U. Nithiyanantham, Yaroslav Grosu, L. González-Fernández, A. Zaki, J. Igartua, A. Faik
The use of thermal energy storage (TES) for electricity production at concentrated solar power (CSP) plants has provided several important benefits, like lower environmental impact and higher dispatchability, compared to other methods. Many investigations have been focused on the enhancement of thermophysical properties of molten salts (TES material for CSP) by the addition of minor percentage of nanoparticles. In the present work, two nanofluids were developed based on the binary eutectic mixture of NaNO3 and KNO3 (mole ratio of 55:45) as base fluid with by addition of a small amount (1wt.%) of commercial Al2O3 and SiO2 nanoparticles. The thermophysical properties of the developed nanofluids have been investigated in terms of enhancement of their heat capacity and thermal conductivity. Firstly, an effective dry method is proposed and validated for the preparation of molten salt based nanofluids. The obtained nanofluids were characterized by different techniques such as scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). Secondly, their thermophysical properties have been investigated by means of differential scanning calorimetry (DSC) and laser flash apparatus (LFA). The developed nanofluids present significant enhancements of the specific heat capacity and thermal conductivity as compared to the base fluid ones. Finally, immersion corrosion tests were conducted under atmospheric conditions for carbon steel (CS) A516.Gr70 in contact with nanofluids at 390 °C, for exposure times of 250, 500, 1000 and 1500 hours. Carbon steel samples were analysed by means of SEM-EDX (surface and cross section), XRD and mass variation. Regarding the corrosion study, the oxidation was determined as the main mechanism of carbon steel degradation upon direct contact with molten nitrate salt. It was found that adding 1%wt of Al2O3 or SiO2 nanoparticles decreases the corrosion layer thickness more than twice as compared to the pure salt.The use of thermal energy storage (TES) for electricity production at concentrated solar power (CSP) plants has provided several important benefits, like lower environmental impact and higher dispatchability, compared to other methods. Many investigations have been focused on the enhancement of thermophysical properties of molten salts (TES material for CSP) by the addition of minor percentage of nanoparticles. In the present work, two nanofluids were developed based on the binary eutectic mixture of NaNO3 and KNO3 (mole ratio of 55:45) as base fluid with by addition of a small amount (1wt.%) of commercial Al2O3 and SiO2 nanoparticles. The thermophysical properties of the developed nanofluids have been investigated in terms of enhancement of their heat capacity and thermal conductivity. Firstly, an effective dry method is proposed and validated for the preparation of molten salt based nanofluids. The obtained nanofluids were characterized by different techniques such as scanning electron microscopy (SEM) ...
{"title":"Development of molten nitrate salt based nanofluids for thermal energy storage application: High thermal performance and long storage components life-time","authors":"U. Nithiyanantham, Yaroslav Grosu, L. González-Fernández, A. Zaki, J. Igartua, A. Faik","doi":"10.1063/1.5117740","DOIUrl":"https://doi.org/10.1063/1.5117740","url":null,"abstract":"The use of thermal energy storage (TES) for electricity production at concentrated solar power (CSP) plants has provided several important benefits, like lower environmental impact and higher dispatchability, compared to other methods. Many investigations have been focused on the enhancement of thermophysical properties of molten salts (TES material for CSP) by the addition of minor percentage of nanoparticles. In the present work, two nanofluids were developed based on the binary eutectic mixture of NaNO3 and KNO3 (mole ratio of 55:45) as base fluid with by addition of a small amount (1wt.