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Yongping Yang - One of the best experts on this subject based on the ideXlab platform.

  • Part Load Performance analysis of a combined cycle with intermediate recuperated gas turbine
    Energy Conversion and Management, 2020
    Co-Authors: Guoqiang Zhang, Ligang Wang, Yongping Yang
    Abstract:

    Abstract In order to improve the Performance of the combined cycle gas turbine (CCGT) under off-design conditions, an intermediate recuperated combined cycle gas turbine (IRCCGT) system was proposed, which was designed to suppress turbine inlet temperature (TIT) from decreasing as the Load drops. In this system, a heat exchanger is installed between the third and fourth turbine stages, wherein a portion of the exhaust from the third turbine stage was used to heat the compressed air. In addition, the system-based operation strategy (maximizing the Load range that employs constant TIT operation mode) was also analyzed. The results indicate that the TIT can be maintained at the design value until the gas turbine power Load is reduced to 49% of the design value. When the inlet guide vane (IGV) angle reached the minimum value, the IRCCGT system increased gas turbine efficiency and combined cycle electrical efficiency by 4.7 and 3.1 percentage points. At the same gas turbine (GT) Load, the maximum gains of GT efficiency and combined cycle efficiency were 2.15 and 1.04 percentage points, respectively. The pressure drops in the recuperator had a great impact on system Performance, while the minimum recuperative mass flow rate had little effect. Overall, the proposed IRCCGT system can reduce the slope of the efficiency and Load curve and improve the operating Performance of the system under off-design conditions.

  • impacts of solar multiples on the Performance of integrated solar combined cycle systems with two direct steam generation fields
    Applied Energy, 2015
    Co-Authors: Yuanyuan Li, Yongping Yang
    Abstract:

    Integrated solar combined cycle (ISCC) systems coupled with direct steam generation (DSG) are more promising in terms of system efficiency and electricity cost than current solar-only power generation systems, as ISCC–DSG offers the advantages of higher net thermal efficiency and lower cost. However, the ISCC systems usually have to be operated at Part-Load conditions with low system efficiency when no or lower insolation than that at design point is available as most of state-of-the-art such systems have no thermal storage equipped. In order to improve system Performance and prolong the system full-Load operation hours, a proper solar field size represented as the solar multiple is a prime parameter to be determined during the design stage of the ISCC system. A too large solar multiple might cause the collected solar thermal energy to become Partially useless without thermal storage and high investment cost, while a smaller one might worsen the Part-Load Performance of the system.

  • impacts of solar multiples on the Performance of integrated solar combined cycle systems with two direct steam generation fields
    Applied Energy, 2015
    Co-Authors: Yongping Yang
    Abstract:

    Abstract Integrated solar combined cycle (ISCC) systems coupled with direct steam generation (DSG) are more promising in terms of system efficiency and electricity cost than current solar-only power generation systems, as ISCC–DSG offers the advantages of higher net thermal efficiency and lower cost. However, the ISCC systems usually have to be operated at Part-Load conditions with low system efficiency when no or lower insolation than that at design point is available as most of state-of-the-art such systems have no thermal storage equipped. In order to improve system Performance and prolong the system full-Load operation hours, a proper solar field size represented as the solar multiple is a prime parameter to be determined during the design stage of the ISCC system. A too large solar multiple might cause the collected solar thermal energy to become Partially useless without thermal storage and high investment cost, while a smaller one might worsen the Part-Load Performance of the system. This paper presents the thermodynamic and economic analysis for an ISCC system with two pressure level DSG solar fields (ISCC–2DSG), aiming to study the impacts of solar multiples on system Performance with or without consideration of thermal storage. In the ISCC–2DSG system, the solar thermal energy produced from two solar fields is only used to supply latent heat for low- and high-pressure water vaporization, respectively. Feedwater preheating and steam superheating are achieved in a HRSG. The annual thermodynamic Performance of several such ISCC–2DSG systems, with different solar multiple values but with identical design parameters in the power subsystem, is characterized. Based on these features, the LEC for each system is calculated and compared. An optimum solar field size (solar multiple), which gives the minimum LEC, for the ISCC–2DSG system can be finally obtained.

