thermodynamic model validation of capstone c30 micro gas turbine

Abstract In this work, a multi-variable multi-objective methodology aimed to perform the validation of the thermodynamic model has been applied to the Capstone C30 micro gas turbine. The methodology is based on a genetic optimization algorithm, where decision variables and objectives are set depending on available experimental data. The results of the studied case highlight the capability of the method to point out some experimental data inconsistencies and that it can lead to a consistency thermodynamic reconstruction of the micro turbine behaviour

Design of a Pilot SOFC System for the Combined Production of Hydrogen and Electricity under Refueling Station Requirements

The objective of the current work is to support the design of a pilot hydrogen and electricity producing plant that uses natural gas (or biomethane) as raw material, as a transition option towards a 100% renewable transportation system. The plant, with a solid oxide fuel cell (SOFC) as principal technology, is intended to be the main unit of an electric vehicle station. The refueling station has to work at different operation periods characterized by the hydrogen demand and the electricity needed for supply and self-consumption. The same set of heat exchangers has to satisfy the heating and cooling needs of the different operation periods. In order to optimize the operating variables of the pilot plant and to provide the best heat exchanger network, the applied methodology follows a systematic procedure for multi-objective, i.e. maximum plant efficiency and minimum number of heat exchanger matches, and multi-period optimization. The solving strategy combines process flow modeling in steady state, superstructure-based mathematical programming and the use of an evolutionary-based algorithm for optimization. The results show that the plant can reach a daily weighted efficiency exceeding 60%, up to 80% when considering heat utilization

A Validation Study for Turbulent Premixed Flame Propagation in Closed Vessels

Pressure rise in closed containments during accidental explosions is an important issue for the safety of nuclear power plants. For numerical prediction, several combustion models have been proposed by researchers to close the averaged balance equations describing the combustion process. In order to simulate these turbulent flame propagations, the combustion models have to be first validated against well performed experiments. This thesis primarily provides a step-by-step approach for validating a premixed turbulent combustion model in closed vessels. The approach used in this thesis consists of the use of an algebraic expression for the local turbulent flame speed which is then used to close the balance equations. Focus is given to select the correct solver which can accurately predict pressure waves during flame propagation. Before validating the calculations with experiments, mesh and time-step independency is checked. Sensitivity of results to the ignition method has also been addressed.Process and EnergyMechanical, Maritime and Materials Engineerin

Solid oxide fuel cell (SOFC) integrated power plants: System and kinetic studies

Increased climate change over past decades has resulted in an increase in the average temperature (also called global warming) of Earth’s climate system. At the recent Paris climate conference (COP21) in 2015, 195 countries in the world have agreed upon a stringent plan to limit global warming below 2oC. This demands a significant reduction in the industrial emission of greenhouse gases, predominantly carbon dioxide (CO2). Existing fossil fuel (coal, natural gas) fired power plants account for the majority share in global carbon dioxide (CO2) and other harmful (SOx , NOx) emissions. Therefore clean, efficient and flexible power plant concepts need to be developed towards upgrading existing power plants and to meet the strict CO2 emission targets. Combined cycle power plants like the integrated gasification combined cycle, IGCC (coal based) and integrated reforming combined cycle, IRCC (natural gas based) can be utilized to produce electricity using fossil fuels at relatively high efficiencies compared to conventional single cycle plants.Possible approaches to make IGCC/IRCC power plants cleaner, efficient and more flexible include biomass utilization (renewable energy source), application of CO2 capture technologies, retrofitting with highly efficient fuel conversion technologies like solid oxide fuel cells (SOFCs) and energy/fuel storage. This dissertation primarily aims to provide design concepts and thermodynamic system analysis for large scale IGCC and IRCC power plants with a focus on achieving high electrical efficiencies, low CO2 emissions and high operational flexibility. SOFCs have been explored as an efficiency augmenting technology and metal hydride based hydrogen storage as a flexibility option. Furthermore, future development of safe and optimally operating hydrocarbon (like natural gas (methane)) fuelled SOFC units on the basis of system and numerical models, requires reliable experimental data and understanding in the underlying reaction kinetics. Thereupon, an extended experimental study has been carried out in this work on methane steam reforming (MSR) kinetics in single operating SOFCs.Energy Technolog

