Automatic generation control of multigeneration power system

Load frequency Control (LFC) is used for many years as part of Automatic Generation Control (AGC) in power system around the world. In a mixed power system, it is usual to find an area regulated by hydro generation interconnected to another area regulated by thermal generation or in combination of both. In the following study, performance of AGC for Thermal, Hydro and Thermal turbine based power system is examined, including how frequency bias setting influences AGC responseand inadvertent interchange. Control performance analysis of three area interconnected systems is simulated and studied through Matlab Simulink software. Integral square error and Integral time absolute error has been used as performance criterion. It is shown that integral timeabsolute error (ITAE) as performance index leads to faster optimization of controller gain

Deep Brain Stimulation (DBS) Applications

The issue is dedicated to applications of Deep Brain Stimulation and, in this issue, we would like to highlight the new developments that are taking place in the field. These include the application of new technology to existing indications, as well as ‘new’ indications. We would also like to highlight the most recent clinical evidence from international multicentre trials. The issue will include articles relating to movement disorders, pain, psychiatric indications, as well as emerging indications that are not yet accompanied by clinical evidence. We look forward to your expert contribution to this exciting issue

Electronic structure of porphyrin-based metal– organic frameworks and their suitability for solar fuel production photocatalysis

Metal–organic frameworks (MOFs) can be exceptionally good catalytic materials thanks to the presence of active metal centres and a porous structure that is advantageous for molecular adsorption and confinement. We present here a first-principles investigation of the electronic structure of a family of MOFs based on porphyrins connected through phenyl-carboxyl ligands and AlOH species, in order to assess their suitability for the photocatalysis of fuel production reactions using sunlight. We consider structures with protonated porphyrins and those with the protons exchanged with late 3d metal cations (Fe2+, Co2+, Ni2+, Cu2+, Zn2+), a process that we find to be thermodynamically favorable from aqueous solution for all these metals. Our band structure calculations, based on an accurate screened hybrid functional, reveal that the bandgaps are in a favorable range (2.0 to 2.6 eV) for efficient adsorption of solar light. Furthermore, by approximating the vacuum level to the pore centre potential, we provide the alignment of the MOFs' band edges with the redox potentials for water splitting and carbon dioxide reduction, and show that the structures studied here have band edges positions suitable for these reactions at neutral pH.Royal Society for an International Exchange Scheme grantVia our membership of the UK's HPC Materials Chemistry Consortium, which is funded by EPSRC (EP/L000202), this work made use of the facilities of ARCHER, the UK's national high-performance computing services, which are funded by the Office of Science and Technology through EPSRC's High End Computing ProgrammeEuropean Research Council through an ERC Starting Grant (ERC2011-StG-279520-RASPA)MINECO (CTQ2013-48396-P)Andalucía Region (FQM-1851)University of Granad

Electronic structure simulations of energy materials: chalcogenides for thermoelectrics and metal-organic frameworks for photocatalysis

A theoretical investigation of the electronic structure of chalcogenides for thermoelectric applications and metal organic frameworks (MOFs) for photocatalytic applications is presented in this thesis. The development of chalcogenide materials for thermoelectric applications presents an opportunity to move away from tellurium based materials, which are not cost-effective. Their mainstream realization is dependent on an increase in their efficiency. A combination of density functional theory and Boltzmann transport theory are used to investigate the electronic and phonon transport properties of chalcogenide materials. In the shandite family, the transport properties of Ni3Sn2S2 provide a useful rationalization of their behaviour. In Co3Sn2S2 indium substitutes tin preferentially at the interlayer sites, and leads to a compositionally induced metal-tosemiconductor-to-metal transition which is critical to its thermoelectric properties. Cu2ZnSnSe4 is the most promising of the quaternary chalcogenides and is investigated for thermoelectric applications. It is a p-type semiconductor and a combined theoretical and experimental analysis shows how its ZT can be optimized through doping. In the second part of this thesis, two classes of MOFs are investigated for their photocatalytic properties, porphyrin based MOFs (PMOFs) and zeolitic imidazolate frameworks (ZIFs). In both materials, DFT calculations are used to obtain the electronic band structure, which is then aligned with a vacuum reference. In these MOFs, as in chalcogenides, chemical substitution can be used to engineer the band structure for their optimal properties. In PMOFs metal substitution at the octahedral metal centre is able tune the band edge positions. Optimal properties were found by partial substitution of Al by Fe at the octahedral sites, while keeping Zn at the porphyrin centres. In ZIFs the band edge positions are mainly determined by the molecular linker and intrinsic photocatalytic activity can be achieved by mixing different linkers

Issues and mitigations of wind energy penetrated network: Australian network case study