%) of commercial Al2O3 and SiO2 nanoparticles. The thermophysical properties of the developed nanofluids have been investigated in terms of enhancement of their heat capacity and thermal conductivity. Firstly, an effective dry method is proposed and validated for the preparation of molten salt based nanofluids. The obtained nanofluids were characterized by different techniques such as scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). Secondly, their thermophysical properties have been investigated by means of differential scanning calorimetry (DSC) and laser flash apparatus (LFA). The developed nanofluids present significant enhancements of the specific heat capacity and thermal conductivity as compared to the base fluid ones. Finally, immersion corrosion tests were conducted under atmospheric conditions for carbon steel (CS) A516.Gr70 in contact with nanofluids at 390 °C, for exposure times of 250, 500, 1000 and 1500 hours. Carbon steel samples were analysed by means of SEM-EDX (surface and cross section), XRD and mass variation. Regarding the corrosion study, the oxidation was determined as the main mechanism of carbon steel degradation upon direct contact with molten nitrate salt. It was found that adding 1%wt of Al2O3 or SiO2 nanoparticles decreases the corrosion layer thickness more than twice as compared to the pure salt.The use of thermal energy storage (TES) for electricity production at concentrated solar power (CSP) plants has provided several important benefits, like lower environmental impact and higher dispatchability, compared to other methods. Many investigations have been focused on the enhancement of thermophysical properties of molten salts (TES material for CSP) by the addition of minor percentage of nanoparticles. In the present work, two nanofluids were developed based on the binary eutectic mixture of NaNO3 and KNO3 (mole ratio of 55:45) as base fluid with by addition of a small amount (1wt.%) of commercial Al2O3 and SiO2 nanoparticles. The thermophysical properties of the developed nanofluids have been investigated in terms of enhancement of their heat capacity and thermal conductivity. Firstly, an effective dry method is proposed and validated for the preparation of molten salt based nanofluids. The obtained nanofluids were characterized by different techniques such as scanning electron microscopy (SEM) ...","PeriodicalId":21790,"journal":{"name":"SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems","volume":"30 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81609833","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shunzhou Chu, F. Bai, Zhiying Cui, Fuliang Nie, Zhifeng Wang
This study investigated the startup characteristics and thermal performance of a heat pipe pressurized air receiver. The heat flux on the receiver of around 130 kW/m2 was tested to be an appropriat...
{"title":"Experimental study of a heat pipe pressurized air receiver","authors":"Shunzhou Chu, F. Bai, Zhiying Cui, Fuliang Nie, Zhifeng Wang","doi":"10.1063/1.5117527","DOIUrl":"https://doi.org/10.1063/1.5117527","url":null,"abstract":"This study investigated the startup characteristics and thermal performance of a heat pipe pressurized air receiver. The heat flux on the receiver of around 130 kW/m2 was tested to be an appropriat...","PeriodicalId":21790,"journal":{"name":"SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems","volume":"73 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76075130","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Montenon, P. Tsekouras, C. Tzivanidis, Mathéou Bibron, C. Papanicolas
The present paper describes with accuracy the thermo-optical properties of the Fresnel collector currently in operation at the Cyprus Institute independently from its global location. It takes into consideration all optical losses in a perfect tracking environment based on the as-built parameters. The map of optical losses methodologically considers angle varying from 0° to 90° on both longitudinal and transversal angles to generate a global map of the losses. It gives an exact estimation of the maximum power that can be harvested on its absorber. The thermal analysis of the LFC receiver is performed in CFD environment (Solidworks Flow Simulation). Initially, the CFD model is compared to literature data and to a mathematical model (1D Heat Transfer Model - HTM) in order to prove the model consistency. Then, the CFD model is adjusted to the specific LFC characteristics, leading to the determination of the receiver heat losses calculations. Finally, parametric simulations are conducted by varying the oil temperature, the DNI level and the mass flow rate in order to assess their impact on the receiver performance.
