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The present research integrates the concept of double-pass (DP) flows with high-temperature solar receivers to introduce an innovative design aimed at minimizing heat losses and optimizing performance. The new DP system was developed using a tubular absorber derived from billboard solar tower technology and operated with air as the heat transfer medium. Computational fluid dynamic models are developed based on an experimental campaign conducted at a solar furnace facility. The computational analyses indicated that employing the DP design instead of single-pass (SP) absorbers results in an average enhancement of energy and exergy efficiency by 35% and 225%, respectively, across all test conditions. However, this enhancement is accompanied by an average increase in pressure drop of ~60%. The detailed exergy analysis also revealed the contribution of each term in the exergetic performance, identifying the exergy destruction between the sun and the absorber as the primary source, accounting for an average of ~65% of the total inlet exergy for both SP and DP absorbers. Consequently, the DP presents itself as a promising alternative design for future solar tower configurations, offering improved Nu numbers up to ~50% in air-based solar systems. [ABSTRACT FROM AUTHOR]

This work presents a numerical study on flow configurations and pressure distribution of cylindrical towers attached with different shapes of vortex generators. The vortex‐generator attachment is done with the main aim of reducing the energy of ventilation for the cylindrical tower. The two different types of vortex generators, namely, a cylindrical‐shaped vortex generator and a diffuser‐shaped vortex generator, are compared with an original square‐shaped vortex generator. The effects of air velocity (2, 4, 6, and 8 m/s) and vortex generator size (D/2, D, and 2D) on flow structure are considered. The finite element method (a commercial code) is selected for the main problem‐solving. The numerical models of the cylindrical towers attached with various vortex generators are validated to confirm the reliability of the numerical results. From the numerical results, it was found that the suctioned updraft speed in the tower was proportional to the crosswind speed. In addition, the vortex generator with h = 2D performs the highest updraft speed, which leads to the best efficiency for ventilation. [ABSTRACT FROM AUTHOR]

The direct measurement of particle temperatures and advective losses from solid particle receiver has been a topic of necessary interest to de-risk the technology and improve its performance. Due to the flow's transient and stochastic nature, it has presented a challenge to traditional thermometry and metrology methods. In this work, a simplified quantitative non-intrusive imaging methodology previously developed is applied to Sandia's falling particle receiver during on-sun tests to collect image sets, which could help estimate the average particle temperature and particle egress rate from the system. Further additions to the technique are presented to permit the estimation of the plume (air and particles) egress rate and total advective heat losses during on-sun operation. The falling particle receiver testing campaign in 2020 and 2021 allowed the team to capture multiple flow configurations and environmental conditions used to build a large database of data captures with different characteristics. Finally, the results captured were used to complete a regression study to gain further insight into the factors which impact the particle egress and the receiver's efficiency. Particle temperature, receiver flow configuration, and wind speed were found to be the most impactful factors in the study. [ABSTRACT FROM AUTHOR]

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The authors' original concept of indirect solar flux mapping of a heliostat field measures CRD using a compact stationary array of moonlight illuminometers on the receiver aperture and a reference moonlight illuminometer on the dual-axis moon tracker. Two sets of moonlight concentration experiments (CCD camera + white target; concentrated lunar beam passing across the linear array of illuminators) were carried out on 63 heliostats at Badaling Solar Tower Power Plant in Beijing on a full moon night in 2018. How the sun and moon shapes differ for CRD as light sources on a solar dish is investigated. Solar/lunar CRDs are similar. Another lunar flux mapping model is also presented, allowing different moon shapes to estimate the solar CRD and contribute improvements in extrapolating measured lunar CRDs to a solar tower working with the real Sun by repeated smooth-filtering. In this paper, some unknown factors, effects, and improvements are carefully considered to enhance the CRD measurement accuracy of a solar tower power plant by using moonlight concentration.

Beam-down solar towers are presented as an alternative to conventional solar towers that allow modular design, easily adaptable to industrial environments. Secondary reflectors are a key component in this type of configuration, due to the high concentration of radiation received from the solar field. The results of a technical and economic study of new secondary reflectors, based on a polished stainless-steel substrate with silver PVD coating and a system of protective layers, are presented and compared with aluminum reflectors, currently used in such configurations. For this, twelve different designs, grouped in three cases are simulated using ray tracing and finite elements. The results show that the steel reflectors reach lower temperatures compared to aluminum reflectors, allowing for greater durability. Additionally, the optical efficiency of the plant was determined, and it was estimated that steel reflectors can reduce the LCOH of the plant by approximately 3.5%.

