Integration Of Power Generation Research Articles

Thermodynamic analysis of KCS/ORC integrated power generation system with LNG cold energy exploitation and CO2 capture

In this paper, an integrated power generation system of Kalina cycle system (KCS) and organic Rankine cycle (ORC) with LNG cold energy exploitation and CO2 capture is introduced. The composite circulation system can fully recover and use the medium and low temperature waste heat to reduce the greenhouse gas emissions. To evaluate the system performances, the thermodynamics model was established and the system was simulated by using Aspen HYSYS software. Thermodynamic analysis has been performed to study the effects of turbine inlet temperature, NH3 mass fraction, evaporation pressure and CO2 capture pressure on the KCS/ORC integrated system. The optimal conditions were also investigated and identified. Exergy analysis of the components operated on KCS or ORC has also been demonstrated. The results showed that the optimal values of the network output, thermal efficiency and CO2 captured quantity of the system were respectively 394.685 kW, 53.25% and 0.3 t/tCO2 (0.6 t/tLNG), while the evaluation indexes of the power recovery efficiency and exergy efficiency were respectively 36% and 41.42%. The exergy loss efficiency of each component was examined. It was indicated that the whole system has significant advantages in waste heat recovery.

Thermal efficiency of advanced integrated coal gasification combined cycle power generation systems with low-temperature gasifier, gas cleaning and CO2 capturing units

Advanced integrated coal gasification combined cycle (A-IGCC) systems have been proposed to obtain higher thermal efficiency than that of IGCC systems by recuperating exhaust heat from a gas turbine to provide the heat source for a gasifier. The performances of the A-IGCC systems with a low-temperature dual-bed fluidized bed gasifier, gas cleaning, CO2 capturing, and the most advanced (1650°C-class) gas turbine units were evaluated using Aspen Plus®. Net thermal efficiency of the A-IGCC model with hot gas desulfurizing unit using ZnO and TiO2 was 53.6% and that with cold gas desulfurizing unit using Selexol® process was 52.0% without CO2 capturing when the cold gas efficiency (CGE) in the gasifier was 80.1%. The net thermal efficiency can be increased to 54.7–57.2% by improving CGE from 80.1 to 85.0%, suggesting the improvement of cold gas efficiency in the gasifier is critical. CO2 emission factors of the A-IGCC system are 505–520kg-CO2/MWh (CGE=80.1%) and 468–490kg-CO2/MWh (CGE=85.0%), and can be decreased to 39.7–112kg-CO2/MWh with 80–95% of CO2 capturing. Compliance to the CO2 emission factor target (<499kg-CO2/MWh) for coal-fired power generation systems can be achieved without CO2 capturing by developing gasifiers whose CGE is 85.0% and integration with 1650°C-glass gas turbine.

Enhanced process integration of black liquor evaporation, gasification, and combined cycle

Energy recovery from black liquor (BL) can be performed through gasification at temperatures above the melting point of inorganic chemicals. Complementarily to BL gasification experimental research, this study is conducted to simulate the thermodynamic modeling of an integrated system for BL evaporation, gasification, and combined cycle for power generation. For BL evaporation, a novel system is proposed based on the concept of exergy recovery to minimize exergy loss, and thus, lower the required energy input for evaporation. From the process design and calculations, higher target solid content leads to lower total required energy for BL evaporation. The lowest required total energy for evaporation can be achieved at a target solid content of 75wt% wb. Furthermore, an integrated power generation system adopting gasification and combined cycle is modeled, and an application of different BL evaporation technologies is also evaluated in terms of net energy efficiency. The integrated system with exergy recovery-based evaporation can achieve a net energy efficiency of 34.5%, which is significantly higher than those of multi-effect evaporators (24.5%) and conventional boiler-based evaporation (14.7%).

Research on Optimal Planning of Access Location and Access Capacity of Large-Scale Integrated Wind Power Plants

This paper proposes a multi-objective optimal planning model of access location and access capacity for large-scale integrated wind power generation considering the mutual restriction between the planning of large-scale wind power plants and the planning of power system network. In this model, the power flow equilibrium degree, investment costs and active network loss are taken as the optimization goals. The improved differential evolution (IDE) algorithm is applied to calculate the Pareto optimal solution set of wind power’s access planning. With the solution results described by the Pareto pattern, all the alternative solutions are then ranked based on the entropy weight method and the final compromised solution is selected by the method of technique for order preference by similarity to ideal (TOPSIS). And the proposed optimal planning model is tested based on a practical planning need of large-scale integrated wind power generation in an actual power grid of China in 2020. The simulation results show that applied with the proposed optimization model and matching algorithm, the planning scheme of large-scale wind power’s access location and access capacity under complex and practical power system circumstances has been successfully optimized.

