فصلنامه مهندسی و مدیریت انرژی
سال سوم شماره 4 (پیاپی 10، زمستان 1392)

This paper presents a comprehensive operation model for micro grids operating in the islanded mode. Various energy sources including diesel engine generator، micro turbine، wind turbine and photovoltaic cell as well as battery storage and AC/DC rectifier/inverter are included in the modeling of the micro grid. Fuel costs، emission costs، and operation and maintenance costs of these sources as well as their operating limits and characteristics and cost of energy not served are considered in the proposed model. Furthermore، an enhanced differential search algorithm (EDSA) is presented to solve the optimization problem of MG operation. The numerical results obtained from the proposed solution approach for test cases with real world data are compared with the results of several other recently published optimization methods. These comparisons confirm the validity of the developed approach.

Nowadays، optimal placement of wind turbines in a wind farm is one of the major concerns of the wind farm designers. This paper concentrates on the optimal placement of wind turbines in a wind farm. The optimal placement of wind turbines has been carried out to maximize the output energy and minimize the investment cost of cable، road and wind turbines. For this purpose، Firstly، it should be determined which turbine and to what extent is in the wake of its upstream turbines، considering the wind speed and direction. Next، the cost of the collector system and road connection has been determined using a proposed mathematical model. In this research، the annual wind data of Milnader region in Iran، which is a suitable region for installing a wind farm due to its high wind speed، has been used. Harmony Search Algorithm (HSA) has been used to implement this optimization problem. To validate the simulation results، the results have been compared with genetic algorithm، practice swarm optimization and MonteCarlo method.

Increasing the demand for electric vehicles، makes the manufactures to concentrate on the research of new energy storage devices، electro motors، and power electronic devices. The main subject in designing an electric motorcycle with four-phase AFPM and its full wave converter is to select suitable energy storage system and add on turbo-acceleration mechanism. Choosing the suitable energy storage system based on battery cost، mass، life-cycle، efficiency and safety can play important role in better operation of electric motorcycle and efficiency improvement. Using combination of battery and ultra-capacitor as the suitable energy storage system can handle the daily driving needs of an electric motorcycle with sufficient cost and improved electric driving range. The Sodium-nickel chloride batteries are the best for electric motorcycle. They have low cost، and their specific energy is high. The main objective of this paper is to add on turbo-acceleration mechanism along with using the combination of ultra-capacitor and sodium-nickel chloride battery to improve the energy efficiency، cost، and electric driving range up to 19%، also to supply access power for additional acceleration in an electric motorcycle that is equipped with four-phase AFPM to have easy recovery of regenerative braking energy and low torque ripple. In order to evaluate the energy efficiency improvement and cost reduction، some simulations are done on an electric motorcycle.

The orientation of the flat solar collectors affects the amount of solar radiation received and absorbed by them. In this study، the optimum tilt angles of flat plat solar collectors in Kashan for the fixed monthly، seasonal، semi-yearly and yearly adjustments have been determined. If the solar calculations are based on the measured data، they produce more accurate results; however in many parts of Iran like Kashan the solar data are not measured. Due to similar climatic conditions of Kashan and Isfahan، in this study the long term measured solar data of Isfahan have been utilized for calculating the optimum tilt angles. Also for making comparison، other estimated values have been used also the optimum tilt predictions of some general correlations proposed by several researchers have been obtained. The comparison stated the weakness of some existing correlations and the validity of the results obtained in this study. The results indicate that for the optimized use of solar energy it is necessary to adjust the tilt at least once in every month and the maximum and minimum slope angles are 60° for Azar and zero for two months of Khordad and Tir، respectively. The optimum tilt for the fixed seasonal adjustments in Spring، Summer، Autumn and Winter are 3°، 14°، 53° and 48°، respectively and for the fixed semi-yearly adjustments in the first and the second six months of the year are 9° and 51°، respectively. Also the fixed annual optimum tilt is 29°، which is very close to the latitude of Kashan (33. 59°).

In this work، the effects of star tube insert as one of the best passive method for enhancement heat transfer in gas water heater are studied. The effects of this tube insert with step 2، 3 and 4. 5 cm on flow characteristics and thermal performance of the gas water heater are investigated using finite volume method. In the cases studied (Reynolds numbers between 5800 and 18600)، Nu Number is obtained much higher than the gas water heater without tube insert. As the average Nu Number in the range of Re Number is 1. 91، 1. 755 and 1. 592 for step 2، 3 and 4. 5، respectively، compared to plain tube without tube insert. In order to evaluate the pressure drop with an increase in heat transfer due to tube insert، the thermal performance factor is used. The Results show that the overall effect of the star tube inserts with different steps on the gas water heater performance is desirable.

Electrical power of salinity gradient is one of the sources for renewable energy. This energy can be obtained by mixing two kinds of water with different concentrations. In a river estuary، fresh water naturally mixes with sea water without any obstruction. Reveres electro dialysis (RED) is one of the suitable and practical methods for controlling this unobstructed mixture and extracting energy from it. Arvand River between Iran and Iraq is one of the fresh water rivers which lead to Persian Gulf. In this research، the salinity of this river’s water is studied by measured physical parameters in three hydrometric stations. Then this salinity is compared with water salinity of Persian Gulf and its extractible electrical energy assesses and analysis theoretically.