Solar energy is not only the most abundant energy on earth but it is also renewable. The use of this energy is expanding very rapidly mainly through photovoltaic technology. However, electricity storage remains a bottleneck in tackling solar resource variability. Thus, solar thermal energy becomes of particular interest when energy storage is required, as thermal energy storage is much cheaper than electricity storage. The objective of this paper is to make a short update on the CSP (Concentrated Solar Power) market as of the year 2023. It is based on the CSP-GURU database, which lists information on CSP power plants all over the world. Although this database is open, it is not easy to find UpToDate analysis. An overview of this expanding technology is presented and offers readable figures with the most important information. This includes the evolution of installed capacities worldwide along with upcoming projects (under construction) and technological trends. The evolution of storage capacities and operating temperatures is discussed. Investment costs and levelized cost of electricity are also provided to obtain reliable data for comparison with other energy technologies. Specific land requirements are highlighted, along with overall efficiency. Relevant examples are discussed in this paper. Eventually, it outlines the evolution of the CSP landscape with useful information for scientific and educational purposes.

Solar energy is not only the most abundant energy on earth but it is also renewable. The use of this energy is expanding very rapidly mainly through photovoltaic technology. However, electricity storage remains a bottleneck in tackling solar resource variability. Thus, solar thermal energy becomes of particular interest when energy storage is required, as thermal energy storage is much cheaper than electricity storage. The objective of this paper is to make a short update on the CSP (Concentrated Solar Power) market as of the year 2023. It is based on the CSP-GURU database, which lists information on CSP power plants all over the world. Although this database is open, it is not easy to find UpToDate analysis. An overview of this expanding technology is presented and offers readable figures with the most important information. This includes the evolution of installed capacities worldwide along with upcoming projects (under construction) and technological trends. The evolution of storage capacities and operating temperatures is discussed. Investment costs and levelized cost of electricity are also provided to obtain reliable data for comparison with other energy technologies. Specific land requirements are highlighted, along with overall efficiency. Relevant examples are discussed in this paper. Eventually, it outlines the evolution of the CSP landscape with useful information for scientific and educational purposes. [ABSTRACT FROM AUTHOR]

The objective of this research is to investigate the implementation of two concentrated solar power (CSP) technologies in the 28 devoted locations in Egypt, in order to select the optimum site-specific CSP technology. This may be achieved by a validated thermo-economic simulation of power plants using the Sam advisory model and an investigation of the two proposed CSP technologies' configurations to fulfill the power plant's thermal demand. Simulations take into consideration the environmental, technical, financial, and economic aspects of the projects. Among many simulated parameters, three are considered to compare the two proposed technologies' configurations in the 28 locations utilizing geographic information system aid. Those parameters are the annual power production, the levelized cost of energy, and water consumption. A comparative analysis indicated that the solar tower requires 25% more land than the parabolic trough. The additional collecting area raised the net capital cost of the solar tower system by 15% over the parabolic trough model. As a result, the solar tower arrangement reduces the levelized cost of energy while increasing the yearly power generated and water required by the power plant. Simulation results favored the proposed solar tower configuration over the parabolic trough and recommended the implementation of such concentrated solar power projects in the central and eastern locations of Egypt. [ABSTRACT FROM AUTHOR]

The modernization, efficiency, and decarbonization of the energy supply systems are among the new challenges to be faced in the coming decades to achieve the targets and objectives dictated by European strategic policies. Despite the countless benefits related to renewable energy sources (RES) integration, this brings key challenges to the power system, such as the risk of imbalance between energy generation and demand, sudden changes in flows in transmission lines with a need for expensive and time-consuming upgrades, and the withdrawal of conventional generation systems with consequent demands for new solutions and innovation to support grid services. A potential solution to limit the huge intermittence and fluctuation in power generation from RES is Concentrated Solar Power (CSP) technology integrated with thermal energy storage. The aim of this paper is to discuss the potential benefits related to the use of CSP technology by presenting innovative industrial solutions developed in the Italian SOLARGRID Project, namely the hybridization of CSP–PV systems and the solar thermo-electric system developed by MAGALDI, the parabolic trough collector of Eni, and the new linear Fresnel reflector configuration of IDEA S.r.l. These plant and component solutions are developed for improving the technical performance of CSP technology and reducing the levelized cost of electricity, thereby fostering an effective and massive deployment and encouraging the creation of new business models. [ABSTRACT FROM AUTHOR]

The performance of open volumetric receivers can profit from advanced control of the heliostat aim points and the air mass flow. Advanced control techniques like model predictive control and state observer are based on dynamic system models. A suitable model for this purpose is introduced and validated with data recorded at the solar tower Jülich. The model shows good performance with respect to the dynamics of individual absorber cups. The simulation of the whole receiver requires an advanced optimization of the model parameters.

