Aristide F. Massardo

Internal Reforming Solid Oxide Fuel Cell-Gas Turbine Combined Cycles (IRSOFC-GT): Part A— Cell Model and Cycle Thermodynamic Analysis

The aim of this work is to investigate the performance of internal reforming solid oxide fuel cell (IRSOFC) and gas turbine (GT) combined cycles. To study complex systems involving IRSOFC a mathematical model has been developed that simulates the fuel cell steady-state operation. The model, tested with a data available in literature, has been used for a complete IRSOFC parametric analysis taking into account the influence of cell operative pressure, cell and stream temperatures, fuel oxidant flow rates and composition, etc. The analysis of IRSOFC-GT combined cycles has been carried out by using the Thermo Economic Modular Program TEMP.The code has been modified to allow IRSOFC, external reformer and flue gas condenser performance to be taken into account. Using as test case the IRSOFC-GT combined plant proposed by Harvey and Richter (1994) the capability of the modified TEMP code has been demonstrated. The thermodynamic analysis of a number of IRSOFC-GT combined cycles is presented and discussed, taking into account the influence of several technological constraints. The results are presented for both atmospheric and pressurized IRSOFC.

Microturbine/fuel-cell coupling for high-efficiency electrical-power generation

Microturbines and fuel cells are currently attracting a lot of attention to meet future users needs in the distributed generation market. This paper addresses a preliminary analysis of a representative state-of-the-art 50-kW microturbine coupled with a high-temperature solid-oxide fuel cell (SOFC). The technologies of the two elements of such a hybrid-power plant are in a different state of readiness. The microturbine is in an early stage of pre-production and the SOFC is still in the development phase. It is premature to propose an optimum solution. Based on todays technology the hybrid plant, using natural gas fuel, would have a power output of about 389 kW, and an efficiency of 60 percent. If the waste heat is used the overall fuel utilization efficiency would be about 80 percent. Major features, parameters, and performance of the microturbine and the SOFC are discussed. The compatibility of the two systems is addressed, and the areas of technical concern, and mismatching issues are identified and discussed. Fully understanding these, and identifying solutions, is the key to the future establishing of an optimum overall system. This approach is viewed as being in concert with evolving technological changes. In the case of the microturbine changes will be fairly minor as they enter production on a large scale within the next year or so, but are likely to be significant for the SOFC in the next few years, as extensive efforts are expended to reduce unit cost. It is reasonable to project that a high performance and cost-effective hybrid plant, with high reliability, will be ready for commercial service in the middle of the first decade of the 21st century. While several microturbines can be packaged to give an increased level of power, this can perhaps be more effectively accomplished by coupling just a single gas turbine module with a SOFC. The resultant larger power output unit opens up new market possibilities in both the industrial nations and developing countries.

Thermoeconomic analysis of mixed gas-steam cycles

Abstract In this paper the direct thermoeconomic analysis approach developed by the authors [ASME Paper 95-CTP-38; ASME Cogen Turbo Power Conference, Wien, 23/25 August, 1995] is applied to the assessment of the thermoeconomic performance of mixed gas–steam cycles such as the steam injected cycle (steam injected gas turbine, STIG), regenerated water injected (RWI) cycle, and humid air turbine (HAT) or evaporative cycle. All the simulations were carried using the thermo-economic modular program (TEMP) code developed at the University of Genoa [ASME Trans., J. Engng. Gas Turbine Power 119 (1997) 885; Thermo-economic and environmental optimisation of energy systems, Tesi di Dottorato, Universita di Genova (DIMSET), 1997] and carefully tested here, mainly for the HAT cycle and saturator, using the experimental data provided by the HAT pilot-plant operating at the Lund University, Sweden [Theoretical and experimental evaluation of the EvGT-process, Thesis for Degree of Licentiate in Engineering, Lund Institute of Technology, Sweden, 1999; Evaporative cycles – in theory and in practice, Doctoral Thesis, Lund Institute of Technology, Sweden, 2000]. Three different mixed cycles (STIG, RWI, and HAT) are analysed in detail together with an additional fourth layout proposed by the authors [Thermoeconomic analysis of STIG, RWI and HAT cycles with carbon dioxide (CO 2 ) emissions penalty, Tesi di laurea, Universita di Genova (DIMSET), 2000], named HAWIT, humid air water injection turbine, that appears to be the most attractive solution. The thermoeconomic results of mixed cycles are presented here for the first time in open literature. These results are compared to the data of a conventional two-pressure level combined cycle considered as representative of the state of the art of high efficiency conversion systems. A new representation proposed by the authors [ASME Trans., J. Engng. Gas Turbine Power 122 (2000)], such as cost of electricity versus cycle efficiency or internal rate of return versus electric efficiency, is used to demonstrate the main features of these types of innovative energy plants.

Saturator analysis for an evaporative gas turbine cycle

Abstract In this paper a thermodynamic assessment and a preliminary cost evaluation are given for an evaporative gas turbine (EvGT) cycle packed humidifier. Both background theory and simulation results are included. Two different approaches were used for the humidifier system modelling: the full integration of the mass-energy balance and mass transfer equations (called SAT model), and an atmospheric cooling tower-based model (called CT model). Both approaches were used to perform component thermodynamic analyses and to determine the humidifier packing design. Within these approaches, two simulation cases are discussed: a test case, with experimental results from the pilot-plant of the University of Lund, and a case study of the saturators for the optimised HAT (humid air turbine) cycles of a plant with a 50 MW power output. The two cases presented consider two different operating conditions for the saturator: the first being a “non-optimised” saturator, and the later the “optimal” configuration with reduced exergetic losses. For the case study, the saturator design and cost evaluation are also included. All simulation results were performed with the in-house SAT (SATurator simulation tool) code.

