Thermal Power Generation System Research Articles

Performance analysis of different ORC configurations for thermal energy and LNG cold energy hybrid power generation system

This paper presents a thermal energy and Liquefied natural gas (LNG) cold energy hybrid power generation system. Performances of four different Organic Rankine cycle (ORC) configurations (the basic, the regenerative, the reheat and the regenerative-reheat ORCs) are studied based on the first and the second law of thermodynamics. Dry organic fluid R245fa is selected as the typical working fluid. Parameter analysis is also conducted in this paper. The results show that regeneration could not increase the thermal efficiency of the thermal and cold energy hybrid power generation system. ORC with the reheat process could produce more specific net power output but it may also reduce the system thermal efficiency. The basic and the regenerative ORCs produce higher thermal efficiency while the regenerative-reheat ORC performs best in the exergy efficiency. A preheater is necessary for the thermal and cold energy hybrid power generation system. And due to the presence of the preheater, there will be a step change of the system performance as the turbine inlet pressure rises.

Resource assessment for hybrid solar-biomass power plant and its thermodynamic evaluation in India

Hybrid solar-biomass thermal power generation systems are important for continuous power generation installations which supplement each other seasonally in India. In this paper, several aspects associated with hybrid biomass-solar power generation installations such as state wise availability of biomass resources, solar direct normal irradiance (DNI) has been discussed. Month wise daily average DNI is considered as 20%, 40%, 60%, and 80% and remaining heat is taken from biomass resource in the proposed hybrid plant. The thermodynamic evaluation (i.e. Energy and Exergy) of hybrid solar-biomass power plant have also been investigated. The total input energy of the proposed hybrid system is taken from the heat transfer fluid through parabolic trough collector (PTC) as per availability of solar resource and remaining from biomass to maintain the steam at superheated state of 500°C and 60bar and supplied to turbine at steam mass flow rate of 5kg/s. The energy and exergy analyses of 5MW hybrid system with series mode was carried out to identify the effects of various operating parameters like DNI, condenser pressure, turbine inlet temperatures, boiler pressure on net power output energy and exergy efficiencies.

In situ synthesis of SiC-bonded cordierite-mullite ceramics for solar thermal energy storage

Cordierite-mullite ceramic has been engaged as one of the most promising substrate materials for thermal storage in the next-generation solar thermal power generation systems. It's expected to possess high thermal conductivity and excellent mechanical strength for a good running. In this study, an in situ reaction bonding technique was developed to prepare SiC-bonded cordierite-mullite composites, using different carbon sources (graphite, phenolic resin) and silicon sources (Si, SiO2) for the synthesis of SiC. The effects of SiC content on performance and structure of the composite ceramics were studied. Results showed that the most effective bonding for SiC with cordierite-mullite was an in situ reaction between silicon (Si) and graphite. Correspondingly, the optimum sample with 40wt% SiC showed an obvious improvement of both mechanical strength and thermal conductivity, which was 109.67MPa and 5.8782 (25°C) W/(mK) respectively. The characterization of the as-synthesized SiC showed a relatively uniform diameter, a much smooth surface and a completely intertwined structure, which formed thermally conductive channels of SiC-SiC and presented mechanical strength enhancement of reinforcing-toughening effect. To understand the synthesis mechanism of SiCw bonded in the composite ceramics, we found that the silicon source played a key role and suggested that the growth mechanism of SiC was a liquid-solid (L-S) mechanism.

Effects of coal characteristics to performance of a highly efficient thermal power generation system based on pressurized oxy-fuel combustion

