Comparison Between Conventional Design and Cathode Gas Recirculation Design of a Direct-Syngas Solid Oxide Fuel Cell–Gas Turbine Hybrid Systems Part I: Design Performance

In this paper, a conventional SOFC–GT hybrid system and a SOFC–GT hybrid system with cathode gas recirculation system fueled with syngas as the main source of energy were analyzed and their performances were compared. In the conventional SOFC–GT hybrid system, the incoming air to the cathode was heated at air recuperator and air preheater to meet the required cathode inlet temperature. In the SOFC–GT hybrid system with cathode gas recirculation, besides air recuperator and air preheater, the recirculation of the cathode exhaust gas was also used to meet the required cathode inlet temperature. The system performances have been analyzed by means of models developed with the computer program Cycle–Tempo. A complete model of the SOFC–GT hybrid system with these two configurations evaluated in terms of energy and exergy efficiencies and their performance characteristics were compared. Simulation results show that the electrical energy and exergy efficiencies achieved in the cathode gas recirculation plant (64.76% and 66.28%, respectively) are significantly higher than those obtained in the conventional plant (54.53% and 55.8%). Article History: Received Feb 23rd 2017; Received in revised form May 26th 2017; Accepted June 1st 2017; Available onlineHow to Cite This Article: Azami, V, and Yari, M. (2017) Comparison between conventional design and cathode gas recirculation design of a direct-syngas solid oxide fuel cell–gas turbine hybrid systems part I: Design performance. International Journal of Renewable Energy Development, 6(2), 127-136.https://doi.org/10.14710/ijred.6.2.127-13

THERMODYNAMIC ANALYSIS OF A COMBINED MICRO TURBINE WITH A MICRO ORC

ABSTRACT In the last years, a big effort has been undergone to improve micro turbines thermal efficiency, actually rated at about 30 %. A value of 40 % is often regarded as a possible target. Such a result could be achieved implementing more complicated thermodynamic cycles, like combined cycles. This paper deals with the hypothesis of bottoming a low pressure ratio, recuperated gas cycle, typically realized in actual micro turbines, with an Organic Rankine Cycle (ORC) with internal heat exchanger (IHE), obtaining a micro-combined-cycle. The results are presented and the influence of the several parameters: Turbine inlet temperature of the micro turbine, compressor pressure ratio, evaporation temperature and evaporator temperature difference are discussed. Both simple ORC and ORC with IHE bottom cycle options are discussed. The dry organic fluids in this study are Isopentane, n-Pentane, n-Heptane, n-Octane, n-Hexane, R113, R123 and Toluene

A comparative thermodynamic analysis of ORC and Kalina cycles for waste heat recovery: A case study for CGAM cogeneration system

A thermodynamic modeling and optimization is carried out to compare the advantages and disadvantages of organic Rankine cycle (ORC) and Kalina cycle (KC) as a bottoming cycle for waste heat recovery from CGAM cogeneration system. Thermodynamic models for combined CGAM/ORC and CGAM/KC systems are performed and the effects of some decision variables on the energy and exergy efficiency and turbine size parameter of the combined systems are investigated. Solving simulation equations and optimization process have been done using direct search method by EES software. It is observed that at the optimum pressure ratio of air compressor, produced power of bottoming cycles has minimum values. Also, evaporator pressure optimizes the performance of cycle, but this optimum pressure level in ORC (11 bar) is much lower than that of Kalina (46 bar). In addition, ORC's simpler configuration, higher net produced power and superheated turbine outlet flow, which leads to a reliable performance for turbine, are other advantages of ORC. Kalina turbine size parameter is lower than that of the ORC which is a positive aspect of Kalina cycle. However, by a comprehensive comparison between Kalina and ORC, it is concluded that the ORC has significant privileges for waste heat recovery in this case

Energy and Exergy Analyses of a New Combined Cycle for Producing Electricity and Desalinated Water Using Geothermal Energy

A new combined cogeneration system for producing electrical power and pure water is proposed and analyzed from the viewpoints of thermodynamics and economics. The system uses geothermal energy as a heat source and consists of a Kalina cycle, a LiBr/H2O heat transformer and a water purification system. A parametric study is carried out in order to investigate the effects on system performance of the turbine inlet pressure and the evaporator exit temperature. For the proposed system, the first and second law efficiencies are found to be in the ranges of 16%–18.2% and 61.9%–69.1%, respectively. For a geothermal water stream with a mass flow rate of 89 kg/s and a temperature of 124 °C, the maximum production rate for pure water is found to be 0.367 kg/s

Thermodynamic Analysis and Optimization of a High Temperature Triple Absorption Heat Transformer

First law of thermodynamics has been used to analyze and optimize inclusively the performance of a triple absorption heat transformer operating with LiBr/H2O as the working pair. A thermodynamic model was developed in EES (engineering equation solver) to estimate the performance of the system in terms of the most essential parameters. The assumed parameters are the temperature of the main components, weak and strong solutions, economizers’ efficiencies, and bypass ratios. The whole cycle is optimized by EES software from the viewpoint of maximizing the COP via applying the direct search method. The optimization results showed that the COP of 0.2491 is reachable by the proposed cycle

Techno-environmental assessment and machine learning-based optimization of a novel dual-source multi-generation energy system

Publisher Copyright: © 2023 The Institution of Chemical EngineersThe utilization of high-temperature hybrid energy systems has a vital and promising role in reducing environmental pollutants and coping with climate change. So, in the present research, a dual-source multigeneration energy system composed of a gas turbine, a supercritical carbon dioxide recompression Brayton cycle, an organic Rankine cycle, an absorption refrigeration system, and a reverse osmosis desalination unit is designed and analyzed from thermodynamic, environmental and economic perspectives. The system supplies power with a stable load to follow the changes in the demand side which is important for off-grid distributed energy systems. The dual-source operation of the system makes it possible to generate sustainable electricity leading to less utilization of fossil fuels in the gas turbine subsystem and reduction in environmental pollution, and furthermore, malfunctioning of a subsystem will not lead to the failure of the entire plant. Three multi-objective optimizations with different objective functions are accomplished using artificial neural network from data learning and genetic and Greywolf algorithms to obtain the best-operating conditions. Under the base conditions, for the total input energy of 699 MW to the entire system, the energy and exergy efficiencies, the unit exergy cost of products, the carbon dioxide emission index, and the payback period, respectively, were found to be 45 %, 54 %, 15.3 $/GJ, 112.2 kg/MWh, and 7.2 years. The net output power of the proposed system was calculated as 288.2 MW. A sensitivity analysis revealed that with a change in the pressure ratio of the supercritical carbon dioxide cycle, the net generated power and overall efficiency take maximum values of 293.9 MW while the unit exergy cost of products and carbon dioxide emission index take minimum values of 15.3$/GJ and 110.1 kg/MWh, respectively. Furthermore, increasing the pressure ratio of the gas turbine leads to maximum values of 45 % and 54 % in overall energy and exergy efficiencies, respectively.Peer reviewe