The Significance of Wind Turbines Layout Optimization on the Predicted Farm Energy Yield

Securing energy supply and diversifying the energy sources is one of the main goals of energy strategy for most countries. Due to climate change, wind energy is becoming increasingly important as a method of CO2-free energy generation. In this paper, a wind farm with five turbines located in Jerash, a city in northern Jordan, has been designed and analyzed. Optimization of wind farms is an important factor in the design stage to minimize the cost of wind energy to become more competitive and economically attractive. The analyses have been carried out using the WindFarm software to examine the significance of wind turbines’ layouts (M, straight and arch shapes) and spacing on the final energy yield. In this research, arranging the turbines facing the main wind direction with five times rotor diameter distance between each turbine has been simulated, and has resulted in 22.75, 22.87 and 21.997 GWh/year for the M shape, Straight line and Arch shape, respectively. Whereas, reducing the distance between turbines to 2.5 times of the rotor diameter (D) resulted in a reduction of the wind farm energy yield to 22.68, 21.498 and 21.5463 GWh/year for the M shape, Straight line and Arch shape, respectively. The energetic efficiency gain for the optimized wind turbines compared to the modeled layouts regarding the distances between the wind turbines. The energetic efficiency gain has been in the range between 8.9% for 5D (rotor diameter) straight layout to 15.9% for 2.5D straight layout

Different no more: Country spreads in advanced and emerging economies

Interest-rate spreads fluctuate widely across time and countries. We illustrate this on the basis of about 3,100 quarterly observations for 21 advanced and 17 emerging economies since the early 1990s. Prior to the financial crisis, spread fluctuations in advanced economies are an order of magnitude smaller than in emerging economies. After 2008 their behavior has largely converged along a number of dimensions. We also provide evidence on the transmission of spread shocks and find it similar across sample periods and country groups. The importance of spread shocks as a source of output fluctuations in advanced economies has increased after 2008

Optimization of the SiC Powder Source Material for Improved Process Conditions During PVT Growth of SiC Boules

We have studied the influence of different SiC powder size distributions and the sublimation behavior during physical vapor transport growth of SiC in a 75 mm and 100 mm crystal processing configuration. The evolution of the source material as well as of the crystal growth interface was carried out using in situ 3D X-ray computed tomography (75 mm crystals) and in situ 2D X-ray visualization (100 mm crystals). Beside the SiC powder size distribution, the source materials differed in the maximum packaging density and thermal properties. In this latter case of the highest packaging density, the in situ X-ray studies revealed an improved growth interface stability that enabled a much longer crystal growth process. During process time, the sublimation-recrystallization behavior showed a much smoother morphology change and slower materials consumption, as well as a much more stable shape of the growth interface than in the cases of the less dense SiC source. By adapting the size distribution of the SiC source material we achieved to significantly enhance stable growth conditions

Influence of Morphological Changes in a Source Material on the Growth Interface of 4H-SiC Single Crystals

In this study, the change of mass distribution in a source material is tracked using an in situ computer tomography (CT) setup during the bulk growth of 4H- silicon carbide (SiC) via physical vapor depostion (PVT). The changing properties of the source material due to recrystallization and densification are evaluated. Laser flash measurement showed that the thermal properties of different regions of the source material change significantly before and after the growth run. The Si-depleted area at the bottom of the crucible is thermally insulating, while the residual SiC source showed increased thermal conductivity compared to the initially charged powder. Ex situ CT measurements revealed a needle-like structure with elongated pores causing anisotropic behavior for the heat conductivity. Models to assess the thermal conductivity are applied in order to calculate the changes in the temperature field in the crucible and the changes in growth kinetics are discussed

Analysis of the Basal Plane Dislocation Density and Thermomechanical Stress during 100 mm PVT Growth of 4H-SiC

Basal plane dislocations (BPDs) in 4H silicon carbide (SiC) crystals grown using the physical vapor transport (PVT) method are diminishing the performance of SiC-based power electronic devices such as pn-junction diodes or MOSFETs. Therefore, understanding the generation and movement of BPDs is crucial to grow SiC suitable for device manufacturing. In this paper, the impact of the cooldown step in PVT-growth on the defect distribution is investigated utilizing two similar SiC seeds and identical growth parameters except for a cooldown duration of 40 h and 70 h, respectively. The two resulting crystals were cut into wafers, which were characterized by birefringence imaging and KOH etching. The initial defect distribution of the seed wafer was characterized by synchrotron white beam X-ray topography (SWXRT) mapping. It was found that the BPD density increases with a prolonged cooldown time. Furthermore, small angle grain boundaries based on threading edge dislocation (TED) arrays, which are normally only inherited by the seed, were also generated in the case of the crystal cooled down in 70 h. The role of temperature gradients inside the crystal during growth and post-growth concerning the generation of shear stress is discussed and supported by numerical calculations

Limitations during Vapor Phase Growth of Bulk (100) 3C-SiC Using 3C-SiC-on-SiC Seeding Stacks

