Gas Turbine Power System Research Articles

Operation and Simulation of Hybrid Wind and Gas Turbine Power System Employing Wind Power Forecasting

Due to the intermittence and fluctuation of wind resource, the integration of large wind farms in a power grid always brings challenges to maintain the stability of a power system. Integrating gas turbine units with wind farms can compensate for their output fluctuation. A methodology for the operation scheduling of a hybrid power system that consists of a large wind farm and gas turbine units is presented. A statistical model based on numerical weather prediction is used to forecast power output of the wind farm. Forecasts of wind power are used for optimizing the operation scheduling. Dynamic modeling of this hybrid power system is addressed. Simulation studies are carried out to evaluate the system performance using real weather data. The simulation results show that the proposed hybrid power system can compensate fluctuating wind power effectively and make wind power more reliable.

Performance evaluation of a direct-biogas solid oxide fuel cell-micro gas turbine (SOFC-MGT) hybrid combined heat and power (CHP) system

The combination of a direct-biogas solid oxide fuel cell (SOFC) with a micro gas turbine (MGT) system offers great potential as a green decentralized combined heat and power (CHP) system. To evaluate the potential use of biogas as the main source of energy for a direct-biogas SOFC-MGT hybrid CHP system, a sensitivity analysis was conducted under diverse operating conditions to investigate the influence of key operating parameters of the hybrid CHP system with the consideration of operational constraints. The key parameters in this study were SOFC reforming agent, SOFC fuel utilization factor (Uf), turbine inlet temperature (TIT), and compression ratio. The influence of variation in operating parameters on plant performance was evaluated for the overall system and SOFC efficiencies as well as the heat-to-power ratio (TER), the power ratio of MGT to SOFC (PMGT/PSOFC), and the size of the SOFC stack. As a reforming agent for direct-biogas SOFC, steam is more preferable than a traditional air–steam mixture in terms of material limitations and SOFC efficiencies; however, an air–steam mixture with a small amount of air boosts the useful heat output and electricity generated by an MGT without significantly affecting overall system efficiency. The increase in Uf improves the electrical power output produced by the SOFC stack, but also requires more fuel to be fed to the burner, resulting in an increase in useful heat energy. Increasing the compression ratio improves the system electrical efficiency but lowers useful heat generation; nevertheless, increasing TIT decreases the system electrical efficiency but improves the efficiency of the CHP system. To achieve the optimum operating conditions of the hybrid CHP system, the operating parameters should be determined based on the desired energy outcomes.

The hybrid solid oxide fuel cell (SOFC) and gas turbine (GT) systems steady state modeling

Solid Oxide Fuel Cells (SOFCs) are of great interest nowadays. The feature of SOFCs makes them suitable for hybrid systems because they work high operating temperature and when combined with conventional turbine power plants offer high cycle efficiencies. In this work a hybrid solid oxide fuel cell and gas turbine power system model is developed. Two models have been developed based on simple thermodynamic expressions. The simple models are used in the preliminary part of the study and a more realistic based on the performance maps. A comparative study of the simulated configurations, based on an energy analysis is used to perform a parametric study of the overall hybrid system efficiency. Some important observations are made by means of a sensitivity study of the whole cycle for the selected configuration. The results of the selected model were compared to an earlier model from an available literature.

Understanding and improving energy conversion systems with the aid of exergy-based methods

Exergy–based methods are powerful tools for developing, evaluating and improving an energy conversion system. Conventional exergy–based analyses have limitations, which are significantly reduced by the so–called advanced analyses. The latter evaluate: (a) the interactions among components of the overall system, and (b) the real potential for improving a system component. The main objective of advanced exergy–based analyses is to provide additional information that is useful improving the design and operation of energy conversion systems. This paper deals with integrated conventional and advanced exergetic, exergoeconomic and exergoenvironmental analyses. The advantages of these analyses are demonstrated using an academic example, an open–cycle gas turbine power system.