本文准确地描述了目前在塞浦路斯研究所独立于其全球位置运行的菲涅耳集热器的热光学特性。它考虑了在一个基于已建参数的完美跟踪环境下的所有光损耗。光学损耗图在方法上考虑了纵角和横角从0°到90°的角度变化，以生成损耗的全局图。它给出了可以在吸收器上收获的最大功率的精确估计。在CFD (Solidworks Flow Simulation)环境下对LFC接收机进行了热分析。首先，将CFD模型与文献数据和数学模型(1D Heat Transfer model - HTM)进行比较，以证明模型的一致性。然后，将CFD模型调整到特定的LFC特性，从而确定接收器的热损失计算。最后，通过改变油温、DNI水平和质量流量进行参数化仿真，以评估它们对接收机性能的影响。
{"title":"Thermo-optical modelling of the linear Fresnel collector at the Cyprus institute","authors":"A. Montenon, P. Tsekouras, C. Tzivanidis, Mathéou Bibron, C. Papanicolas","doi":"10.1063/1.5117613","DOIUrl":"https://doi.org/10.1063/1.5117613","url":null,"abstract":"The present paper describes with accuracy the thermo-optical properties of the Fresnel collector currently in operation at the Cyprus Institute independently from its global location. It takes into consideration all optical losses in a perfect tracking environment based on the as-built parameters. The map of optical losses methodologically considers angle varying from 0° to 90° on both longitudinal and transversal angles to generate a global map of the losses. It gives an exact estimation of the maximum power that can be harvested on its absorber. The thermal analysis of the LFC receiver is performed in CFD environment (Solidworks Flow Simulation). Initially, the CFD model is compared to literature data and to a mathematical model (1D Heat Transfer Model - HTM) in order to prove the model consistency. Then, the CFD model is adjusted to the specific LFC characteristics, leading to the determination of the receiver heat losses calculations. Finally, parametric simulations are conducted by varying the oil temperature, the DNI level and the mass flow rate in order to assess their impact on the receiver performance.","PeriodicalId":21790,"journal":{"name":"SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems","volume":"53 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87957115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Ortiz, M. Binotti, M. Romano, J. Valverde, R. Chacartegui
Dispatchability is a key issue to increase the competitiveness of concentrating solar power plants. Thermochemical energy storage systems are a promising alternative to molten salt-based storage because of the higher energy storage density and the possibility of increasing the storage period. Among possible thermochemical systems, the Calcium-Looping process, based on the multicycle calcination-carbonation of CaCO3, is a main candidate to be integrated as energy storage system within a scenario of massive deployment of concentrating solar power plants. The present manuscript goes beyond previous works by developing an off-design model of the system that leads to a more accurate discussion on system size and plant efficiency. A capacity factor as high as 58% is calculated with lower mass of stored products than in commercial solar plants while the calculated solar-to-electric daily efficiency varies between 17.1% and 20.1%. Simulation results suggest an interesting attractive potential of the Calcium-Looping integration.Dispatchability is a key issue to increase the competitiveness of concentrating solar power plants. Thermochemical energy storage systems are a promising alternative to molten salt-based storage because of the higher energy storage density and the possibility of increasing the storage period. Among possible thermochemical systems, the Calcium-Looping process, based on the multicycle calcination-carbonation of CaCO3, is a main candidate to be integrated as energy storage system within a scenario of massive deployment of concentrating solar power plants. The present manuscript goes beyond previous works by developing an off-design model of the system that leads to a more accurate discussion on system size and plant efficiency. A capacity factor as high as 58% is calculated with lower mass of stored products than in commercial solar plants while the calculated solar-to-electric daily efficiency varies between 17.1% and 20.1%. Simulation results suggest an interesting attractive potential of the Calcium-Loopi...
