Analyses of Thermal Performance of Solar Power Tower Station Based on a Supercritical CO2 Brayton Cycle

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Lijun Fang ◽  
Yang Li ◽  
Xue Yang ◽  
Zeliang Yang
Keyword(s):  
Heat Transfer ◽  
Thermal Efficiency ◽  
Power Plants ◽  
Solar Power ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Levelized Cost Of Electricity ◽  
Heat Receiver ◽  
Overall Performance ◽  
Solar Power Tower

Abstract Concentrating solar power (CSP) technology, possessing an inherent capacity to couple with energy storage ideally, attracts a great deal of attention nowadays. However, these power plants with various types of CSP system still cannot compete with the traditional thermal power plants in terms of levelized cost of electricity (LCOE), and their potential for utilizing clear and renewable solar energy cannot be overestimated. To improve the total efficiency of the solar power tower (SPT) plant is the key factor for its development. In this present paper, a SPT plant based on an S-CO2 Brayton cycle (with S-CO2 serving as heat transfer and working fluid) is proposed. A numerical simulation is carried out to calculate the effects of key operating parameters, including power cycle and subsystem parameters, on the overall performance of the SPT plant. The results show that there is an optimum value for the compression ratio for the SPT plant. For the heat receiver, the trends of exergy and thermal efficiency varying with turbine inlet temperature are reversed, because of the significant energy loss caused by high temperature of the surface of the heat receiver. As for the overall performance, the SPT plant proposed in this paper is better than other SPT plants based on a steam Rankine system and an S-CO2 Brayton system with molten salt serving as heat transfer fluid (HTF) operating under the similar condition. Its overall thermal efficiency is 1.04% and 3.42% higher than that of two other SPT plants, respectively.

Thermal Performance of Steam Receiver in Tower-Type Solar Power Plants

2017 ◽  
Author(s):  
Kai Yan ◽  
Xiaojiang Wu ◽  
Jianbin Liu
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Power Plants ◽  
Solar Power ◽  
Working Fluid ◽  
Receiver Design ◽  
Solar Power Plants ◽  
Performance Calculation

In this paper, the thermal performance of steam receiver in tower-type solar power plants has been performed using the tower-type solar receiver design program developed by Shanghai boiler works Co Ltd. In the program, the integrated effect of three types of heat transfer, i.e. heat conduction, convection and radiation, in the process of heat transfer of receivers has been considered. With integrating the characteristics and the working conditions of receivers of both steam and molten salt, the developed program can be used to perform the thermal performance calculations for the receivers of both working fluids. The proposed program was validated through Solar Two project and the satisfactory results achieve. A steam receiver in a tower-type solar power plant with double superheats is selected as an example for thermal performance calculation. In view of the receiver operating in subcritical status, the thermal performance calculation is carried out for two sections, the one for evaporation and that for superheat. In evaporation section, the working fluid is circulated with a circulating pump at a very high circulating ratio. At the outlet of panels, the qualities of working fluid can reach to maximum about 0.35. Besides, the great difference of qualities of working fluid at the outlet of panels is observed. Even for some pipes of some panels, the working fluid at the outlet is in liquid phase. The distribution of metal temperature at fin end of panels in the evaporation region varies dramatically from place to place and reaches to over 520 °C. In superheat region, the temperature of the outer front crown of tubes is concerned. The highest front point temperature of pipe, which reaches to maximum over 660 °C, is in the middle region of the last parts of the primary superheat pass. The thermal efficiency distribution of the receiver, including the evaporation and the superheat regions, are also performed. The results show that the averaged efficiency is about 86%. Besides, the phenomenon of negative thermal efficiency happens in both two regions. That is because the solar incidence cannot compensate the natural heat loss due to incident radiation reflection, the pipe wall infrared radiation and convective heat loss.

