage wave shapes are determined by the circuit configuration and switching pattern. These waves are rich in harmonics. IX-T* *T`U_ -mrrru. rv» <D-^ PU ARRAY INUERTER UT ILIT V QRID INPUT FILTER OUTPUT FILTER Figure 2. Block diagram of the PV system simulated by using PSpice Figure 3. Characteristics of a solar cellRs I î I * * l IU<2pİ İDippSRCLoad) iii»»l Figüre 4. Solar celi equivalent circuit The inverter is provided with a filter, to make the output voltage (nearly) sinusoidal. in this study, a band-pass filter is chosen, as it is a simple and economical solution for the system. The transformer coupling to the grid supplies the filtered output voltage of the inverter into the grid. The model of ali components of the system is constituted by using their equivalent circuits and the system is simulated completely step by step. 178

ABSTRACT PhD Thesis INFLUENCES OF EL NINO AND LA NINA EVENTS ON STREAMFLOW AND PRECIPITATION PATTERNS IN TURKEY M. Çağatay KARABÖRK Selçuk University Graduate School of Natural and Applied Sciences Department of Civil Engineering Supervisor : Assoc. Prof. Dr. Ercan KAHYA 2000, 110 Pages Jury : Prof. Dr. A. Ünal Sorman Prof. Dr. Tülay Özbek Assoc. Prof. Dr. Nizamettin Çiftçi Assoc. Prof. Dr. Ercan Kahya Assoc. Prof. Dr. Ali Berktay Temporal climatic anomalies which are observed throughout the world are in relation with El Nino and La Nina events, the extreme phases of Southern Oscillation, originally appearing in equatorial Pacific Ocean. El Nino and La Nina events related temporal climatic variations and their impacts on precipitation and streamflow patterns have been fairly documented with a great number of global and regional scale studies especially since early 1980's. Nevertheless, the effects of these extreme events on Turkey's precipitation and streamflow patterns have not been revealed yet. In this study, by using monthly mean streamflows from 76 stramflow gauging stations and monthly precipitation totals from 94 gauging stations, the influences of El Nino and La Nina events on Turkey's precipitation and streamflow patterns have been examined in detail and thus the magnitudes, phases and geographic extents of these atmospheric forcings were determined. The first harmonics extracted from 24 months composites of stations were assumed to be the responses of the hydrometeorological parameters to El Nino and La Nina events. The candidate regions were identified by the vectorial display of these harmonics on a map and then coherent regions were determined by analyzing the temporal coherence of El Nino and La Nina related signals. The statistical significance of the relationships between precipitation and streamflow anomalies and the extreme phases of Southern Oscillation were quantified by a hypergeometric distribution model. As the results of these analyses, for El Nino events two regions which are separately located in the east and west part of Turkey were identified having El Nino related wet seasons for both precipitation and streamflow anomalies. For La Nina events, only one region located in eastern Turkey having a consistent La Nina related dry season was found out for both precipitation and streamflow anomalies. Modular time series of coherent regions were subjected to spectral analysis and some harmonics with El Nino related periods were considered statistically significant and to be an extra confirmation. Keywords : El Nino, La Nina, ENSO, precipitation, streamflow, Southern Oscillation, climatic variability, harmonic analysis, spectral analysis. iv ÖZET Doktora Tezi EL NİNO VE LA NİNA OLAYLARININ TÜRKİYE'DEKİ NEHİR AKIMLARI VE YAĞIŞ DEĞERLERİ ÜZERİNDEKİ ETKİLERİ M. Çağatay KARABÖRK Selçuk Üniversitesi Fen Bilimleri Enstitüsü İnşaat Mühendisliği Anabilim Dalı Danışman : Doç. Dr. Ercan KAHYA 2000, 110 Sayfa Jüri : Prof. Dr. A. Ünal Sorman Prof. Dr. Tülay Özbek Doç. Dr. Nizamettin Çiftçi Doç. Dr. Ercan Kahya Doç. Dr. Ali Berktay Dünyanın pek çok yerinde görülen iklim değişikleri, Tropikal Pasifik Okyanusu'nda ortaya çıkan ve Güney Salınımı'nın ekstrem fazlarını oluşturan El Nino ve La Nina olayları ile ilişkilidir. El Nino ve La Nina ilişkili iklim değişiklikleri ile bunların yağış ve akım paternleri üzerindeki etkileri ağırlıklı olarak 1980'li yılların başından itibaren yapılan global ve bölgesel ölçekli pek çok çalışma ile ortaya konulmuştur. Bununla beraber, adı geçen olayların Türkiye'nin yağış ve akım paternleri üzerindeki etkileri açıklığa kavuşturulmuş değildir. Bu çalışmada, 76 akım gözlem istasyonunda ölçülen aylık ortalama akım değerleri ve 94 istasyonda ölçülen aylık toplam yağış değerleri kullanılmak suretiyle El Nino ve La Nina olaylarının Türkiye'nin yağış ve akım paternleri üzerindeki etkileri detaylı olarak incelenmiş ve bu etkilerin şiddetleri, fazlan ve coğrafik uzanımları belirlenmiştir. İstasyonların 24 aylık El Nino ve La Nina kompozitlerine uygulanan birinci harmonikler söz konusu olaylara bu hidrometeorolojik parametrelerin tepkisi olarak kabul edilmiştir. Birinci harmoniklerin haritada vektörel gösterimi ile aday bölgeler belirlenmiş, daha sonra bu bölgelerdeki El Nino ve La Nina sinyallerinin kararlılık analizi yapılarak El Nino ve La Nina olaylarına tepki veren kararlı bölgeler ortaya konulmuştur. Güney Salınımı'nın eksrem fazlarının kararlı bölgelerdeki yağış ve akım serileri ile olan ilişkisinin istatistiksel önemi hipergeometrik dağılımla belirlenmiştir. Bu analizlerin sonucunda, hem yağış hem de akım değerleri için, ülkenin doğu ve batısında El Nino ilişkili ıslak sezonlara sahip bölgeler belirlenmiştir. La Nina olayları içinse ülkenin sadece doğusunda La Nina ilişkili kurak sezona sahip bölgeler belirlenmiştir. El Nino ilişkili kararlı bölgelerin modüler yıllık ve sezonluk yağış ve akım serileri üzerinde gerçekleştirilen spektral analiz sonucu El Nino ilişkili sayılan periyotlardaki harmonikler önemli bulunmuş ve bu durumun çalışmadaki diğer bulguları desteklediği sonucuna varılmıştır. Anahtar Kelimeler : El Nino, La Nina, ENSO, yağış, nehir akımı, Güney Salımmı, iklim değişikliği, harmonik analiz, spektral analiz. m 110