Longest geographically connected Australian power system is undergoing an unprecedented transition, under the effect of increased integration of renewable energy systems. This change in generation mix has implications for the whole interconnected system designs, its operational strategies and the regulatory framework. Frequency control policies about real-time balancing of demand and supply is one of the prominent and priority operational challenge requiring urgent attention. This paper reviews the Australian electricity market structure in presence of wind energy and its governance. Various issues related to increased wind generation systems integration are discussed in detail. Currently applied mitigations along with prospective mitigation methods requiring new or improved policies are also discussed. It is concluded that developing prospective frequency regulation ancillary services market desires further encouraging policies from governing authority to keep pace with current grid transition and maintain its security

Comportement hydromécanique des remblais miniers en pâte cimentés et des chantiers miniers remblayés

Avec la forte demande en métaux dans les pays émergents à travers le monde, la production minière a atteint un régime soutenu. De ce fait, l’industrie minière contribue énormément au PIB de nombreux pays miniers. Mais en même temps, l’exploitation de plus en plus intense des gisements génère également des rejets solides (résidus et roches stériles) qui sont entreposés en surface dans des aires d’accumulation. Cependant, les aires d’accumulation des résidus, aussi appelés parcs à résidus, nécessitent un suivi et une gestion particulière pendant de très longues périodes afin d’éviter tout drainage minier acide (DMA), résultat de l’oxydation des sulfures de fer et les minéraux métalliques contenus dans les résidus. Dans le cas d’une exploitation souterraine, une partie des résidus est parfois renvoyée sous terre sous forme de remblai en pâte cimenté (RPC). Le RPC est constitué de résidus, d’eau de mélange et d’un agent liant. Le RPC est ainsi destiné à augmenter la stabilité des épontes des excavations minières permettant d’optimiser l’exploitation des gisements sous terre (taux d’extraction élevé) et aussi d’améliorer la sécurité des travailleurs et de réduire l’empreinte écologique de la mine. Cependant, le coût de l’agent liant représente en moyenne entre 12% et 16% des coûts d’opération d’une mine utilisant le RPC (Belem et Benzaazoua, 2008). D’où une quête incessante d’optimiser les coûts des opérations de remblayage tout en atteignant les cibles de résistance visée. Un des aspects importants est le comportement du RPC une fois sous terre. La distribution des contraintes dans le chantier remblayé est un phénomène qui requiert encore une investigation dans le but d’éclaircir certains principes. D’autant plus, les pressions exercées par le remblai sur les barricades construites pour retenir ce dernier dans les chantiers, ont un comportement différent qui influence sa construction. L’analyse de l’impact de la cure sur les chantiers est un élément essentiel dans la séquence de minage. Il sera aussi question de déterminer les différences au niveau des différents paramètres entre un chantier remblayé et un modèle physique au laboratoire. C’est dans ce but que nous avons porté notre esprit critique. Il s’agira aussi de comparer les contraintes dans les chantiers remblayés avec différents types de liants, différentes séquences de remblayage. Pour ce faire, des essais de cisaillement ont été réalisés afin de déterminer les caractéristiques du remblai et ensuite une estimation des contraintes selon les différentes situations

Comportement hydromécanique des remblais miniers en pâte cimentés et des chantiers miniers remblayés