This work demonstrates methods of mapping high-spatial-resolution direct normal irradiance (DNI) data from satellites, Total Sky Imagers (TSIs), and analogous data sources onto a heliostat field for characterizing the spatial and temporal variation of the incident flux on a central receiver tower during cloud transient events. The mapping methods are incorporated into an optical software module that interfaces with CoPylot–SolarPILOT’s python API– to provide computationally efficient optical simulation of the heliostat field and the solar power tower. Eventually, this optical model will be incorporated into optimization models whereby a plant operator can understand the effects of cloud transient events on overall power production and receiver lifetime due to creep-fatigue damage and therefore make better informed decisions about receiver shutdown events. By more accurately modelling the effects of cloud events on receiver flux maps, this work may determine the magnitude and frequency of thermal cycling on receiver tubes and panels using actual or realistic cloud shapes instead of averaged DNI values–which may undercount the total cycle number. This work may also prevent unnecessary plant shutdowns due to overly precautionary control strategies and characterize the relative impact of various cloud types on receiver life. We plan to eventually integrate this methodology into the System Advisor Model (SAM) to improve performance model accuracy during periods of cloudiness. In this paper, we demonstrate generating DNI maps and mapping them to a solar field in CoPylot using 10 m resolution data from publicly available Sentinel-2 satellite data over the Crescent Dunes plant.

This study examines the incorporation of solar tower technology with a Solid Oxide Fuel cell, and a steam turbine to produce power from solar energy. The various subsystems are combined to accomplish high overall energy efficiency, provide steady operation, as well as decrease rate of exergy destruction. In order to ensure a continuous operation, power is produced during the discharge cycle by the Solid Oxide Fuel Cell (SOFC), utilizing the hydrogen produced by the Solid Oxide Electrolysis Cell (SOEC). The energetic and exergetic analyses, as well as the exergoeconomic technique, are applied to evaluate the system's performance indexes. Simulation is conducted for Yazd, Iran, utilizing the maximum solar irradiation. The exergy and economic results of the suggested system demonstrate that the solar tower has the most considerable exergy destruction rate as well as capital investment cost, which is 296.4 MW and 2515$/h, respectively. As a result, this examined work is computed to have 12.73% energy efficiency and 13.39% exergy efficiency. • The performance of a novel solar tower power system based on hydrogen is evaluated. • Combination of SOEC and SOFC is analyzed by exergy-economic method. • SOFC and ST have the most share of the cost of exergy destruction. • The energy and exergy efficiencies of the system are highly affected by SOEC temperature. [ABSTRACT FROM AUTHOR]

The National Renewable Energy Laboratory (NREL) has been conducting exposure experiments on solar reflectors for over four decades. Thousands of mirror samples from over 100 suppliers have been exposed to and monitored in a range of relevant environments. These test conditions include outdoor test settings and several controlled laboratory environments. These samples have been rigorously individually characterized using a series of reflectance measurements, visual inspections and, in some cases, in-depth composition analysis to identify degradation modes, reflectance losses, and other mirror properties integral to understanding the solar reflector's life cycle. This article compiles the decades of measurement data into a concise statistical analysis. It includes exposure and degradation data for numerous reflector types, including secondary-surface reflector permutations of polymer and glass superstrates with silver and aluminum reflectors as well as front-surface reflectors. The results herein are intended to analyze environmental stressors and degradation trends among various historical and state-of-the-art solar reflectors. This article may be used to support solar reflector design, effective testing methodology, and inform manufacturing decisions moving forward. Presented are the results of the compiled database and an initial analysis for degradation rate modeling using full-spectrum and wavelength-dependent approaches. The database is a growing resource hosted on a live, publicly accessible website. In conjunction with the analysis presented here, the database provides a valuable resource to the solar reflector manufacturing and testing industry. [ABSTRACT FROM AUTHOR]