Abstract The aim of this study is to evaluate the incremental innovation performance of nuclear energy projects. Within this context, a novel model is generated which consists of two different stages, and large nuclear reactors are taken into consideration. Firstly, the Pythagorean fuzzy DEMATEL is used to weight the phases of technology S-Curve for nuclear energy projects. Moreover, the second stage includes the ranking two-generation technology S-curve with integer patterns for nuclear energy projects. In this framework, the best combinations are selected for innovation life cycle pattern with the integer code series. The findings demonstrate that the nuclear energy companies need to consider the two-generation technology S-Curve because continuous technological developments are occurring for nuclear power generation. It is also determined that aging in the first generation is the most significant period of two-generation technology S-Curve for nuclear energy projects. In this process, critical decisions should be made regarding future technological investments. In addition, the growth phase in the second generation is also important for the effectiveness of the nuclear energy technology. Conducting effective evaluations in these processes will contribute to increasing the efficiency of companies.

This paper presents an overview of 67 ongoing certification initiatives to safeguard the sustainability of bioenergy. Most recent initiatives are focused on the sustainability of liquid biofuels. Content-wise, most of these initiatives have mainly included environmental principles. Despite serious concerns in various parts of the world on the socio-economic impacts of bioenergy production, these are generally not included in existing bioenergy initiatives. At the same time, the overview shows a strong proliferation of standards. The overview shows that certification has the potential to influence direct, local impacts related to environmental and social effects of direct bioenergy production. Key recommendations to come to an efficient certification system include the need for further harmonization, availability of reliable data and linking indicators on a micro, meso and macro levels. Considering the multiple spatial scales, certification should be combined with additional measurements and tools on a regional, national and international level. The role of bioenergy production on indirect land use change (ILUC) is still very uncertain and current initiatives have rarely captured impacts from ILUC in their standards. Addressing unwanted LUC requires first of all sustainable land use production and good governance, regardless of the end-use of the product. It is therefore recommended to extend measures to mitigate impacts from LUC to other lands and feedstock. PDF (776 K)

Moisture availability is a strong determinant of decomposition rates in forests worldwide. Climate models suggest that many terrestrial ecosystems are at risk from future droughts, suggesting moisture limiting conditions will develop across a range of forests worldwide. The impacts of increasing drought conditions on forest carbon (C) fluxes due to shifts in organic matter decay rates may be poorly characterised due to limited experimental research. To appraise this question, we conducted a meta-analysis of forest drought experiment studies worldwide, examining spatial limits, knowledge gaps and potential biases. To identify limits to experimental knowledge, we projected the global distribution of forest drought experiments against spatially modelled estimates of (i) future precipitation change, (ii) ecosystem total above-ground C and (iii) soil C storage. Our assessment, involving 115 individual experimental study locations, found a mismatch between the distribution of forest drought experiments and regions with higher levels of future drought risk and C storage, such as Central America, Amazonia, the Atlantic Forest of Brazil, equatorial Africa and Indonesia. Decomposition rate responses in litter and soil were also relatively under-studied, with only 30 experiments specifically examining the potential experimental impacts of drought on C fluxes from soil or litter. We propose new approaches for engaging experimentally with forest drought research, utilising standardised protocols to appraise the impacts of drought on the C cycle, while targeting the most vulnerable and relevant forests.