Characteristics of high quality ZnO thin films deposited by pulsed laser deposition

This paper show that under optimized deposition condition, films can be grown having a full width at half maximum (FWHM) value of the (002) x-ray diffraction (XRD) line a factor of 4 smaller than the previously published results using PLD and among the best reported so far by any technique. Under optimized conditions, c-axis oriented ZnO films having a FWHM value of the (002) XRD reflection line less than 15°, electrical resistivities around 5 × 10-2 Ω cm and optical transmittance higher than 85% in the visible region of the spectrum were obtained. Refractive index was around 1.98 and the Eg = 3.26 eV, values characteristic of very high quality ZnO thin films

Demonstration of sustained and useful converter responses during balanced and unbalanced faults in microgrids

In large power grids where converter penetration is presently low and the network impedance is predominantly reactive, the required response from converters during faults is presently specified by phrases such as “maximum reactive output”. However, in marine and aero power systems most faults are unbalanced, the network impedance is resistive, and converter penetration may be high. Therefore a balanced reactive fault current response to an unbalanced fault may lead to over-voltages or over/under frequency events. Instead, this paper presents a method of controlling the converter as a balanced voltage source behind a reactance, thereby emulating the fault response of a synchronous generator (SG) as closely as possible. In this mode there is a risk of converter destruction due to overcurrent. A new way of preventing destruction but still providing fault performance as close to a SG as possible is presented. Demonstrations are presented of simulations and laboratory testing at the 10kVA 400V scale, with balanced and unbalanced faults. Currents can be limited to about 1.5pu while still providing appropriate unbalanced fault response within a resistive network

Modelling the impact of micro generation on the electrical distribution system

In the UK and elsewhere there is considerable debate as to the future form of the electricity distribution system. The coming years will see a rise in the amount of micro-generation connected to the network at low voltages and the emergence of highly-distributed power systems (HDPS). However, there is considerable uncertainty as to the impact that this micro-generation will have on the quality of power supplied to our homes or to the stability of the electricity system as a whole. To address these engineering challenges the UK Engineering and Physical Sciences Research Council (EPSRC) is funding a three year research programme featuring a multi-disciplinary team from a variety of UK Universities: Supergen HDPS. This paper documents one piece of work emerging from the consortium, where a multi-tool approach is used to analyse the impact of micro-generation on the electricity system. This used a building simulation tool to produce electrical generation profiles for domestic cogeneration device models. These, along with profiles produced for other micro-generation technology models and electrical load profiles are then replicated and aggregated using a customised statistical approach. The profiles were then used as boundary conditions for a set of electrical load flow simulations on a model of a section of real network, where the number of microgenerators was varied according to different scenarios for the future of the UK electricity grid. The results indicate that a significant number of micro-generation devices can be accommodated before any power quality problems arise, however this is dependent upon maintaining a robust central grid

Growth of ZnO thin films on GaAs by pulsed laser deposition

ZnO thin films have been grown on GaAs substrates using the pulsed laser deposition technique with or without a photodeposited SiO2 buffer layer. The presence of the SiO2 layer has a beneficial effect on the crystalline quality of the grown ZnO films. Highly c-axis oriented ZnO films having a full width at half maximum value of the (002) X-ray diffraction line of less than 0.13 ° have been grown on such buffer layers at a substrate temperature of only 350 °C

Electricity network scenarios for 2020

This report presents a set of scenarios for the development of the electricity supply industry in Great Britain in the years to 2020. These scenarios illustrate the varied sets of background circumstances which may influence the industry over the coming years – including political and regulatory factors, the strength of the economy and the level to which environmentally-driven restrictions and opportunities influence policy and investment decisions. Previous work by the authors (Elders et al, 2006) has resulted in a set of six scenarios illustrating possible developments in the electricity industry in the period up to 2050. While such scenarios are valuable in gauging the long-term direction of the electricity industry and its economic and environmental consequences, shorter-range scenarios are useful in assessing the steps necessary to achieve these long-range destinations, and to determine their relationship to current trends, policies and targets. In this chapter, a set of medium-range scenarios focused on the year 2020 is developed and described. These scenarios are designed to be consistent both with the current state of the electricity supply industry in Great Britain, and with the achievement of the ultimate electricity generation, supply and utilisation infrastructure and patterns described in each of the 2050 scenarios. The consequences of these scenarios in terms of the emissions of carbon dioxide are evaluated and compared with other predictions. The SuperGen 2020 scenarios described in this report were developed as a collaborative effort between the SuperGen project team and the ITI-Energy Networks Project team both based at the University of Strathclyde