Andreas K Friedrich - One of the best experts on this subject based on the ideXlab platform.

  • analysis of the influence of heat transfer on the stationary operation and Performance of a solid oxide fuel cell gas turbine hybrid power plant
    Applied Energy, 2018
    Co-Authors: Mike Steilen, Costanza Saletti, Marc P Heddrich, Andreas K Friedrich
    Abstract:

    Abstract Hybrid power plants consisting of solid oxide fuel cells (SOFC) and a gas turbine (GT) can play an essential role in the future energy scenario due to the expected high electrical efficiency, fuel flexibility and good Part-Load Performance. A demonstration SOFC/GT hybrid power plant is being setup in Stuttgart with state of the art, commercially available electrolyte supported cell (ESC) stacks and its operation is being simulated by means of a overall system model. However, the model used in this paper, in contrast to most models in literature, accounts for heat transfer based on actual geometries and materials. In the present study, the system model is integrated with a set of sub-models that predict the heat losses of the components of the hybrid power plant with a feasible computational speed. This allows for an improved prediction of the operating range as well as for the prevention of undesired operating conditions. The results of the simulations of the stationary operation of the hybrid power plant with varying heat losses are shown and discussed. Operating limitations are analyzed as well as system Performance. It is shown that it is possible to operate the hybrid power plant from design power output to 30% of it. A system electrical efficiency higher than 0.55 considering the fuel’s higher heating value is maintained throughout the entire range. Further design choices and developments could lead to an improvement of this condition. In addition, an adiabatic assumption can lead to about 4 percentage points overestimation of electrical efficiency and reduces the high power operating range by about 10%. This approach opens up a new perspective on the simulation of this type of power plant.

Jeong L. Sohn - One of the best experts on this subject based on the ideXlab platform.

  • Performance characteristics of a solid oxide fuel cell gas turbine hybrid system with various Part Load control modes
    Journal of Power Sources, 2007
    Co-Authors: Jin Sik Yang, Jeong L. Sohn
    Abstract:

    The purpose of this study is to compare the Part-Load Performance of a solid oxide fuel cell/gas turbine (SOFC/GT) hybrid system in three different control modes: fuel-only control, rotational speed control, and variable inlet guide vane (VIGV) control. While the first mode maintains a constant air supply and reduces the supplied fuel to achieve Part-Load operation, the other modes are distinguished by the simultaneous controls of the air and fuel supplied to the system. After the Performance analysis of a SOFC/GT hybrid system under Part-Load operating conditions, it was concluded that the rotational speed control mode provided the best Performance characteristics for Part-Load operations. In spite of worse Performance than the rotational speed control mode, the VIGV control mode can be a good candidate for Part-Load operation in a large-scale hybrid system in which the rotational speed control is not applicable. It was also found that, in spite of a relatively small contribution to the total system power generation, the gas turbine plays an important role in Part-Load operation of a SOFC/GT hybrid system.

  • strategies to enhance the Part Load Performance of a sofc gt hybrid system
    ASME Turbo Expo 2007: Power for Land Sea and Air, 2007
    Co-Authors: Jin Sik Yang, Jeong L. Sohn
    Abstract:

    In spite of the high Performance characteristics of the solid oxide fuel cell / gas turbine (SOFC/GT) hybrid system, it is very difficult to maintain the high level Performance under real application conditions, which generally require Part-Load operations. The Performance loss of SOFC/GT hybrid systems under Part-Load operating conditions is closely related to that of the gas turbine. The power generated by the gas turbine in a hybrid system is much smaller than that generated by the SOFC. However, its contribution to the system efficiency is very important especially at Part-Load operating conditions. Therefore, to enhance the Part-Load Performance of hybrid systems, it is useful to reduce the relative amount of power generated by a gas turbine that delivers lower Performance than a SOFC. In the present study, several Part-Load operation strategies related to the gas turbine are studied and their impacts on the Performance of a SOFC/GT hybrid system are discussed.Copyright © 2007 by ASME

Christoph Stiller - One of the best experts on this subject based on the ideXlab platform.