Résumé Avec la forte demande en métaux dans les pays émergents à travers le monde, la production minière a atteint un régime soutenu. De ce fait, l’industrie minière contribue énormément au PIB de nombreux pays miniers. Mais dans le même temps, l’exploitation de plus en plus intense des gisements génère également des rejets solides (résidus et roches stériles) qui sont entreposés en surface dans des aires d’accumulation. Cependant, les aires d’accumulation des résidus, aussi appelés parcs à résidus, nécessitent un suivi et une gestion particulière pendant de très longues périodes afin d’éviter tout drainage minier acide (DMA), résultat de l’oxydation des sulfures de fer et les minéraux métalliques contenus dans les résidus. Dans le cas d’une exploitation souterraine, une partie des résidus est renvoyée sous terre sous forme de remblai en pâte cimenté (RPC). Le RPC est constitué de résidus, d’eau de mélange et d’un agent liant. Le RPC est ainsi destiné à augmenter la stabilité des épontes des excavations minières permettant d’optimiser l’exploitation des gisements sous terre (taux d’extraction élevé) et aussi d’améliorer la sécurité des travailleurs et de réduire l’empreinte écologique de la mine. Cependant, le coût de l’agent liant représente en moyenne entre 12% et 16% des coûts d’opération d’une mine utilisant le RPC. D’où une quête incessante d’optimiser les coûts des opérations de remblayage tout en atteignant les cibles de résistance visée. Un des aspects importants est le comportement du RPC une fois sous terre. La distribution des contraintes dans le chantier remblayé est un phénomène qui requiert encore une investigation dans le but d’éclaircir certains principes. D’autant plus, les pressions exercées par le remblai sur les barricades construites pour retenir ce dernier dans les chantiers, ont un comportement différent qui influence sa construction. L’analyse de l’impact de la cure sur les chantiers est un élément essentiel dans la séquence de minage. Il sera aussi question de déterminer les différences au niveau des différents paramètres entre un chantier remblayé et un modèle physique au laboratoire. C’est dans ce but que nous avons porté notre esprit critique. Il s’agira aussi de comparer les contraintes dans les chantiers remblayés avec différents types de liants, différentes séquences de remblayage. Pour ce faire, des essais de cisaillement ont été réalisés afin de déterminer les caractéristiques du remblai et ensuite une estimation des contraintes selon les différentes situations. ---------- ABSTRACT The growth of the mining economy generates significant revenue for many companies. The exploitation also generates an increase amount of tailings that are stored at the surface. Tailings accumulation areas, also known as tailings ponds, require special monitoring and management for very long periods of time to avoid acid mine drainage (AMD), the result of the association between iron sulphides and metallic minerals. In order to reduce the amount of these tailings, they are returned underground in the form of cemented paste backfill (CPB). The cemented paste backfill, while reducing the amount of tailings, increases the stability of the structures and walls to optimize the operation of underground construction sites by increasing the reserves and also improving the safety of the workers. However, the CPB consisting of tailings, water and cement has a high financial cost of operation to the point of reaching ¼ of the overall financial costs of the mine. A regular quest of optimization, while meeting the targets for underground mining, has been the main focus of many researches with encouraging results at the end. One of the important points is the behavior of this CPB once underground. The distribution of stresses inside the stopes is a phenomenon that requires more investigation to clarify some of the principles already defined in the literature. Especially, the pressure the CPB exerts on the fences built to keep him in the stope have different behaviour toward it and it factors in the building of the fence. Even less the impact of the cure time is an important detail in the mining plan of the secondary stopes. The differences in the parameters of a real stope and one that has been filled in the laboratory with reduce size will be a main topic. These are where we will carry out critical spirit. It will also be a matter of comparing the stress in the backfilled stopes with different types of binders, different backfilling sequences in order to perform shear tests to determine the characteristics of the CPB and then an estimation of the stress according to different situations

Electron and phonon transport in shandite-structured Ni3Sn2S2

The shandite family of solids, with hexagonal structure and composition A3M 2X 2 (A = Ni, Co, Rh, Pd, M = Pb, In, Sn, Tl, X = S, Se), has attracted recent research attention due to promising applications as thermoelectric materials. Herein we discuss the electron and phonon transport properties of shandite-structured Ni3Sn2S2, based on a combination of density functional theory (DFT), Boltzmann transport theory, and experimental measurements. Ni3Sn2S2 exhibits a metallic and non-magnetic groundstate with Ni0 oxidation state and very low charge on Sn and S atoms. Seebeck coefficients obtained from theoretical calculations are in excellent agreement with those measured experimentally between 100 and 600 K. From the calculation of the ratio σ/τ between the electronic conductivity and relaxation time, and the experimental determination of electron conductivity, we extract the variation of the scattering rate (1/τ ) with temperature between 300 and 600 K, which turns out to be almost linear, thus implying that the dominant electron scattering mechanism in this temperature range is via phonons. The electronic thermal conductivity, which deviates only slightly from the Wiedemann-Franz law, provides the main contribution to thermal transport. The small lattice contribution to the thermal conductivity is calculated from the phonon structure and third-order force constants, and is only ∼2 Wm−1K −1 at 300 K (less than 10% of the total thermal conductivity), which is confirmed by experimental measurements. Overall, Ni3Sn2S2 is a poor thermoelectric material (ZT ∼ 0.01 at 300 K), principally due to the low absolute value of the Seebeck coefficient. However, the understanding of its transport properties will be useful for the rationalization of the thermoelectric behavior of other, more promising members of the shandite family

Electron and phonon interactions and transport in the ultrahigh-temperature ceramic ZrC

We have simulated the ultrahigh-temperature ceramic zirconium carbide (ZrC) in order to predict electron and phonon scattering properties, including lifetimes and transport. Our predictions of heat and charge conductivity, which extend to 3000 K, are relevant to extreme-temperature applications of ZrC. Mechanisms are identified on a first-principles basis that considerably enhance or suppress heat transport at high temperature, including strain, anharmonic phonon renormalization, and four-phonon scattering. The extent to which boundary confinement and isotope scattering effects lower thermal conductivity is predicted