نشریه انرژی ایران
سال سیزدهم شماره 4 (پیاپی 49، زمستان 1389)

Gas distribution networks in some cold regions of Iran face pressure dropand as a result,the gas cut off in winters. most of the time the increasing consumption in winter is stated as the main reason for this problem, while the increasing consumption, which is natural to some extent and also is a designing key parameter of the network, is not the only reason for gas cut off. Non-optimized network is a significant reason for gas pressure drop. In this research the gas distribution network of Babariz village, nearSanandaj city, is optimized by a heuristic algorithm. The results show that of the gas pipelines are over designed creates an additional cost of more than in the execution process of the gas network. Non-optimized gas distribution networks cause extra capital costs and execution expenses. Such networks make troubles in distributing and delivering gas to the consumers during critical periods of consumption.

The purposes of this research are the simulation of a flat solar collector and checking the fluid temperature variation in the shortest and longest days of the year in Tehran city. A complete simulation of flat collector has been performed numerically. The real initial geometric dimensions and boundary condition have been used with pump and without pump in the present research. It was found that during cold days of year the collector would be able to convert the solar energy to the fluid heating satisfactorily.

Flexible Dye-Sensitized Solar Cells (DSSCs) are new generation of photovoltaic solar cells that imitate the naturalphotosynthesis process. DSSCs have been extensively studied in recent years because they provide high-efficient energy conversion, low cost production and environmentally friendly advantages. These cells work by absorbing photons on an inexpensive thin-film composed of dye molecules attached to a titanium oxide layer on a plastic substrate. This research is focused on fabrication technology of flexible dye sensitized solar cell on plastic substrate. The solar energy conversion efficiencies () forfabricated cells (25×25 millimeter) operated with graphite, gold and platinum counter electrode were about 0.363%, 0.551% and 0.816% respectively under 1000 W/m2 illumination.

Most villages in our country recives 98.5 to 99.5 percentage of their electrical energy from national distribution network. Since some of them are faraway villages so connecting them to national network is expensive andcauses increase rate losses. Nowadays different sources of energy especially renewable energies are used to answer the energy growth demand. Fortunately Iran is rich in renewable energy resources such as solar, wind and etc. Therefore using different energy resources in faraway villages lead toimprovement of national electrical network independence. In this paper a wind- photovoltaic hybrid system which has battery backup will be designedin order to feed ice landing load. The goal is preparing energy for load and minimization total production cost over the life of the system. For these purpose Imperialistic Competitive Algorithm is used which has good speed of convergence. This article determines the optimal size of each source and minimizes the cost function. Simulation results show the ability of designed system in different conditions. Actual data of load profile and climatic condition are used. The case study is Jolfa in North West of Iran.

In this study, the effect of elimination of Subsidy of energy carrierson two variables of economic growth and inflation in Iran is evaluated to help a macro econometric model. In this regardusing time series data for 1976-2007 and Auto-Regressive Distributed Lag model (ARDL), equations and the sectors of economic relations within the three markets of goods and services, labor market and money market were estimated. Establishing classic properties of errors perused for all equations and also to ensure long-term equilibrium relationship between variables, Banerjee test was for all equations. By assistance of dynamic simulation in the form of a macroeconomic model, the estimated equations was solved simultaneously. Considering the direction of simulated values and actual values of variables and quantitative statistical used to measure the validity of the model, the results of simulations were satisfactory. Furthermore in order to predict endogenous variables of model for the period of 2008-2012, exogenous variables of mention period were predicted using time series model (ARIMA). Based on forecast, economic growth rate for years 2008 and 2009 were obtained 2.34 and 1.04 percent respectively, according to the latest report of the Central Bank of Iran's economic developments in the real sector in the first half of 2008 and the International money fund (IMF) report, results are not very far from reality. As then, the impacts of prices increase of energy carriers (the way was announced in the late November 2010) on two variables of economic growth and an inflation rate are predicted under different scenarios for the years 2010 to 2012. According to different scenarios, implementation of the plan will have positive impact on economic growth and negative effect on inflation. The results also show that if the plan for reforming energy carriesr prices is accompanied by improvement of productivity, itwill leave positive effects on economy.

One of the most important factors and parameters that improves its effective role in reducing losses and thereby increases productivity and efficiency is power factor of network. Due to existence of inductive resistance elements such as cooler, machine stand, electric fan types, refrigerators and fluorescent lamps which have major contribution in domestic and industrial consumers, power factor is less than unity, so that inductive parameter has formed. Poor power factor condition makes corrective intelligent systems necessary for our country. Research performed on the inductive power optimizer system shows that usage of such systems is very effective. This paper provides an effective and economical solution for this problem. Smart Optimizers of power consumption rate are proper options for improvement and compensation for reactive(inductive) load. Calculation based on this measurmentindicatesthe ability to improve power factor to 98 percent, which reduces overall current consumption, as well as the apparent power and reduce reductive losses of wires.

This paper presents two new methodologies for optimal placement of distributed generation (DG) in a locational marginal price (LMP) based on wholesale electricity market. A Gravitational Search Algorithm (GSA) is proposed for simultaneous power quality improvement, optimal placement and sizing of fixed capacitor banks in radial distribution networks with nonlinear loads and distributed generation (DG) imposing voltagecurrent harmonics. In distribution systems, nonlinear loads and DGs are often considered as harmonic sources. For optimizing capacitor placement and sizing in the distribution system, objective function includes the cost of power losses, energy losses and capacitor banks. In this study, new fitness function is used to solve the constrained optimization problem with discrete variables. Simulation results for modified 12 IEEE are presented and solutions for the proposed method are compared with previous methods. The proposed methods complyengineering aspects of system operation and economic aspects of market operation and act as good indicators for the placement of DG, especially in a market environment. In order to provide a scenario for DGs available, several cost characteristics are assumed. For each DG cost characteristic, an optimal placement and size are identified for each of the objectives. Results show that proposed GSA method could be effectively used for optimal capacitor placement and sizing in distorted distribution systems.