Heat collection performance simulations using the system advisor model (SAM) with typical meteorological year weather data from four geographic locations are used to investigate (a) the optimum overall tilt of piecewise-focusing (PWF) collectors, and (b) PWF collector performance in comparison to the SAM default central receiver system. Results show that the overall tilt angle is not critical, but values up to 50 deg are best at non-tropical latitudes, even when output in summer is more valuable than in winter. For tropical latitudes, 40 deg of tilt is sufficient. Increasing PWF collector width relative to height is advantageous. Depending on location, PWF collector performance is 66-90% better than for the SAM default 100 MWe central receiver system, per square meter of reflector or heliostat. Using SAM's detailed control over system parameters, it is shown that the PWF collector's superior performance is derived mainly from better geometry (smaller cosine losses), but the near-absence of atmospheric attenuation and the smaller receiver heat losses are also significant. [ABSTRACT FROM AUTHOR]

The world is undergoing an energy transformation, from a system based on fossil fuels to a system based on renewable energy, in order to reach the Paris Agreement target. Chile is no exception, and through the Asociación de Concentración Solar de Potencia (ACSP) has generated a new cost structure for tower-based Concentrated Solar Power (CSP) technology in the framework of the Long-Term Energy Plan, which updates the costs reported in previous studies. The changes experienced in this cost structure make it necessary to study the impact of this cost structure on the levelized cost of energy (LCOE). This work develops simulations of CSP tower plants analyzing their generation and the LCOE based on the new cost structure mentioned, for the north of Chile between the Arica and Parinacota region and the Coquimbo region. The most relevant results show a significant reduction in the LCOE, compared to studies from 2020, reaching a minimum LCOE value of 52,6 USD/MWh. On the other hand, the impact on the net social benefit of including the green tax to the merit order of each of the generating plants that make up the electric park until 2021 is studied, which yields a negative impact under current legislation.

This work introduces a sample-efficient algorithm to optimize the control parameters of an aim point controller for solar power tower plants. Optimizing the control parameters increases the performance of the aim point controller, and thus the efficiency of the plant. However, optimizing the parameters in simulation will not yield the true optimal parameters at the real plant due to mismatches between simulation and reality. Thus, optimization must be done at the real tower to find a true optimum. As this can be time consuming and costly, the optimizer should require a minimum number of steps. Hence, a sample-efficient optimization strategy is needed. This work introduces a new algorithm based on Bayesian Optimization (BO), which leverages multiple sets of simulation data to accelerate the optimization. The algorithm is tested on a six-dimensional test function representing an arbitrary aim point controller. The proposed algorithm outperformed standard Bayesian Optimization by reaching near optimal parameter configurations of 95% accuracy within 33% less optimization steps. In a second test, the proposed algorithm is used to optimize a simulated Vant-Hull aim point controller with two hyperparameters. Here, the algorithm also needs 33% less optimization iterations than the standard BO.

Ever-increasing impact of burning carbon fuels puts a worldwide trend to shift to renewable energy resources to contribute to a sustainable environment, energy and economy. Concentrated Solar Power (CSP) technologies are some of the world's most prospective clean technologies for energy and a complete evaluation of the systems is necessary to explore their optimum potential. This study provides a detailed overview of the most common and fundamental CSP technologies: Parabolic Trough Collector (PTC), Linear Fresnel Reflector (LFR), Solar Parabolic Dishes (SPD), and Solar Power Tower (SPT); and analyzes the trend of change in designs to enhance the thermal-hydraulic and optical performance of the collectors. Several design modifications have been applied to PTCs in terms of reflector, receiver, and tracking system while different arrangements of thermal energy storage (TES) systems are being integrated to ensure maximum performance, and modifying TES geometry by inserting fins can enhance the discharge efficiency up to 24%. Primary reflector and receiver are the two most important components of LFRs and modifications techniques including them are showing significant prospects regarding their application on a commercial scale. Evacuated tube LFRs with secondary reflectors deflect up to 90% of incident solar radiation, outperforming cavity receivers. In terms of SPDs, promising design areas include the adjustment and optimization of the concentrator, receiver, engine, and tracking system. Stirling receivers demonstrated 90% effectivity in transferring energy, which is 10% more than Brayton receivers. Optimizing the size and layout of heliostats is necessary for the economical installation of the SPT system. Different combinations of geometry for the liquid, gas and particle-based receiver are in use for SPTs and among them, volumetric gas receivers and particle receivers can achieve temperatures higher than 1000 °C. This article provides the overall design modification trend of CSP technology and compares their effectiveness which can help identify particular areas for increasing the performance of CSP design. Moreover, in the future, the techno-economic viability of deploying CSP can be assessed for pragmatic applications.

