scholarly journals CFD Simulation and Heat Loss Analysis of the Solar Two Power Tower Receiver

2012 ◽  
Author(s):  
Joshua M. Christian ◽  
Clifford K. Ho
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Molten Salt ◽  
Heat Loss ◽  
Convective Heat ◽  
Thermal Power ◽  
Heat Losses ◽  
Heat Transfer Fluid ◽  
Outlet Temperature ◽  
Receiver System

Solar Two was a demonstration of the viability of molten salt power towers. The power tower was designed to produce enough thermal power to run a 10-MWe conventional Rankine cycle turbine. A critical component of this process was the solar tower receiver. The receiver was designed for an applied average heat flux of 430 kW/m2 with an outlet temperature of 565°C (838.15 K). The mass flow rate could be varied in the system to control the outlet temperature of the heat transfer fluid, which was high temperature molten salt. The heat loss in the actual system was calculated by using the power-on method which compares how much power is absorbed by the molten salt when using half of the heliostat field and then the full heliostat field. However, the total heat loss in the system was lumped into a single value comprised of radiation, convection, and conduction heat transfer losses. In this study, ANSYS FLUENT was used to evaluate and characterize the radiative and convective heat losses from this receiver system assuming two boundary conditions: (1) a uniform heat flux on the receiver and (2) a distributed heat flux generated from the code DELSOL. The results show that the distributed-flux models resulted in radiative heat losses that were ∼14% higher than the uniform-flux models, and convective losses that were ∼5–10% higher due to the resulting non-uniform temperature distributions. Comparing the simulations to known convective heat loss correlations demonstrated that surface roughness should be accounted for in the simulations. This study provides a model which can be used for further receiver design and demonstrates whether current convective correlations are appropriate for analytical evaluation of external solar tower receivers.

scholarly journals Parametric Analysis of Parasitic Pressure Drop and Heat Losses for a Parabolic Trough With Considerations of Varying Aperture Sizes and Receiver Sizes

2011 ◽  
Author(s):  
Kyle W. Glenn ◽  
Clifford K. Ho ◽  
Gregory J. Kolb
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Heat Loss ◽  
Heat Losses ◽  
Heat Transfer Fluid ◽  
Aperture Size ◽  
Parabolic Trough ◽  
Pressure Drops ◽  
Loss Efficiency

The collector aperture and diameter of the receiver of a parabolic trough were studied to investigate the relative impacts of parasitic pressure drop, heat losses, and heat flux intercepted by the receiver tube. The configuration of an LS-2 parabolic trough was used as the baseline, and the size of the HCE and collector aperture were parametrically varied using values between the baseline and twice their original size. A Matlab computer model was created to determine the flux on the receiver, heat loss from the HCE, and pressure drop within the heat transfer fluid (HTF) at each combination of aperture size and receiver diameter. Flux on the receiver is calculated for each geometry assuming a Gaussian flux distribution. Based on pressure data from SEGS VII, the standard Darcy-Weisbach equation for the pressure drop was modified to include the contribution that connective joints of varying quantities and types have on the pressure drop within the HTF. The model employs the Sandia thermal resistive network and iteratively solves for the temperatures accounting for various heat transfer modes that contribute to the heat lost by the HCE. The Matlab model expresses pressure drop and heat losses in terms of electric power. It does this by calculating both the power required to pump the HTF for varying pressure drops and the power that could have been produced if heat was not lost to the environment. The Matlab model displays the results in the form of surface plots that represent the values of heat loss, efficiency, pumping power, etc. as a function of aperture size and receiver diameter. The combined effects of pressure drop, heat loss, and heat flux intercepted by the receiver tube were evaluated, and results show that configurations with receiver diameters ranging from 85–90 millimeters and large (up to 10 meter) aperture sizes minimize the overall power consumption and maximize the efficiency of a single loop. Structural effects, wind and gravity loads, and factors associated with the balance of plant were not considered.

Central Receiver System Solar Power Plant Using Molten Salt as Heat Transfer Fluid

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
J. Ignacio Ortega ◽  
J. Ignacio Burgaleta ◽  
Félix M. Téllez
Keyword(s):  
Heat Transfer ◽  
Power Generation ◽  
Molten Salt ◽  
Thermal Power ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Solar Thermal Power ◽  
Central Receiver ◽  
Spanish Legislation ◽  
Solar Thermal Power Generation

Of all the technologies being developed for solar thermal power generation, central receiver systems (CRSs) are able to work at the highest temperatures and to achieve higher efficiencies in electricity production. The combination of this concept and the choice of molten salts as the heat transfer fluid, in both the receiver and heat storage, enables solar collection to be decoupled from electricity generation better than water∕steam systems, yielding high capacity factors with solar-only or low hybridization ratios. These advantages, along with the benefits of Spanish legislation on solar energy, moved SENER to promote the 17MWe Solar TRES plant. It will be the first commercial CRS plant with molten-salt storage and will help consolidate this technology for future higher-capacity plants. This paper describes the basic concept developed in this demonstration project, reviewing the experience accumulated in the previous Solar TWO project, and present design innovations, as a consequence of the development work performed by SENER and CIEMAT and of the technical conditions imposed by Spanish legislation on solar thermal power generation.