The growth of 3C-SiC shows technological challenges, such as high supersaturation, a silicon-rich gas phase and a high vertical temperature gradient. We have developed a transfer method creating high-quality 3C-SiC-on-SiC (100) seeding stacks, suitable for use in sublimation “sandwich” epitaxy (SE). This work presents simulation data on the change of supersaturation and the temperature gradient between source and seed for the bulk growth. A series of growth runs on increased source to seed distances was characterized by XRD and Raman spectroscopy. Results show a decrease in quality in terms of single-crystallinity with a decrease in supersaturation. Morphology analysis of as-grown material indicates an increasing protrusion dimension with increasing thickness. This effect limits the achievable maximal thickness. Additional polytype inclusions were observed, which began to occur with low supersaturation (S ≤ 0.06) and prolonged growth (increase of carbon gas-species)

Slaughterhouse Wastewater Treatment: A Review on Recycling and Reuse Possibilities

Slaughterhouses produce a large amount of wastewater, therefore, with respect to the increasing water scarcity, slaughterhouse wastewater (SWW) recycling seems to be a desirable goal. The emerging challenges and opportunities for recycling and reuse have been examined here. The selection of a suitable process for SWW recycling is dependent on the characteristics of the wastewater, the available technology, and the legal requirements. SWW recycling is not operated at a large scale up to date, due to local legal sanitary requirements as well as challenges in technical implementation. Since SWW recycling with single-stage technologies is unlikely, combined processes are examined and evaluated within the scope of this publication. The process combination of dissolved air flotation (DAF) followed by membrane bioreactor (MBR) and, finally, reverse osmosis (RO) as a polishing step seems to be particularly promising. In this way, wastewater treatment for process water reuse could be achieved in theory, as well as in comparable laboratory experiments. Furthermore, it was calculated via the methane production potential that the entire energy demand of wastewater treatment could be covered if the organic fraction of the wastewater was used for biogas production.DFG, 414044773, Open Access Publizieren 2021 - 2022 / Technische Universität Berli

Epitaxial Metal Halide Perovskites by Inkjet‐Printing on Various Substrates

Metal‐halide‐perovskites revolutionized the field of thin‐film semiconductor technology, due to their favorable optoelectronic properties and facile solution processing. Further improvements of perovskite thin‐film devices require structural coherence on the atomic scale. Such perfection is achieved by epitaxial growth, a method that is based on the use of high‐end deposition chambers. Here epitaxial growth is enabled via a ≈1000 times cheaper device, a single nozzle inkjet printer. By printing, single‐crystal micro‐ and nanostructure arrays and crystalline coherent thin films are obtained on selected substrates. The hetero‐epitaxial structures of methylammonium PbBr3 grown on lattice matching substrates exhibit similar luminescence as bulk single crystals, but the crystals phase transitions are shifted to lower temperatures, indicating a structural stabilization due to interfacial lattice anchoring by the substrates. Thus, the inkjet‐printing of metal‐halide perovskites provides improved material characteristics in a highly economical way, as a future cheap competitor to the high‐end semiconductor growth technologies.DFG, 404984854, Bleifreie Perovksite für die RöntgendetektionDFG, 399073171, GRK 2495: Energiekonvertierungssysteme: von Materialien zu Bauteile

Genome-wide analysis identifies 12 loci influencing human reproductive behavior.

The genetic architecture of human reproductive behavior-age at first birth (AFB) and number of children ever born (NEB)-has a strong relationship with fitness, human development, infertility and risk of neuropsychiatric disorders. However, very few genetic loci have been identified, and the underlying mechanisms of AFB and NEB are poorly understood. We report a large genome-wide association study of both sexes including 251,151 individuals for AFB and 343,072 individuals for NEB. We identified 12 independent loci that are significantly associated with AFB and/or NEB in a SNP-based genome-wide association study and 4 additional loci associated in a gene-based effort. These loci harbor genes that are likely to have a role, either directly or by affecting non-local gene expression, in human reproduction and infertility, thereby increasing understanding of these complex traits

Genome-wide interaction study of a proxy for stress-sensitivity and its prediction of major depressive disorder

Individual response to stress is correlated with neuroticism and is an important predictor of both neuroticism and the onset of major depressive disorder (MDD). Identification of the genetics underpinning individual differences in response to negative events (stress-sensitivity) may improve our understanding of the molecular pathways involved, and its association with stress-related illnesses. We sought to generate a proxy for stress-sensitivity through modelling the interaction between SNP allele and MDD status on neuroticism score in order to identify genetic variants that contribute to the higher neuroticism seen in individuals with a lifetime diagnosis of depression compared to unaffected individuals. Meta-analysis of genome-wide interaction studies (GWIS) in UK Biobank (N = 23,092) and Generation Scotland: Scottish Family Health Study (N = 7,155) identified no genome-wide significance SNP interactions. However, gene-based tests identified a genome-wide significant gene, ZNF366, a negative regulator of glucocorticoid receptor function implicated in alcohol dependence (p = 1.48x10-7; Bonferroni-corrected significance threshold p < 2.79x10-6). Using summary statistics from the stress-sensitivity term of the GWIS, SNP heritability for stress-sensitivity was estimated at 5.0%. In models fitting polygenic risk scores of both MDD and neuroticism derived from independent GWAS, we show that polygenic risk scores derived from the UK Biobank stress-sensitivity GWIS significantly improved the prediction of MDD in Generation Scotland. This study may improve interpretation of larger genome-wide association studies of MDD and other stress-related illnesses, and the understanding of the etiological mechanisms underpinning stress-sensitivity