{"title":"Off-design model of concentrating solar power plant with thermochemical energy storage based on calcium-looping","authors":"C. Ortiz, M. Binotti, M. Romano, J. Valverde, R. Chacartegui","doi":"10.1063/1.5117755","DOIUrl":"https://doi.org/10.1063/1.5117755","url":null,"abstract":"Dispatchability is a key issue to increase the competitiveness of concentrating solar power plants. Thermochemical energy storage systems are a promising alternative to molten salt-based storage because of the higher energy storage density and the possibility of increasing the storage period. Among possible thermochemical systems, the Calcium-Looping process, based on the multicycle calcination-carbonation of CaCO3, is a main candidate to be integrated as energy storage system within a scenario of massive deployment of concentrating solar power plants. The present manuscript goes beyond previous works by developing an off-design model of the system that leads to a more accurate discussion on system size and plant efficiency. A capacity factor as high as 58% is calculated with lower mass of stored products than in commercial solar plants while the calculated solar-to-electric daily efficiency varies between 17.1% and 20.1%. Simulation results suggest an interesting attractive potential of the Calcium-Looping integration.Dispatchability is a key issue to increase the competitiveness of concentrating solar power plants. Thermochemical energy storage systems are a promising alternative to molten salt-based storage because of the higher energy storage density and the possibility of increasing the storage period. Among possible thermochemical systems, the Calcium-Looping process, based on the multicycle calcination-carbonation of CaCO3, is a main candidate to be integrated as energy storage system within a scenario of massive deployment of concentrating solar power plants. The present manuscript goes beyond previous works by developing an off-design model of the system that leads to a more accurate discussion on system size and plant efficiency. A capacity factor as high as 58% is calculated with lower mass of stored products than in commercial solar plants while the calculated solar-to-electric daily efficiency varies between 17.1% and 20.1%. Simulation results suggest an interesting attractive potential of the Calcium-Loopi...","PeriodicalId":21790,"journal":{"name":"SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems","volume":"112 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80668416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Modeling and simulation activities play a key role in the design phase and performance optimization of complex energy processes. It is also expected that they will play a significant role in the future for power plant maintenance and operation (load variation, system startup, system shutdown …). Molten salt technology represents nowadays the most cost- effective technology for electricity generation for solar power plant. The molten salt tower receiver is based on a field of individually sun-tracking mirrors (heliostats) that reflect the incident sunshine to a receiver at the top of a centrally located tower. The molten salt tower receiver is based on a field of individually sun-tracking mirrors (heliostats) that reflect the incident sunshine to a receiver at the top of a centrally located tower. Typically 90 to 95 percent of the reflected energy is absorbed into the working fluid (molten salt), which is pumped through the receiver. The objective of this study is to evaluate the risk of salt crystallization in the receiver tubes for the gravity drainage scenario in the case of absence of solar irradiation. The temperature of the molten salt in the pipes will be calculated during the drainage of the receiver. A detailed dynamic model of Solar Two molten salt central receiver has been developed. The component model is meant to be used for receiver modeling with the ThermoSysPro library, developed by EDF and released under open source license. The paper gives a detailed description of the model, data and the results of the dynamic simulation for several scenarios.Modeling and simulation activities play a key role in the design phase and performance optimization of complex energy processes. It is also expected that they will play a significant role in the future for power plant maintenance and operation (load variation, system startup, system shutdown …). Molten salt technology represents nowadays the most cost- effective technology for electricity generation for solar power plant. The molten salt tower receiver is based on a field of individually sun-tracking mirrors (heliostats) that reflect the incident sunshine to a receiver at the top of a centrally located tower. The molten salt tower receiver is based on a field of individually sun-tracking mirrors (heliostats) that reflect the incident sunshine to a receiver at the top of a centrally located tower. Typically 90 to 95 percent of the reflected energy is absorbed into the working fluid (molten salt), which is pumped through the receiver. The objective of this study is to evaluate the risk of salt crystallizati...