5MW급 바이오 가스터빈용 전처리시스템 설계연구

Korea is the 11th largest energy consumption country and 96% of its total energy consumption depends on imports from overseas. Therefore it is a very important task to secure renewable energy sources which can reduce both the carbon-dioxide emission and dependency on overseas energy imports. Among the various renewable energy sources, organic wastes are important sources. In Korea, 113 million toe of methane is generated from organic wastes annually, but only 3.7% is effectively used for energy conversion. Thus, it is very important to make better use of organic wastes, especially for power generation. The goals of this project are to develope the fuel supplying system of Bio Gasturbine (GT) for 5MW-class co-generation system. The fuel supplying system mainly consists of <TEX>$H_2S$</TEX> removal system, Bio Gas compression system, Siloxane removal system and moisture separating systems. The fuel requirement of 5MW-class GT is at around 60% of <TEX>$CH_4$</TEX>, <TEX>$H_2S$</TEX> (<30 ppm), Siloxane(<10 mg/<TEX>$nm^3$</TEX>) and supply pressure (> 25 bar) from biogas compressor. Main mechnical charateristics of Bio Gasturbine system have the specific performance; 1) high speed turbine speed (12,840 rpm) 2) very clean emmission NOx (<50 ppm) 3) high efficiency of energy conversion rate. This paper focuses on the development of design technology for food waste biogas pretreatment system for 5MW-class biogas turbine. The study also has the plan to replace the fuel of gas turbine and other distributed power systems. As the increase of bioenergy, this system help to contribute to spread more New & Renewable Energy and the establishment of Renewable Portfolio Standards (RPS) for Korea.

Maintenance management of gas turbine power plant systems

Over the years, electric power generation and supply has not been steady and sufficient in Nigeria. Breakdown of machinery and equipment is being identified as some of the major factors for continuous state of affairs. Given the abundant availability of gas and the significant installed capacity of the electricity from Gas Turbine Power Systems; effective maintenance of Gas Turbine Power Plants in Nigeria could be the panacea for achieving regular power generation and supply. The study identified environmental impact on the machines, economic limitation, government policies, inconsistency in following maintenance procedures and bottlenecks as some of the serious constraints affecting maintenance of Gas Turbine Power Plants in Nigeria. Maintenance models that could be considered in Afam power station are highlighted and analyzed in the context of these constraints. Also necessary recommendations that will improve maintenance and operations of Gas Turbine Power Plants in Nigeria are proposed.

Process characteristics of pretreatment system under H2S circumstance for bio-gas micro gas turbine power generation

As distributed generation becomes more reliable and economically feasible, it is expected that a higher application of the distributed generation such as Micro Gas Turbine Power system would be interconnected to the existing grids. This paper describes the results for the mechanical and environmental tests of pretreatment system for Livestock bio-energy Micro Gas Turbine (MGT) Combined Heat & power. It is very important for bio-energy pretreatment system to design MGT power generation. Especially, mechanical and corrosion characteristics of H2S removal system make differences between parent and weldment material, notch existence/non-existence and air/H2S conditions. As a result, the life of pipelines needs to be maintained and fit for the operating period. Based on actual situations, the tension test of pipe welding-parts is carried out varying the exposure time to hydrogen sulfide and a fatigue resistance test is also performed inserting a notch into the pipe welding part, being exposed to the hydrogen sulfide environment for 180, 360, 540, 720 hours.

Numerical analyses and experiment investigations of an annular micro gas turbine power system using fuels with low heating values