A Study of Supercritical Carbon Dioxide Power Cycle for Concentrating Solar Power Applications Using an Isothermal Compressor

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Jin Young Heo ◽  
Jinsu Kwon ◽  
Jeong Ik Lee
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Thermal Efficiency ◽  
Solar Power ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Concentrating Solar Power ◽  
Power Cycle ◽  
Compressor Inlet ◽  
Supercritical Carbon

For the concentrating solar power (CSP) applications, the supercritical carbon dioxide (s-CO2) power cycle is beneficial in many aspects, including high cycle efficiencies, reduced component sizing, and potential for the dry cooling option. More research is involved in improving this technology to realize the s-CO2 cycle as a candidate to replace the conventional power conversion systems for CSP applications. In this study, an isothermal compressor, a turbomachine which undergoes the compression process at constant temperature to minimize compression work, is applied to the s-CO2 power cycle layout. To investigate the cycle performance changes of adopting the novel technology, a framework for defining the efficiency of the isothermal compressor is revised and suggested. This study demonstrates how the compression work for the isothermal compressor is reduced, up to 50%, compared to that of the conventional compressor under varying compressor inlet conditions. Furthermore, the simple recuperated and recompression Brayton cycle layouts using s-CO2 as a working fluid are evaluated for the CSP applications. Results show that for compressor inlet temperatures (CIT) near the critical point, the recompression Brayton cycle using an isothermal compressor has 0.2–1.0% point higher cycle thermal efficiency compared to its reference cycle. For higher CIT values, the recompression cycle using an isothermal compressor can perform above 50% in thermal efficiency for a wider range of CIT than the reference cycle. Adopting an isothermal compressor in the s-CO2 layout can imply larger heat exchange area for the compressor which requires further development.

scholarly journals Thermo-economic optimization of supercritical CO2 Brayton cycle on the design point for application in solar power tower system

2021 ◽  
Vol 242 ◽  
pp. 01002
Author(s):  
Tianye Liu ◽  
Jingze Yang ◽  
Zhen Yang ◽  
Yuanyuan Duan
Keyword(s):  
Ambient Temperature ◽  
Thermal Efficiency ◽  
High Efficiency ◽  
Solar Power ◽  
Inlet Temperature ◽  
Brayton Cycle ◽  
Economic Optimization ◽  
Compressor Inlet ◽  
Solar Power Tower ◽  
Tower System

The supercritical CO2 Brayton cycle integrated with a solar power tower system has the advantages of high efficiency, compact cycle structure, strong scalability, and great power generation potential, which can positively deal with the energy crisis and global warming. The selection and optimization of design points are very important for actual operating situations. In this paper, the thermodynamic and economic models of the 10 MWe supercritical CO2 Brayton cycle for application in solar power tower system are established. Multi-objective optimizations of the simple recuperative cycle, reheating cycle, and recompression cycle at different compressor inlet temperature are completed. The thermal efficiency and the levelized energy cost are selected as the fitness functions. The ranges of the optimal compressor inlet pressure and reheating pressure on the Pareto frontier are analyzed. Finally, multiobjective optimizations and analysis of the supercritical CO2 Brayton cycle at different ambient temperature are carried out. This paper investigates the influence of the compressor inlet temperature and ambient temperature on the thermal efficiency and economic performance of the supercritical CO2 Brayton cycle.

scholarly journals Supercritical CO2 Mixtures for Advanced Brayton Power Cycles in Line-Focusing Solar Power Plants

2019 ◽  
Vol 10 (1) ◽  
pp. 55 ◽  
Author(s):  
Robert Valencia-Chapi ◽  
Luis Coco-Enríquez ◽  
Javier Muñoz-Antón
Keyword(s):  
Supercritical Co2 ◽  
Power Plants ◽  
Solar Power ◽  
Plant Performance ◽  
Design Parameters ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Power Cycles ◽  
Solar Power Plants ◽  
Dry Cooling

