scholarly journals Study on Outlet Temperature Control of External Receiver for Solar Power Tower

Energies ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 340
Author(s):  
Qiang Zhang ◽  
Kaijun Jiang ◽  
Yanqiang Kong ◽  
Jiangbo Wu ◽  
Xiaoze Du
Keyword(s):  
Temperature Control ◽  
Control Strategy ◽  
Solar Power ◽  
Heat Transfer Fluid ◽  
Weather Data ◽  
Unstable State ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Power Load ◽  
Solar Power Tower

Due to the change of direct normal irradiance (DNI) and the change of output power load, the receiver of the solar tower is in an unstable state in the actual operation. In this paper, a 100 MW external cylindric receiver is designed and modelled. The dynamic and comprehensive model is established for the receiver, including the thermal and mechanical equations. The temperature control strategy is applied to the receiver model. The validity of the control strategy is verified by disturbance experiments, including DNI, the inlet temperature of the heat transfer fluid (HTF), and the weather data on a cloudy day. The response characteristics of the receiver are demonstrated. Its thermal lag characteristics and restraining effect on the fluctuating environment are revealed. The dangerous occasion of the receiver during operation are detected, including the overheat of the local panel, and the dissociation point of the molten salt. Both the robustness and the deficiency of the control strategy of the receiver are pointed out. The research results will contribute to the control strategy formulation of the SPT (solar power tower) station.

Experimental and Numerical Heat Transfer Analysis of an Air-Based Cavity-Receiver for Solar Trough Concentrators

2012 ◽  
Vol 134 (2) ◽  
Author(s):  
R. Bader ◽  
A. Pedretti ◽  
A. Steinfeld
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Solar Power ◽  
Power Input ◽  
Heat Transfer Analysis ◽  
Heat Transfer Fluid ◽  
Inlet Temperature ◽  
Transfer Model ◽  
Outlet Temperature ◽  
Solar Receiver

We report on the field testing of a 42 m-long full-scale solar receiver prototype installed on a 9 m-aperture solar trough concentrator. The solar receiver consists of a cylindrical cavity containing a tubular absorber with air as the heat transfer fluid (HTF). Experimental results are used to validate a heat transfer model based on Monte Carlo ray-tracing and finite-volume techniques. Performance predictions obtained with the validated model yield the following results for the receiver. At summer solstice solar noon, with HTF inlet temperature of 120 °C and HTF outlet temperature in the range 250–450 °C, the receiver efficiency ranges from 45% to 29% for a solar power input of 280 kW. One third of the solar radiation incident on the receiver is lost by spillage at the aperture and reflection inside the cavity. Other heat losses are due to natural convection (9.9–9.7% of solar power input) and re-radiation (6.1–17.6%) through the cavity aperture and by natural convection from the cavity insulation (5.6–9.1%). The energy penalty associated with the HTF pumping work represents 0.6–24.4% of the power generated.

scholarly journals Calorimetric Evaluation of Novel Concentrating Solar Receiver Geometries With Enhanced Effective Solar Absorptance

2016 ◽  
Author(s):  
Jesus D. Ortega ◽  
Julius E. Yellowhair ◽  
Clifford K. Ho ◽  
Joshua M. Christian ◽  
Charles E. Andraka
Keyword(s):  
Thermal Efficiency ◽  
Solar Power ◽  
Solar Furnace ◽  
Heat Transfer Fluid ◽  
Discrete Ordinates ◽  
Base Case ◽  
Outlet Temperature ◽  
Black Paint ◽  
Solar Absorptance ◽  
Flow Rates