{"title":"Detailed dynamic model for the gravity drainage of a tower solar receiver, with ThermoSysPro library - Time needed to completely drain the receiver and salt temperature as a function of the ambient conditions","authors":"B. E. Hefni","doi":"10.1063/1.5117531","DOIUrl":"https://doi.org/10.1063/1.5117531","url":null,"abstract":"Modeling and simulation activities play a key role in the design phase and performance optimization of complex energy processes. It is also expected that they will play a significant role in the future for power plant maintenance and operation (load variation, system startup, system shutdown …). Molten salt technology represents nowadays the most cost- effective technology for electricity generation for solar power plant. The molten salt tower receiver is based on a field of individually sun-tracking mirrors (heliostats) that reflect the incident sunshine to a receiver at the top of a centrally located tower. The molten salt tower receiver is based on a field of individually sun-tracking mirrors (heliostats) that reflect the incident sunshine to a receiver at the top of a centrally located tower. Typically 90 to 95 percent of the reflected energy is absorbed into the working fluid (molten salt), which is pumped through the receiver. The objective of this study is to evaluate the risk of salt crystallization in the receiver tubes for the gravity drainage scenario in the case of absence of solar irradiation. The temperature of the molten salt in the pipes will be calculated during the drainage of the receiver. A detailed dynamic model of Solar Two molten salt central receiver has been developed. The component model is meant to be used for receiver modeling with the ThermoSysPro library, developed by EDF and released under open source license. The paper gives a detailed description of the model, data and the results of the dynamic simulation for several scenarios.Modeling and simulation activities play a key role in the design phase and performance optimization of complex energy processes. It is also expected that they will play a significant role in the future for power plant maintenance and operation (load variation, system startup, system shutdown …). Molten salt technology represents nowadays the most cost- effective technology for electricity generation for solar power plant. The molten salt tower receiver is based on a field of individually sun-tracking mirrors (heliostats) that reflect the incident sunshine to a receiver at the top of a centrally located tower. The molten salt tower receiver is based on a field of individually sun-tracking mirrors (heliostats) that reflect the incident sunshine to a receiver at the top of a centrally located tower. Typically 90 to 95 percent of the reflected energy is absorbed into the working fluid (molten salt), which is pumped through the receiver. The objective of this study is to evaluate the risk of salt crystallizati...","PeriodicalId":21790,"journal":{"name":"SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems","volume":"71 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85129300","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This experimental study outlines a method to calculate the design wind loads on heliostats, based on peak wind load coefficients reported in the heliostat literature and aerodynamic shape factors derived from high-frequency pressure measurements on an isolated heliostat at different elevation and azimuth angles in a boundary layer wind tunnel. The results show that the aerodynamic shape factors are largest for a range of heliostat configurations, including elevation angles of 15°, 30° and 45°and azimuth angles of 0° and 45°. The distribution of shape factors indicates that the leading edge of the heliostat is most vulnerable to wind-induced mirror damage in this range of critical elevation angles for heliostat design wind loads. The method proposed in the current study for heliostats conforms to the procedure used in design wind codes and standards for buildings and roof-mounted solar panels.This experimental study outlines a method to calculate the design wind loads on heliostats, based on peak wind load coefficients reported in the heliostat literature and aerodynamic shape factors derived from high-frequency pressure measurements on an isolated heliostat at different elevation and azimuth angles in a boundary layer wind tunnel. The results show that the aerodynamic shape factors are largest for a range of heliostat configurations, including elevation angles of 15°, 30° and 45°and azimuth angles of 0° and 45°. The distribution of shape factors indicates that the leading edge of the heliostat is most vulnerable to wind-induced mirror damage in this range of critical elevation angles for heliostat design wind loads. The method proposed in the current study for heliostats conforms to the procedure used in design wind codes and standards for buildings and roof-mounted solar panels.