Performance Analysis, Modeling and Control of Multi-Port DC-DC Boost Converter for an Integrated Power Generation System.

Objective: This paper presents a new DC-DC boost converter for renewable hybrid power generation scheme is designed using five controllable switches in its unified structure. Methods/ Statistical Analysis: In this research work, converter operation is discussed with four different operating modes based on the renewable resources availability. To rectify the difficulties associated with controller design of this converter, multi input - multi output controller design is obtained by deducing the small signal equations and state space modeling for all the operating modes. In this study, MATLAB/Simulink is used to design the model for DC-DC boost converter. A strategy to manage the power flow between the different energy sources is presented. Findings: Uncomplicated structure, centralized control, transformer-less operation, less weight, highly stable and increased output voltage is the best qualities of the designed converter. This study demonstrates that the overall power management is efficient and demand is balanced successfully. Applications/Improvement: This research helps to find the best power electronic converter structure for renewable based hybrid power generation system.

Simulation of an integrated gasification combined cycle with chemical-looping combustion and carbon dioxide sequestration

Chemical-looping combustion is an interesting technique that makes it possible to integrate power generation from fuels combustion and sequestration of carbon dioxide without energy penalty. In addition, the combustion chemical reaction occurs with a lower irreversibility compared to a conventional combustion, leading to attain a somewhat higher overall thermal efficiency in gas turbine systems. This paper provides results about the energetic performance of an integrated gasification combined cycle power plant based on chemical-looping combustion of synthesis gas. A real understanding of the behavior of this concept of power plant implies a complete thermodynamic analysis, involving several interrelated aspects as the integration of energy flows between the gasifier and the combined cycle, the restrictions in relation with heat balances and chemical equilibrium in reactors and the performance of the gas turbines and the downstream steam cycle. An accurate thermodynamic modeling is required for the optimization of several design parameters. Simulations to evaluate the energetic efficiency of this chemical-looping-combustion based power plant under diverse working conditions have been carried out, and a comparison with a conventional integrated gasification power plant with precombustion capture of carbon dioxide has been made. Two different synthesis gas compositions have been tried to check its influence on the results. The energy saved in carbon capture and storage is found to be significant and even notable, inducing an improvement of the overall power plant thermal efficiency of around 7% in some cases.

Diffusion of low emission vehicles and their impact on CO2 emission reduction in Japan

In order to achieve the long-term CO2 emission reduction target in Japan, diffusion of low emission vehicles can contribute by integration of intermittent renewable energy by demand side management using low emission vehicles, such as smart charging battery electric vehicle (BEV), in addition to improvement of energy efficiency and carbon intensity. In this study, impact of the low emission vehicles is assessed using AIM/Enduse model with 10 regions in Japan. The model is revised to integrate power generation sector and to separate the transportation demand into small, medium and large size vehicles in order to reflect the availability of BEV and fuel-cell electric vehicle (FCEV) in each vehicle size. In the Reference case, hybrid vehicle accounts for more than a half of transport demand in 2050. However, by introducing the carbon tax to achieve the 2 degree target, the share of both BEV and FCEV in 2050 reaches around 90% and 60% in passenger and freight transport, respectively. In addition, electricity demand pattern is transformed by demand side management in 2050 while integrating more intermittent renewable energy into electricity system. As a result, the CO2 emissions from transport sector in 2050 decreases by approximately 81% compared to the 1990 level.

A Research Summary on Combined Peaking Load Strategies of Nuclear Power Plant

Based on extensive research, introduced the peak load regulation characteristics and capacity of different nuclear power plant (NPP) in this paper. The running mode of NPP participating in peak load regulation of power system, combined operation tactics of NPP with other peaking power source and synergistic scheduling of an integrated power generation system with wind, photovoltaic, energy storage unit and NPP were summarized, technology development trend of NPP participating in peak load regulation of power system was analyzed and forecasted.

Experimental Investigation on Biogas Reforming for Syngas Production over an Alumina based Nickel Catalyst

Biogas is a green sustainable source of energy. Biogas mainly consists of combustible methane and non combustible carbon dioxide. Dry reforming reaction is of particular interest in the context of biogas as both main components of biogas (methane and carbon dioxide) are consumed to produce hydrogen rich syngas. Design and development of a fixed bed type reactor was carried out for reforming of biogas. The chemical equilibrium model was used for predicting the dry reforming reaction product composition followed by experimentation. In prediction of the product gas two ratios for biogas CH4: CO2=1:1 and CH4: CO2=1.5:1 were considered in the temperature range of 300 to 1000°C with the pressure at atmospheric. The catalyst γ -Al2O3 with 10% Ni was used for the dry reforming reaction. Experimentations were conducted with different Gas Hourly Space Velocity, temperature and biogas composition. Encouraging simulated and experimental results were obtained with the yield of almost 49% volume of H2 and 45% volume of CO with very low levels of CO2. Product syngas can be used in the engine for complete combustion and to fulfill the stringent emission norms. Syngas can be used as fuel in the fuel cell application for the remote integrated power generation system.

