Optimal active OPF with FACTS devices by an innovativeload-equivalent approach

In this letter, a load-equivalent model suitable for FACTS devices is proposed for use in optimal active power flow computations. Specified power value or voltage-dependent loads can represent a FACTS device. The power flow of the power system including FACTS devices can be solved with slight modification of the conventional power flow program to include the effects of the introduced equivalent loads     

A new approach for design of organic electrochromic devices with inter-digitated electrode structure

We present a new approach for design of organic electrochromic devices (ECD) with inter-digitated electrode (IDE) structure and three-electrode dynamic operation. The advantages of the IDE design include the ability to produce fast and homogenous color change over large areas. In addition, it enables fabrication of multi-color devices. Our method involves photolithographic etching of ITO followed by electrophoretic deposition (EPD) and mechanical compression of porous titania to produce finely patterned electrodes with high surface area. The titania layer is chemically modified by new stable and reversible electrochromic viologen derivatives involving phenylphosphonic acid anchoring moiety. The new device demonstrates reversible and strong color change from colorless to deep blue and yellow.     

A new hybrid approach for nonconvex economic dispatch problem with valve-point effect

In literature, economic dispatch problems are generally categorized as convex and nonconvex optimization problems. In this study, a solution is proposed for economic dispatch problem with valve point effect, which is one of the nonconvex optimization problems. For this reason the hybrid approach used for solution of this problem is formed as a combination of modified subgradient (MSG) and harmony search (HS) algorithms. This approach (MSG-HS) is applied in three different lossy test systems (Three machines 6-bus, IEEE 5-machines 14-bus, IEEE 6-machines 30-bus systems) solved with different methods in the literature. System losses are calculated by using B loss matrix. The resulting optimal solution values are compared with the solution values in the literature and the results are discussed.     

Energy storage devices for future hybrid electric vehicles

Powertrain hybridization as well as electrical energy management are imposing new requirements on electrical storage systems in vehicles. This paper characterizes the associated vehicle attributes and, in particular, the various levels of hybrids. New requirements for the electrical storage system are derived, including: shallow-cycle life, high dynamic charge acceptance particularly for regenerative braking and robust service life in sustained partial-state-of-charge usage. Lead/acid, either with liquid or absorptive glass-fibre mat electrolyte, is expected to remain the predominant battery technology for 14 V systems, including micro-hybrids, and with a cost-effective battery monitoring system for demanding applications. Advanced AGM batteries may be considered for mild or even medium hybrids once they have proven robustness under real-world conditions, particularly with respect to cycle life at partial-states-of-charge and dynamic charge acceptance. For the foreseeable future, NiMH and Li-ion are the dominating current and potential battery technologies for higher-functionality HEVs. Li-ion, currently at development and demonstration stages, offers attractive opportunities for improvements in performance and cost. Supercapacitors may be considered for pulse power applications. Aside from cell technologies, attention to the issue of system integration of the battery into the powertrain and vehicle is growing. Opportunities and challenges for potential “battery pack” system suppliers are discussed.     

A genetic evolving ant direction DE for OPF with non-smooth cost functions and statistical analysis

This paper proposes an evolving ant direction differential evolution (EADDE) algorithm for solving the optimal power flow problem with non-smooth and non-convex generator fuel cost characteristics. The EADDE employs ant colony search to find a suitable mutation operator for differential evolution (DE) whereas the ant colony parameters are evolved using genetic algorithm approach. The Newton–Raphson method solves the power flow problem. The feasibility of the proposed approach was tested on IEEE 30-bus system with three different cost characteristics. Several cases were investigated to test and validate the robustness of the proposed method in finding the optimal solution. Simulation results demonstrate that the EADDE provides superior results compared to a classical DE and other methods recently reported in the literature. An innovative statistical analysis based on central tendency measures and dispersion measures was carried out on the bus voltage profiles and voltage stability indices.     

