Energy Engineering

"Singular spectrum analysis (SSA) is a technique that decomposes a time series into a
set of components, such as, trend, harmonics, and residuals. Leaving out the residual components
and adding up the others, the time series can be smoothed. This procedure has been used to model
Brazilian electricity consumption and flow series. The PAR(p), periodic autoregressive models, has been
broadly used in modelling energy series in Brazil. This paper presents an approach of this decomposition
method, by fitting the PAR(p), considering its multivariate version known as multivariate SSA (MSSA).
The method was applied to a vector of two wind speed series recorded at two locations in the Brazilian
Northeast region. The obtained results, when compared to the univariate decomposition of each series,
were far superior, showing that the spatial correlation between the two series were considered by MSSA
decomposition stage."

"Neste trabalho é descrita uma metodologia para previsão do consumo de energia elétrica da
classe residencial, na qual são consideradas diversas estatísticas produzidas pelo IBGE, em
especial, nas PNADs, nos Censos demográficos e nas projeções demográficas."

This paper is intended to present a plan for installing a network of electric vehicle charging stations in the city of Rio de Janeiro. It is important to underline the fact that this text results from a research and development project called Planning and Analysis Methodology for the Implementation of Electric Vehicles in Transport Activities in the realm of the Brazilian electric energy regulatory agency, ANEEL, carried out by the distribution power company Light S.E.S.A. in partnership with the Vehicle Propulsion Systems and Electrochemical Sources Laboratory of the Rio de Janeiro State University – UERJ.

The Periodic Autoregressive Model Family Box & Jenkins - PAR(p) has been employed in the prediction of Affluent Natural Energy (ENA), an important variable in the energetic operation planning of hydroelectric systems. In order to increase the accuracy of the ENA’s predictions obtained by the PAR(p) model, we propose the application of Multi-Channel Singular Spectrum Analysis - MSSA in the simultaneous filtering of the ENA series of the four subsystems that comprise the National Interconnected System. The PAR(p) models are adjusted to the filtered time series and the resulting predictions are compared with those obtained by models PAR(p) adjusted to the original time series. The results presented in the paper show the effectiveness of filtering in improving the accuracy of ENA’s predictions obtained by the PAR(p) model.

Turkish coal is generally poor quality and the levels of chemical and radiological toxic trace elements in it are higher with respect to mean values of activity concentrations given in United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) Report. The main pathways through which the population living around soal-fired power plant (CFPP) is exposed to natural radionuclides are external and internal (ingestion and inhalation) dose and fly ash particles are the major component of the risk. It is estimated that the people working or living near the CFPP in Turkey receive a dose in between 0.1 mSv to 1 mSv extra from CFPP because nearly all the region of Turkey uranium (U) and thorium (Th) content in the coal are higher than 5 ppm to 7 ppm and around 25 ppm to 40 ppm respectively. Continuous monitoring is essential to determine occupational exposure levels in all stages of the coal fuel-cycle and proper measures should be taken to prevent direct contact of the ash pile with the top soil and local drainage systems.

An induction generator (IG) is preferred to a synchronous generator in many renewable energy applications. In order to achieve proper control of an induction generator it is important to have accurate knowledge of its model parameters. In this paper, an Improved Particle Swarm Optimization (IPSO) approach is used to estimate the model parameters of an IG. The IPSO is executed based on the response of the active and reactive power flows associated with the IG to a change in the frequency of the external system, which the IG is connected to. This change in frequency is applied when the IG is operating in steady state, to represent the scenario where the IG parameters must be estimated on-line, and during a large disturbance to the system equilibrium. This approach is in contrast to others in the literature that estimate the parameters of an induction machine based on its start-up behavior, or the results of mechanical tests. Therefore, this approach should offer benefits when the parameters of the IG being modeled may vary over time and need to be estimated on-line.

The surface atomic structure and chemical state of Pt is consequential in a variety of surface-intensive devices. Herein we present the direct interrelationship between the growth scheme of Pt films, the resulting atomic and electronic structure of Pt species, and the consequent activity for methanol electro-oxidation in Pt/TiO2 nanotube hybrid electrodes. X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) measurements were performed to relate the observed electrocatalytic activity to the oxidation state and the atomic structure of the deposited Pt species. The atomic structure as well as the oxidation state of the deposited Pt was found to depend on the pretreatment of the TiO2 nanotube surfaces with electrodeposited Cu. Pt growth through Cu replacement increases Pt dispersion, and a separation of surface Pt atoms beyond a threshold distance from the TiO2 substrate renders them metallic, rather than cationic. The increased dispersion and the metallic character of Pt results in strongly enhanced electrocatalytic activity toward methanol oxidation. This study points to a general phenomenon whereby the growth scheme and the substrate-to-surface-Pt distance dictates the chemical state of the surface Pt atoms, and thereby, the performance of Pt-based surface-intensive devices.

