Performance of a 100 kWth Concentrated Solar Beam-Down Optical Experiment

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Marwan Mokhtar ◽  
Steven A. Meyers ◽  
Peter R. Armstrong ◽  
Matteo Chiesa
Keyword(s):  
Flux Distribution ◽  
Thermal Flux ◽  
Heat Transfer Fluid ◽  
Distribution Data ◽  
Fluid Temperature ◽  
Aperture Size ◽  
Optical Efficiency ◽  
Optimal Receiver ◽  
Daily Average ◽  
Optical Experiment

An analysis of the beam down optical experiment (BDOE) performance with full concentration is presented. The analysis is based on radiation flux distribution data taken on Mar. 21st, 2011 using an optical-thermal flux measurement system. A hypothetical thermal receiver design is used in conjunction with the experimental data to determine the optimal receiver aperture size as a function of receiver losses and flux distribution. The overall output of the plant is calculated for various operating temperatures and three different control strategies namely, constant mass flow of the heat transfer fluid (HTF), constant outlet fluid temperature and real-time optimal outlet fluid temperature. It was found that the optimal receiver aperture size (radius) of the receiver ranged between (1.06 and 1.71 m) depending on temperature. The optical efficiency of the BDOE ranged from 32% to 37% as a daily average (average over the ten sunshine hours). The daily average mean flux density ranged between 9.422 kW/m2 for the 1.71 m-receiver and 20.9 kW/m2 for the 1.06 m-receiver. Depending on the control parameters and assuming an open receiver with solar absorptivity of 0.95 and longwave emissivity of 0.10. The average receiver efficiency varied from 71% at 300 °C down to 68% at 600 °C. The overall daily average thermal efficiency of the plant was between 28% and 24%, respectively for the aforementioned temperatures. The peak of useful power collected in the HTF was around 105 kWth at 300 °C mean fluid temperature and 89 kWth at 600 °C.

Comparison of Two Linear Collectors in Solar Thermal Plants: Parabolic Trough vs Fresnel

2011 ◽  
Author(s):  
A. Giostri ◽  
M. Binotti ◽  
P. Silva ◽  
E. Macchi ◽  
G. Manzolini
Keyword(s):  
Power Plants ◽  
Thermal Power ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Steam Generation ◽  
Parabolic Trough ◽  
Research Activity ◽  
Optical Efficiency ◽  
Synthetic Oil ◽  
Yearly Average

Parabolic trough can be considered the state of the art for solar thermal power plants thanks to the almost 30 years experience gained in SEGS and, recently, Nevada Solar One plants in US and Andasol plants in Spain. One of the major issues that limits the wide diffusion of this technology is the high investment cost of the solar field and, particularly, of the solar collector. For this reason, since several years research activity has been trying to develop new solutions with the aim of cost reduction. This work compares commercial Fresnel technology with conventional parabolic trough plant based on synthetic oil as heat transfer fluid at nominal conditions and evaluates yearly average performances. In both technologies, no thermal storage system is considered. In addition, for Fresnel, a Direct Steam Generation (DSG) case is investigated. Performances are calculated by a commercial code, Thermoflex®, with dedicated component to evaluate solar plant. Results will show that, at nominal conditions, Fresnel technology have an optical efficiency of 67% which is lower than 75% of parabolic trough. Calculated net electric efficiency is about 19.25%, while parabolic trough technology achieves 23.6%. In off-design conditions, the gap between Fresnel and parabolic trough increases because the former is significantly affected by high radiation incident angles. The calculated sun-to-electric annual average efficiency for Fresnel plant is 10.2%, consequence of the average optical efficiency of 38.8%, while parabolic trough achieve an overall efficiency of 16%, with an optical one of 52.7%. An additional case with Fresnel collector and synthetic oil outlines differences among investigated cases. Finally, because part of performance difference between PT and Fresnel is simple due to different definitions, additional indexes are introduced in order to make a consistent comparison.

