فصلنامه مهندسی و مدیریت انرژی
سال یازدهم شماره 1 (پیاپی 39، بهار 1400)

In this paper, a bi-level optimization problem is formulated to find the optimal strategy of energy retailer in integrated energy market using the smart energy hub concept. In the upper level problem, the energy retailer determines the price of energy carriers and the purchase amount from the wholesale market while aiming to maximize his own profits. The consumers decide on their purchase amount of energy carriers minimizing their energy bills. All market participants, including energy retailer, rival retailers, and consumers are assumed to be smart energy hubs to increase the competition in the market. In other words, all market participants have the ability to generate power. To evaluate the performance of the proposed model, the research has implemented a case study with one main energy retailer, two rivals, and 10 consumers. The results show the optimal behavior of the energy retailer in the market.

The design of energy management strategy is one of the main challenges in the development of fuel cell electric vehicles. The proposed strategy should be well responsive to provide the demanded power of fuel cell vehicle for motion, acceleration, and different driving conditions resulting in reduced fuel consumption, the increased lifetime of power sources and overall fuel efficiency. The purpose of this paper is to identify precisely the different driving conditions, to separate the battery state of charge regions based on combined efficiency and its mathematical calculations, to determine the fuel value of each gram of hydrogen in generating electric power, to classify the fuel cell output power, to extract the required information quickly, and to distribute power optimally regarding efficiency and lifetime.This paper presents a new multi-level online energy management strategy that is based on operational mode control aiming to operate at minimum equivalent consumption. Battery charging is also done at the optimum point of the fuel cell so that along increasing total efficiency, subsequent maximum instantaneous power is also satisfied. The simulation results of the proposed strategy indicate a reduction in fuel consumption and an increment in energy consumption efficiency compared to other energy management methods.

Because of high energy storage capability, Permanent Magnet Synchronous Motors are very important in electrical drive industry. Speed control of these motors suffer from parameter variations such as variable inductance. In this paper, The Integral-Terminal Sliding Mode Control (ITSMC) method is used to control the speed (torque) along with d-axis current control. This method like classic sliding control is robust to motor variable parameters variations; in addition, it has a higher dynamic response, and its output error in a finite time will converge to zero. In this paper, the results of simulation with Simulink/Matlab and experimental implementation of ITSMC based on a TMS320F28335 processor are presented.

Increase in energy use in the world, limited fossil fuel reserves, and environmental issues lead researchers to study about renewable energy resources like biofuels. Biodiesel is a kind of biofuel that can be derived from biomasses like microalgae. These biomasses grow in the southern areas of Iran. Thus, suitable strategies should be determined to develop biodiesel production from these biomasses. In this paper, strategic factors (strength, weakness, opportunity, and threat (SWOT) analyses) are determined by considering literature review and expert opinions. Based on SWOT analysis, suitable strategies (alternatives) are determined and ranked considering strategic factors (as criteria) and using a group-decision-making method in the fuzzy environment. First, criteria are weighed. To increase weighing reliability, a subjective (step-wise weight assessment ratio analysis (SWARA)) and an objective (entropy) method are integrated. Finally, strategies are ranked by a developed mixed integer linear programming (MILP) problem based on goal programming approach. Finally, determining subsidies and financial policies by the government are selected as the best strategies.

Electricity is one of the most important carriers of energy used in buildings. By introducing energy smart grids (SG) and energy micro smart grids (MSGs) alongside smart buildings, a good platform has been provided to optimize electricity production and consumption. In this paper, an MSG consists of renewable resources, diesel generators, and cell batteries in bidirectional connection with an SG is modeled, which is connected to a smart building, including lighting, temperature, and air conditioning loads on the consumer side Fuzzy controllers have been used to implement intelligent building management systems and MSG to manage power generation and sales with SG. The decision variables are fuzzy controller rules optimized by an NSGAII multi-objective optimization algorithm with five different objective functions. The results show that the fuzzy controllers work better than the methods directly using the power allocated to the building loads as the decision variable.