Summary Because of its fuel flexibility and high efficiency, pressurized oxy-fuel combustion has recently emerged as a promising approach for efficient carbon capture and storage. One of the important options to design the pressurized oxy-combustion is to determine method of coal (or other solid fuels) feeding: dry feeding or wet (coal slurry) feeding as well as grade of coals. The main aim of this research is to investigate effects of coal characteristics including wet or dry feeding on the performance of thermal power plant based on the pressurized oxy-combustion with CO2 capture versus atmospheric oxy-combustion. A commercial process simulation tool (gCCS: the general carbon capture and storage) was used to simulate and analyze an advanced ultra-supercritical(A-USC) coal power plant under pressurized and atmospheric oxy-fuel conditions. The design concept is based on using pure oxygen as an oxidant in a pressurized system to maximize the heat recovery through process integration and to reduce the efficiency penalty because of compression and purification units. The results indicate that the pressurized case efficiency at 30 bars was greater than the atmospheric oxy-fuel combustion (base line case) by 6.02% when using lignite coal firing. Similarly, efficiency improvements in the case of subbituminous and bituminous coals were around 3% and 2.61%, respectively. The purity of CO2 increased from 53.4% to 94% after compression and purification. In addition, the study observed the effects of coal-water slurry using bituminous coal under atmospheric conditions, determining that the net plant efficiency decreased by 3.7% when the water content in the slurry increased from 11.12% to 54%. Copyright © 2016 John Wiley & Sons, Ltd.

Mathematical modeling and evaluation of new long single slope still for utilization of hot wastewater

Various thermal power systems use water as a coolant and their discharge contains enormous amount of energy, which remains unutilized and released into the atmosphere to its remarkable extent. The aim of present work was to propose a model to recover this unutilized energy by developing an efficient distillation system which may be coupled in between the output of thermal power generation system and chiller unit. For the purpose, analytical model was developed and obtained results were found to be in good agreement with experimental observations. In the proposed model, long still has been developed and fed with a hot wastewater having temperature of 70±1°C at a constant flow rate of 1100 l/h. It was observed that the theoretical and experimental results are almost comparable within 0.6–1.2m length and variation of about 20.91% is observed below 0.6m length of developed still, which might be due to higher temperature of inlet water at the entry point and unaccountable variance in ambient conditions. As a concluding remark, it has been observed that the proposed still produces maximum yield toward the inlet and decreases toward the outlet, which may be due to the lowering of water temperature with length, which further reduces rate of evaporation and yield.

TRANSIENT THERMAL PERFORMANCE PREDICTION METHOD FOR PARABOLIC TROUGH SOLAR COLLECTOR UNDER FLUCTUATING SOLAR RADIATION

As the effect of the global warming is becoming noticeable, the importance for environmental sustainability has been raised. Parabolic trough solar thermal collector system, which is one of the solutions to reduce the carbon dioxide emission, is a mature technology for electricity generation. Malaysia is a tropical country with long daytime, which makes suitable for solar thermal applications with parabolic trough solar thermal collectors. However, the high humidity causes the solar radiation to fluctuate. In order to simulate the solar thermal collectors’ performance at an early design stage of solar thermal power generation systems, fast still accurate transient thermal performance prediction methodis required. Although multiple transient thermal simulation methodologies exist, they are not suited especially at an early design stage where quick but reasonably accurate thermal performance prediction is needed because of their long calculation time. In this paper, a transient thermal prediction method is developed to predict exit temperature of parabolic trough collectors under fluctuating solar radiation. The method is governed by simple summation operations and requires much less calculating time than the existing numerical methods. If the radiation heat loss at the parabolic trough collector tube surface is small, the working fluid temperature rise may be approximated as proportional to the receiving heat flux. The fluctuating solar radiation is considered as a series of heat flux pulses applied for a short period of time. The time dependent solar collector exit temperature is approximated by superimposing the exit temperature rise caused by each heat flux pulse. To demonstrate the capabilities of the proposed methodology, the solar collector exit temperature for one-day operation is predicted. The predicted solar collector exit temperature captures the trend of a finite element analysis result well. Still, the largest temperature difference is 38.8K and accuracy is not satisfactory. Currently, the accuracy of the proposed method is being improved. At the same time, its capabilities are being expanded.

CONCEPT STUDY OF MICROGRID DISPATCH STRATEGY FOR SOLAR THERMAL POWER PLANT WITH THERMAL STORAGE

Complex grid systems have been gradually replaced by smaller and simpler grid systems called Microgrids. Integration of a solar thermal power generation systems into Microgrids open a new horizon of renewable energy power generation to achieve the supply and demand balance of electricity. Microgrid dispatch strategy is a control method of energy balance between power generation and electricity consumption. A thermal storage integrated into the system buffers the intermittency of solar radiation used as the heat source of the power generation system. The daily starting time for the power generation is determined by the dispatch strategy in search of minimum power from the conventional grid and maximum electricity generation from the solar thermal power generation system. In the simulation stage, the heat energy available for power generation and amount of thermal energy saved in the thermal storage is calculated at each time step using measured solar radiation data as the heat source and load profile data as the consumption required. Based on the simulation result, the power generation starting time for the next day is determined. The effectiveness of the proposed dispatch strategy is demonstrated by obtaining the best starting time and identifying minimum power requiredfrom the conventional grid. The power supply from the conventional grid is reduced by 10% by applying the proposed methodology.