  • simulation of an oxygen membrane based combined cycle power plant Part Load operation with operational and material constraints
    Energy and Environmental Science, 2009
    Co-Authors: Konrad Eichhorn Colombo, Olav Bolland, V V Kharton, Christoph Stiller
    Abstract:

    This paper presents the design and Part-Load Performance of a natural gas-fired oxy-combustion combined cycle power plant for CO2 capture. The combustion chamber of a conventional gas turbine was replaced by a membrane reactor, making it possible to obtain a highly concentrated CO2 stream for long-term storage. The focus was on power plant operation with a view to operational and material constraints of individual process components to ensure their proper Performance and required lifetime. In this respect, the mixed-conducting membrane modules were of Particular interest. Temperature as well as concentration limitations for CO2 and other chemical species narrowed the operating window. Other critical reactor components added further constraints. For Part-Load operation of the power plant, two Load control strategies were analysed for the gas turbine operating at constant rotational speed. In the first Load control strategy, variable guide vanes were used to manipulate the mass flow of air to the gas turbine compressor. This degree of freedom was used to control the turbine exit temperature. In the second control strategy, variable guide vanes were not used and the turbine exit temperature was allowed to vary. For both Load control strategies, the mean solid-wall temperature of the membrane modules was maintained close to its design value, which led to improved stability. The Load-control strategy using variable guide vanes was superior to the strategy without variable guide vanes due to higher combined cycle efficiencies and increased Load-reduction capability. Moreover, the Performance of the catalytic combustors in the membrane reactor, operating at near stoichiometric conditions, also improved as a result of increased oxygen concentrations at Part-Load operation. Relevant process components were based on spatially distributed conservation balances for energy, species, mass, and momentum. A stability diagram was incorporated into the membrane module model to investigate the risk of degradation. Performance maps were used for turbomachinery components.

  • control strategy for a solid oxide fuel cell and gas turbine hybrid system
    Journal of Power Sources, 2006
    Co-Authors: Christoph Stiller, Olav Bolland, Bjorn Thorud, Rambabu Kandepu, Lars Imsland
    Abstract:

    This paper presents a multi-loop control strategy for a SOFC/GT hybrid system. A detailed dynamic model of the system is presented and its Part-Load Performance is studied. The control objectives are discussed, with the main issue being a fairly constant fuel cell temperature under all conditions. Based on the system configuration and Part-Load Performance, input and output variables of the control system are detected. Control cycles are introduced and their design is discussed. The responses of the resulting system on Load changes, external disturbances as well as malfunction and degradation incidents are investigated. The system is stable under all incidents. An error in fuel flow measurement or assumed fuel quality provokes a steady-state fuel cell temperature offset. For a degraded system, it may be advisable to readjust the control system to the new characteristics.

Y. Tian - One of the best experts on this subject based on the ideXlab platform.

  • modelling for Part Load operation of solid oxide fuel cell gas turbine hybrid power plant
    Journal of Power Sources, 2003
    Co-Authors: S.h. Chan, Y. Tian
    Abstract:

    Abstract This paper presents the work on Part-Load operation of a power generation system composed of a solid oxide fuel cell and a gas turbine (SOFC–GT) which operate on natural gas. The system consists of an internal reforming SOFC (IRSOFC) stack, an external combustor, two turbines, two compressors, two recuperators and one heat-recovery steam generator (HRSG). Based on experience in different levels of modelling of the fuel cell, fuel cell stack and integrated system and the inherent characteristics of a IRSOFC–GT hybrid power plant, a practical approach for simplifying Part-Load operation of the system is proposed. Simulation results show that an IRSOFC–GT hybrid system could achieve a net electrical efficiency and system efficiency (including waste heat recovery for steam generation) of greater than 60 and 80%, respectively, under full-Load operation. Due to the complexity of the interaction of the components and safety requirements, the Part-Load Performance of a IRSOFC–GT hybrid power plant is poorer than that under full-Load operation.