On direct internal methane steam reforming kinetics in operating solid oxide fuel cells with nickel-ceria anodes

Major operating challenges remain to safely operate methane fuelled solid oxide fuel cells due to undesirable temperature gradients across the porous anode and carbon deposition. This article presents an experimental study on methane steam reforming (MSR) global kinetics for single operating SOFCs with Ni-GDC (gadolinium doped ceria) anodes for low steam to carbon (S/C) ratios and moderate current densities. The study points out the hitherto insufficient research on MSR global and intrinsic kinetics for operating SOFCs with complete Ni-ceria anodes. Further, it emphasizes the need to develop readily applicable global kinetic models as a subsequent step from previously reported state-of-art and complex intrinsic models. Two rate expressions of the Power law (PL) and Langmuir-Hinshelwood (LH) type have been compared and based on the analysis, limitations of using previously proposed rate expressions for Ni catalytic beds to study MSR kinetics for complete cermet anodes have been identified. Firstly, it has been shown that methane reforming on metallic (Ni) current collectors may not be always negligible, contrary to literature reports. Both PL and LH kinetic models predict significantly different local MSR reaction rate and species partial pressure distributions along the normalized reactor length, indicating a strong need for further experimental verifications.Energy TechnologyShip Design, Production and Operation

Study of methane steam reforming kinetics in operating solid oxide fuel cells: influence of current density

SOFCs are often designed to operate with specific fuels, quite often natural gas. CFD modeling is often used to arrive at efficient and safe SOFC designs. Therefore, when an SOFC is fed with different fuels, i.e., biosyngas, CFD can be used as a tool to predict whether the cell and stack will be safe and operate efficiently, and thus can give suggestions for the operation strategies for SOFCs. For that reason, a combined mass and heat transport model of an SOFC (single channel) has been developed for an anode-supported SOFC fed with biosyngas with special attention to the reaction kinetics of the direct internal reforming (DIR) reaction together with the water–gas shift reaction. An SOFC design jointly developed by ECN and Delft University of Technology is employed for the calculations. This work aims to predict the influence of different reforming reaction kinetic parameters on the cell performance by using an anode-supported intermediate temperature DIR planar solid oxide fuel single channel model, under co-flow operation. The DIR reaction of methane, the water–gas shift reaction and the electrochemical oxidation of hydrogen are being considered. As different reaction kinetic models are available in literature and employing them in CFD calculations will yield different results, a comparative analysis is carried out. Several cases were studied with a variety of DIR and water gas shift reaction kinetic parameters available from literature. For the different cases considered, the modeling results show differences in the current density distribution and temperature profile in the channel and in gas concentration profile along the channel. These differences are presented and discussed in detail. Predictions of the behaviors of internal reforming reaction in the reaction zone, and the possibilities of unwanted side reactions such as carbon deposition and Ni oxidation are given with constructive suggestions for future lab experiments

Solid Oxide Fuel Cells fuelled with biogas: Potential and constraints

Anaerobic Digestion (AD) is used worldwide for treating organic waste and wastewater. Biogas produced can be converted using conventional energy conversion devices to provide energy efficient, integrated waste solutions. Typically, the electrical conversion-efficiency of these devices is 30–40% and is lowered due to biogas utilization instead of high pure refined natural gas. The Solid Oxide Fuel Cell (SOFC) as an alternative device offers high (50–60%) electrical efficiency with low emissions (CO2, NOx) and high temperature residual heat. The high quality residual heat from SOFCs could be used to improve biogas production through thermal pre-treatment of the substrate for anaerobic digestion. This work discusses the advantages and challenges of integrated AD-SOFC systems against the most recent scientific and practical developments in the AD and SOFC domain. First, the biogas production process and its influence on the composition and level of contaminants in biogas are explained. Subsequently, the potential of various biogas cleaning techniques is discussed in order to remove contaminants that threaten stable and long-term SOFC operation. Since SOFCs utilize H2 and/or CO as fuel, possibilities for internal and external reforming are explained in detail. Special attention is given to biogas dry reforming in which CO2 naturally present in the biogas is utilized effectively in the reforming process. A detailed discussion on the choice of SOFC materials is presented, with a focus on biogas internal reforming. Various integrated SOFC system models with multiple configurations are also reviewed indicating the overall efficiencies. Some biogas SOFC pilot-plants are described and discussed to conclude with the techno-economic aspects of biogas SOFC systems.Energy TechnologySanitary Engineerin