A new approach in tracking maximum power under partially shaded conditions with consideration of converter losses

The fact that photovoltaic panels are very sensitive to non-uniform insolation conditions, which can occur several times a day, causes a decrease of efficiency and so increases time for return on investment. This work presents a maximum power point tracking algorithm (MPPT) operating on the load characteristic in order to take the converters losses into account. In addition, the proposed MPPT deals with the problems of shadowing for which the power-load characteristic can present two or more local maximums close to each other. Considering the converters losses it can be shown that the maximum output power of the photovoltaic panels does not necessarily coincide with the maximum output power of the converters. The proposed MPPT algorithm tracks the maximum power with the intention of reducing the total losses including those of converters. Its performance is verified by simulation and confirmed by experimental results.     

A corrected hybrid approach for wind speed prediction in Hexi Corridor of China

Wind energy has been well recognized as a renewable resource in electricity generation, which is environmentally friendly, socially beneficial and economically competitive. For proper and efficient evaluation of wind energy, a hybrid Seasonal Auto-Regression Integrated Moving Average and Least Square Support Vector Machine (SARIMA-LSSVM) model is significantly developed to predict the mean monthly wind speed in Hexi Corridor. The design concept of combining the Seasonal Auto-Regression Integrated Moving Average (SARIMA) method with the Least Square Support Vector Machine (LSSVM) algorithm shows more powerful forecasting capacity for monthly wind speed prediction at wind parks, when compared with the single Auto-Regression Integrated Moving Average (ARIMA), SARIMA, LSSVM models and the hybrid Auto-Regression Integrated Moving Average and Support Vector Machine (ARIMA-SVM) model. To verify the developed approach, the monthly data from January 2001 to December 2006 in Mazong Mountain and Jiuquan are used for model construction and model testing. The simulation and hypothesis test results show that the developed method is simple and quite efficient.     

Engineering of hybrid interfaces in organic photovoltaic devices

In this study, we engineer and investigate the interface structure and chemistry at the indium tin oxide (ITO) anode (front-side electrode) as well as at the Mg−Ag cathode (back-side electrode) in metal phthalocyanine (MePc)/C₆₀ organic solar cells (OSCs).For the front-side electrode, Zn-phthalocyaninetetraphosphonic acid (Zn-PTPA) and Sn-phthalocyanine axially substituted with tartaric acid (Sn-PTA) have been used for the surface termination of ITO coated glass substrates. Both terminations yielded OSCs with higher fill factors and open circuit voltages, thus increasing the power conversion efficiency by 33% and 67%, respectively. A possible influence of a chemisorbed Zn-PTPA on the film growth of the adjacent ZnPc absorber in the vicinity of the hybrid interface is discussed using X-ray reflectivity and near edge X-ray absorption fine structure data. Distinct effects of the Zn-PTPA and Sn-PTA terminations on the electronic properties of the ITO surface were found by X-ray photoelectron spectroscopy (XPS) measurements at the valence band edge. We demonstrate the possibility to engineer the hybrid interface without additional buffer.For the back-side electrode we report the formation of buffer-free charge carrier selective Mg−Ag cathodes, which are applied for bulk heterojunction organic absorbers consisting of copper phthalocyanine (CuPc) donor and fullerene C₆₀ acceptor materials. The chemical and structural properties of the CuPc:C₆₀/Mg−Ag interface are investigated by element depth profiling using secondary ion mass spectrometry (SIMS), grazing incidence X-ray diffraction analysis (GI-XRD) and XPS.We demonstrate that an optimum charge carrier selectivity is achieved with Mg:Ag/Ag cathode structures, where the Mg:Ag alloy layer has a composition close to that of Ag₃Mg. In addition, Mg diffusion into CuPc:C₆₀ layer is observed. As a result, an interaction between Mg and Cu²⁺ with a concurrent change in oxidation state of both metals takes place. However, no formation of MgPc is observed.The findings of this work are discussed against the background of the performance and electrical properties of the corresponding MePc/C₆₀-based organic solar cells.     