This study investigates the effects of using fuels with low heating values on the performance of an annular micro gas turbine (MGT) experimentally and numerically. The MGT used in this study is MW-54, whose original fuel is liquid (Jet A1). Its fuel supply system is re-designed to use biogas fuel with low heating value (LHV). The purpose is to reduce the size of a biogas distributed power supply system and to enhance its popularization. This study assesses the practicability of using fuels with LHVs by using various mixing ratios of methane (CH4) and carbon dioxide (CO2). Prior to experiments, the corresponding simulations, aided by the commercial code CFD-ACE+, were carried out to investigate the cooling effect in a perforated combustion chamber and combustion behavior in an annular MGT when LHV gas was used. The main purposes are to confirm that there are no hot spots occurring in the liners and the exhaust temperatures of combustor are lower than 700°C when MGT is operated under different conditions. In experiments, fuel pressure and mass flow rate, turbine rotational speed, generator power output, and temperature distribution were measured to analyze MGT performance. Experimental results indicate that the presented MGT system operates successfully under each tested condition when the minimum heating value of the simulated fuel is approximately 50% of pure methane. The power output is around 170 W at 85000 r/min as 90% CH4 with 10% CO2 is used and 70 W at 60000 r/min as 70% CH4 with 30% CO2 is used. When a critical limit of 60% CH4 is used, the power output is extremely low. Furthermore, the best theoretical Brayton cycle efficiency for such MGT is calculated as 23% according to the experimental data while LHV fuel is used. Finally, the numerical results and experiment results reveal that MGT performance can be improved further and the possible solutions for performance improvement are suggested for the future studies.

Estimating the quality of metal in cast working blades made of the nickel alloy ChS88U-VI

Results are presented from a study of the metal in the working blades for a gas turbine power system made of the nickel alloy ChS88U-VI in its initial heat treated state. It is found that cooled working blades in the first and second stages meet the engineering requirements, while large uncooled blades in the third and fourth stages deviate from the specifications for a turbine system in terms of their macrostructure and mechanical properties.

Thermodynamic analysis of a combined gas turbine power system with a solid oxide fuel cell through exergy

This paper examines the exergetic performance of a high-temperature solid oxide fuel cell (SOFC) combined with a conventional recuperative gas turbine (GT) plant. Individual models are developed for each component, specifically for SOFC and a combustor that is located downstream of the cell stack. The exergy destruction and efficiency of each component are derived and presented. Furthermore, the overall system is analyzed and its exergy efficiency, as well as exergy destruction, is computed. An assessment of the cycle is performed for an actual system and the results for certain operating conditions are compared with past published results. The comparisons provide useful verification of the thermal simulations in the present work. Further outcomes indicate that increasing the turbine inlet temperature (TIT) results in decreasing the exergy and thermal efficiencies of the cycle, whereas it improves the total specific power output. Also, an increase in either TIT or compression ratio ( r p) leads to a higher rate of exergy destruction of the plant. A comparison between the GT–SOFC plant and a traditional GT cycle, based on identical operating conditions, is also made. The superior performance of a GT–SOFC, in terms of thermal and exergy efficiencies, over a traditional GT cycle is evident: 26.6% and 27.8% better exergetic and energetic performance, respectively, than a traditional GT plant. In this case, the exergy and thermal efficiencies of the integrated cycle become as high as 57.9% and 60.6%, respectively, at the optimum compression ratio.

208 液化石油ガスを燃料とするマイクロガスタービン・固体酸化物形燃料電池ハイブリッド発電システムの熱的性能解析(熱力学2)

208 液化石油ガスを燃料とするマイクロガスタービン・固体酸化物形燃料電池ハイブリッド発電システムの熱的性能解析(熱力学2)

Solar-Assisted Small Solar Tower Trigeneration Systems

Solar-hybrid gas turbine power systems offer a high potential for cost reduction of solar power. Such systems were already demonstrated as test systems. For the market introduction of this technology, microturbines in combination with small solar tower plants are a promising option. The combination of a solarized microturbine with an absorption chiller was studied; the results are presented in this paper. The solar-hybrid trigeneration system consists of a small heliostat field, a receiver unit installed on a tower, a modified microturbine, and an absorption chiller. The components are described, as well as the required modifications for integration to the complete system. Several absorption chiller models were reviewed. System configurations were assessed for technical performance and cost. For a representative site, a system layout was made, using selected industrial components. The annual energy yield in power, cooling, and heat was determined. A cost assessment was made to obtain the cost of electricity and cooling power, and eventually additional heat. Various load situations for electric and cooling power were analyzed. The results indicate promising niche applications for the solar-assisted trigeneration of power, heat, and cooling. The potential for improvements in the system configuration and the components is discussed, also the next steps toward market introduction of such systems.