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.

Effects of Multi-Walled Carbon Nanotubes on Enhancing the Thermodynamics Characteristic of Alkali Nitrate and Chlorate Salt for Concentration Solar Plants

2013 ◽  
Vol 805-806 ◽  
pp. 63-69 ◽  
Author(s):  
Di Wu ◽  
Shi Liu
Keyword(s):  
Heat Transfer ◽  
Carbon Nanotubes ◽  
Molten Salt ◽  
Fossil Fuels ◽  
Thermal Power ◽  
Thermal Storage ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Solar Thermal Power ◽  
The Future

Solar thermal power generation technology is the most feasible technology to compete with fossil fuels in the economy, and is considered to be one of the most promising candidates for providing a major share of the clean and renewable energy needed in the future. The appropriate heat transfer fluid and storage medium is a key technological issue for the future success of solar thermal technologies. Molten salt is one of the best heat transfer and thermal storage fluid for both parabolic trough and tower solar thermal power system. It is very important that molten salt heat transfer mechanisms are understood and can be predicted with accuracy. But studies on molten salts heat transfer are rare. This study will lay a foundation for the application of carbon nanotubes in molten salt which can remarkably improve the stability and capacity of thermal storage. Thermal analysis methods and scanning electron microscope (SEM) are utilized to provide a review of thermophysical properties and thermochemical characteristics of the MWCNTs-salt composite materials.

scholarly journals Numerical Simulation of Natural Convection in Solar Cavity Receivers

2012 ◽  
Author(s):  
James K. Yuan ◽  
Clifford K. Ho ◽  
Joshua M. Christian
Keyword(s):  
Heat Flux ◽  
Natural Convection ◽  
Heat Loss ◽  
Convective Heat ◽  
Heat Losses ◽  
Flat Plates ◽  
Convective Heat Loss ◽  
Software Packages ◽  
Receiver Model ◽  
Cubical Cavity

Cavity receivers used in solar power towers and dish concentrators may lose considerable energy by natural convection, which reduces the overall system efficiency. A validated numerical receiver model is desired to better understand convection processes and aid in heat loss minimization efforts. The purpose of this investigation was to evaluate heat loss predictions using the commercial computational fluid dynamics software packages FLUENT 13.0 and SolidWorks Flow Simulation 2011 against experimentally measured heat losses for a heated cubical cavity model [1] and a cylindrical dish receiver model [2]. Agreement within 10% was found between software packages across most simulations. However, simulated convective heat loss was under predicted by 45% for the cubical cavity when experimental wall temperatures were implemented on cavity walls, and 32% when implementing the experimental heat flux from the cavity walls. Convective heat loss from the cylindrical dish receiver model was accurately predicted within experimental uncertainties by both simulation codes using both isothermal and constant heat flux wall boundary conditions except at inclination angles below 15° and above 75°, where losses were under- and over-predicted by FLUENT and SolidWorks, respectively. Comparison with empirical correlations for convective heat loss from heated cavities showed that correlations by Siebers and Kraabel [1] and for an assembly of heated flat plates oriented to the cavity geometry [3] predicted heat losses from the cubical cavity within experimental uncertainties, while correlations by Clausing [4] and Paitoonsurikarn et al. [8] were able to do the same for the cylindrical dish receiver. No single correlation was valid for both receiver models. Different turbulence and air-property models within FLUENT were also investigated and compared in this study.

Research and Application of Heat Transfer Fluids in Solar Thermal Power

2013 ◽  
Vol 815 ◽  
pp. 415-422 ◽  
Author(s):  
Xiao Min Cheng ◽  
Chuang Zhu ◽  
Han Zhang ◽  
Xian Jie Yang
Keyword(s):  
Heat Transfer ◽  
Molten Salt ◽  
Liquid Alloy ◽  
Thermal Power ◽  
Heat Transfer Fluid ◽  
Future Research ◽  
Research Directions ◽  
Heat Transfer Fluids ◽  
Future Research Directions ◽  
And Storage

mproving the thermophysical properties of heat transfer fluid is always a research hotspot and difficult subject in the application of solar energy for medium and high temperature. The research and application of these heat transfer fluid, including steam, heat transfer oil, molten salt, air, liquid alloy and nanofluids, were summarized in this paper. After comparing their characteristics, it is found that molten salt, air and liquid alloy have greater application and development prospects. Future research directions include extending the temperature span of operating condition, enhancing the efficiency of heat transfer and storage, lengthening service life and finding out the correlation between microstructure and related performance.

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