Direct solar power receivers consist of tubular arrays, or panels, which are typically tubes arranged side by side and connected to an inlet and outlet manifold. The tubes absorb the heat incident on the surface and transfer it to the fluid contained inside them. To increase the solar absorptance, high temperature black paint or a solar selective coating is applied to the surface of the tubes. However, current solar selective coatings degrade over the lifetime of the receiver and must be reapplied, which reduces the receiver thermal efficiency and increases the maintenance costs. This work presents an evaluation of several novel receiver shapes which have been denominated as fractal like geometries (FLGs). The FLGs are geometries that create a light-trapping effect, thus, increasing the effective solar absorptance and potentially increasing the thermal efficiency of the receiver. Five FLG prototypes were fabricated out of Inconel 718 and tested in Sandia’s solar furnace at two irradiance levels of ∼15 and 30 W/cm2 and two fluid flow rates. Photographic methods were used to capture the irradiance distribution on the receiver surfaces and compared to results from ray-tracing models. This methods provided the irradiance distribution and the thermal input on the FLGs. Air at nearly atmospheric pressure was used as heat transfer fluid. The air inlet and outlet temperatures were recorded, using a data acquisition system, until steady state was achieved. Computational fluid dynamics (CFD) models, using the Discrete Ordinates (DO) radiation and the k-ω Shear Stress Transport (SST) equations, were developed and calibrated, using the test data, to predict the performance of the five FLGs at different air flow rates and irradiance levels. The results showed that relative to a flat plate (base case), the new FLGs exhibited an increase in the effective solar absorptance from 0.86 to 0.92 for an intrinsic material absorptance of 0.86. Peak surface temperatures of ∼1000°C and maximum air temperature increases of ∼200°C were observed. Compared to the base case, the new FLGs showed a clear air outlet temperature increase. Thermal efficiency increases of ∼15%, with respect to the base case, were observed. Several tests, in different days, were performed to assess the repeatability of the results. The results obtained, so far, are very encouraging and display a very strong potential for incorporation in future solar power receivers.

Design of a Micromix Fuel Injector for High Temperature Hybrid Concentrated Solar Power Plants

2014 ◽  
Author(s):  
Shane Coogan ◽  
Klaus Brun ◽  
David Teraji
Keyword(s):  
Power Plants ◽  
Solar Power ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Fuel Injector ◽  
Concentrated Solar Power ◽  
Output Variability ◽  
Increased Risk ◽  
In Series ◽  
Solar Power Plants

The hybrid air Brayton concentrated solar power plant (CSP) combines a natural gas fired combustor in series with a traditional CSP system. The combination boosts turbine inlet temperature above the receiver temperature and reduces output variability. However, a combustor operating in this mode must tolerate an inlet air temperature equal to the solar receiver outlet temperature, which is expected to be as much as 1,000°C for next generation designs. High inlet temperature hybrid combustors must achieve low NOx emissions in spite of the increased risk for autoignition and flashback. In addition, the hybrid injector must be able to adjust to the variability inherent to the solar source. The design of a multibank micromix injector that meets these challenges is described with emphasis on its NOx and CO emissions characteristics.

scholarly journals Development of Steelmaking Slag Based Solid Media Heat Storage for Solar Power Tower Using Air as Heat Transfer Fluid: The Results of the Project REslag

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 6092
Author(s):  
Michael Krüger ◽  
Jürgen Haunstetter ◽  
Joachim Hahn ◽  
Philipp Knödler ◽  
Stefan Zunft
Keyword(s):  
Heat Transfer ◽  
Solar Power ◽  
Axial Flow ◽  
Cost Effective ◽  
Heat Transfer Fluid ◽  
Steelmaking Slag ◽  
Solid Media ◽  
Partial Load ◽  
Solar Power Tower ◽  
Eu Project

Solar power towers with thermal energy storage based on direct-flow regenerators have the potential to generate cost-effective base-load electricity. An inventory option that opens up further cost-saving potential but has not yet been extensively investigated for this application is slag from electric arc furnace. This use has not only economic advantages, but also serves environmental protection, since a large proportion of this type of slag is currently not used any further, but is disposed of in landfills. In the completed EU project REslag, various subsequent uses of the slag were investigated, including the possibility presented here of using sintered slag pebbles as an inventory for regenerators in solar power towers with air as the heat transfer fluid. The main results from the different phases of the project are presented, with a focus on the investigations not yet published. In addition to results from thermal simulations on different designs and on the partial load and off-design behavior of the storage lead concept “Axial flow—standing”, these are mainly results from fluid mechanical calculations on the distributor design of the storage and from material investigations on the slag. In summary, it can be stated that the sintered slag pebbles are thermally, mechanically and chemically competitive with conventional inventory materials and the principle feasibility of a slag-based storage was confirmed by the results of these investigations. The defined storage lead concept was elaborated in detail and the performance of the design was confirmed by simulations and experiments.

scholarly journals Heat Transfer Fluid Temperature Control in a Thermoelectric Solar Power Plant

Energies ◽  
2017 ◽  
Vol 10 (8) ◽  
pp. 1078 ◽  
Author(s):  
Lourdes Barcia ◽  
Rogelio Peon ◽  
Juan Díaz ◽  
A.M. Pernía ◽  
Juan Martínez
Keyword(s):  
Heat Transfer ◽  
Power Plant ◽  
Temperature Control ◽  
Solar Power ◽  
Heat Transfer Fluid ◽  
Fluid Temperature ◽  
Solar Power Plant