An autonomous hybrid energy system of wind/tidal/microturbine/battery storage

This paper focuses on dynamic modeling, simulation, control and energy management in an isolated integrated power generation system consisting of a 315kW offshore wind turbine, a 175kW tidal turbine, a 290kW microturbine, and a 3.27kAh lead acid battery storage. A first, due to efficient and economical utilization of the renewable energy resources, optimal sizing of the hybrid system is accomplished based on economic analysis using genetic algorithms. A model of power-consumption for a microturbine is obtained using least square estimation algorithm based on capstone™ company data and is suggested for implementing at economic analysis. For extraction of maximum energy from a variable speed wind turbine, a developed Lyapunov model reference adaptive feedback linearization method accompanied by an indirect space vector control is applied. Because of more reliability, more fuel flexibility, less environmental pollution, less noise generation and less power fluctuation in comparison with a diesel generator, a microturbine integrated with battery storage is suggested as a back up for this system.A supervisory controller is designed for energy management between the maximum energy captured from the wind turbine and consumed energies of the load, dump load, energy of the battery based on state of charge and generated energy by the microturbine. Dynamic modeling and simulation are fulfilled using MATLAB Simulink™7.2.

Development of integrated reformer systems for syngas production

Precision Combustion, Inc. (PCI) has developed autothermal reformer (ATR) units based on its patented Microlith® technology and demonstrated stable, coke-free operation using JP-8 consisting of up to 70 ppmw sulfur for 1100 h with complete fuel conversion and reforming efficiency of ∼85%. The feasibility of operating ATR reformers with distillate fuels containing higher sulfur (up to 400 ppmw) has also been demonstrated for 55 h, while producing syngas (i.e., H2 and CO) at >80% reforming efficiency and at complete fuel conversion. Reformer test results, demonstrating water neutral operation, catalyst sulfur tolerance, removal of sulfur to <1 ppmv, and maintenance of higher hydrocarbons to levels acceptable for fuel cell stacks, provide a measure of the ATR performance that can be expected under realistic conditions with readily available fuels. The results also give valuable insights to the system design and operation strategy for integrated power generation systems.

Thermodynamic analysis of an integrated power generation system driven by solid oxide fuel cell

A new integrated power generation system driven by the solid oxide fuel cell (SOFC) is proposed to improve the conversion efficiency of conventional energy by using a Kalina cycle to recover the waste heat of exhaust from the SOFC-GT. The system using methane as main fuel consists an internal reforming SOFC, an after-burner, a gas turbine, preheaters, compressors and a Kalina cycle. The proposed system is simulated based on the developed mathematical models, and the overall system performance has been evaluated by the first and second law of thermodynamics. Exergy analysis is conducted to indicate the thermodynamic losses in each components. A parametric analysis is also carried out to examine the effects of some key thermodynamic parameters on the system performance. Results indicate that as compressor pressure ratio increases, SOFC electrical efficiency increases and there is an optimal compressor pressure ratio to reach the maximum overall electrical efficiency and exergy efficiency. It is also found that SOFC electrical efficiency, overall electrical efficiency and exergy efficiency can be improved by increasing air flow rate. Also, the largest exergy destruction occurs in the SOFC followed by the after-burner, the waste heat boiler, the gas turbine. The compressor pressure ratio and air flow rate have significant effects on the exergy destruction in some main components of system.

Thermodynamic and Economic Assessment of Integrated Desalination and Power Generation