{"title":"A method for the calculation of the design wind loads on heliostats","authors":"M. Emes, A. Jafari, F. Ghanadi, M. Arjomandi","doi":"10.1063/1.5117532","DOIUrl":"https://doi.org/10.1063/1.5117532","url":null,"abstract":"This experimental study outlines a method to calculate the design wind loads on heliostats, based on peak wind load coefficients reported in the heliostat literature and aerodynamic shape factors derived from high-frequency pressure measurements on an isolated heliostat at different elevation and azimuth angles in a boundary layer wind tunnel. The results show that the aerodynamic shape factors are largest for a range of heliostat configurations, including elevation angles of 15°, 30° and 45°and azimuth angles of 0° and 45°. The distribution of shape factors indicates that the leading edge of the heliostat is most vulnerable to wind-induced mirror damage in this range of critical elevation angles for heliostat design wind loads. The method proposed in the current study for heliostats conforms to the procedure used in design wind codes and standards for buildings and roof-mounted solar panels.This experimental study outlines a method to calculate the design wind loads on heliostats, based on peak wind load coefficients reported in the heliostat literature and aerodynamic shape factors derived from high-frequency pressure measurements on an isolated heliostat at different elevation and azimuth angles in a boundary layer wind tunnel. The results show that the aerodynamic shape factors are largest for a range of heliostat configurations, including elevation angles of 15°, 30° and 45°and azimuth angles of 0° and 45°. The distribution of shape factors indicates that the leading edge of the heliostat is most vulnerable to wind-induced mirror damage in this range of critical elevation angles for heliostat design wind loads. The method proposed in the current study for heliostats conforms to the procedure used in design wind codes and standards for buildings and roof-mounted solar panels.","PeriodicalId":21790,"journal":{"name":"SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems","volume":"182 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80349702","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
CFD models have been used to show the potential of using corrugated tubes instead of smooth tubes at a solar thermal receiver using molten salt as heat transfer fluid. The results were compared on the basis of a 700 MWth receiver. Absorber tubes with an inner diameter between 32.8mm and 70 mm using a helical ribbed structure have been analyzed. The results show that a positive effect can only be achieved for configurations where the fluid velocity is lower than for the base hydraulic design with a fully developed turbulent flow. The presented approach proposes therefore tubes with larger inner diameter and reduced fluid velocity and pressure drop. The difference in pressure drop to the base design can then be used to introduce a swirl flow which leads to better mixing of the fluid and therefore lowers the temperatures of the tube wall, the fluid and also the thermal gradients. Corrugated tubes can be used to add an additional design parameter for a thermo-hydraulic optimization of the receiver.CFD models have been used to show the potential of using corrugated tubes instead of smooth tubes at a solar thermal receiver using molten salt as heat transfer fluid. The results were compared on the basis of a 700 MWth receiver. Absorber tubes with an inner diameter between 32.8mm and 70 mm using a helical ribbed structure have been analyzed. The results show that a positive effect can only be achieved for configurations where the fluid velocity is lower than for the base hydraulic design with a fully developed turbulent flow. The presented approach proposes therefore tubes with larger inner diameter and reduced fluid velocity and pressure drop. The difference in pressure drop to the base design can then be used to introduce a swirl flow which leads to better mixing of the fluid and therefore lowers the temperatures of the tube wall, the fluid and also the thermal gradients. Corrugated tubes can be used to add an additional design parameter for a thermo-hydraulic optimization of the receiver.
{"title":"Using corrugated tubes in external molten salt receivers","authors":"R. Uhlig, C. Frantz, R. Buck","doi":"10.1063/1.5117573","DOIUrl":"https://doi.org/10.1063/1.5117573","url":null,"abstract":"CFD models have been used to show the potential of using corrugated tubes instead of smooth tubes at a solar thermal receiver using molten salt as heat transfer fluid. The results were compared on the basis of a 700 MWth receiver. Absorber tubes with an inner diameter between 32.8mm and 70 mm using a helical ribbed structure have been analyzed. The results show that a positive effect can only be achieved for configurations where the fluid velocity is lower than for the base hydraulic design with a fully developed turbulent flow. The presented approach proposes therefore tubes with larger inner diameter and reduced fluid velocity and pressure drop. The difference in pressure drop to the base design can then be used to introduce a swirl flow which leads to better mixing of the fluid and therefore lowers the temperatures of the tube wall, the fluid and also the thermal gradients. Corrugated tubes can be used to add an additional design parameter for a thermo-hydraulic optimization of the receiver.CFD models have been used to show the potential of using corrugated tubes instead of smooth tubes at a solar thermal receiver using molten salt as heat transfer fluid. The results were compared on the basis of a 700 MWth receiver. Absorber tubes with an inner diameter between 32.8mm and 70 mm using a helical ribbed structure have been analyzed. The results show that a positive effect can only be achieved for configurations where the fluid velocity is lower than for the base hydraulic design with a fully developed turbulent flow. The presented approach proposes therefore tubes with larger inner diameter and reduced fluid velocity and pressure drop. The difference in pressure drop to the base design can then be used to introduce a swirl flow which leads to better mixing of the fluid and therefore lowers the temperatures of the tube wall, the fluid and also the thermal gradients. Corrugated tubes can be used to add an additional design parameter for a thermo-hydraulic optimization of the receiver.","PeriodicalId":21790,"journal":{"name":"SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems","volume":"38 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86551527","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rafael López-Martín, G. S. Vicente, Á. Morales, L. Valenzuela
