Harmonic analysis of a single-phase rectifier with a DC filter capacitor

A single-phase diode bridge rectifier with a filter capacitor on the dc side is often employed to convert ac input into a dc voltage. The input current of the rectifier contains harmonic currents which cause undesirable power line effects. Recently, a method using the time domain analysis has been proposed to calculate the harmonic currents of rectifier considering noninfinite capacitance, i.e., non-zero dc side impedance. This method is very accurate, but it requires a long computing time and a complicated algorithm. This paper proposes a new method that makes it possible to easily calculate the harmonic currents taking into account the effects of the ac and dc side impedances of rectifier. The proposed method, which is based on the frequency domain method, can be executed only with the algebraic computation, and its accuracy is quite high. The validity of the proposed method is also demonstrated by comparison with the results of time simulation.     

Small-sample modeling method for nonstationary reactor noise analysis

A method of time-series analysis, applicable to nonstationary data, was developed to be used as a tool for surveillance and diagnosis of nuclear power plants. In this method, the nonstationary data are divided into a set of consecutive blocks and a parametric model, called the autoregressive (AR) model, is estimated for each of the blocks. The model parameters are determined by a least-squares algorithm based on the Householder transformation, which ensures a high numerical stability even when the number of samples used for model determination is small. Time-dependent variations of the statistical properties of the measured noise data are characterized by the blockwise evolution of the noise signatures derived from the AR models. As an empirical evaluation, the method was applied to data generated by simulation, and to data obtained from a BWR also. The advantages of the present method over the conventional AR method in numerical stability, spectral resolution and detectability of anomalies have been demonstrated through the analysis of these sample problems.     

InGaAsP double-channel- planar-buried-heterostructure laser diode (DC-PBH LD) with effective current confinement

A new high-performance 1.3-μm InGaAsP semiconductor laser is described, in which effective current confinement into the active region has been realized. A p-n-p-n current blocking structure is made by liquid-phase epitaxy (LPE) on both sides of the active-stripe mesa which is defined by a pair of channels in the double-heterostructure wafer. The double-channel-planar-buried-heterostructure laser diodes (DC-PBH LD's) exhibit high-laser performances, such as a high differential quantum efficiency of 78-percent maximum, which results in high electrical to optical power conversion efficiency 43 percent, and high light output power of over 50 mW, as a result of the improvement in the current blocking structure. The threshold current temperature sensitivity is found experimentally to be reduced remarkably by increasing the doping concentration in the p-cladding layer. Characteristic temperature as high as 100 K has been obtained. CW operation is possible up to 130°C.     

A review on the renewable energy development in Algeria: Current perspective,energy scenario and sustainability issues

The quality of life and safeness of the present and future generations are strongly intertwined with the availability of energy sources and the sustainability of the energy infrastructure. Energy consumption in developed countries grows at a rate of approximately 1% per year, and that of developing countries, 5% per year (Muneer et al., 2005 [1]). Present reserves of oil and natural gas can only cover consumption at this rate for the next 50 years in the case of oil, and for the next 70 years in the case of natural gas. Therefore, one of the fundamental priorities for a country such as Algeria is to use several renewable energies (RE) sources and environmentally friendly energy conversion technologies. Algeria is endowed with large reserves of energy sources, mainly hydrocarbons and a considerable potential for the utilisation of RE sources especially with respect to solar energy. Algeria has the potential to be one of the major contributors in solar energy and become a role model to other countries in the world. RE are now one of the major elements of Algeria's energy policy and in view of boosting the national effort in terms of RE beyond 2011, Algeria has developed a national programme for the period 2011–2030 to promote concrete actions in the fields of energy efficiency and RE in line with the approach adopted by the government on February 3, 2011. Besides, it confirms Algerian's ambition to become an international hub for industrial and energy production and exportation in the solar sector. With this in mind, along with the environmental responsibility issues, public awareness gradually increased over the last seven years and alternative energy resources have become a new area of interest. As a tangible target, the Ministry of Energy and Mines (MEM) strategic plan aims to reach a 40% share of RE (mainly solar) in electric energy production by 2030. The various future projects are all factors that will undoubtedly give Algeria an important role in the implementation of RE technology in North Africa, the capacity for providing sustainable supply of cost-effective electricity from RE sources for the needs of the population, and the possibility of even exporting 10,000 MW to neighbouring and European market. This paper provides a detailed analysis of the existing renewable energy sector and a forecast for demand growth, additional capacity, investment requirements and Algeria's ambitious objectives of use of RE and environment protection. The paper also discusses the current energy scenario and explores the alternative energy like solar and wind to ensure energy security supply, reliability, greater efficiency in energy conversion, transmission and utilisation. Particular attention is paid to Algeria's global and sustainable solutions of the environmental challenges and the problems of conservation of fossil energy resources under the clean development mechanism (CDM) structure. The report also provides a detailed analysis of the existing renewable energy sector and a forecast for demand growth, additional capacity, and investment requirements     