There have been a number of studies regarding the efficiency of state-of-the-art thermal (Multi-Effect Distillation, MED), power driven (sea water reverse osmosis, SWRO) and hybrid (MED/SWRO) desalination systems. The comparisons between desalination technologies can be made on a number of critical parameters such as (i) cost of produced water, (ii) energy efficiency, (iii) environmental impact, (iv) reliability and (v) footprint. Whilst the reported relative advantages with respect to parameters (iii) through (v) are conclusive, there remain conflicting recommendations with respect to parameters (i) and (ii), partly due to energy pricing assumptions. Furthermore, existing studies work on the implicit assumption that there is demand for surplus power from integrated power generation and desalination systems. The presented assessments compare the different thermal, power driven and hybrid desalination systems for output (water/power) achieved from identical energy inputs into thermal power and co-generation cycles for different ratios of desired water and power outputs. This eliminates energy and water pricing issues from the analysis and makes the findings applicable to a range of conventional (e.g. natural gas) and renewable (e.g solar) thermal energy sources. A number of simulations studies have been performed to identify the most energy efficient and cost effective desalination technologies for different water and power generation needs. The key parameters such as power and heat requirements and capital expenditures used in the thermodynamic and economic assessments are in line with ranges reported in the literature and existing plant data. Trade-offs between capital intensity and energy efficiency, which are particularly pronounced in thermal technologies, have also been studied. The paper makes clear recommendations as to the preferred desalination technology for a given seawater quality and water and power demand situation. The paper further explores the impact of technological advances in the form of lower capital costs and higher energy efficiency in the two broad classes of (i) power driven, and (ii) thermal desalination technology. All studies have been performed for seawater qualities observed in the Arabian Gulf.

An integrated power generation system combining solid oxide fuel cell and oxy-fuel combustion for high performance and CO 2 capture

An integrated power generation system combining solid oxide fuel cell (SOFC) and oxy-fuel combustion technology is proposed. The system is revised from a pressurized SOFC-gas turbine hybrid system to capture CO 2 almost completely while maintaining high efficiency. The system consists of SOFC, gas turbine, oxy-combustion bottoming cycle, and CO 2 capture and compression process. An ion transport membrane (ITM) is used to separate oxygen from the cathode exit air. The fuel cell operates at an elevated pressure to facilitate the use of the ITM, which requires high pressure and temperature. The remaining fuel at the SOFC anode exit is completely burned with oxygen at the oxy-combustor. Almost all of the CO 2 generated during the reforming process of the SOFC and at the oxy-fuel combustor is extracted from the condenser of the oxy-combustion cycle. The oxygen-depleted high pressure air from the SOFC cathode expands at the gas turbine. Therefore, the expander of the oxy-combustion cycle and the gas turbine provides additional power output. The two major design variables (steam expander inlet temperature and condenser pressure) of the oxy-fuel combustion system are determined through parametric analysis. There exists an optimal condenser pressure (below atmospheric pressure) in terms of global energy efficiency considering both the system power output and CO 2 compression power consumption. It was shown that the integrated system can be designed to have almost equivalent system efficiency as the simple SOFC-gas turbine hybrid system. With the voltage of 0.752 V at the SOFC operating at 900 °C and 8 bar, system efficiency over 69.2% is predicted. Efficiency penalty due to the CO 2 capture and compression up to 150 bar is around 6.1%.

High-power density miniscale power generation and energy harvesting systems

This paper reports design, analysis, evaluations and characterization of miniscale self-sustained power generation systems. Our ultimate objective is to guarantee highly-efficient mechanical-to-electrical energy conversion, ensure premier wind- or hydro-energy harvesting capabilities, enable electric machinery and power electronics solutions, stabilize output voltage, etc. By performing the advanced scalable power generation system design, we enable miniscale energy sources and energy harvesting technologies. The proposed systems integrate: (1) turbine which rotates a radial- or axial-topology permanent-magnet synchronous generator at variable angular velocity depending on flow rate, speed and load, and, (2) power electronic module with controllable rectifier, soft-switching converter and energy storage stages. These scalable energy systems can be utilized as miniscale auxiliary and self-sustained power units in various applications, such as, aerospace, automotive, biotechnology, biomedical, and marine. The proposed systems uniquely suit various submersible and harsh environment applications. Due to operation in dynamic rapidly-changing envelopes (variable speed, load changes, etc.), sound solutions are researched, proposed and verified. We focus on enabling system organizations utilizing advanced developments for various components, such as generators, converters, and energy storage. Basic, applied and experimental findings are reported. The prototypes of integrated power generation systems were tested, characterized and evaluated. It is documented that high-power density, high efficiency, robustness and other enabling capabilities are achieved. The results and solutions are scalable from micro (∼100 μW) to medium (∼100 kW) and heavy-duty (sub-megawatt) auxiliary and power systems.

Power Generation Expansion Planning Model Towards Low-Carbon Economy and Its Application in China

Climate change poses a huge threat to human welfare. Hence, developing a low-carbon economy has become a prevailing and inevitable trend. Decarbonization of power generation, especially converting the current power mix into a low-carbon structure, will be a critical option for CO2 emission mitigation. In this paper, an integrated power generation expansion (PGE) planning model towards low-carbon economy is proposed, which properly integrates and formulates the impacts of various low-carbon factors on PGE models. In order to adapt to the characteristics of PGE models based on low-carbon scenario, a compromised modeling approach is presented, which reasonably decreases complexities of the model, while properly keeping the significant elements and maintaining moderate precision degree. In order to illustrate the proposed model and approach, a numerical case is studied based on the background of China's power sector, making decisions on the optimal PGE plans and revealing the prospects and potentials for CO2 emission reduction.