Heat loss of receiver tubes is related with the radiant emittance of absorbers. This parameter can be obtained using an IR spectrophotometer to measure the spectral hemispherical reflectance of absorber tube samples which requires the breaking of a receiver tube. Nevertheless, radiant emittance can be also obtained indirectly testing a complete receiver tube in a test device to measure its heat losses by radiation. This paper shows results of tests performed to different receivers applying both methodologies to calculate their emittance. One conclusion is the importance of performing measurements in an evacuated atmosphere when the non-destructive method is applied; this is to eliminate convective heat transfer to the surroundings, especially at low temperature when convective heat losses may have a much greater influence on the accuracy of emittance results.Heat loss of receiver tubes is related with the radiant emittance of absorbers. This parameter can be obtained using an IR spectrophotometer to measure the spectral hemispherical reflectance of absorber tube samples which requires the breaking of a receiver tube. Nevertheless, radiant emittance can be also obtained indirectly testing a complete receiver tube in a test device to measure its heat losses by radiation. This paper shows results of tests performed to different receivers applying both methodologies to calculate their emittance. One conclusion is the importance of performing measurements in an evacuated atmosphere when the non-destructive method is applied; this is to eliminate convective heat transfer to the surroundings, especially at low temperature when convective heat losses may have a much greater influence on the accuracy of emittance results.
{"title":"Radiant emittance calculated by heat transfer analysis of a PTC receiver tested with vacuum versus measurement of an absorber sample using spectrophotometer","authors":"Rafael López-Martín, G. S. Vicente, Á. Morales, L. Valenzuela","doi":"10.1063/1.5117628","DOIUrl":"https://doi.org/10.1063/1.5117628","url":null,"abstract":"Heat loss of receiver tubes is related with the radiant emittance of absorbers. This parameter can be obtained using an IR spectrophotometer to measure the spectral hemispherical reflectance of absorber tube samples which requires the breaking of a receiver tube. Nevertheless, radiant emittance can be also obtained indirectly testing a complete receiver tube in a test device to measure its heat losses by radiation. This paper shows results of tests performed to different receivers applying both methodologies to calculate their emittance. One conclusion is the importance of performing measurements in an evacuated atmosphere when the non-destructive method is applied; this is to eliminate convective heat transfer to the surroundings, especially at low temperature when convective heat losses may have a much greater influence on the accuracy of emittance results.Heat loss of receiver tubes is related with the radiant emittance of absorbers. This parameter can be obtained using an IR spectrophotometer to measure the spectral hemispherical reflectance of absorber tube samples which requires the breaking of a receiver tube. Nevertheless, radiant emittance can be also obtained indirectly testing a complete receiver tube in a test device to measure its heat losses by radiation. This paper shows results of tests performed to different receivers applying both methodologies to calculate their emittance. One conclusion is the importance of performing measurements in an evacuated atmosphere when the non-destructive method is applied; this is to eliminate convective heat transfer to the surroundings, especially at low temperature when convective heat losses may have a much greater influence on the accuracy of emittance results.","PeriodicalId":21790,"journal":{"name":"SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86810492","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In view of the adoption of thermocline Thermal Energy Storage (TES) systems for Concentrated Solar Power (CSP) plants the thermocline behavior needs to be modeled to correctly predict the plant’s yearly energy yield and to specify and tune plant’s process control (e.g. solar field temperature control requirements, electric production scheduling based on estimation of the TES state of charge, etc.). Indeed the thermocline evolution influences the ratio between the nominal TES capacity and the effective one, therefore the potential degradation of the thermocline, when subject to arbitrary charge/discharge cycles, off-design temperature input from the solar field and/or incomplete charging cycles in periods or low Direct Normal Irradiation (DNI) must be taken into account. This paper illustrates the development of a thermocline TES dynamic model sufficiently accurate to predict the TES behavior but sufficiently simple to allow a fast execution of the simulation in the time domain. The TES model is implemente...