This work quantifies the impact of using sCO2-mixtures (s-CO2/He, s-CO2/Kr, s-CO2/H2S, s-CO2/CH4, s-CO2/C2H6, s-CO2/C3H8, s-CO2/C4H8, s-CO2/C4H10, s-CO2/C5H10, s-CO2/C5H12 and s-CO2/C6H6) as the working fluid in the supercritical CO2 recompression Brayton cycle coupled with line-focusing solar power plants (with parabolic trough collectors (PTC) or linear Fresnel (LF)). Design parameters assessed are the solar plant performance at the design point, heat exchange dimensions, solar field aperture area, and cost variations in relation with admixtures mole fraction. The adopted methodology for the plant performance calculation is setting a constant heat recuperator total conductance (UAtotal). The main conclusion of this work is that the power cycle thermodynamic efficiency improves by about 3–4%, on a scale comparable to increasing the turbine inlet temperature when the cycle utilizes the mentioned sCO2-mixtures as the working fluid. On one hand, the substances He, Kr, CH4, and C2H6 reduce the critical temperature to approximately 273.15 K; in this scenario, the thermal efficiency is improved from 49% to 53% with pure s-CO2. This solution is very suitable for concentrated solar power plants coupled to s-CO2 Brayton power cycles (CSP-sCO2) with night sky cooling. On the other hand, when adopting an air-cooled heat exchanger (dry-cooling) as the ultimate heat sink, the critical temperatures studied at compressor inlet are from 318.15 K to 333.15 K, for this scenario other substances (C3H8, C4H8, C4H10, C5H10, C5H12 and C6H6) were analyzed. Thermodynamic results confirmed that the Brayton cycle efficiency also increased by about 3–4%. Since the ambient temperature variation plays an important role in solar power plants with dry-cooling systems, a CIT sensitivity analysis was also conducted, which constitutes the first approach to defining the optimum working fluid mixture for a given operating condition.

scholarly journals Assessment of Solar Power Tower Driven Ultrasupercritical Steam Cycles Applying Tubular Central Receivers With Varied Heat Transfer Media

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Csaba Singer ◽  
Reiner Buck ◽  
Robert Pitz-Paal ◽  
Hans Müller-Steinhagen
Keyword(s):  
Heat Transfer ◽  
Cost Reduction ◽  
Power Plants ◽  
Reduction Potential ◽  
Solar Power ◽  
Power Level ◽  
Scale Up ◽  
Reference Case ◽  
Solar Power Tower ◽  
Significant Cost Reduction

For clean and efficient electric power generation, the combination of solar power towers (SPTs) with ultrasupercritical steam cycle power plants could be the next development step. The methodology of the European concentrated solar thermal roadmap study was used to predict the annual performance and the cost reduction potential of this option applying tubular receivers with various appropriate high temperature heat transfer media (HTM). For the assessment, an analytical model of the heat transfer in a parametric 360 deg cylindrical and tubular central receiver was developed to examine the receiver’s efficiency characteristics. The receiver’s efficiency characteristics, which are based on different irradiation levels relative to the receiver’s design point, are, then, used to interpolate the receiver’s thermal efficiency in an hourly based annual calculation of one typical year that is defined by hourly based real measurements of the direct normal irradiance and the ambient temperature. Applying appropriate cost assumptions from literature, the levelized electricity costs (LEC) were estimated for each considered SPT concept and compared with the reference case, which is a scale-up of the state of the art molten salt concept. The power level of all compared concepts and the reference case is 50 MWel. The sensitivity of the specific cost assumptions for the LEC was evaluated for each concept variation. No detailed evaluation was done for the thermal storage but comparable costs were assumed for all cases. The results indicate a significant cost reduction potential of up to 15% LEC reduction in the liquid metal HTM processes. Due to annual performance based parametric studies of the number of receiver panels and storage capacity, the results also indicate the optimal values of these parameters concerning minimal LEC.

Application of Microscale Devices for Megawatt Scale Concentrating Solar Power Plants

2015 ◽  
Author(s):  
Kyle R. Zada ◽  
M. Kevin Drost ◽  
Brian M. Fronk
Keyword(s):  
Thermal Efficiency ◽  
Power Plants ◽  
Solar Power ◽  
Modular Design ◽  
Building Blocks ◽  
Surface Fluxes ◽  
Electricity Production ◽  
Working Fluid ◽  
High Heat Flux ◽  
Central Receiver

