An energy system that produces work, heat and so forth, contains unintended remaining flows of matter or energy called residues. In the conventional thermo economic cost accounting methods, as it is already known, the problem of the residues cost has not been considered thoroughly. The residues cost allocation is a complex problem practically, because it is intertwined with the nature of such flows and the way they are formed. There are several options for the residues cost allocation among which two more important options are: (1) distribution of the residues cost proportionally to the exergy and (2) distribution of the residues cost proportionally to the entropy generation or negentropy. In this paper, for the residues cost distribution ratio, two alternative options are proposed. The proposed options are applied to a combined cycle and results are compared with two different possible options. The results suggest that the proposed options are more proper and reasonable than the alternative options. تفاصيل المقالة

Solar energy is a renewable source that can be used for a wide range of applications especially for power generation. In this paper, thermoeconomic analysis is performed for a steam Rankine cycle whereas solar energy is used for producing steam using parabolic trough solar collectors (PTSC). For this purpose, firstly the modeling of the solar collectors is performed. Then the mass and energy equations are solved to obtain the thermodynamic state of each point. The cost of each component is calculated using the purchase costs of the system components as a function of thermodynamic parameters. The effect of active parameters such as inlet temperature and pressure of steam turbine, solar irradiation intensity, pinch point, interest rate, and lifetime are investigated on the number of solar collectors in rows, the total aperture area, the thermal efficiency and the average cost of electricity. The results shows that the average cost of electricity decreases with increasing the inlet temperature and pressure of steam turbine. The average cost of electricity is calculated to be less than 3 cent/kWh while it is normally more than 10 cent/kWh. تفاصيل المقالة

Biomass is considered as an effective energy carrier to meet the needs of clean energy for the whole world, which need to have sustainable renewable energy. Among the various methods of biomass, gasification is commendable. It is considered as one of the most important restoration and thermochemical methods for converting biomass energy into gaseous fuels, thermal and electrical energies, as well as its use for the production of biofuels. But there are some obstacles, which can be solve by more research in this area. In this article, various obstacles such as supply chain management include harvesting the waste, collection on the site, transportation to gasification site and storage are each a part of this chain. biomass pretreatment, generic low biomass resources and syngas conditioning from biomass energy conversion have been mentioned. Based on recent studies, the biggest challenges for biomass gasification is to produce heat and power. Also, different technologies of reactor design until reaching to the most efficient and high-efficiency reactor have been discussed in this paper. Ultimately, the most advanced gasification system with the most efficient gas conditioning technology can overcome all the mentioned obstacles. تفاصيل المقالة

In this study, the turbulent fluid flow and heat transfer performance of a concentric two-tube (air-nanofluid) heat exchanger with a helical turbulator is studied using STAR-CCM+. First, the computational code is validated according to the related experimental data and its simulation results for air and water. Then, the heat transfer performance and the effect of the different pitches of the helical turbulators are analyzed by replacing nanofluid instead of water for heat removal. The results show that the turbulator and nanoparticle has a high impact on heat transfer capability of the heat exchanger. The result shows that, the heat transfer is increased using turbulators in comparison with smooth tube for pitches of 15, 30 and 45 mm, respectively. In addition, the STAR-CCM+ is a proper tool for simulation of a complex geometries in three-dimensional. It is not only the CFD solver, STAR- CCM+ is an entire engineering process for solving problems involving flow (of fluids or solids), heat transfer and stress. It provides a suite of integrated components that combine to produce a powerful package that can address a wide variety of modeling needs. These components include: • 3D-CAD Modeler • CAD Embedding • Surface Preparation Tools • Automatic Meshing Technology • Physics Models • Post-processing تفاصيل المقالة

A photovoltaic (PV) panel consists of several photovoltaic cells designed to convert solar radiation into electrical energy. Cooling of PV cells is an important task to increase PV panel efficiency, improve output power and optimize performance parameters. There are various methods for PV cooling. Phase change materials (PCMs) can be used to cool PV panels. The integrated system is called PV-PCM system. This paper provides an overview of the history, applications, mathematical modeling and economic evaluation for PV-PCM systems. The focus of this study is on the cooling of the PV cells using PCMs. Furthermore, the other types of PV systems (hybrid systems) are investigated. The effects of main parameters on the performance of PV or PV-PCM systems are investigated, too. Mathematical modeling including thermal and electrical models are presented. Finally, the advantages and disadvantages of PV-PCM system and its future overview are discussed. The results discover that the PV panel temperature up to 20 °C and electrical efficiency up to 5% can be reduced by PCM.. The results discover that the PV panel temperature up to 20 °C and electrical efficiency up to 5% can be reduced by PCM. تفاصيل المقالة

Residues are disposal remaining flows of matter or energy that are produced by energy systems. Residues cost allocation is a complex problem. One of the most important criteria for residues cost allocation is distributed entropy method. In this method, the fuel-product (FP) table (a mathematical representation of the thermoeconomic model) is used as input data. Average cost theory (ACT) method is one of the most important conventional exergoeconomic methods that can be applied to energy systems. In this paper, distributed entropy method and ACT method are applied to a combined cycle and a cogeneration system. Fuel and product costs for each component are obtained and compared with each other. Specific cost of product for each component is calculated, too. تفاصيل المقالة

As any energy system produces functional products, such as work, heat, etc., it produces unintended remaining flows of matter or energy, too, which are called residues. One of the objectives of exergoeconomic analysis is to understand the cost formation process and the flow of costs in the system. In the conventional thermoeconomic methods, however, the problem of the cost of residues has not been perceived soundly. One of the complex problems in the cost assessment is residues cost allocation in a rational way. Two more important methods of the residues cost allocation are distribution of the cost of the residues proportionally to the exergy as well as to the entropy generation or negentropy. In this paper, a new method for the residues cost allocation is proposed. This new method uses the fuel-product (FP) table, a mathematical representation of the thermoeconomic model, as the input data. In order to represent the proposed method, a cogeneration system that produces 34MW of electricity and 18kg/s of saturated steam at 20bar is selected. For the optimization of this system, first, a code has been developed based on the real coding evolutionary algorithm and optimal solution is to be obtained; then, he proposed method is applied to the cogeneration system. For comparison of the results, two other methods have also been applied to the system. The results of the comparison show that the proposed method is more suitable and rational than the two other ones. تفاصيل المقالة