Laminar film condensation driven latent thermal energy storage in rectangular containers

This paper focuses on numerically analyzing the thermal transport phenomena in the transient conjugate problem of melting and laminar film condensation. The key focus is to identify an optimum container aspect ratio/shape and conditions for which the heat storage time and the storage capacity are minimum and maximum respectively. Since most solid–liquid phase change materials (PCMs) suffer from poor thermal conductivities, the major resistance to heat transfer comes from PCM. Hence, high thermal conductivity, low-cost metal foam is suggested for use along with PCM to minimize this resistance. The conjugate transient problem of film condensation driven solid–liquid phase change of PCM impregnated inside porous metal foam is numerically analyzed. An effective heat capacity formulation is employed for modeling the transient PCM phase change in porous foam and is solved using finite element method. It is coupled with laminar film condensation on the outside of the storage container. The model is then used for selecting the best aspect ratio for thermal energy storage (TES) containers that enables to store comparatively the maximum heat. The results of the developed model showed that the major resistance to heat transfer and hence efficient thermal energy storage depends strongly on the aspect ratio of the PCM storage containers.     

High-power single-longitudinal-mode operation of 1.3 ?m DFB-DC-PBH LD

CW light output power as high as 38 mW at room temperature and with a CW operable temperature as high as 80°C, both under single-longitudinal-mode operation, has been achieved for the first time in newly developed 1.3 ?m distributed-feedback (DFB) laser diodes with a double-channel planar buried heterostructure (DC-PBH).     

AC side harmonic and phenomena accompanying DC-injection of utility-interactive PV system

The experiments investigated phenomena related to direct contact between the DC output of a PV array and the AC power from the utility grid. The results show that the DC power flows through the distribution transformers (DC-injection) saturating their magnetic circuits. The saturation of magnetic circuits makes peak currents, incorporating a large portion of even harmonics, flow through the high-voltage side of the distribution transformer, adding the level of harmonic distortion of its exciting current. With the increase of injecting DC-current to the utility grid, peak currents at the primary side of distribution transformer increases the most, and even among the same effective (rms) values, the increase of primary side current is larger than that of the secondary side current.     

1.5 mu m band travelling-wave semiconductor optical amplifiers with window facet structure

1.5 mu m band travelling-wave semiconductor optical amplifiers (TWAs), characterised by their window facet structure and symmetrised active waveguide, have been developed. 1.5 dB spectral gain ripple and 1.3 dB TE-TM mode gain difference at 22 dB signal gain were achieved simultaneously. An average facet reflectivity as low as 0.06% was estimated.<>     

Fluid flow and heat transfer of opposing mixed convection adjacent to downward‐facing,inclined heated plates

Experimental investigations were carried out for opposing mixed convective flows of air adjacent to downward‐facing, inclined heated plates. The experiments covered the ranges of the Reynolds and modified Rayleigh numbers from Re_L=400 to 4600 and Ra_L^*=1.0×10⁷ to 5.4×10⁸, and the inclination angles from θ=15 to 75^° from horizontal. The flow fields over the plates were visualized with smoke. The results showed that a separation of forced boundary layer flow occurs first at the bottom edge of the plate, and then the separation point shifts toward upstream with increasing wall heat flux, and finally, reaches the top edge of the plates. It was found that the separations at the bottom and top edges are predicted with a non‐dimensional parameter (Gr_Lθ^*/Re_L^2.5)=0.35 and 1.0, respectively. The local heat transfer coefficients of the inclined plates were also measured and the results showed that the minimum coefficients appear in the separation region. Moreover, it was revealed that forced, natural, and combined convective flows can be classified by the non‐dimensional parameter (Gr_Lθ^*/Re_L^2.5). © 2008 Wiley Periodicals, Inc. Heat Trans Asian Res; Pub‐ lished online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20233