POSS based ionic liquid as an electrolyte for hybrid electrochromic devices

The main objective of this study was to broaden the assortment of I⁻/I₃⁻ redox ionic liquids using polyhedral oligomeric silsesquioxanes (POSS) acting as nanobuilding blocks for the construction of functionalized 1,3-alkylimidazolium iodide solid (melting temperature 150-200 °C) and room temperature (RT) ionic liquids.The structural characteristics of the synthesised final ionic liquids and the corresponding intermediates were determined using ¹H, ²⁹Si NMR and infrared spectroscopic measurements. Raman spectra were next reported, in order to demonstrate the presence of polyiodides formed after the addition of iodine and the formation of redox electrolytes. Ionic conductivity values obtained from the impedance (EIS) spectra were determined in the temperature interval from room temperature up to 100 °C. Finally, a hybrid electrochromic cell was constructed from room temperature MePrIm⁺I_x⁻ IO₇ T₈ POSS (x=1, 1.2, 3 and 5) ionic liquids encapsulated between a lithiated WO₃ working and Pt counter-electrode, and colouring-bleaching changes assessed for cells cycled up to 1000 repetitive cycles.     

Determination of loss coefficients for high-temperature flow devices: An entropy-based approach

Thermodynamic analysis of a high-temperature confined turbulent gas-jet is presented in this paper. The numerical model is two dimensional, steady, and includes the effect of gravity in the governing equations. Computations are carried out with a commercial CFD code and the local exergy losses are determined as post processed quantities. The analysis takes into account the second law effects of viscous dissipation, heat conduction and convection, and radiative heat transfer. The study is extended by conducting a parametric investigation to determine the effects of Reynolds number, inlet fluid temperature, optical thickness, and Planck number on the exergy loss coefficient, which is defined as the total exergy destroyed per unit mechanical energy input. The results show that exergy loss trough radiation entropy production is higher than that due to heat conduction and convection when the inlet gas temperature is high. It has also been found that in contrast to the conventional head loss coefficient, the exergy loss coefficient increases with inlet gas temperature, optical thickness, and Planck number.     

Solid hybrid polyelectrolyte with high performance in electrochromic devices: Electrochemical stability and optical study

This paper presents a high-stability, single-phase hybrid polyelectrolyte (SPHP) applied in a large EC device (5×10 cm²) using WO₃ (electrochromic) and CeO₂–TiO₂ (counter-electrode–ion storage) electrodes, both produced by Leibniz—Institut of New Materials (Leibniz—INM, Germany). The electrochromic device exhibited excellent color and bleach reversibility, high coloration efficiency (>35 cm²/C) from the first cycle up to more than 60,000 CA cycles, and a maximum constant rate of deintercalation/intercalation (O_out/Q_in=1). Its remarkable behavior and high stability render this material an excellent candidate for application in electrochromic devices.     

A consideration of possible receiver designs for solar tower plants

The 500-kW Solar Tower Plant in Almeria, Spain, will be provided with a sodium primary circuit. In the present paper detailed information is given on the basic investigations and on the design of the solar receiver of this circuit. Considerations concerning the optimum geometry as well as thermodynamic behaviour are described. Different design possibilities and the respective behaviour of the receiver with respect to short term transients due to cloud passage, heliostat field or mass flow failure, as well as with respect to optimum operational conditions are discussed. Special stress is placed upon a comparison between receivers with or without a large thermal mass.     

A novel staggered hybrid SSF approach for efficient conversion of cellulose/hemicellulosic fractions of corncob into ethanol

The following study reports bioconversion of corncob into ethanol using hybrid approach for co-utilization of dilute acid hydrolysate (pentose rich stream) and hexose rich stream obtained by enzymatic saccharification employing commercial cellulase Cellic CTec2 as well as in-house cellulase preparations derived from Malbranchea cinnamomea, Scytalidium thermophilium and a recombinant Aspergillus strain. Acid hydrolysis (1% H₂SO₄) of corncob at 1:15 solid liquid ratio led to removal of 80.5% of hemicellulosic fraction. The solid glucan rich fraction (63.5% glucan, 8.3% pentosans and 27.9% lignin) was hydrolysed at 10% substrate loading rate with different enzymes for 72 h at 50 °C resulting in release of 732 and 535 (mg/g substrate) total sugars by Cellic CTec2 and M. cinnamomea derived enzymes, respectively. The fermentation of enzyme hydrolysate with co-culture of Saccharomyces cerevisiae and Pichia stipitis added in sequential manner resulted in 3.42 and 2.50% (v/v) ethanol in hydrolysate obtained from commercial Cellic CTec2 and M. cinnamomea, respectively. Employing a hybrid approach, where dilute acid hydrolysate stream was added to solid residue along with enzyme Cellic CTec2 during staggered simultaneous saccharification and fermentation at substrate loading rate of 15% resulted in 252 g ethanol/kg corncob.     