{"title":"Modelling thermocline storage for CSP yield assessment and process control simulation","authors":"M. Falchetta, M. Binotti, F. Avallone","doi":"10.1063/1.5117733","DOIUrl":"https://doi.org/10.1063/1.5117733","url":null,"abstract":"In view of the adoption of thermocline Thermal Energy Storage (TES) systems for Concentrated Solar Power (CSP) plants the thermocline behavior needs to be modeled to correctly predict the plant’s yearly energy yield and to specify and tune plant’s process control (e.g. solar field temperature control requirements, electric production scheduling based on estimation of the TES state of charge, etc.). Indeed the thermocline evolution influences the ratio between the nominal TES capacity and the effective one, therefore the potential degradation of the thermocline, when subject to arbitrary charge/discharge cycles, off-design temperature input from the solar field and/or incomplete charging cycles in periods or low Direct Normal Irradiation (DNI) must be taken into account. This paper illustrates the development of a thermocline TES dynamic model sufficiently accurate to predict the TES behavior but sufficiently simple to allow a fast execution of the simulation in the time domain. The TES model is implemente...","PeriodicalId":21790,"journal":{"name":"SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83581705","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Parabolic Dish concentrators are a well-known solution for many applications such as Concentrated Solar Power (CSP), solar metallurgical processes, solar reactors for fuel production, etc. Nevertheless, this technology is facing a tremendous challenge to become more efficient and competitive (especially within CSP field) in comparison with other technologies, namely Central Tower Receivers. A possible path to achieve this goal is to use a Cassegranian approach which enables a top-down design, placing the receiver closer to the ground and with potential higher concentration. In this paper, the theoretical limit of such configurations and a practical solution is presented with a discussion of its advantages and possible drawbacks.Parabolic Dish concentrators are a well-known solution for many applications such as Concentrated Solar Power (CSP), solar metallurgical processes, solar reactors for fuel production, etc. Nevertheless, this technology is facing a tremendous challenge to become more efficient and competitive (especially within CSP field) in comparison with other technologies, namely Central Tower Receivers. A possible path to achieve this goal is to use a Cassegranian approach which enables a top-down design, placing the receiver closer to the ground and with potential higher concentration. In this paper, the theoretical limit of such configurations and a practical solution is presented with a discussion of its advantages and possible drawbacks.
{"title":"Simultaneous multiple surface method for the design of new parabolic dish-type concentrator using a Cassegranian approach","authors":"Diogo Canavarro, J. Chaves, M. Collares-Pereira","doi":"10.1063/1.5117584","DOIUrl":"https://doi.org/10.1063/1.5117584","url":null,"abstract":"Parabolic Dish concentrators are a well-known solution for many applications such as Concentrated Solar Power (CSP), solar metallurgical processes, solar reactors for fuel production, etc. Nevertheless, this technology is facing a tremendous challenge to become more efficient and competitive (especially within CSP field) in comparison with other technologies, namely Central Tower Receivers. A possible path to achieve this goal is to use a Cassegranian approach which enables a top-down design, placing the receiver closer to the ground and with potential higher concentration. In this paper, the theoretical limit of such configurations and a practical solution is presented with a discussion of its advantages and possible drawbacks.Parabolic Dish concentrators are a well-known solution for many applications such as Concentrated Solar Power (CSP), solar metallurgical processes, solar reactors for fuel production, etc. Nevertheless, this technology is facing a tremendous challenge to become more efficient and competitive (especially within CSP field) in comparison with other technologies, namely Central Tower Receivers. A possible path to achieve this goal is to use a Cassegranian approach which enables a top-down design, placing the receiver closer to the ground and with potential higher concentration. In this paper, the theoretical limit of such configurations and a practical solution is presented with a discussion of its advantages and possible drawbacks.","PeriodicalId":21790,"journal":{"name":"SOLARPACES 2018: International Conference on Concentrating Solar Power and Chemical Energy Systems","volume":"35 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91299455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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