Molten salts are commonly used in solar thermal power plants to store heat when sunlight is unavailable. However, solidifying the salts can lead to operational interruptions and prevent an optimal energy output. A self-adaptive heat extraction method has been proposed to regulate salt pipeline temperatures, enabling continuous operations that mitigate unplanned shut-downs. Such a method focuses on maintaining operational temperatures and preventing interferences caused by the freezing of the salts. The proposed Self-Adaptive Heat Extraction Controller (SAHEC) relies on fuzzy logic integrated into MATLAB Simulink to ensure optimal heat extraction control utilizing four distinct temperature variables. Modeling this approach through a created MATLAB-based simulation reveals that SAHEC offers an undeniable improvement over standard conventional methods for manipulating temperatures.

Solar power plants have received much attention in recent years due to the use of renewable energy sources, no production of polluting gases, high concentration ratio, and proper thermal efficiency. But solar radiation's absence at night prevents the uniform and continuous production of electricity. Also, the challenge of the ever-increasing accumulation of municipal waste has caused the waste fuel-based power plants to attract the attention of many industrialized and developing countries. In the present research, a practical solution is proposed to solve the challenge of not producing electricity in solar tower power plants during the night by using waste as the input fuel of the power plant. The results obtained from the case study of the investigated cogeneration system show that the electric powers produced by the subsystems of the air Brayton cycle, the reheat Rankine cycle, and the organic Rankine cycle are equal to 4502.6 KW, 2640.3 KW, and 118 KW, respectively. The central receiver of the solar tower has the highest rate of irreversibility, accounting for 34% of the total exergy destruction rate. Based on the parametric study results, the irreversibility of the entire cogeneration system has a direct relationship with the inlet temperature of the turbine. Increasing the moisture of the waste also leads to a decrease in the temperature and percentage of syngas produced, and causes a decrease in the overall performance of the system. The net power of the cogeneration system increases first and then decreases with the increase in the temperature of the gasification process. [ABSTRACT FROM AUTHOR]

An innovative polygeneration system is proposed to generate power, heat, hydrogen, and oxygen simultaneously. The system integrates a solar central tower system and the heliostat field, a gas turbine cycle, a supercritical carbon dioxide cycle, an Organic Rankine Cycle with a cyclopentane working fluid, and a Rankine steam cycle, and a Proton Exchange Membrane electrolyzer. In this study, to reduce the gas cycle fuel consumption, the solar tower system is integrated with the gas cycle. In the studied system, a Supercritical Carbon Dioxide cycle and an Organic Rankine Cycle have been used to heat recovery of the exhaust gases of the gas turbine. In addition, Energy, Exergy, Exergoeconomic, Exergoenvironmental, Emergoeconomic, and Emergoenvironmental analyses have been performed for this system hour by hour. A computer code was developed in MATLAB for these analyses, and the results are validated by simulation in Thermoflex software and primary references with high accuracy. A systematic approach based on thermodynamic analysis and a combination of Genetic Programming and Artificial Neural Networks is proposed for optimal design. Multi‐Objective Genetic Optimization has been employed to find optimum design parameters. Due to the reduction of computation time of optimization, the integration of Genetic Programming and Artificial Neural networks have been employed to generate correlations for objective functions based on the decision variables. By adding the solar system, the mass flow rate of natural gas consumption in the gas cycle decreases by about 9% and reaches 1.53 kg/s. Utilizing solar energy and the Rankine steam cycle, the production capacity of the considered cycle increases from 43 to 66 MW. Also, the performance analysis of the Proton Exchange Membrane electrolyzer and the primary cycle shows that this equipment can produce 0.01 g/s of hydrogen from 5 g/s of water entering the equipment per second by consuming 2.33 kW of power. The results show that when the decision variables are considered at the optimal performance point, the exergy efficiency, the total cost, the rate of destruction related to environmental impacts, cost based on emergy, and the rate of destruction environmental effects based on energy improve. The highest percentage of improvement among the objective functions compared to the initial state is related to the exergy efficiency with 46%, and then the environmental impact rate based on emergy with an improvement of 36%. [ABSTRACT FROM AUTHOR]

When exposed to high non-uniform heat fluxes on the receiving surface, significant temperature gradients develop in the tubes, producing thermal stress and deformations in the receivers. This paper reports a detailed investigation of the thermal and structural performance of a solar tower system that operates with direct steam generation tubes when the fins are added to the internal surface and thickness varies. Six tubes were evaluated, two without fins varying the wall thickness (5 mm and 3 mm) and four with fins under different configurations. The thermal system corresponds to a representative tube of an external tubular receiver of a central tower system. The thermal receiver operates with direct steam generation under a non-uniform concentrated solar flux with a maximum value of 0.93 MW/m2. The best configuration of the tube was with fins on the frontal surface of the tube, maintaining a receiving wall thickness of 3 mm and an adiabatic wall thickness of 5 mm. It could reduce maximum thermal gradients and temperature by 31% and 14%, respectively, maximum thermal stresses by 38%, and maintain vapor mass flow at the output (276 kg/h). [ABSTRACT FROM AUTHOR]