Potential of innovative ceramics for turbine applications

Improving the thermal efficiency of aircraft gas turbines and of thermal power generation systems is of great interest for industry. Despite the various studies performed to increase their heat resistance, the use of nickel-based superalloys at temperatures beyond 1150 °C will be difficult. For higher temperatures, new high-temperature structural materials are required. In this context, ceramics offer many advantages compared to Ni-based superalloys: a lower density and a better resistance to oxidation and abrasion. Two kinds of ceramics are investigated at ONERA: Si3N4-based materials for use up to 1400–1500 °C and directionally solidified eutectic (DSE) ceramics up to 1700 °C. For both materials, improving toughness is a challenge. This paper presents the processing techniques, the microstructural features and the resulting mechanical properties.

Influences of installation and tracking errors on the optical performance of a solar parabolic trough collector

The parabolic trough collector is an important component of parabolic trough solar thermal power generation systems. Coordinate transformations and the Monte Carlo Ray Trace (MCRT) method were combined to simulate the circumferential flux distribution on absorber tubes. The simulation model includes the optics cone with non-parallel rays, geometric concentration ratios (GCs), the glass tube transmissivity, the absorber tube absorptance and the collector surface reflectivity. The mode is used to analyze the effects of absorber tube installation errors and reflector tracking errors. The results are compared with reference data to verify the model accuracy. Influences of installation and tracking errors on the flux distribution are analyzed for different errors, incident angles and GCs. For a GC of 20 and 90° rim angle, X direction installation errors are −0.2%∼0.2%, Y direction installation errors are −1.0%–0.5%, and the tracking error should be less than 4 mrad. As the incident angle increases, the errors become larger, but the errors become smaller as concentration ratios are increased. The results provide foundations for heat transfer analysis of the absorber tube, for parabolic trough plant to ensure the safe intensity, and for economic analysis of the installation process and control system.

A novel vacuum discharge thermal energy combined desalination and power generation system utilizing R290/R600a

The aim of this research is to analyse the performance of a new combined vacuum desalination and power system as a heat recovery unit. Here, DTECD-ORC (Discharge Thermal Energy Combined Desalination-Organic Rankine Cycle) is a developed form of the DTECD (discharge thermal energy combined desalination) unit. This system can run on waste steam and an organic working fluid. Here, a gas recovery plant is considered as a base case to couple with this cogeneration system. Four scenarios were modelled incorporating different mixture of the propane (R290) and isobutane (R600a) to find the more efficient option. Exergy and parametric analyses were conducted to predict the efficiency of the proposed model. Based on the proposed scenarios, up to 26% improvement in the exergy flow is achievable compared with the base case. Utilizing this system recovers the discharge thermal energy and reduces CO2 emission level. Besides, an economic analysis performed and the result indicates that the system is economic. The result illustrated that the overall performance of the introduced system is comparable with the primary DTECD system utilizing ammonia mixture. However, the proposed system produces more fresh water; it involves simple process; its working fluid is less corrosive and more convenient to operate.

勿来発電所 10 号機（IGCC）の運転状況

An integrated coal gasification combined cycle (IGCC) is a high thermal efficiency power generation system that uses a gasifier to convert coal to synthesis gas (syngas), a gas turbine burning the syngas, and a steam turbine generating additional electricity from exhaust heat. Nakoso IGCC is the only commercial IGCC power plant in Japan, which adopts an air-blown type gasifier. This report overviews current status of the Nakoso IGCC. During the operation, it was found that the thermal efficiency can be increased more by adjusting the amount or oxygen concentration of gasifying agent (oxygen-enriched air).

