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Rajaei A.,Power and Water University of Technology, Tehran | Barzegar Avval H.,Energy Optimization Research and Development Group EORDG | Eslami E.,Power and Water University of Technology, Tehran
International Journal of Chemical Engineering | Year: 2016

Recuperator is a heat exchanger that is used in gas turbine power plants to recover energy from outlet hot gases to heat up the air entering the combustion chamber. Similarly, the combustion chamber inlet air can be heated up to temperatures up to 1000 (°C) by solar power tower (SPT) as a renewable and environmentally benign energy source. In this study, comprehensive comparison between these two systems in terms of energy, exergy, and environmental impacts is carried out. Thermodynamic simulation of both cycles is conducted using a developed program in MATLAB environment. Exergetic performances of both cycles and their emissions are compared and parametric study is carried out. A new parameter (renewable factor) is proposed to evaluate resources quality and measure how green an exergy loss or destruction or a system as a whole is. Nonrenewable exergy destruction and loss are reduced compared to GT with recuperator cycle by 34.89% and 47.41%, respectively. Reductions in CO2, N O x, and CO compared to GT with recuperator cycle by 49.92%, 66.14%, and 39.77%, respectively, are in line with renewable factor value of around 55.7 which proves the ability of the proposed green measure to evaluate and compare the cycles performances. © 2016 Ali Rajaei et al. Source


Kaviri A.G.,University of Technology Malaysia | Jaafar M.N.M.,University of Technology Malaysia | Lazim T.M.,University of Technology Malaysia | Barzegaravval H.,Energy Optimization Research and Development Group EORDG
Energy Conversion and Management | Year: 2013

Combined cycle power plants (CCPPs) are preferred technology for electricity generation due to less emission and high efficiency. These cycles are made of a gas turbine, a steam turbine and Heat Recovery Steam Generator (HRSG). In the present research study, a combined cycle power plant with dual pressure and supplementary firing is selected. The optimum design procedure included designing objective function, exergy destruction per unit of inlet gas to the HRSG subject to a list of constraints. The design parameters (design variables) were drum pressure and pinch temperature difference as well as steam mass flow of HRSG high and low pressure levels. The influence of HRSG inlet gas temperature on the steam cycle efficiency is discussed. The result show increasing HRSG inlet gas temperature until 650 °C leads to increase the thermal efficiency and exergy efficiency of the cycle and after that has less improvement and start to decrease them. And also from the exergy analysis of each part of HRSG, it is cleared that the HP-EV and 2st HP-SH have the most exergy destruction respectively. In other hand, effects of HRSG inlet gas temperature on SI (sustainability index) and CO2 emission are considered. © 2012 Elsevier B.V. All rights reserved. Source


Ghaebi H.,Sharif University of Technology | Saidi M.H.,Sharif University of Technology | Ahmadi P.,Energy Optimization Research and Development Group EORDG
Applied Thermal Engineering | Year: 2012

In the present study, exergoeconomic optimization of a trigeneration system for cooling, heating and power purposes has been carried out. The system is made up of air compressor, combustion chamber, gas turbine, dual pressure heat recovery steam generator and absorption chiller in order to produce cooling, heating and power. The design parameters of this study are selected as: air compressor pressure ratio, gas turbine inlet temperature, pinch point temperatures in dual pressure heat recovery steam generator, pressure of steam that enters the generator of absorption chiller, process steam pressure and evaporator of the absorption chiller chilled water outlet temperature. The economic model used in this research is according to the total revenue requirement (TRR) and the cost of the total system product was defined as our objective function and optimized using a Genetic Algorithm technique. Results of exergoeconomic optimization are compared with corresponding features of the base case system. It has seen that objective function was modified about 15 percent after optimization. Furthermore, a sensitivity analysis has been presented in order to investigate the effects of decision variables on the different objective functions. Decision makers may find the methodology explained in this paper, very useful for optimal comparison and selection of trigeneration systems. © 2011 Published by Elsevier Ltd. All rights reserved. Source


Tajik Mansouri M.,Niroo Research Institute | Ahmadi P.,Energy Optimization Research and Development Group EORDG | Ganjeh Kaviri A.,University of Technology Malaysia | Jaafar M.N.M.,University of Technology Malaysia
Energy Conversion and Management | Year: 2012

In the present research study, the effect of HRSG pressure levels on exergy efficiency of combined cycle power plants is investigated. Hence, three types of gas turbine combined cycles, with the same gas turbine as a topping cycle are evaluated. A double pressure, and two triple pressure HRSGs (with and without reheat) are modeled. The results show how an increase in the number of pressure levels of the HRSG affect the exergy losses due to heat transfer in the HRSG and the exhaust of flue gas to the stack. Moreover, the results show that an increase in the number of pressure levels affects the exergy destruction rate in HRSG, and as a result, it causes a tangible increase in exergy efficiency of the whole cycle. The results from thermodynamic analysis show that the losses due to heat transfer in the HRSG and the exhaust of flue gas to the stack in a triple pressure reheat combined cycle are less than the other cases. From the economic analysis, it is found that increasing the number of pressure levels of steam generation leads to an increase for the total and specific investment cost of the plant for about 6% and 4% respectively. The net present value (NPV) of the plant increases for about 7% for triple pressure reheat compared to with the double pressure CCPP. Therefore, the results of economic analysis show that it is economically justifiable to increase the number of pressure levels of steam generation in HRSG. © 2012 Elsevier Ltd. All rights reserved. Source


Ehyaei M.A.,Islamic Azad University at Tehran | Ahmadi P.,Energy Optimization Research and Development Group EORDG | Atabi F.,Islamic Azad University at Tehran | Heibati M.R.,Islamic Azad University at Tehran | Khorshidvand M.,Islamic Azad University at Dezful
Energy and Buildings | Year: 2012

In this research technical, economical, and environmental feasibility study of applying internal combustion (IC) engines for supplying the required electricity, domestic hot water (DHW), heating and cooling energy loads in a typical 10-floor 40-units residential building located in Tehran city has been carried out using exergy analysis. The building has the area of 200 m 2 at each unit. The peak demands of electricity, DHW, heating and cooling loads of the building are 32.96 kW, 0.926 kW, 1590 kW and 2028 kW, respectively. The results show that considering the geographical situation and climatic conditions of Tehran, five units of G3306B IC engine and combined heat and power (CHP) internal combustion engine can meet the required energy of this building. Exergy and economic analysis of the system has been assessed with consideration of the external costs of the pollutants including CO2, CO, and NO in the flue gas of the internal combustion engine. The annual average electricity cost of this system to be equal to 0.05 (US$/kWh) and the annual entropy generation of this system to be equal to 29,903 (GJ/year). © 2012 Elsevier B.V. All rights reserved. Source

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