Performance analysis of combined humidified gas turbine power generation and multi-effect thermal vapor compression desalination systems: Part 2: The evaporative gas turbine based system and some discussions

This is Part 2 of the paper “Performance analysis of combined humidified gas turbine power generation and multi-effect thermal vapor compression desalination systems — Part 1: The desalination unit and its combination with a steam-injected gas turbine power system”. A combined power and water system based on the evaporative gas turbine (EvGT) is studied, and major features such as the fuel saving, power-to-water ratio, energy and exergy utilization, and approaches to performance improvement, are presented and discussed in comparison with STIG- and EvGT- based systems, to further reveal the characteristics of these two types of combined systems. Some of the main results of the paper are: the fuel consumption of water production in STIG-based combined system is, based on reference-cycle method, about 45% of a water-only unit, and that in an EvGT-based system, it is 31–54%; compared with the individual power-only and water-only units, the fuel savings of the two combined systems are 12%–28% and 10%–21%, respectively; a water production gain of more than 15% can be obtained by using a direct-contact gas-saline water heat exchanger to recover the stack heat; and the combined system are more flexible in its power-to-water ratio than currently used dual-purpose systems. Further studies on aspects such as operation, hardware cost, control complexity, and environmental impact, are needed to determine which configuration is more favorable in practice.

Performance analysis of combined humidified gas turbine power generation and multi-effect thermal vapor compression desalination systems — Part 1: The desalination unit and its combination with a steam-injected gas turbine power system

Humidified gas turbines (HGT) have been identified as a promising way of producing power. The use of the steam-injected gas turbine (STIG) HGT cycle in a combined power and water desalination system was analyzed using energy and exergy performance criteria. A brief description and rationale of the background of HGT cycles and dual-purpose power and water systems is given. A thermal desalination unit was modeled and analyzed, and the results led to the selection of a multi-effect thermal vapor compression (METVC) unit for producing fresh water from seawater for both general use and humidification; then the performance of a STIG-based combined system was investigated. The analysis performed improved the understanding of the combined STIG power and water desalination process and of ways to improve and optimize it. Some specific conclusions are that: (1) a METVC desalination system is preferred to a multieffect evaporation one when the pressure of the motive steam is high enough, >∼3 bar, to run a steam jet ejector; (2) the steam injection rate in the STIG cycle has a strong effect on water and power production, offering good flexibility for design and operation; (3) higher pressure ratios and higher steam injection rates in the STIG cycle increase power generation, but decrease water production rates, and higher turbine inlet temperatures increased both power and water production; (4) a distinct water production gain can be obtained by recovering the stack gas energy. The results indicate that such dual-purpose systems have good synergy, not only in fuel utilization, but also in operation and design flexibility.

Simulation and exergy analysis of a hybrid Solid Oxide Fuel Cell (SOFC)–Gas Turbine System

The simulation and exergy analysis of a hybrid Solid Oxide Fuel Cell–Gas Turbine (SOFC–GT) power system are discussed in this paper. In the SOFC reactor model, it is assumed that only hydrogen participates in the electrochemical reaction and that the high temperature of the stack pushes the internal steam reforming reaction to completion; the unreacted gases are assumed to be fully oxidized in the combustor downstream of the SOFC stack. Compressors and GTs are modeled on the basis of their isentropic efficiency. As regards the heat exchangers and the heat recovery steam generator, all characterized by a tube-in-tube counterflow arrangement, the simulation is carried out using the thermal efficiency-NTU approach. Energy and exergy balances are performed not only for the whole plant but also for each component in order to evaluate the distribution of irreversibility and thermodynamic inefficiencies. Simulations are performed for different values of operating pressure, fuel utilization factor, fuel-to-air and steam-to-fuel ratios and current density. Results showed that, for a 1.5 MW system, an electrical efficiency close to 60% can be achieved using appropriate values of the most important design variables; in particular, the operating pressure and cell current density. When heat loss recovery is also taken into account, a global efficiency of about 70% is achieved.