Development of a Brushless DC Generator for the Micro Solar-Thermal Power Generation System for Societal Applications

This paper describes the work performed on the design and development of 1KW Brushless DC generator: armature stator and permanent magnet rotor assembly for a Micro Solar Thermal Power Generation System for societal applications. A Solar Thermal Electricity generating system is an emerging renewable energy technology, where we generate the thermal energy by concentrating the direct solar radiation at high temperature. The resulting thermal energy is used in a thermodynamic cycle to produce electricity, by running a turbine which rotates the generator to produce electricity. The brushless dc generator armature design is a three phase star connected winding housed in the magnetic core. The magnetic circuit of the stator is designed to meet the required power output. The rotor assembly has high energy rare earth permanent magnets to produce required flux for the voltage generation. The armature stator and permanent magnet rotor is modeled in two dimensional finite element based electromagnetic software to validate the flux density at the airgap, tooth and back iron. The proto model generator is realized and tested for its performance with load.

清掃工場におけるエネルギー利用の実態調査

In the big cities, a large amount of garbage has been incinerated in the incineration plant. In the large-scale plant, steam power cycle using incineration exhaust heat to the heat source has been introduced. In this steam cycle, unlike the commercial thermal power generation system, the condensation of the vapor is carried out using an air-cooled condenser, influenced by the outdoor temperature. Therefore, in the high temperature summer season, the power generation amount is decreased and also a higher temperature waste heat is released to the atmosphere. Therefore, in this study, in a large-scale incineration plant in Osaka City, the actual situation of energy use was investigated twice in the summer and winter. Specifically, seasonal changes in the amount of power generation as well as the condenser exhaust gas temperature were investigated. Moreover, based on the measurement result, some points of performance improvement were revealed by the exergy analysis.

중유용 분산제 구조에 따른 중유 분산 특성

Heavy oil production is receiving significant attention because of increased demands for thermal power generation systems of the diesel engine and boilers. However, asphaltene, which is a heavy oil components (6-8 wt%), reduces the heat efficiency of the fuels owing to its agglomerated sludge of asphaltene during the burning process. Therefore, for hassle-free operation, we should develop asphaltene dispersants to suppress the formation of the sludge. We prepare variable salt-type polymeric dispersants using poly(isobutenyl succinic anhydride) and poly(amine) through both condensation esterification and acid-base neutralization reactions, which we subsequently evaluate for dispersing performance, using Turbiscan measurement. Total acid number (TAN) and total base number (TBN) of 75Lec-25SynDis.2 composed of lecithin and the prepared polymeric salt having the ratio of 3 : 1 are 18.9 and 33.7 mg KOH/g, respectively, which are comparable to those of the commercial dispersants (15.8 and 26.5 mg KOH/g). We determine the initial turbidity observed for 15 min of the polymeric dispersant was determined with transmittance (%), which can be calculated to separability number (SN). The SN value of 75Lec-25SynDis.2 is close to zero, which is superior to that of commercial dispersants and lecithin (0.015 and 0.017).

Thermodynamics investigation of a solar power system integrated oil and molten salt as heat transfer fluids

In this paper, a new parabolic trough solar power system that incorporates a dual-solar field with oil and molten salt as heat transfer fluids (HTFs) is proposed to effectively utilize the solar energy. The oil is chosen as a HTF in the low temperature solar field to heat the feeding water, and the high temperature solar field uses molten salt to superheat the steam that the temperature is higher than 773 K. The produced superheated steam enters a steam turbine to generate power. Energy analysis and exergy analysis of the system are implemented to evaluate the feasibility of the proposed system. Under considerations of variations of solar irradiation, the on-design and off-design thermodynamic performances of the system and the characteristics are investigated. The annual average solar-to-electric efficiency and the nominal efficiency under the given condition for the proposed solar thermal power generation system reach to 15.86% and 22.80%, which are higher than the reference system with a single HTF. The exergy losses within the solar heat transfer process of the proposed system are reduced by 7.8% and 45.23% compared with the solar power thermal systems using oil and molten salt as HTFs, respectively. The integrated approach with oil and molten salt as HTFs can make full use of the different physical properties of the HTFs, and optimize the heat transfer process between the HTFs and the water/steam. The exergy loss in the water evaporation and superheated process are reduced, the system efficiency and the economic performance are improved. The research findings provide a new approach for the improvement of the performances of solar thermal power plants.