The kinematic history of the Khlong Marui and Ranong Faults, southern Thailand

The Khlong Marui Fault (KMF) and Ranong Fault (RF) are major NNE-trending strike-slip faults which dissect peninsular Thailand. They have been assumed to be conjugate to the NW-trending Three Pagodas Fault (TPF) and Mae Ping Fault (MPF) in Northern Thailand, which experienced a diachronous reversal in shear sense during India–Eurasia collision. It follows that the KMF and RF are expected to show the opposite shear sense and a slip sense reversal at a similar time to the TPF and MPF. New field data from the KMF and RF reveal two phases of ductile dextral shear separated by Campanian magmatism. Paleocene to Eocene post-kinematic granites date the end of this phase, while a brittle sinistral phase deforms the granites, and has exhumed the ductile fault rocks. The timing of these movements precludes formation of the faults in response to Himalayan extrusion tectonics. Instead, they formed near the southern margin of a Late Cretaceous–Paleocene orogen, and may have been influenced by variations in the rate of subduction ahead of India and Australia. North-south compression prior to reactivation of the subduction zone around southern Sundaland in the Eocene caused widespread deformation in the overriding plate, including sinistral transpression on the KMF and RF

Superconducting fault current limiter application in a power-dense marine electrical system

Power-dense, low-voltage marine electrical systems have the potential for extremely high fault currents. Superconducting fault current limiters (SFCLs) have been of interest for many years and offer an effective method for reducing fault currents. This is very attractive in a marine vessel in terms of the benefits arising from reductions in switchgear rating (and consequently size, weight and cost) and damage at the point of fault. However, there are a number of issues that must be considered prior to installation of any SFCL device(s), particularly in the context of marine applications. Accordingly, this study analyses several such issues, including: location and resistance sizing of SFCLs; the potential effects of an SFCL on system voltage, power and frequency; and practical application issues such as the potential impact of transients such as transformer inrush. Simulations based upon an actual vessel are used to illustrate discussions and support assertions. It is shown that SFCLs, even with relatively small impedances, are highly effective at reducing prospective fault currents; the impact that higher resistance values has on fault current reduction and maintaining the system voltage for other non-faulted elements of the system is also presented and it is shown that higher resistance values are desirable in many cases. It is demonstrated that the exact nature of the SFCL application will depend significantly on the vessel’s electrical topology, the fault current contribution of each of the generators, and the properties of the SFCL device, such as size, weight, critical current value and recovery time

Spatial and temporal clustering of fault events on the GB transmission network

The UK is subject to changing weather patterns due to the global process of climate change. The full extent of these changes is not currently known; however, it is possible that the UK will be subject to more extreme or more frequent severe weather events (or both). As 50% of the faults on the transmission network in Britain are weather related it is likely that any change in weather patterns for the worse would increase the number of faults the network experiences. This paper describes a review of fault records in one region of the UK in order to understand the potential impact on system operation of clusters of weather related network faults. Based on the patterns of identified clusters, it suggests some potential impacts of climate change

Effects of laser wavelength and fluence on the growth of ZnO thin films by pulsed laser deposition

Transparent, electrically conductive and c-axis oriented ZnO thin films have been grown by the pulsed laser deposition (PLD) technique on silicon and Corning glass substrates employing either a KrF excimer laser (¿ = 248 nm) or a frequency-doubled Nd:YAG laser (¿ = 532 nm). The crystalline structure, surface morphology, optical and electrical properties of the deposited films were found to depend not only on the substrate temperature and oxygen partial pressure, but also on the irradiation conditions. The quality of the ZnO layers grown by the shorter wavelength laser was always better than that of the layers grown by the longer wavelength, under otherwise identical deposition conditions. This behaviour was qualitatively accounted for by the results of the numerical solution of a one-dimensional heat diffusion equation which indicated a strong superheating effect of the melted target material for the case of frequency-doubled Nd:YAG laser irradiations. By optimizing the deposition conditions we have grown, employing the KrF laser, very smooth c-axis oriented ZnO films having a full-width at half-maximum value of the (002) X-ray diffraction value less than 0.16° and optical transmittance around 85% in the visible region of the spectrum at a substrate temperature of only 300°C

Electricity Network Scenarios for Great Britain in 2050

The next fifty years are likely to see great developments in the technologies deployed in electricity systems, with consequent changes in the structure and operation of power networks. This paper, which forms a chapter in the forthcoming book Future Electricity Technologies and Systems, develops and presents six possible future electricity industry scenarios for Great Britain, focussed on the year 2050. The paper draws upon discussions of important technologies presented by expert authors in other chapters of the book to consider the impact of different combinations of key influences on the nature of the power system in 2050. For each scenario there is a discussion of the effects of the key parameters, with a description and pictorial illustration. Summary tables identify the role of the technologies presented in other chapters of the book, and list important figures of interest, such as the capacity and energy production of renewable generation technologies