Journal of Renewable Energy and Environment
Volume:2 Issue: 2, Spring 2015

Encountering series-compensated transmission lines, sub-synchronous resonance (SSR) may strike the power system by jeopardizing its stability and mechanical facilities. This paper aims to verify the capability of static synchronous series compensator (SSSC) in mitigating the mechanical and electrical oscillations such as SSR in wind farm integrations. A wind turbine with a self–excited induction generator (SEIG) represents the wind farm and it is connected to the system through a transmission line compensated by a series capacitor. Both the induction–generator (IG) effect and torsional interaction (TI) on SSR occurrence are examined. Simulations are carried out using EMTDC/ PSCAD on the IEEE first SSR benchmark model along with a SEIG based wind turbine. Also a Fast Fourier Transform (FFT) analysis is performed to determine the dominant torsional mode existing in the turbine generator system. The SSSC impact on SSR mitigation is interrogated in various case studies. A SSSC with a simple power flow control in its base case is first considered. It is shown that the SSSC can damp the SSR even without any specific auxiliary controller. In the following the same SSSC is shown to effectively damp SSR when equipped with an auxiliary SSR damping (SSRD) controller.

Energy, exergy and exergoeconomic (3E) evaluation are performed to assess the performance of a NH3/H2O cycle integrated with parabolic trough solar collectors (PTSC). To provide continuous electricity produced by generator when solar beam radiation is insufficient a stabilizer temperature subsystem is utilized. The major thermodynamic parameters and climate conditions variations are selected to investigate, for their effects on the energy efficiency, exergy efficiency and unit cost of electricity of the overall system. The results reveal that the solar collectors exhibit the worst exergy and exergoeconomic performance, so that when system is only fuelled by solar energy, elevation of solar beam irradiation around 40% reduces the efficiencies and electricity production cost within 23% and 0.4%, respectively. It is found that the increment of ammonia basic concentration, turbine inlet pressure, evaporator inlet temperature and evaporator pinch temperature lead to elevation of energy and exergy efficiencies and decrement of electricity production cost. Then, the single and multi-objective optimizations are performed to maximize the energy and exergy efficiencies and minimize the electricity production cost based on genetic algorithm (GA). Results indicate that the electricity production cost obtained through economic optimization is less than around 2% and 2.2% compared to the optimization based on the first and second laws of thermodynamics. Multi objective optimization causes reduction of electricity production cost around 14% and enhancement the energy and exergy efficiencies 8.5% and 6.7%, respectively too.

In recent years, energy predicament and environmental problems in the world caused by fossil fuels combustion make us to pay serious attention to optimizing energy consumption and using renewable energies. One of the potential renewable energies which can be helpful in electricity generation is harness wind and water energy or using these two kinds of energy simultaneously. In this study, to provide a part of electricity in Azadi complex, 2 wind turbines with 12 different scenarios are used. In addition to provide some parts of the consumed electricity, they provide consumed electricity for water pumps which pump the sport complex lake water to a reservoir with 30000 cubic meters capacity and 20 meters height which provides remainder the consumed electricity. In this model, with regard to the uncertain amount of electricity consumption, 3consumption scenarios with three probabilities are pumped every day into a pool and a few of it is used for electricity consumption and the surplus is sold to the agricultural sector and irrigation of green spaces. The GAMS software and two stage optimization methods in two states, with and without considering the risk for optimization are used and in both states, profit and net profit in each scenario are computed.

Zinc oxide nanorod arrays (ZnO NRs) were grown on the ZnO seed layers via an aqueous solution using hydrothermal method and their photovoltaic properties were investigated. It was found that the growth period of 20 minutes is the optimum condition for ZnO nanorods growth, the cell containing these nanorods was considered as a reference cell. In order to further increase the cell performance, ZnS quantum dots (QDs) were fabricated on the ZnO NRs (reference cell) by SILAR technique with different number of cycles. The effect of the number of SILAR cycle (n) on structural and photovoltaic properties was studied. The optimum number of SILAR cycles for ZnS QDs was obtained (n=4). Experimental results showed that using ZnS QDs as light absorber material is an effective way to improve device performance. Morphology, crystalline structure and optical absorption of layers were analyzed by a scanning electron microscope (SEM), X-ray diffraction (XRD) and UV-Visible absorption spectra, respectively. The maximum power conversion efficiency of 3.59% in the inverted configuration of ITO/ZnO film/ZnO NR(20)/ZnS(n) QDs/P3HT/PCBM/Ag hybrid solar cell was achieved for a device based on ZnS(4) under an illumination of one Sun (AM 1.5G, 100 mW/cm2).

A three-dimensional computational fluid dynamics model of a proton exchange membrane fuel cell (PEMFC) with both gas distribution flow channels and Membrane Electrode Assembly (MEA) is developed. A set of conservation equation is numerically solved by developing a CFD code based on the finite volume technique and SIMPLE algorithm. In this research, some parameters like oxygen consumption, water production, velocity distribution, liquid water activity and the fuel cell performance for conventional cases (base Cases) are presented and compared to those in cases with semicircular prominences. The numerical simulations indicated that prominent gas diffusion layer (GDL) could improve the transport of the species through the porous layers and this leads to increment in fuel cell performance. Hence, prominent gas diffusion layers would result in higher current density. Finally the numerical results for the base Cases were compared with the experimental data, which represented reasonable agreement.

This study shows the design of a new hybrid power generation system, photovoltaic panel (PV)–coupled solid oxide fuel cell (SOFC) and gas turbine (GT)–electrolyser. Three objectives (cost, pollutant emissions, and reliability), which are usually in conflict, are considered simultaneously. The design of a hybrid system, considering the three mentioned objectives, poses a very complex problem of optimization. A multi-objective optimization method (PESA) is considered to obtain the best combinations for the hybrid system. In this work, the effect of panel's angle change and SOFC-GT fuel type are considered too. In order to study the effect of fuel price, this study is done about two fuel prices: Iran fuel price and international fuel price.

In present research work, anion exchange membranes based on quaternized polysulfone with ammonium cation moieties (QAPSF) were prepared by chloromethylation, amination and alkalization. The chloromethylated polysulfone were characterized by 1HNMR spectroscopy and functionalization degree was determined according to peak area integration. Ion transport properties (ionic conductivity, ion exchange capacity, activation energy for ion transport) and water content associated properties (water uptake, swelling ratio, hydrated number) were measured for the prepared anion exchange membranes. The ion exchange capacity for these membranes varied from 0.96 to 1.73 meq/gr while the degree of chloromethylation increased from 82% to 143%. The membrane with IEC value of 1.73 meq/gr showed the highest ionic conductivity in the range of 15.87-34.01 mS/cm at 25-80 °C. The activation energy for ion transport, water uptake and swelling ratio of this membrane were measured to be 11.99 kJ/mol, 37.41% and 14.71%, respectively which demonstrated the reasonable performance of the prepared anion exchange membranes. Based on the obtained results, prepared anion exchange membranes could be proposed as good candidates for solid alkaline fuel cells.