A 3-D Model Simulation of High Temperature Solar Cavity Receiver

2017 ◽  
Author(s):  
Huayi Feng ◽  
Yanping Zhang ◽  
Chongzhe Zou
Keyword(s):  
Heat Transfer ◽  
Radiation Intensity ◽  
Large Scale ◽  
Model Simulation ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Outlet Temperature ◽  
Fluid Temperature ◽  
Heat Transfer Efficiency ◽  
Direct Normal Irradiance

In this paper, a 3-D numerical model is proposed to investigate the capability of generating high operating temperature for a modified solar cavity receiver in large-scale dish Stirling system. The proposed model aims to evaluate the influence of radiation intensity on the cavity receiver performance. The properties of the heat transfer fluid in the pipe and heat transfer losses of the receiver are investigated by varying the direct normal irradiance from 400W/m2 to 1000W/m2. The temperature of heat transfer fluid, as well as the effect of radiation intensity on the heat transfer losses have been critically presented and discussed. The simulation results reveal that the heat transfer fluid temperature and thermal efficiency of the receiver are significantly influenced by different radiation flux. With the increase of radiation intensity, the efficiency of the receiver will firstly increase, then drops after reaching the highest point. The outlet working fluid temperature of the pipe will be increased consistently. The results of the simulations show that the designed cylindrical receiver used in dish Stirling system is capable to achieve the targeted outlet temperature and heat transfer efficiency, with an acceptable pressure drop.

scholarly journals Analysis of Heat Transfer Mechanism for Shelf Vacuum Freeze-Drying Equipment

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Hong-Ping Cheng ◽  
Shian-Min Tsai ◽  
Chin-Chi Cheng
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Low Temperature ◽  
Temperature Gradient ◽  
Freeze Drying ◽  
Heat Transfer Fluid ◽  
Processing Temperature ◽  
Fluid Temperature ◽  
Three Dimension ◽  
Flow Rates

Vacuum freeze-drying technology is applicable to the process of high heat-sensitive products. Due to the long drying period and extremely low processing temperature and pressure, the uniform and efficiency of heat transfer fluid temperature in shelf are critical for product quality. Therefore, in this study, the commercial computer fluid dynamics (CFD) software, FLUENT, was utilized for three-dimension numerical simulation of the shelf vacuum freeze-drying process. The influences of different inlet and outlet positions for shelves on the uniformity of the flow rate and temperature were discussed. Moreover, it explored the impacts on the temperature gradient of shelves after heat exchange of different flow rates and low temperature materials. In order to reduce the developing time and optimize the design, the various secondary refrigerants in different plies of shelves were investigated. According to the effect of heat exchange between different flow rates and low temperature layer material shelves on the temperature gradient of shelves surface, the minimum temperature gradient was 20 L/min, and the maximum was 2.5 L/min.

A Numerical Model for Off-Design Performance Calculation of Parabolic Trough Based Solar Power Plants

2010 ◽  
Author(s):  
Andrea Giostri ◽  
Claudio Saccilotto ◽  
Paolo Silva ◽  
Ennio Macchi ◽  
Giampaolo Manzolini
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Design Calculation ◽  
Fluid Temperature ◽  
Parabolic Trough ◽  
Design Algorithm ◽  
Energy Balances ◽  
Steam Cycle

The paper deals with the development and testing of an innovative code for the performance prediction of solar trough based CSP plants in off-design conditions. The code is developed in MS Visual Basic 6.0 with Excel as user interface. The proposed code originates from a previously presented algorithm for on-design sizing and cost estimation of the solar field lay-out, as well as of the main components of the plant, including connecting piping and the steam cycle. Off-design calculation starts from data obtained through the on-design algorithm and considers steady-state situations. Both models are implemented in the same software, named PATTO (PArabolic Trough Thermodynamic Optimization), which is very flexible: the optical-thermal model of collectors can simulate different kinds of parabolic trough systems in commerce, including a combination of various mirrors, receivers and supports. The code is also flexible in terms of working fluid, temperature and pressure range, and can also simulate direct steam generation plants (DSG). Regarding the power block, a conventional steam cycle with super-heater, eventually a re-heater section, and up to seven regenerative bleedings is adopted. The off-design model calculates thermal performance of collectors taking into account proper correlations for convective heat transfer coefficients, considering also boiling regime in DSG configurations. Solar plant heat and mass balances and performances at off-design conditions are estimated by accounting for the constraints imposed by the available heat transfer areas in heat exchangers and condenser, as well as the characteristic curve of the steam turbine. The numerical model can be used for a single calculation in a specific off-design condition, as well as for a whole year estimation of energy balances with an hourly resolution. The model is tested towards real applications and reference values found in literature; in particular, focusing on SEGS VI plant in the USA and SAM® code. Annual energy balances with ambient condition taken from TMY3 database are obtained, showing good accuracy of predicted performances. The code potentiality in the design process reveals twofold: it can be used for plant optimization in feasibility studies; moreover it is useful to find the best control strategy of a plant, especially the mass flow of heat transfer fluid in each operating condition.

