فصلنامه مهندسی و مدیریت انرژی
سال دوم شماره 3 (پیاپی 5، پاییز 1391)

Depleting fossil fuels and ever-increasing environmental have attracted much attention to the renewable energy resources. The Micro-Grid (MG) concept is an appropriate means for increasing the adaptation of these resources with current power system architecture. In this paper a new method is used to solve the problem of unit sizing in a grid-connected MG providing electrical and thermal loads simultaneously. Our main goal is to reduce the fossil fuels dependency of the MG which includes a photovoltaic (PV)/ wind hybrid system with storage energy system including electrolyzer, hydrogen tank, CHP based fuel cell, heater and boiler. The heater is used as the provider of part of the thermal load when the generated power is more than the load and the capacity of the storage system is not adequate, and the boiler is used as backup unit for supplying thermal load. Due to high importance of the pollution problems, this subject is considered in objective function as cost term. Reliability index is used as limitative subject and interruption cost considered in the objective function. IEEE load data and real case study in Ardabil region for wind speed and solar radiation has been used. Modified Particles Swarm Optimization (MPSO) Algorithm is used to obtain global optimal solution.

Using the renewable energy is the better option to supply demined in the standalone area. World’s most fast-growing renewable energy resource is the wind energy. One of the main disadvantages of this system, however, is that naturally variable wind speed causes power fluctuation problems at the load side. Besides, long-term storage of power generated by wind turbines is considered as a limitation on the part of remote locations. Batteries can be used to store a limited amount of energy for a short time. Applied hybrid energy is a good idea for supply demand in the discrete wind speed region. The present study was aimed at analyzing the energy flow analysis of a hybrid wind turbine-fuel cell system. Such system consists of wind turbines, electrolyzer, fuel cell and hydrogen tank for long time energy storage. A case study is done using practical data from the Abarkoh region in Iran. The result revealed, the percentage of energy generated by the wind turbines and used to cover the electrical demand is 56% and the percentage of the demand covered by the fuel cell 44%.

The main aim of blasting operations in mining and civil engineering projects is size reduction of the rock-mass. Particle size reduction (P.S.R) affects the efficiency of the loading, haulage and milling equipments. Therefore, prediction of mean fragment size in designing optimum blasting patterns is crucial. In this research, a model is presented for predicting mean fragment size caused by blasting, using a combination of Grady & Kipp model (considering the number of radial cracks in the vicinity of the blast-hole) and concept of the mean fragment size. The proposed model shows that mean fragment size is a function of rock-mass characteristics, fracture toughness (KIC), explosive characteristics such as velocity of detonation, specific density and geometrical blasting parameters like burden, spacing, blast-hole diameter, etc. Considering validation of this model at the rock-fill mines of Gotvand Olya Dam, in real-scale, application of this model is recommended in open-pit mines blasting.

This study attempts to provide a model for prioritizing energy recovery equipment according to environmental regulations and economic factors considered by investors. One of the important outcomes of this research is to create a model for investment management in energy recovery equipment in line with economic goals, and reduction in environmental pollution and global warming, leading to best investment decisions based on current country specific laws and regulations. In fact, using the above method can guide investments toward more environmentally compatible methods and equipment, which itself will result in further development of environmentally compatible equipment.

The object of this study is to investigate experimentally the effects of Flue Gas Recirculation technique on exhaust gases temperature and also the NOx levels of gasoil and biodiesel (made of sunflower oil) combustion. The tests were carried out for different levels of FGR ranged from 0 to 30% and for three inlet air flow rates i.e.: 3.5, 4.5 and 5.5 m3.min-1. Experimental results indicate that in the case of oil and B20 and B40 fuels, increasing the rate of recirculated gases up to 30% decreases maximum flame temperature and NOx emission. Moreover in the case of biodiesel fuels, increasing the volume percent of biodiesel fuel in the mixed fuel from 0% to 40%, increases exhaust gases temperature and NOx emission. Comparison among the obtained results and similar experiments of other researchers, indicates a great qualitative compliance.

This research analyzes an integrated refrigeration system including a microturbine, a compression chiller and an absorption chiller. The power from the microturbine utilized in the compression chiller compressor, air fans and absorption chiller pump and the waste heat from the exhaust operates the absorption chiller. Four various integrated configuration of the compression and absorption cycles is described and the effect of ambient temperature on the overall efficiency is analyzed. From the results obtained, it is concluded that the use of integrated refrigeration system is more efficient than the system without absorption chiller.