Physical Investigations on ZnO:Ni Layers Deposited by Spray Pyrolysis

Nickel-doped ZnO (ZnO:Ni) layers have been deposited on glass substrates by a spray pyrolysis method using zinc acetate and nickel sulphate as precursors. The layers were grown at different substrate temperatures, Ts, that vary in the range 250–350°C. During deposition, the precursor concentration and Ni-doping content were maintained constant at 0.1 M and 10%, respectively. The X-ray diffraction (XRD) analysis showed that all the layers were polycrystalline in nature with the (002) plane as the preferred orientation and exhibited hexagonal wurtzite structure. A sharp increment in the intensity of predominant peak with the substrate temperature was observed consistently that indicated an improvement in the crystallinity of the layers. The Raman studies confirmed the hexagonal wurtzite crystal structure of ZnO and indicated defect states. The X-ray photoelectron spectroscopy (XPS) studies revealed the characteristic peaks of the elements involved in the films and their ionic states. The optical transmittance of the films was higher than 80% and the evaluated energy band gap decreased from 3.17 eV to 3.13 eV with the increase of substrate temperature.

Hydrogen Production Technologies: Current State and Future Developments

Hydrogen (H2) is currently used mainly in the chemical industry for the production of ammonia and methanol. Nevertheless, in the near future, hydrogen is expected to become a significant fuel that will largely contribute to the quality of atmospheric air. Hydrogen as a chemical element (H) is the most widespread one on the earth and as molecular dihydrogen (H2) can be obtained from a number of sources both renewable and nonrenewable by various processes. Hydrogen global production has so far been dominated by fossil fuels, with the most significant contemporary technologies being the steam reforming of hydrocarbons (e.g., natural gas). Pure hydrogen is also produced by electrolysis of water, an energy demanding process. This work reviews the current technologies used for hydrogen (H2) production from both fossil and renewable biomass resources, including reforming (steam, partial oxidation, autothermal, plasma, and aqueous phase) and pyrolysis. In addition, other methods for generating hydrogen (e.g., electrolysis of water) and purification methods, such as desulfurization and water-gas shift reactions are discussed.

Grid Code Requirements for Wind Power Integration in Europe

As the capacity of wind power continues to increase globally, stricter requirements regarding grid connection of wind generators are introduced by system operators. The development of wind turbine technology is inevitably affected by the new grid codes, and wind power plants are expected to support the grid and provide ancillary services much like conventional power plants. The most demanding regulations are found in Europe where wind penetration levels are higher. This paper presents the main aspects of current grid code requirements for the integration of wind power in European countries and suggests performance characteristics in order to satisfy the most demanding requirements. The dynamic behavior of wind turbines with doubly fed induction generators is investigated and a solution for low voltage ride through compliance is presented.

State of Art of Solar Photovoltaic Technology

Solar electricity is more expensive than that produced by traditional sources. But over the past two decades, the cost gap has been closing. Solar photovoltaic (SPV) technology has emerged as a useful power source of applications such as lightning, meeting the electricity needs of villages, hospitals, telecommunications, and houses. The long and increasing dominance of crystalline silicon in photovoltaic (PV) market is perhaps surprising given the wide variety of materials capable of producing the photovoltaic effect. PV based on silicon wafers has captured more than 90% market share because it is more reliable and generally more efficient than competing technologies. The crystalline silicon PV is reliable as far as long term stability in real field but it is not economically viable due to starting material silicon itself costly. But still, research continues on developing a diverse set of alternative photovoltaic technology. Now PV technology is being increasingly recognized as a part of the solution to the growing energy challenge and an essential component of future global energy production. In this paper, we give a brief review about PV technology particularly crystalline silicon PV including the world and Indian PV scenarios.

The Performance of a New Hybrid PLL in an Interconnected Renewable Energy Systems under Fault Ride Through Operation

Modern renewable energy systems (RES) require fault ride through (FRT) operation in order to provide voltage and frequency support to the power grid when faults occur. The grid synchronization of a RES could be ensured by the appropriate operation of a phase-locked loop (PLL). A new hybrid PLL (dαβPLL) has recently been suggested by the authors and could operate accurately and faster than the other existing PLLs. The dαβPLL could be a very useful tool in the FRT operation of a RES, since the faster performance of the new PLL could boost the time performance of the FRT algorithm when a disturbance occurs. This paper investigates the performance of the flexible positive and negative sequence control (FPNSC) when the new dαβPLL is used. The paper also deals with the improvement on the FRT operation of the RES that could be obtained from the outstanding performance of the dαβPLL.

Novel Catalytic Systems for Hydrogen Production via the Water-Gas Shift Reaction

The present work reports on the development of new catalysts for the production of hydrogen via the water-gas shift (WGS) reaction. In particular, the effect of Ce/La atom ratio on the catalytic performance of 0.5 wt% Pt supported on Ce1−xLaxO2−δ (x=0.0,0.2,0.5,0.8,1.0) mixed metal oxides for the WGS reaction was investigated. It was found that the addition of 20 at.% La3+ in CeO2 lattice increased significantly the catalytic activity and stability of 0.5 wt% Pt/Ce0.8La0.2O2−δ solid. More precisely, a lower amount of “carbon” was accumulated on the catalyst surface, whereas surface acidity and basicity studies showed that Ce0.8La0.2O2−δ had the highest concentration of labile oxygen and acid sites, and the lowest concentration of basic sites compared to the other Ce1−xLaxO2−δ mixed metal oxide supports (x=0.2,0.5,0.8).

A Finite Element Approach for the Elastic-Plastic Behavior of a Steel Pipe Used to Transport Natural Gas

A finite element technique, with two-dimensional isoparametric elements, is developed, for the analysis of a steel pipe, with a circular cross-section. The pipe is installed above the ground and is used to transport natural gas at very high pressures. The material of the pipe is assumed to obey a bilinear elastic-plastic model. Double symmetry is considered when setting up the mathematical model problem and creating the finite element mesh. Step increments or decrements on the internal pressure are applied (cyclic loading). Yielding is detected by the Von Mises yield criterion. Also, a flow rule is employed to handle the plastic strain component. A four-point Gauss-Legendre quadrature is used to numerically perform all necessary integrations. Finally, the so-called “shakedown phenomenon” is studied when cyclic loading is applied after the commencement of plastic deformations on the pipe. Numerical results obtained by the method compare favorably with the analytic solution.

Antireflective Nanocomposite Based Coating on Crystalline Silicon Solar Cells for Building-Integrated Photovoltaic Systems

Building-integrated photovoltaic (BIPV) systems represent an interesting, alternative approach for increasing the available area for electricity production and potentially for further reducing the cost of solar electricity. In BIPV systems, the visual impression of a solar module becomes important, including its color. However, the range of solar cell colours and shapes currently on offer to architects and BIPV system designers is still very limited, and this is a barrier to the widespread use of PV modules as a constructional “material.” The color of a solar module is determined by the color of the cells in the module, which is given by the antireflection coating (ARC). However, access to efficient, but differently colored, solar cells is important for the further development of BIPV systems. In this paper, we have used Diamond-like nanocomposite layer as an Antireflective Nanocomposite based (ARNAB) coating material for crystalline silicon solar cell, and the impact of varying the color of an ARC upon the optical characteristics and efficiency of a solar cell is investigated. In addition to a comparison of the optical characteristics of such solar cells, the effect of using colored ARCs on solar cell efficiency is quantified using the solar cell modeling tool PC1D.