A Comparative Study on the Options in Combining Solid Oxide Fuel Cell With Gas Turbine

Author(s):  
Ji Hye Yi ◽  
Ju Hwan Choi ◽  
Tong Seop Kim

Various options in combining a solid oxide fuel cell (SOFC) with a gas turbine (GT) were compared in this study. The combination of an SOFC with either a simple gas turbine or a gas/steam turbine combined cycle was investigated. For each combined system, the effect of using a recuperative heat exchanger was examined. The design parameters of a state-of-the-art gas turbine for central power stations were used. The GT modeling included modulation of turbine coolant flow depending on turbine working conditions. An SOFC temperature of 900°C was used. Given a currently available reference voltage, pressure-dependent SOFC cell voltage was used. The analysis was divided into two parts. In the first part, the turbine inlet temperature of the reference gas turbine was given and the influence of pressure ratio was analyzed. In the second part, the influence of varying turbine inlet temperature was analyzed to search for optimal design conditions. The results showed that the SOFC/GTCC systems would provide considerably higher efficiencies than the SOFC/GT systems. The optimal pressure ratio in terms of system efficiency is over 30 for non-recuperated systems but is around 10 for recuperated systems. Reducing the extra fuel to the gas turbine combustor improves system efficiency, especially in the SOFC/GT systems. With zero extra fuel, efficiencies of all of the four systems exceed 70%, the highest of which is obtained by the recuperated SOFC/GTCC layout.

Author(s):  
Yousef Haseli ◽  
Ibrahim Dincer ◽  
Greg F. Naterer

This paper undertakes a thermodynamic analysis of a high-temperature solid oxide fuel cell, combined with a conventional recuperative gas turbine. In the analysis the balance equations for mass, energy and exergy for the system as a whole and its components are written, and both energy and exergy efficiencies are studied for comparison purposes. These results are also verified with data available in the literature for typical operating conditions, the predictive model of the system is validated. The energy efficiency of the integrated cycle is obtained to be as high as 60.55% at the optimum compression ratio. These model findings indicate the influence of different parameters on the performance of the cycle and irreversibilities therein, with respect to the exergy destruction rate and/or entropy generation rate. The results show that a higher ambient temperature would lead to lower energy and exergy efficiencies, and lower net specific power. Furthermore, the results indicate that increasing the turbine inlet temperature results in decreasing both the energy and exergy efficiencies of the cycle, whereas it improves the total specific power output. However, an increase in either the turbine inlet temperature or compression ratio leads to a higher rate of irreversibility within the plant. It is shown that the combustor and SOFC contribute predominantly to the total irreversibility of the system; about 60 percent of which takes place in these components at a typical operating condition, with 31.4% for the combustor and 27.9% for the SOFC.


2021 ◽  
Author(s):  
L. Mantelli ◽  
M. L. Ferrari ◽  
A. Traverso

Abstract Pressurized solid oxide fuel cell (SOFC) systems are one of the most promising technologies to achieve high energy conversion efficiencies and reduce pollutant emissions. The most common solution for pressurization is the integration with a micro gas turbine, a device capable of exploiting the residual energy of the exhaust gas to compress the fuel cell air intake and, at the same time, generating additional electrical power. The focus of this study is on an alternative layout, based on an automotive turbocharger, which has been more recently considered by the research community to improve cost effectiveness at small size (< 100 kW), despite reducing slightly the top achievable performance. Such turbocharged SOFC system poses two main challenges. On one side, the absence of an electrical generator does not allow the direct control of the rotational speed, which is determined by the power balance between turbine and compressor. On the other side, the presence of a large volume between compressor and turbine, due to the fuel cell stack, alters the dynamic behavior of the turbocharger during transients, increasing the risk of compressor surge. The pressure oscillations associated with such event are particularly detrimental for the system, because they could easily damage the materials of the fuel cells. The aim of this paper is to investigate different techniques to drive the operative point of the compressor far from the surge condition when needed, reducing the risks related to transients and increasing its reliability. By means of a system dynamic model, developed using the TRANSEO simulation tool by TPG, the effect of different anti-surge solutions is simulated: (i) intake air conditioning, (ii) water spray at compressor inlet, (iii) air bleed and recirculation, and (iv) installation of an ejector at the compressor intake. The pressurized fuel cell system is simulated with two different control strategies, i.e. constant fuel mass flow and constant turbine inlet temperature. Different solutions are evaluated based on surge margin behavior, both in the short and long terms, but also monitoring other relevant physical quantities of the system, such as compressor pressure ratio and turbocharger rotational speed.