Concentrated solar power (CSP) plants have the potential to reduce the consumption of non-renewable resources and greenhouse gas emissions in electricity production. In CSP systems, a field of heliostats focuses solar radiation on a central receiver, which is ultimately transferred to thermal electrical power plant at high temperature. However, the maximum receiver surface fluxes are low (30–100 W cm−2) with high thermal losses, which has limited the market penetration of CSP systems. Recently, small (∼ 4 cm2), laminated micro-channel devices have shown potential to achieve concentrated surface fluxes over 100 W cm−2 using supercritical CO2 as the working fluid. The present study explores the feasibility of using these microscale devices as building blocks for a megawatt scale (250 MW thermal) open solar receiver. This allows for a modular design of the central receiver with non-standard shapes customized to the heliostat field. The results show that the microscale unit-cells have the potential to be scaled to megawatt applications while providing high heat flux and thermal efficiency. At the design incident flux and surface emissivity, a global receiver thermal efficiency of > 90% can be achieved.

scholarly journals Comparative Modeling of a Parabolic Trough Collectors Solar Power Plant with MARS Models

Energies ◽  
2017 ◽  
Vol 11 (1) ◽  
pp. 37 ◽  
Author(s):  
Jose Rogada ◽  
Lourdes Barcia ◽  
Juan Martinez ◽  
Mario Menendez ◽  
Francisco de Cos Juez
Keyword(s):  
Heat Transfer ◽  
Water Vapor ◽  
Power Plant ◽  
Solar Radiation ◽  
Thermal Energy ◽  
Power Plants ◽  
Solar Power ◽  
Rankine Cycle ◽  
Heat Transfer Fluid ◽  
Solar Field

Power plants producing energy through solar fields use a heat transfer fluid that lends itself to be influenced and changed by different variables. In solar power plants, a heat transfer fluid (HTF) is used to transfer the thermal energy of solar radiation through parabolic collectors to a water vapor Rankine cycle. In this way, a turbine is driven that produces electricity when coupled to an electric generator. These plants have a heat transfer system that converts the solar radiation into heat through a HTF, and transfers that thermal energy to the water vapor heat exchangers. The best possible performance in the Rankine cycle, and therefore in the thermal plant, is obtained when the HTF reaches its maximum temperature when leaving the solar field (SF). In addition, it is necessary that the HTF does not exceed its own maximum operating temperature, above which it degrades. The optimum temperature of the HTF is difficult to obtain, since the working conditions of the plant can change abruptly from moment to moment. Guaranteeing that this HTF operates at its optimal temperature to produce electricity through a Rankine cycle is a priority. The oil flowing through the solar field has the disadvantage of having a thermal limit. Therefore, this research focuses on trying to make sure that this fluid comes out of the solar field with the highest possible temperature. Modeling using data mining is revealed as an important tool for forecasting the performance of this kind of power plant. The purpose of this document is to provide a model that can be used to optimize the temperature control of the fluid without interfering with the normal operation of the plant. The results obtained with this model should be necessarily contrasted with those obtained in a real plant. Initially, we compare the PID (proportional–integral–derivative) models used in previous studies for the optimization of this type of plant with modeling using the multivariate adaptive regression splines (MARS) model.

scholarly journals Solar Thermal Power: Appraisal of Solar Power Towers

2018 ◽  
Vol 225 ◽  
pp. 04003
Author(s):  
Hashem Shatnawi ◽  
Chin Wai Lim ◽  
Firas Basim Ismail
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Solar Power ◽  
Thermal Power ◽  
Tube Material ◽  
Power Cycles ◽  
Solar Thermal Power ◽  
Central Receiver ◽  
Receiver System ◽  
Solar Power Tower

This study delves into several engineering procedures related to solar power tower plants. These installations come with central receiver system technologies and high-temperature power cycles. Besides a summary emphasizing on the fundamental components of a solar power tower, this paper also forwards a description of three receiver designs. Namely, these are the tubular receiver, the volumetric receiver and the direct absorber receiver. A variety of heat transfer mediums were assessed, while a comprehensive explanation was provided on the elements of external solar cylindrical receivers. This explanation covers tube material, molten salt, tube diameter and heat flux.

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