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 Heat Transfer Performance of Fruit Juice in a Heat Exchanger Tube Using Numerical Simulations

2020 ◽  
Vol 10 (2) ◽  
pp. 648
Author(s):  
Juan Ignacio Córcoles ◽  
Ernesto Marín-Alarcón ◽  
Jose Antonio Almendros-Ibáñez
Keyword(s):  
Heat Transfer ◽  
Activation Energy ◽  
Newtonian Fluid ◽  
Food Industry ◽  
Fruit Juice ◽  
Heat Transfer Process ◽  
Heat Transfer Fluid ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
The Difference

Enhancing heat transfer rates in heat exchangers is essential in many applications, such as in the food industry. Most fluids used in the food industry are non-Newtonian, whose viscosity is not uniform, and depends on the shear rate and temperature gradient. This is important in the selection of equipment and type of processing. The aim of this work was to numerically simulate, with a non-Newtonian fluid in laminar regime, the heat transfer process in a tube with a curved elbow. The numerical model was validated with published correlations using water as heat transfer fluid. A commercially available fruit juice was used as a non-Newtonian fluid. Its rheological properties were measured using a Modular Compact Rheometer, as well as the activation energy. The difference between outlet temperature and inlet temperature was higher for the laminar simulation (approximately 4 °C) than for the turbulent one (approximately 0.7 °C). The highest dynamic viscosity values were found at the centre of the pipe (between 0.05 and 0.09 Pa·s), with the lowest values at the wall (0.0076 Pa·s). This behaviour is explained by the pseudoplastic condition of the fruit juice. The activation energy did not yield high values, showing a moderate viscosity variation with the temperature change.

Control strategy of molten salt solar power tower plant function as peak load regulation in grid

2021 ◽  
Vol 294 ◽  
pp. 116967
Author(s):  
Qiang Zhang ◽  
Kaijun Jiang ◽  
Zhihua Ge ◽  
Lijun Yang ◽  
Xiaoze Du
Keyword(s):  
Molten Salt ◽  
Control Strategy ◽  
Solar Power ◽  
Peak Load ◽  
Load Regulation ◽  
Solar Power Tower

scholarly journals Coupled Optical-Thermal-Fluid Modeling of a Directly Heated Tubular Solar Receiver for Supercritical CO2 Brayton Cycle

2015 ◽  
Author(s):  
Jesus D. Ortega ◽  
Sagar D. Khivsara ◽  
Joshua M. Christian ◽  
Julius E. Yellowhair ◽  
Clifford K. Ho
Keyword(s):  
Solar Power ◽  
Fluid Model ◽  
Cfd Modeling ◽  
Radiation Absorption ◽  
Discrete Ordinates ◽  
Outlet Temperature ◽  
Brayton Cycle ◽  
Inlet Conditions ◽  
Solar Power Tower ◽  
Solar Receiver

Recent studies have evaluated closed-loop supercritical carbon dioxide (s-CO2) Brayton cycles to be a higher energy-density system in comparison to conventional superheated steam Rankine systems. At turbine inlet conditions of 923K and 25 MPa, high thermal efficiency (∼50%) can be achieved. Achieving these high efficiencies will make concentrating solar power (CSP) technologies a competitive alternative to current power generation methods. To incorporate a s-CO2 Brayton power cycle in a solar power tower system, the development of a solar receiver capable of providing an outlet temperature of 923 K (at 25 MPa) is necessary. The s-CO2 will need to increase in temperature by ∼200 K as it passes through the solar receiver to satisfy the temperature requirements of a s-CO2 Brayton cycle with recuperation and recompression. In this study, an optical-thermal-fluid model was developed to design and evaluate a tubular receiver that will receive a heat input ∼2 MWth from a heliostat field. The ray-tracing tool SolTrace was used to obtain the heat-flux distribution on the surfaces of the receiver. Computational fluid dynamics (CFD) modeling using the Discrete Ordinates (DO) radiation model was used to predict the temperature distribution and the resulting receiver efficiency. The effect of flow parameters, receiver geometry and radiation absorption by s-CO2 were studied. The receiver surface temperatures were found to be within the safe operational limit while exhibiting a receiver efficiency of ∼85%.

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