Author(s):  
Xiaojing Lv ◽  
Chaohao Lu ◽  
Xinjian Zhu ◽  
Yiwu Weng

The effect of biomass gas on the safety performance of a solid oxide fuel cell (SOFC)/micro gas turbine (GT) hybrid system was studied with consideration of the fuel cell working temperature, fuel cell temperature gradient requirement, compressor surge zone, and turbine inlet temperature (TIT). The safety performance of the hybrid system on the design condition and off-design condition was also analyzed. Results show that the hybrid system is good adaptability to low concentrations of biomass gas. The electrical efficiency could reach 50% with different biomass gases and is higher than the other combined power systems that used biomass gas. The wood chip gas (WCG) would make the fuel cell or GT easier overheat than the other three gases. The cotton wood gas (CWG) and corn stalk gas (CSG) are easy to cause the TIT too low or the compressor surge. In the safety zone, considering the hybrid system load adjustment range, the effecting order (from large to small, following is same) is WCG, grape seed gas (GSG), CSG, and CWG. Considering the hybrid system electric efficiency, the effecting order is WCG, GSG, CWG, and CSG.


2018 ◽  
Vol 228 ◽  
pp. 1953-1965 ◽  
Author(s):  
Danylo Oryshchyn ◽  
Nor Farida Harun ◽  
David Tucker ◽  
Kenneth M. Bryden ◽  
Lawrence Shadle

2017 ◽  
Vol 1 ◽  
pp. U96IED ◽  
Author(s):  
Valentina Zaccaria ◽  
David Tucker ◽  
Alberto Traverso

Abstract Coupling a solid oxide fuel cell (SOFC) with a gas turbine provides a substantial increment in system efficiency compared to the separate technologies, which can potentially introduce economic benefits and favor an early market penetration of fuel cells. Currently, the economic viability of such systems is limited by fuel cell short lifetime due to a progressive performance degradation that leads to cell failure. Mitigating these phenomena would have a significant impact on system economic feasibility. In this study, the lifetime of a standalone, atmospheric SOFC system was compared to a pressurized SOFC gas turbine hybrid and an economic analysis was performed. In both cases, the power production was required to be constant over time, with significantly different results for the two systems in terms of fuel cell operating life, system efficiency, and economic return. In the hybrid system, an extended fuel cell lifetime is achieved while maintaining high system efficiency and improving economic performance. In this work, the optimal power density was determined for the standalone fuel cell in order to have the best economic performance. Nevertheless, the hybrid system showed better economic performance, and it was less affected by the stack cost.


2017 ◽  
Vol 6 (2) ◽  
pp. 127 ◽  
Author(s):  
Vahid Azami ◽  
Mortaza Yari

In this paper, a conventional SOFC–GT hybrid system and an SOFC–GT hybrid system with cathode gas recirculation system fuelled 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 is heated at the air recuperator and air preheater to meet the required cathode inlet temperature while in the SOFC–GT hybrid system with cathode gas recirculation, in addition to the air recuperator and air preheater, also the recirculation of the cathode exhaust gas is 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%).Keywords: Solid oxide fuel cell, Gas turbine, Cathode gas recirculation, Exergy.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 Develeopment, 6(2), 127-136.https://doi.org/10.14710/ijred.6.2.127-136


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