Towards retrofitting integrated gasification combined cycle (IGCC) power plants with solid oxide fuel cells (SOFC) and CO₂ capture: A thermodynamic case study

This article presents a detailed thermodynamic case study based on the Willem-Alexander Centrale (WAC) power plant in the Netherlands towards retrofitting SOFCs in existing IGCC power plants with a focus on near future implementation. Two systems with high percentage (up to 70%) biomass co-gasification (based on previously validated steady state models) are discussed: (I) a SOFC retrofitted IGCC system with partial oxy-fuel combustion CO2 capture (II) a redesigned highly efficient integrated gasification fuel cell (IGFC) system with full oxy-fuel CO2 capture. It is concluded that existing IGCC power plants could be operated without major plant modifications and relatively high electrical efficiencies of more than 40% (LHV) by retrofitting SOFCs and partial oxy-combustion CO2 capture. In order to apply full scale CO2 capture, major process modification and redesign needs to be carried out, particularly in the gas turbine unit and heat recovery steam generator (HRSG). A detailed exergy analysis has also been presented for both the systems indicating significant efficiency improvement with the utilization of SOFCs. Additional discussions have also been presented on carbon deposition in SOFCs and biomass CO2 neutrality. It is suggested that scaling up of the SOFC stack module be carried out gradually, synchronous with latest technology development. The thermodynamic analysis and results presented in this article are also helpful to further evaluate design challenges in retrofitted IGCC power plant systems for near future implementation, gas turbine part load behaviour, to devise appropriate engineering solutions and for techno-economic evaluations.Energy Technology3mE Algemee

Thermodynamic System Studies for a Natural Gas Combined Cycle (NGCC) Plant with CO2 Capture and Hydrogen Storage with Metal Hydrides

Flexibility in natural gas combined cycle power plants (NGCC) with pre-combustion CO2 capture could be introduced with co-production of hydrogen and subsequent hydrogen storage with metal hydrides (MH). The current work presents a thermodynamic analysis and comparison between steady state ASPEN Plus models of a reference case NGCC plant with no capture and H2 storage, an NGCC plant with pre-combustion capture using gas heated - auto thermal reformer (GHR-ATR) combined with a sorption enhanced water gas shift (SEWGS) unit and a NGCC model with capture and a metal hydride (MH) based hydrogen storage unit. Results have been presented for a high temperature hydride (MgH2) and a medium temperature hydride (Na3AlH6). A net plant efficiency of about 48% was achieved for the system with only capture. Addition of hydrogen storage in this system shows that such plants can be still operated at comparable time based average efficiency of about 47% with an appropriate heat integration in the system. Operating the metal hydride at different temperatures does not reflect reduction in efficiency but a lower equilibrium temperature seems more beneficial particularly for a practical economizer in the HRSG. It is concluded that MH based hydrogen storage in NGCC plants with pre-combustion CO2 capture is a promising option to manage fluctuations in power demand and further investigations are required particularly on heat integration, effect of H2 purification technologies and economic assessment.Process and EnergyMechanical, Maritime and Materials Engineerin

Experimental model validation and thermodynamic assessment on high percentage (up to 70%) biomass co-gasification at the 253 MWe integrated gasification combined cycle power plant in Buggenum, The Netherlands

Energy TechnologyProcess and Energ