A novel approach for the modeling of advanced photovoltaic devices using the SILVACO/ATLAS virtual wafer fabrication tools

In this paper a new method for developing a realistic model of any type of solar cell is presented. Taking into account the high cost of research and experimentation involved with the development of advanced cells, we present here this novel methodology. In our opinion, the introduction of this modeling technique to the photovoltaic community will prove to be of great importance in aiding in the design and development of advanced solar cells. Two models of a single GaAs and an InGaP/GaAs/Ge multi-junction solar cell are prepared and are fully simulated. The major stages of the process are explained and the simulation results are compared to published experimental data to demonstrate the accurate results produced by the model utilizing this technique. The flexibility of the proposed methodology is illustrated and example results are shown throughout the whole process, demonstrating some of the different parameters effects on the model performance.     

A hybrid approach to the estimation of undiscovered oil resources in the United States

This paper deals with the problem of estimating cumulative reserves and cumulative production of crude oil in the United States. We first demonstrate that these cumulative values depend on technological change and the price of crude oil. The results suggest that approx. 205 billion barrels of oil are ultimately recoverable and producible at a price of $29 per barrel. Of this total, 114 billion barrels have been produced through the end of 1977.     

A hybrid method of LMDI,symmetrical components,and SFA to estimate the distribution of energy-saving potential with consideration of unbalanced components in decomposition analysis

This paper proposes a hybrid method of logarithmic mean divisia index (LMDI), symmetrical components (SC), and stochastic frontier analysis (SFA) to estimate the distribution of energy-saving potential in industrial sectors, while taking into consideration unbalanced components in decomposition analysis. The proposed method uses LMDI to decompose actual energy consumption into activity, structural, and intensity factors, which serve as inputs to SC. In general the results of the decomposition analysis contain some degree of imbalance. The imbalance between these factors may affect economic development of industrial sectors. Since LMDI cannot be used for analyzing the unbalance, SC is used to analyze this. According to this technique, any set of three unbalanced factors could be expressed as the sum of three symmetrical sets of balanced factors. In this research, activity, structural, and intensity factors are selected as unbalanced components. Also, the mean energy consumption is estimated using SC. In this study, SFA is used to measure the technical efficiency of energy conversion in industrial sectors. Therefore, a feasible stochastic frontier production function, which requires only the actual consumption as input and the estimated mean consumption (output from SC) as output, is estimated. Finally, potential savings in these sectors are calculated as technical efficiency. The proposed method is validated by its application to estimate the distribution of energy-saving potential of the selected group of Canadian industrial sectors. The outcome of this study will assist policymakers in reducing industrial energy consumption.     

A staggered grid arrangement for solving incompressible flows with hybrid unstructured meshes

This work presents an alternative to the discretization of the Navier–Stokes equations using a finite volume method for hybrid unstructured grids with a staggered grid arrangement of variables. It has developed a numerical scheme, analogous to the element-based finite volume method, for the solution of 2-D incompressible fluid flow problems using several coupling strategies. All velocity components are stored at each face of the elements (pressure control volumes), following the usual procedure of staggering velocity and pressure. With this staggered arrangement, the balance of mass and momentum is satisfied, simultaneously, for the same set of variables, rendering numerical stability when compared to the nonstaggered arrangement.     

A review of standards for hybrid CPV-thermal systems

A comprehensive review on standards for actively-cooled CPV and CPV-T systems is presented. Since these systems lack specific standardisation, this review concludes that the current standards, including the photovoltaic IEEE 1513 and IEC 62108, and the solar thermal EN-12975-2:2006 and ISO 9806-2:1995, are insufficient for qualifying these types of actively-cooled concentrator systems. Additional test specifications for adapting the IEC 62108 and EN-12975-2:2006 standards for actively-cooled CPV and CPV-T systems have been proposed.