04/02808 Probabilistic analysis of a solid-oxide fuel-cell based hybrid gas-turbine system: Gorla, R. S. R. Applied Energy, 2004, 78, (1), 63–74

Two, simple, solid-oxide fuel-cell (SOFC) power systems fed by hydrogen and methane, respectively, are examined. While other models available in the literatures focus on complicated hybrid SOFC and gas-turbine (GT) power systems, this study focuses on simple SOFC power systems with detailed thermodynamic modeling of the SOFC. All performance-related parameters of the fuel-cell such as respective resistivity of the components, anode and cathode exchange current density, limiting current density, flow diffusivity, etc. are all expressed as a function of temperature, while the flow through of each nodes of the system is described as a function of thermodynamic state. Full analysis of the energy and exergy at each node of the system is conducted and their respective values are normalized by the lower heating value (LHV) of the fuel and its chemical exergy, respectively. Thus, the normalized electrical energy outputs directly indicate the first law and second law efficiencies, respectively, of the fuel-cell power systems.

Energy and exergy analysis of simple solid-oxide fuel-cell power systems

Two, simple, solid-oxide fuel-cell (SOFC) power systems fed by hydrogen and methane, respectively, are examined. While other models available in the literatures focus on complicated hybrid SOFC and gas-turbine (GT) power systems, this study focuses on simple SOFC power systems with detailed thermodynamic modeling of the SOFC. All performance-related parameters of the fuel-cell such as respective resistivity of the components, anode and cathode exchange current density, limiting current density, flow diffusivity, etc. are all expressed as a function of temperature, while the flow through of each nodes of the system is described as a function of thermodynamic state. Full analysis of the energy and exergy at each node of the system is conducted and their respective values are normalized by the lower heating value (LHV) of the fuel and its chemical exergy, respectively. Thus, the normalized electrical energy outputs directly indicate the first law and second law efficiencies, respectively, of the fuel-cell power systems.

Advances in solid oxide fuel cell technology

High temperature solid oxide fuel cells (SOFCs) offer a clean, pollution-free technology to electrochemically generate electricity at high efficiencies. These fuel cells provide many advantages over traditional energy conversion systems including high efficiency, reliability, modularity, fuel adaptability, and very low levels of NO x and SO x emissions. Furthermore, because of their high temperature of operation (∼1000°C), natural gas fuel can be reformed within the cell stack eliminating the need for an expensive, external reformer. Also, pressurized SOFCs can be successfully used as replacements for combustors in gas turbines; such hybrid SOFC–gas turbine power systems are expected to reach efficiencies over 70%. This paper reviews the materials and fabrication methods used for the different cell components, and discusses the performance of cells fabricated using these materials; it also discusses the materials and processing studies that are under investigation to reduce the cell cost. Finally, the paper summarizes the recently built power generation systems that employed state-of-the-art SOFCs. A new design SOFC that combines the seal-less feature of tubular cells and a flattened air electrode with integral ribs is also described; this new design has a shortened current path and hence lower cell resistance and higher power output than tubular cells.

Power generation with gas turbine systems and combined heat and power

This article gives an overview of power generation with gas turbine and combined heat and power (CHP) systems. It also presents the European Union strategy for developing gas turbines and CHP systems. Ways to improve the performance of the several types of gas turbine cycle will be a major objective in the coming years. The targets are combined cycle efficiencies above 60% industrial gas turbine system efficiencies of at least 50% and small gas turbines efficiencies above 35% and designs for the use of fuels with less than 25% heating value of that of natural gas. The main CHP targets are the reduction of the overall costs and the development of above 40 kW biomass-fired systems.

Revealing the cost-efficiency trends of the design concepts of energy-intensive systems

Design models for the components of an energy system concept are used to extract the information relevant to the prediction of the cost and performance of the system. The information is directed towards seeking an optimal design point for the system and then redirected towards predicting its performance at off-design points. The design model of a heat exchanger is used as an example for information extraction. Few gas turbine power systems are considered for optimal design. The part-load operation of the optimized simple combined cycle is then computed. The methodology in more detail is referred to elsewhere.