Optimum design and operation under uncertainty of power systems using renewable energy sources and hydrogen storage

The presented work addresses the design and optimization under uncertainty of power generation systems using renewable energy sources and hydrogen storage. A systematic design approach is proposed that enables the simultaneous consideration of synergies developed among numerous sub-systems within an integrated power generation system and the uncertainty involved in the system operation. The Stochastic Annealing optimization algorithm is utilized to handle the increased combinatorial complexity and to enable the consideration of different types of uncertainty in the performed optimization. A parallel adaptation of this algorithm is proposed to address the associated computational requirements through execution in a Grid computing environment. The proposed developments are implemented in a system that consists of photovoltaic panels, wind generators, accumulators, an electrolyzer, storage tanks, a compressor, a fuel cell and a diesel generator. Numerous design and operating parameters are considered as decision variables, while uncertain parameters are associated with weather fluctuations and operating efficiency of the employed sub-systems. The obtained results indicate robust performance under realizable system designs, in response to external or internal operating variations.

Integrated power characteristic study of DFIG and its frequency converter in wind power generation

A doubly fed induction generator (DFIG) is a variable speed induction machine. It is a standard, wound rotor induction machine with its stator windings directly connected to the grid and its rotor windings connected to the grid through a back-to-back AC/DC/AC PWM converter. The power generation of a DFIG includes power delivered from two paths, one from the stator to the grid and the other from the rotor, through the frequency converter, to the grid. The power production characteristics, therefore, depend not only on the induction machine but also on the two PWM converters as well as how they are controlled. This paper investigates power generation characteristics of a DFIG system through computer simulation. The specific features of the study are (1) a steady-state model of a DFIG system in d– q reference frame, (2) a simulation mechanism that reflects decoupled d– q control strategies, (3) power characteristic simulation for both generator and converter, and (4) an integrative study combining stator, rotor and converter together. An extensive analysis is conducted to examine integrated power generation characteristics of DFIG and its frequency converter under different wind and d– q control conditions so as to benefit the development of advanced DFIG control technology.

Exergetic Performance Analysis of a Gas Turbine Cycle Integrated With Solid Oxide Fuel Cells

Energy and exergy assessments are reported of integrated power generation using solid oxide fuel cells (SOFCs) with internal reforming and a gas turbine cycle. The gas turbine inlet temperature is fixed at 1573 K and the high-temperature turbine exhaust heats the natural gas and air inputs, and generates pressurized steam. The steam mixes at the SOFC stack inlet with natural gas to facilitate the reformation process. The integration of solid oxide fuel cells with gas turbines increases significantly the power generation efficiency relative to separate processes and reduces greatly the exergy loss due to combustion, which is the most irreversible process in the system. The other main exergy destruction is attributable to electrochemical fuel oxidation in the SOFC. The energy and exergy efficiencies of the integrated system reach 70–80%, which compares well to the efficiencies of approximately 55% typical of conventional combined-cycle power generation systems. Variations in the energy and exergy efficiencies of the integrated system with operating conditions are provided, showing, for example, that SOFC efficiency is enhanced if the fuel cell active area is augmented. The SOFC stack efficiency can be maximized by reducing the steam generation while increasing the stack size, although such measures imply a significant and nonproportional cost rise. Such measures must be implemented cautiously, as a reduction in steam generation decreases the steam/methane ratio at the anode inlet, which may increase the risk of catalyst coking. A detailed assessment of an illustrative example highlights the main results.

고온형 연료전지 기반 통합형 발전시스템 - 연구개발 동향 고찰 -

Fuel cells are expected to be promising future power sources in both aspects of thermal efficiency and environmental friendliness. Accordingly, worldwide research and development efforts have been enormously increasing recently in various applications such as power plants, transportation and portable power sources. Among others, high temperature fuel cells, such as solid oxide fuel cells and molten carbonate fuel cells, are suitable for electric power plants. Moreover, their high operating temperature is quite appropriate to construct further advanced integrated systems. This paper reviews recent literatures on research and development of integrated power generation systems based on high temperature fuel cells. Research and development efforts are summarized in the area of fuel cell/ gas turbine hybrid systems, application of carbon capture technology to fuel cell systems, integration of coal gasification with fuel cells, and the use of alternative fuels.