Experimental and Numerical Investigation of Various Tube Geometries for Improved Heat Transfer in Solar Central Receivers

2020 ◽  
Author(s):  
Salman M. Ismail ◽  
Mohammed M. Rashwan ◽  
Saud Ghani
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Circular Tube ◽  
Radiation Heat Transfer ◽  
Fluid Mixing ◽  
Heat Transfer Fluid ◽  
Bulk Temperature ◽  
Fluid Temperature ◽  
Bulk Fluid ◽  
Central Receiver

Abstract Central receiver of Concentrated Solar Power technology constitutes 15% of the total initial cost and plays an important role in achieving high operating temperatures. Central receiver systems are composed of tubes with heat transfer fluid flowing inside that transports heat from radiation on the outer wall of tubes. This work investigates radiation heat transfer to fluid in tubes of various geometries. Experimental and numerical analysis were conducted to observe the boundary layer temperatures, bulk fluid temperatures, and fluid mixing near the tube walls. Four different samples of corrugated tubes adopted from literature were compared to a circular tube and a generic tube designed to provide larger surface area exposed to radiation without corrugation. The circular tube had high temperature in the boundary layer but low bulk fluid temperature due to lack of fluid mixing at wall. A spirally corrugated tube was found to have the highest bulk fluid temperature due to turbulent mixing and low temperature at boundary layer. The generic tube had higher bulk temperature compared to circular tube and two other corrugated tubes.

Solar Driven Absorption Chiller for Medium Temperature Food Refrigeration, a Study for Application in Indonesia

2014 ◽  
Vol 493 ◽  
pp. 167-172 ◽  
Author(s):  
I Nyoman Suamir
Keyword(s):  
Renewable Energy ◽  
Solar Energy ◽  
Weather Conditions ◽  
Heat Transfer Fluid ◽  
Cfd Modeling ◽  
Fluid Temperature ◽  
Renewable Energy Resources ◽  
Absorption Chiller ◽  
Total Energy Consumption ◽  
Medium Temperature

Indonesia has abundant renewable energy resources. In 2005 this country, however, only consumed 0.38% renewable energy of the total energy consumption. Most of the energy sources of the country are from fossil fuels which result in high CO2 emissions. Solar energy systems would be as an option to reduce the CO2 emissions of this country. This paper studied the application of solar energy to provide cooling for medium temperature food refrigeration based on Indonesian weather conditions. The paper additionally analyzed the environmental impact relating to CO2 emissions, and investigated the economical aspect. CFD-Fluent software was applied on modeling the modification of the absorption chiller generator to enable it to operate with heat from solar radiation, while F-Chart and Microsoft Excel spreadsheet were used to analyze the solar system and the economical viability of the technology. The results showed that the optimum modification of the absorption chiller was to use a jacket for heat addition. CFD modeling with Fluent using Diphyl THT as the heat transfer fluid (HTF) indicated that the system would function optimally at fluid temperature input of 180°C, whereas the optimum average temperature of the chiller generator would be 170 °C. The proposed technology was found economically less viable for food refrigeration compared to the vapor compression cycle using R-404A but it could provide a significant impact on the environment by a reduction of 37% CO2 emissions.

Experimental Study of the Influence of Light Intensity on Solar ORC Power Generation System

2015 ◽  
Author(s):  
Yuping Wang ◽  
Lei Tang ◽  
Yiwu Weng
Keyword(s):  
Power Generation ◽  
Light Intensity ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Fluid Temperature ◽  
System Efficiency ◽  
Generation System ◽  
Thermoelectric Efficiency ◽  
Turn Point ◽  
Power Generation System

A low temperature (<393K) solar Organic Rankine Cycle (ORC) power generation experimental facility was designed and built. The heat pipe evacuated tubular collector was selected as the solar collector. A scroll expander was used as the expander and the working fluid was R600a. The influence of light intensity variation on system performance has been studied. The results indicate that the system efficiency and thermoelectric efficiency of the experimental facility can reach to 2.2% and 4.4%, respectively. The thermoelectric efficiency and power decrease with the decrease of the heat transfer fluid temperature. There is a turn point in the variation of these performance parameters at high flow rate. The heat transfer fluid temperature at the turn point is about 75°C at the working fluid flow rate of 200L/h. The system efficiency decreases with the decrease of light intensity. There is a turn point light intensity Itpi. The system efficiency varies slowly when the light intensity is higher than Itpi. The experimental results are of great significance for the new design of low temperature solar ORC power generation system.

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