The Wind-structure Interaction Analysis and Optimization of Parabolic Trough Collector

Abstract The mechanical properties and economic performance of solar collector have an important influence on solar thermal power generation system. The parabolic trough collector with torque-box is taken as the research object in this paper. Firstly, the geometric model is established with SolidWorks software. Then, the wind load of collector is simulated with ANSYS CFX software in order to achieve the more accurate result. Based on the work above, wind-structure interaction of collector is realized taking advantages of Workbench and the maximum deformation of the reflecting mirrors differs with the maximum deformation of single physical model about 30.3%. In the end, the cross-section sizes of the beam of torque-box and the cantilever beam are optimized based on the mechanical characteristics of variable cross-section beam. The simulation results show that the maximum deformation of the reflecting mirrors is reduced about 4.6% and the weight of the collector is reduced about 5.8% compared with the initial model. The methods provide the reference for the analysis and optimization of other solar collectors.

The Simulation Model of Flux Density Distribution on an Absorber Tube

Abstract A parabolic trough collector (PTC) is an important component of parabolic trough solar thermal power generation system. The main purposes of calculating the flux density distribution are as follows: (1) the heat flux distribution on the absorber tube surface is a key boundary condition in the heat transfer performance analysis; (2) it can present a reference for design and optimization of PTCs, and make PTCs more cost effective. In this paper, coordinate transformations and Monte Carlo Ray Trace (MCRT) method are combined to simulate the circumferential flux distribution of absorber tubes. In the simulation process, non-parallelism of solar rays with cone optics, geometric concentrating ratio (GC), rim angle, transmittance of the glass tube, absorption of the absorber tube, reflectivity of the glass tube and reflectivity of the parabolic trough mirror are considered. The results show good agreement with references.

Experimental and Numerical Investigations on Plate-Type Heat Exchanger Performance

Low-grade Thermal Energy Conversion (LTEC) is a potential source of renewable energy. One of its forms is the Ocean Thermal Energy Conversion (OTEC) in which the temperature difference between the warm surface water and the cold deep water of the ocean is utilized in driving a heat engine cycle. Unlike the conventional thermal power generation systems, the temperature difference between the heat source and heat sink in OTEC system is relatively small. Therefore, efficient heat exchangers should be used since heat exchangers play a major role in the overall system performance and economics. Due to their efficiency even in operating at small temperature difference, plate heat exchangers are strong candidates in OTEC systems. In this study, performance of a herringbone plate-type heat exchanger is experimentally investigated. Moreover, numerical simulation results obtained by using Fluent CFD software are compared with the experimental results and found in good agreement.

Preparation and Performance of β-Sialon/Si<sub>3</sub>N<sub>4</sub> Composite Ceramics for Solar Heat Absorber

β-Sialon/Si3N4composite ceramic were prepared from starting materials of α-Si3N4, AlN and Al2O3by pressureless sintering. The physical properties, phase composition and microstructure were tested by modern testing technology. The effect of different additives such as Y2O3, La2O3and borax on the sintering temperature and physical properties was studied. The results show that D3 is the best formula, firing shrinkage rate of the sample is 14.14%, water absorption 3.16%, porosity 9.02%, bulk density 2.85g·cm-3and bending strength 193.87MPa after firing at 1580°C. XRD analysis indicates that the main phases of D3 are β-Sialon, β-Si3N4and corundum. SEM analysis shows that the microstructure of D3 sample is quite dense and the pores distribution is uniform, the diameter of the pore is about 1~5μm. β-Sialon/Si3N4composite ceramic has high bulk density, bending strength and fine microstructure, which is a new choice of the heat absorb material for solar thermal power generation system.

Research Status and Prospect of Dish-Stirling System

Solar energy is a kind of clean and green energy, its use can reduce the dual pressure of resources and environmental pollution. Firstly, this paper introduces groove, tower and dish type solar thermal power generation system. Then it introduces the components of dish-stirling system and the principle and features of stirling engine. The system has simple structure, reliable operation, high efficiency, low noise, low cost of power generation and good commercial prospects. But for some key parts of system, there are many problems that need to be solved. The main research of dish-stirling system is to optimize the key parts of system and reduce the system costs.