"The present work deals with the thermodynamic evaluation
of combined cycle with re-heat in gas turbine using the latest
gas turbines namely ABB GT26 gas turbine (advanced) in
which reheat is used and the blade cooling is done by air bled
from compressor. The same turbine is subjected to closed loop
steam cooling. Parametric study has been performed on plant
efficiency and specific work for various independent
parameters such as turbine inlet temperature, compressor
pressure ratio, reheating pressure ratio, reheater inlet
temperature, blade temperature, etc.. It has been observed that
due to higher compressor pressure ratio involved in reheat gas
turbine combined cycle and higher temperature of exhaust, the
plant efficiency and specific work are higher with the advanced
reheat gas/steam combined cycle over the simple combined
cycle. Steam cooling offers better performance over aircooling."

Titanium dioxide nanotubes offer distinct advantages over films of the same material in the production of hydroxyl radicals and subsequent inactivation of Escherichia coli in wastewater. However, their visible light absorption capabilities are limited. Semiconducting nanocrystals of cadmium sulfide have been used to increase the sensitivity of TiO2 nanotubes to visible light. A small applied potential, using CdS-coated TiO2 nanotube arrays, allowed for total inactivation of E. coli in hitherto record short time.

A significant enhancement in the photoconversion efficiency of anodically grown, thermally annealed titania nanotube array photoanodes was observed when subjected to an ethanol vapor treatment that resulted in improved crystallization. Ethanol vapor treatment of 6 mu m long vertically aligned titania nanotube array films initially annealed at 580 degrees C for 6 h in an oxygen environment, under autogeneous pressure at 140 degrees C (approximate to 50 psi), resulted in an increase of up to similar to 30% in the photoconversion efficiency. A significant improvement in the crystallinity as revealed by glancing angle X-ray diffraction (GAXRD) and Raman spectroscopy studies as well as incident photon to current conversion efficiency (IPCE) is observed in the vapor treated samples.

Crystalline TiO2 nanotube arrays are synthesized using a two-step process. The Ti foil sample is first treated with an oxidizing agent-containing electrolyte, either H2O2 or (NH4)(2)S2O8 then anodized at constant voltage in a fluoride-containing electrolyte. The resulting films are directly used for water photoelectrolysis and in dye-sensitized solar cells

A significant enhancement in the photoconversion efficiency of anodically grown titania nanotube array photoanodes is observed when crystallized using an infrared annealing process. This infrared (IR) annealing treatment is performed over relatively short periods, 5-15 min, over the temperature range 300-600 degrees C with the anatase crystallite size increasing with annealing temperature and duration. Used as photoanodes to photoelectrochemically split water, the 15 min, 600 degrees C IR crystallized nanotube arrays show a three-electrode photoconversion efficiency of 13.13% under UV illumination (100 mW/cm(2) 320-400 nm, 1 M KOH). A reduction in the carrier trap states and an increased charge carrier transport due to reduction of the barrier layer thickness are believed responsible for the significant conversion efficiency seen with the IR annealed samples

Self-ordered, highly oriented arrays of titanium−niobium−zirconium mixed oxide nanotube films were fabricated by the anodization of Ti35Nb5Zr alloy in aqueous and formamide electrolytes containing NH4F at room temperature. The nanostructure topology was found to depend on the nature of the electrolyte and the applied voltage. Our results demonstrate the possibility to grow mixed oxide nanotube array films possessing several-micrometer-thick layers by a simple and straightforward electrochemical route. The fabricated Ti−Nb−Zr−O nanotubes showed a 17.5% increase in the photoelectrochemical water oxidation efficiency as compared to that measured for pure TiO2 nanotubes under UV illumination (100 mW/cm2, 320−400 nm, 1 M KOH). This enhancement could be related to a combination of the effect of the thin wall of the fabricated Ti−Nb−Zr−O nanotubes (10 ± 2 nm) and the formation of Zr oxide and Nb oxide layers on the nanotube surface, which seems to slow down the electron−hole recombination in a way similar to that reported for Grtzel solar cells.