The exploitation of solar energy has become a major concern, especially since our country holds a significant solar potential during the year. We can use concentrated solar energy to produce electricity or heat. This contribution consists, from simulations, in the parametric analysis of the operation of a solar concentration thermal installation, highlighting the direction of the variation of the thermal efficiency as a function of the low pressure for a machine working according to the ideal cycle of RANKINE. We were interested too:  In the sense of the variation of the thermal efficiency as a function of the temperature of the superheat for an improved installation working according to the ideal cycle of HIRN  At the influence of the overheating temperature for the HIRN cycle and low pressures for both cycles (RANKINE and HIRN), on the yield in order to propose a possible improvement. Simulations for different modifications on the RANKINE and HIRN cycles show that for an increase in the superheat temperature, the reduction of the low-pressure lead to a better yield. [ABSTRACT FROM AUTHOR]

• Design and modeling of three concentrating solar power plants in Bangladesh. • Optimization of the power plants using several crucial plant parameters. • Detailed technical and economic analysis of the power plants for their suitability in Bangladesh. • For practical implementation, choice of the right technology depends on the key criteria under consideration. Bangladesh, a fast-progressing country in terms of economy, infrastructure, and industries faces the risk of power shortage in the near future as its energy sector is heavily dependent on non-renewable resources. To achieve the target of gaining the status of a developed country set by the government of Bangladesh within 2041, an uninterrupted power supply is essential to support the ever-increasing demand. Hence, the country needs to focus on power generation by employing renewable sources. Bangladesh receives an adequate amount of solar energy throughout the year and thus solar thermal energy can be harnessed efficiently using various concentrating solar power (CSP) technologies like parabolic trough collector (PTC), solar tower, and linear Fresnel reflector (LFR). This study carries out a detailed technical and economic feasibility assessment of different CSP technologies for large-scale (100 MW) power generation to find the optimal technology for the climate of Bangladesh. After modeling, optimizing, and carrying out in depth sensitivity analysis of three power plants operated by PTC, solar tower, and LFR CSP technologies and simulating them using System Advisor Model (SAM), it is seen that the PTC plant generates maximum annual electricity (345.3 GWh) while operating at the highest efficiency (18.61 %) and capacity factor (39.5 %). Meanwhile, the solar tower plant provides the lowest levelized cost of electricity (LCOE) which is 6.18 Cents/kWh and the LFR-CSP plant needs the least land area among the three technologies. The selection of a specific technology for Bangladesh depends on the criteria that needs more emphasis for sustainable development of the energy arena. [ABSTRACT FROM AUTHOR]

Solar aided coal-fired power generation technologies have proven to be effective in reducing fossil fuel consumption and greenhouse gas emission. In this research, a high-proportion solar tower aided coal-fired power generation system integrated with thermal energy storage system is proposed. According to the constraint conditions, the integration scheme with the highest solar coupling capacity is obtained, and its thermodynamic, economic and environmental performances are researched. The results indicate that the solar coupling capacity that can be accommodated by the 660 MW coal-fired unit after parameter optimization is 339.532 MW th. As the load rate decreases, the power generated from solar and solar to electricity efficiency gradually decreases while the proportion of power from solar increases. The proportion of power from solar reaches a maximum of 24.28 % at 50 % load rate. The effects of different thermal energy storage hours on the levelized cost of electricity are investigated, and the results show that the lowest levelized cost of electricity is only 41.62 $/MWh in the high-level direct normal irradiance area. The new system can reduce about 272,921 tons of CO 2 emissions in a year at 100 % load rate. This study contributes to further promoting the development of a high-proportion solar aided coal-fired power generation system and realizing the low-carbon transition of coal-fired power generation industry. • A high proportion solar tower aided coal-fired power generation system is proposed. • Decisive parameters of new system are analyzed with respect to safety constraints. • The maximum solar coupling capacity after parameters optimization is 329.532MW th. • The maximum solar power proportion of new system is 24.28 % at 50 % load rate. • New system can reduce 272,921 tons of CO 2 emissions in a year at 100 % load rate. [ABSTRACT FROM AUTHOR]

