فصلنامه مهندسی و مدیریت انرژی
سال نهم شماره 1 (پیاپی 31، بهار 1398)

Demand Response (DR) program is one of the measures, performing with both of Retail Electricity Companies (Recos) and market's operator. This paper aims to provide a novel framework for optimal congestion management via encouraging a collaboration between the independent system operator (ISO) and Retail electricity companies (Recos) in implementing demand response (DR) programs based on the market mechanism. The merit of the paper is to increase the market efficiency. Economic signals specified by the ISO, are used for assisting Recos in evaluating any benefits from implementing DR in various network buses. A Stackelberg game is adopted for designing a DR trade between Recos and demand response aggregators to help Recos identifying their optimal demands in the market which are then used by the ISO to analyze grid congestion and consequently to re-specify the new economic signals. The game is repeated until the Nash equilibrium point, the optimal congestion reduction and the optimal Recos' demands, are obtained. The performance of the proposed framework are assessed using a test power system, The paper demonstrates an effective performance for the proposed framework.

Abstract: In traditional generation systems, energy from fuel is simply converted into electrical energy, while in the combined heat and power (CHP) systems, fuel energy, in addition to generating electricity, also generates thermal energy. Therefore, the efficiency of these systems is considerably higher than traditional systems, and this justifies the need for CHP systems. The emergence of CHP systems alongside fossil fuels power plants makes the economic dispatch of power and heat between the energy generating units with the lowest cost one of the important issues of power systems utilization. In this regard, the need to consider emissions from energy generating units along with other operational constraints of power plants complicates the economic dispatch. The presence of multiple objective functions, and in some cases opposites, transforms the above problem into a multi-objective optimization problem. This paper, while investigating the problem of economic dispatch of load in power plants along with the CHP and heat generating units, uses the meta-heuristic method of multi-objective harmony search algorithm (MOHS) in solving the problem of economic power and heat dispatch. To demonstrate the efficiency of the proposed method, a system with 4 units of electric power generation, 2 units of CHP and one unit of heat generation is used. The performance of the proposed algorithm is shown by comparing with other advanced multi-objective optimization methods such as NSGA-II and MOPSO.

With recent advances in power-electronics, inverter-based microgrids are gaining great attention. Droop control is one of the main methods to share the real and reactive power among distributed energy resources (DERs) in an islanded microgrids. Due to different characteristics of microgrid feeders, reactive power sharing is not fully accurate and consequently, some DERs may face overload. To address this problem, this paper presents a droop-based method using virtual impedance concept in the DER control system. The resultant voltage drop on the virtual impedance increases reactive power sharing accuracy. To adjust this virtual impedance, the local controllers of DERs exchange the required data with the microgrid management center using the low bandwidth communication links. Then, a virtual impedance‒reactive power droop characteristic is proposed to calculate the value of virtual impedance. The slope of this characteristic is adaptively adjusted based on the microgrid load. To verify the effectiveness of the proposed method, various scenarios are tested on the benchmark low voltage microgrid network.

WBANs (Wireless Body Area Network) are expected to consume very low electrical power. One of the most important factors of energy consumption in WBAN is the presence of interference between the transmitter and receiver nodes. In this paper, a fuzzy- genetic based power control method is proposed to intelligently align transmission power of sensor nodes within a WBAN. This technique utilizes the concepts of genetic algorithms to set up membership functions of fuzzy controller and its knowledge base so that by controlling the level of transmission power of each sensor, the entire network energy consumption is reduced by mitigating the impact of interference in neighborhood nodes. Compared to distributed Greedy power control algorithm, it is shown that the proposed genetic-fuzzy power control approach can reduce power consumption by at least 34 percent.

Abstract: This paper proposes a modified energy saving glass (MESG) for energy management of air conditioning system and transmission improvement of in-service and applicable frequency bands. For a typical float glass, the transmission of IR signals is about 98.2% which diminishes to 43% by the deployment of an ESG. Utilization of ESGs although yields energy consumption reduction, but simultaneously demonstrates destructive attenuating effects on 0.8-6.0 GHz frequency band including mobile communication, GSM, and GPS frequency bands. The presented MESG is a typical ESG in which elliptical rings are etched on the metallic oxide layer which improves the transmission of 0.8-6.0 GHz frequency band by 20.22 dB. By the proposed MESG structure, transmission rate of the 0.8-6.0 GHz frequency bands increases from 68.78% for a typical ESG to about 87.75%, showing 18.97% enhancement. It is worth noting that transmission of IR frequency band increases from 43% to 45.49% through the utilization of MESG which ends in 2.5% increment which is negligible compared to the great transmission enhancement in 0.8-6.0 GHz. The proposed MESG structure and the obtained improvements in energy saving and signal transfer issues are discussed in detail throughout the paper.

Abstract : The efficiency of a natural gas-fired aluminium melting furnace in a caster plant is examined using energy and exergy methods, to improve understanding of the burner system in the furnace and so that potential improvements can be identified. Such improvements not only reduce fuel consumtion, but also mitigate environmental emissions and impacts such as climate change. In this study, the energy efficiency of the Aluminum melting furnace obtained 10% and its exergy efficiency 6%. The results confirm that exergy analysis can be used beneficially to analyze and improve the furnace efficiency and that exergy efficiency is a more practical measure in reality. The insights gained through the assessments into the melting furnace are described and potential improvements indicated are discussed. By reviewing of results, It was suggested the solutions to optimize energy consumption include adding regenerative burners and regenerators, preheating ingots, using compressed natural gas, reclaiming heat from cooling water, and replacing combustion air. It is anticipated that the results will be of interest and benefit to designers of new and retrofit systems.

Exergy analysis is a method of evaluating the proportion of each process on the transmission of system availability and determining how the useful energy is loosed. In this research, a turboprop engine is simulated using GASTURB 10 commercial software which is developed based on zero-dimensional approach. The performance of turboprop engine is calculated at design point and some off-design points and thermodynamic properties of engine components at different flight altitudes and Mach numbers are calculated. After that, by defining exergy terms and using related exergy equilibrium equations, the necessary conceptual basis for exergy analysis is introduced. Then thermodynamic data obtained from GASTURB software are used to exergy analysis of engine components. Results show that combustion process has the dominant portion of the system irreversibility.

Electrification to rural and remote areas with limited or no access to grid connection is one of the most challenging issues in developing countries like Iran. Most of electricity demand is met by diesel generators in Iran remote areas, although they create environmental problems and economic concern. These issues can be minimized by hybrid renewable energy systems. This research paper aims at analyzing a hybrid system based on the wind, photovoltaic (PV) panels, diesel generators, storage batteries, for rural electrification in an off-grid village of 10 families, Dameghan Province, situated in the central part of Iran using HOMER software System was simulated by using HOMER software to optimize system control variables, based on load management strategies. The results show that current net system cost and pollutants emission rate are 75315 dollars and 6470 kg/year respectively. This analyzed hybrid energy system might be applicable for other Iran regions.