This research aims to model and study the techno-economic aspects of grid-connected distributed photovoltaic systems for use in the residential sector in several large cities of Iran including Esfahan, Bandar Abbas, Tehran, Tabriz, Shiraz, and Yazd. The dynamic modelling is performed using hourly metrological data and hourly electricity demand of the households. The impacts of pricing policies and governmental incentives on the economy of photovoltaic systems have been studied under six different scenarios. The results show that electricity production of a one-kilowatt system with fixed angles is in the range of 1437-1536 kWh from which only 44.1-49.4% can be sold to the electricity grid by applying net metering policy. Using 1-axis and 2-axes solar tracker, the electricity production and the sold electricity to the grid are increased by 26.8-44.4% and 35.6-62.8% respectively. Guaranteed purchase of excess electricity cannot make use of photovoltaic systems economically viable. Besides, by applying the incentive policies in supplying the initial costs of investment and increasing electricity tariffs, it is possible to reduce the payback period to about 6 years except for Bandar Abbas. The results show that according to the climate conditions, appropriate and specific incentive policies should be adopted by the government in each region.

The process of roomchr('39')s air-conditioning system is used to enhance thermal comfort and to reduce energy consumption. Although most of the researches have concentrated more on flow rate and optimum temperature of inlet air, the present study software was used to obtain the best possible locations for inlet and outlet channels for 20 samples of room using Ansys Fluent. Three factors including ventilation efficiency, effective average temperature, and vertical temperature gradient were considered to find the best location for inlet and outlet port locations. As a result, model 20, where inlet channel placed in the middle of opposite wall from manikin and the outlet channel located at the bottom of the same wall, was approved. In this sample, the average temperature was 23.68; the ventilation efficiency was 2.36; and the average effective temperature was -1.01. Moreover, the analysis of rooms with area of 12 𝑚2, 16 𝑚2, and 20 𝑚2 showed that by increasing the area, the ventilation efficiency decreased by 11.86%, and by increasing the air flow from 0.045 to 0.134 m3/s, the average temperature room decreases 12.54%.

In this study, the thermal performance of collectors with analytic and quasi-dynamic method is evaluated based on energy balance equations for each part of the U-pipe evacuated tube solar collector. Using this approach, the effect of different parameters such as tube size, overall heat loss coefficient, absorber tube absorptivity, mass flow rate, and air layer thermal resistance on the thermal performance of the collector were analyzed. The results show that collector efficiency is increased with an increase in the length of the tube for a fixed tube diameter, but this increase is very small if the length of the tube increases more than two meters. Under the same conditions, collector efficiency increases with an increase in tube diameter for a fixed tube length. An optimum flow rate is obtained for different climate condition in which collector efficiency is maximum. It shows different values for different climates. A correlation is obtained for optimum flow rate based on average annual total solar radiation.

In this paper, the cooling system of the air humidifier, which is fully powered by solar energy, is designed and optimized. In this cooling system, the ammonia absorption refrigeration system has been used instead of conventional compression cooling systems. Its design was done in a way that the performance of the system has increased remarkably in the environments with high temperatures. The ammonia absorption refrigeration is completely fed from parabolic solar collectors. The device has been designed in such a way that the fan is positioned at the beginning of the cooling system. Thus, to increase the efficiency of the fan and the system, the optimization of some axial fan characteristics has been performed and verified using simulation and testing. Furthermore, for the improvement of the heat transfer to air, the appropriate location of the heat exchanger inside the air duct channel has been determined by finite element analysis in Ansys CFX software. In the next step, the thermodynamic analysis of the ammonia absorption refrigeration and the amount of energy required for air cooling have been calculated using numerical analysis in EES software. The results indicate that utilizing three solar collectors can provide the energy needed for the cooling system. Therefore, the proposed system can be applied to reduce production costs in various sectors of food industry.

Today, the agricultural sector is heavily dependent on energy to meet the growing demand of worldchr('39')s growing population for food. This study aims to determine energy indices and equations based on energy consumption and production. 380 farmers out of the total number of 31190 irrigated wheat farmers of Isfahan were selected across the 24 boroughs of the province (based on Cochranchr('39')s relationship), and the required information was acquired for calculating energy consumption indices and energy equations. According to the results, the total amount of energy consumed and produced by wheat in Isfahan province was estimated to be 92714.8 MJ/ha and 131958.8 MJ/ha respectively. The total energy consumption consisted of 55820.6 MJ/ha renewable and 36894 MJ/ha non-renewable energy. The results of the energy production function showed that only fertilizers and transport energy coefficients were significant at 10% level. Regarding the return rate scale that was in the third region of productions, more energy consumption will reduce the energy production of wheat.