A computational fluid dynamics study about the aerodynamic loads over a heliostat due to an atmospheric boundary layer flow using a modified k-ɛ turbulence model is presented. A new formulation is used, in which the model quantities vary with the velocity field. Modified wall functions for roughness were used at the bottom of the computational domain to achieve horizontal homogeneity of the airflow. Good horizontal homogeneity for the streamwise and spanwise velocity and turbulence intensity profiles were found. The incident profiles were compared with the inlet ones. The average percentage differences were 0.22% for velocity and 0.43% for turbulent intensity. Good agreement was found between the numerical data and theoretical values of the streamwise and spanwise shear stress at the bottom of the domain. The aerodynamic coefficients of the heliostat at different elevation angles were obtained, and a good agreement was found between the numerical data concerning the wind tunnel experimental values. An average percentage difference of 3.1% was found for drag, 6.5% for lift, and 6.0% for overturning. A significant improvement was obtained by using this new formulation with respect to a non-modified k-ɛ turbulence model. The average differences of the aerodynamic coefficients were 6.6% for drag, 12.4% for lift, and 10.1% for overturning. The velocity, turbulent kinetic energy, and pressure fields at different elevation angles were analyzed. It was found that at an elevation of 60 deg, the stagnation point of the flow occurs at the superior edge of the heliostat, causing the maximum lift force over the structure. [ABSTRACT FROM AUTHOR]

• The operation of solar tower external receiver is dynamically simulated in Modelica. • The creep-fatigue lifetime of each receiver panel is estimated for three materials. • Temperature spikes due to clouds passages significantly affect the panels lifetime. • Creep-fatigue analysis based on clear-sky operation leads to 30% error on lifetime. This paper proposes a methodology for the dynamic thermal analysis of solar tower external receivers and for the assessment of their lifetime. A dynamic thermal model is implemented in Modelica to assess the temperature distributions of receiver tubes and heat transfer fluid (HTF), considering real weather data with a 10-minute time resolution and PI controllers based mass flow rate control. Three representative days are simulated, and the resulting tubes temperature distributions are used to assess the elastic stresses distributions during the investigated days. Subsequently, the creep-fatigue lifetime of each receiver panel is evaluated accounting for material plasticity and creep-induced stress relaxation. The developed methodology is applied to compare three materials for solar receivers: Inconel 740H, Haynes 230, and Incoloy 800H. Results show that fatigue can be negligible with respect to creep for all investigated materials and the shortest lifetime is obtained for 800H, followed by H230, and 740H. The approximation of a receiver operation for 365 clear-sky days per year leads to errors around 30 % on the lifetime. For 740H and 800H, the damage accumulation during cloudy days with high DNI peaks is greater than during clear-sky days due to the remarkable creep damage originated during temperature spikes which follow clouds passages. H230 instead, accumulates more creep damage during clear-sky operation. This emphasizes the potential of the developed methodology to compare different HTF mass flow rate control strategies as well as receiver geometries and materials, HTFs, and heliostats aiming strategies, accounting for the trade-off between energy yield and receiver lifetime. [ABSTRACT FROM AUTHOR]

Concentrated solar-thermal power towers are increasingly migrating toward sand-based particle receiver designs to improve thermal efficiency and reach temperatures above 1000 °C for air Brayton power cycles and supercritical CO2 power cycles. However, utilizing sand affords complexities in modeling particle flow characteristics due to variable geometric shape, size, and composition. Thus, the objective of this study is to model the particle flow characteristics of sand through variable angled chevron shapes and receiver hoppers to help formulate robust modeling for flow dynamics. Treating the chevrons as an array of apertures, a novel method of calculating sand particle mass flowrate across angled apertures and surfaces is developed. Employing high-speed photography and particle imaging velocimetry techniques, our results incorporate the impact of effective angles upon velocity, residence time, and breakage profiles of falling sand particles. This study determines that a Beverloo equation incorporating effective angles for velocity and aperture size effectively predicts mass flowrate through chevrons, which can serve as a reference for future particulate flow modeling in this field. Furthermore, increasing hopper and chevron tip angles resulted in a more significant decrease in particle diameter and curtain opacity after sand flow trials. [ABSTRACT FROM AUTHOR]