Recuperated gas turbine aeroengines, part II: engine design studies following early development testing

Purpose – To advance the design of heat exchanged gas turbine propulsion aeroengines utilising experience gained from early development testing, and based on technologies prevailing in the 1970‐2000 time frame.Design/methodology/approach – With emphasis on recuperated helicopter turboshaft engines, particularly in the 1,000 hp (746 kW) class, detailed performance analyses, parametric trade‐off studies, and overall power plant layouts, based on state‐of‐the‐art turbomachinery component efficiencies and high‐temperature heat exchanger technologies, were undertaken for several engine configuration concepts.Findings – Using optimised cycle parameters, and the selection of a light weight tubular heat exchanger concept, an attractive engine architecture was established in which the recuperator was fully integrated with the engine structure. This resulted in a reduced overall engine weight and lower specific fuel consumption, and represented a significant advancement in technology from the modified simple‐cycle ...

Parametric Performance of Combined-Cogeneration Power Plants With Various Power and Efficiency Enhancements

The design-point performance characteristics of a wide variety of combined-cogeneration power plants, with different amounts of supplementary firing (or no supplementary firing), different amounts ...

A Hybrid System Based on a Personal Turbine (5 kW) and a Solid Oxide Fuel Cell Stack: A Flexible and High Efficiency Energy Concept for the Distributed Power Market

In this paper a high efficiency and flexible hybrid system representing a new total energy concept for the distributed power market is presented. The hybrid system is composed of a very small size (5 kW) micro gas turbine (named personal turbine-PT) presented in a companion paper by the authors coupled to a small size solid oxide fuel cell (SOFC) stack. The power of the whole system is 36 kW depending on the design parameters assumed for the stack. The design and off-design performance of the hybrid system have been obtained through the use of an appropriate modular code named HS-SOFC developed at the University of Genoa and described in detail in this paper. The results of the simulation are presented and discussed with particular regards to: choice of the hybrid system (HS) design point data, HS design point performance, off-design performance of PT and SOFC stack, and off-design performance of the whole HS. Some preliminary economic results are also included based on different fuel and capital cost scenarios and using the cost of electricity as the parameter for comparison between PT and HS.

Design and Testing of Ejectors for High Temperature Fuel Cell Hybrid Systems

Our goal in this work is the improvement of the ejector performance inside hybrid systems supporting the theoretical activity with experimental tests. In fact, after a preliminary ejector design, an experimental rig has been developed to test single stage ejectors for hybrid systems at different operative conditions of mass flow rates, pressures, and temperatures. At first, an open circuit has been built to perform tests at atmospheric conditions in the secondary duct. Then, to emulate a SOFC anodic recirculation device, the circuit has been closed, introducing a fuel cell volume in a reduced scale. This configuration is important to test ejectors at pressurized conditions, both in primary and secondary ducts. Finally, the volume has been equipped with an electrical heater and the rig has been thermally insulated to test ejectors with secondary flows at high temperature, necessary to obtain values in similitude conditions with the real ones. This test rig has been used to validate simplified and CFD models necessary to design the ejectors and investigate the internal fluid dynamic phenomena. In fact, the application of CFD validated models has allowed us to improve the performance of ejectors for hybrid systems optimizing the geometry in terms of primary and secondary ducts, mixing chamber length, and diffuser. However, the simplified approach is essential to start the analysis with an effective preliminary geometry.

Heat Exchangers for Fuel Cell and Hybrid System Applications

The fuel cell system and fuel cell gas turbine hybrid system represent an emerging technology for power generation because of its higher energy conversion efficiency, extremely low environmental pollution, and potential use of some renewable energy sources as fuels. Depending upon the type and size of applications, from domestic heating to industrial cogeneration, there are different types of fuel cell technologies to be employed. The fuel cells considered in this paper are mainly the molten carbonate (MCFC) and the solid oxide (SOFC) fuel cells, while a brief overview is provided about the proton exchange membrane (PEMFC). In all these systems, heat exchangers play an important and critical role in the thermal management of the fuel cell itself and the boundary components, such as the fuel reformer (when methane or natural gas is used), the air preheating, and the fuel cell cooling. In this paper, the impact of heat exchangers on the performance of SOFC, MCFC gas turbine hybrid systems and PEMFC systems is investigated. Several options in terms of cycle layout and heat exchanger technology are discussed from the on-design, off-design and control perspectives. A general overview of the main issues related to heat exchangers performance, cost and durability is presented and the most promising configurations identified.

WIDGET-TEMP: A Novel Web-Based Approach for Thermoeconomic Analysis and Optimization of Conventional and Innovative Cycles

In a deregulated energy market the adoption of multipurpose and flexible software tools for the optimal design and sizing of energy systems is becoming mandatory. For these reasons, we have developed WIDGET-TEMP (Web-based Interface and Distributed Graphical Environment for TEMP, ThermoEconomic Modular Program), a tool which is the result of an interdisciplinary research which applied recent IT innovations such as XML and web-based approaches to the analysis and optimization of energy plant layouts on a thermoeconomic basis. WIDGET provides an interface for remotely accessing the internal thermoeconomic analysis, the full life-cycle cost and investment assessment, which includes the economic impact of environmental costs due to pollutant emissions. This approach reduces the requirements for the local machine in terms of processor time and memory, and allows users to exploit the tool just when needed. An initial functional productive diagram of the plant is now automatically drawn and is available to the user on a visual basis. We present a general description of the tool organization and outline the approach for modeling the technical performance and cost of the component. Then, we describe the latest upgrades of TEMP, and report the new gas turbine cost equations. Finally, the tool is applied to a conventional simple and combined cycle, showing both the usability of the new tool and the reliability of the results.