Supercritical carbon dioxide (SCO2) Brayton cycle has been proved to be an efficient power cycle to replace the traditional steam Rankine cycle. The thermal efficiency of SCO2 cycle can be further improved by coupling another type of cycle (the bottom cycle) at the waste heat end. A supercritical carbon dioxide recompression Brayton cycle (SCRBC) coupled organic Rankine cycle (ORC) based on solar tower is designed and established. According to the requirements of the waste heat temperature range of the top cycle, R600 is selected as the working medium of ORC. Under the design conditions, the effects of split ratio on the net power, the thermal efficiency, and the exergy loss of the combined cycle are studied. The variation of thermal efficiency of each part of the system with split ratio under different turbine inlet pressures and temperatures is further analyzed, and the influence of turbine inlet pressure and working fluid mass flow ratio e (mass flow ratio of CO2 to R600) on the system performance is analyzed. Genetic algorithm-based multiobjective optimization is used to obtain the Pareto solution set for the thermal performance and unit investment cost of the system. The results show that the thermal efficiency of the combined cycle can be increased by more than 2% compared with that of a single top cycle. There is an optimal split ratio to maximize the thermal efficiency of the combined cycle, and the positions of the optimal split ratio are different for different turbine inlet pressures. Finally, through the multiobjective optimization method, several groups of Pareto solutions can be found, which can provide some reference for engineering design. [ABSTRACT FROM AUTHOR]

The exploitation of solar irradiation is a critical weapon for facing the energy crisis and critical environmental problems. One of the most emerging solar technologies is the use of solar towers (or central receiver systems) coupled with high-performance thermodynamic cycles. In this direction, the present investigation examines a solar tower coupled to a closed-loop Brayton cycle which operates with supercritical CO2 (sCO2) as the working medium. The system also includes a storage system with two molten salt tanks for enabling proper thermal storage. The sCO2 is an efficient fluid that presents significant advancements, mainly reduced compression work when it is compressed close to the critical point region. The novelty of the present work is based on the detailed dynamic investigation of the studied configuration for the year period using adjustable time step and its sizing for achieving a continuous operation, something that makes possible the establishment of this renewable technology as a reliable one. The analysis is conducted with a developed model in the Modelica programming language by also using the Dymola solver. According to the simulation results, the yearly solar thermal efficiency is 50.7%, the yearly thermodynamic cycle efficiency is 42.9% and the yearly total system efficiency is 18.0%.

Solar reactors for batch processes have a varying heat demand over time. The receiver of large-scale solar chemical plants consists of several of these reactors to quasi-continuously use the solar resource. For this, the heliostat field needs to provide a non-uniform time-varying flux density distribution. As this differs from the heliostat field control of a typical CSP plant, it challenges its control. Here, we propose a cascade controller for a coupled system of heliostat field and receiver consisting of 19 thermochemical batch reactors for hydrogen generation. In the receiver controller, a fast long short-term memory (LSTM) neural network model predicts the future temperatures and the ceria reduction extends in the reactors as a function of the flux density. It is trained with data from a thermochemical reactor model. The trained LSTM neural network is embedded in a hybrid automaton to model the continuous batch process states. Discrete state changes are made when certain conditions are reached. In this way, the receiver controller determines flux density setpoints leading to high efficiencies for each reactor. The heliostat field controller applies aim point optimization to provide flux densities close to these setpoints. With this cascade control, reactor array efficiencies of 79% are obtained simulatively. Moreover, the individual reactors operate within their material limits and come close to their optimal efficiency. In addition, it is found that secondary concentrators complicate the control and decrease the reactor array efficiency. However, they still increase the overall efficiency by 51.3% due to a significantly higher optical efficiency. [Display omitted] • Reactor arrangement of 19 reactors for solar thermochemical hydrogen production. • Cascade control coupling inner heliostat field and outer receiver control loop. • Safe operation of receiver-reactor array with 79% array efficiency. • Application of secondary concentrators improves the overall efficiency by over 50% • Fast reactor model based on an LSTM neural network achieves over 98% accuracy. [ABSTRACT FROM AUTHOR]

Solar air Brayton cycle is a promising option to adjust the renewable power fluctuation due to its quick load regulation capacity. For the successful design and deployment of the solar air Brayton cycle system, the dynamic operation performance of solar collectors under real operating conditions are of great importance. In this study, experiments of a solar collector consisting of the heliostat field and the air receiver are carried out. Based on the experimental investigation of the operating characteristics for the solar collector, a dynamic model is further developed and well-validated to couple the heliostat field and air receiver. The dynamic performance of the air receiver is studied with various factors, including the DNI change and the receiver heat capacity. The results show that the receiver outlet temperature can reach up to 882 °C with a pressure loss of 7.10 kPa and a thermal power of 132 kW during the experiment. Two operation strategies of the air receiver are compared by carrying out the intraday simulation and the constant-outlet-temperature control strategy is more suitable for fast start-up. The method developed in this paper can serve as an efficient tool for the understanding, design and optimization of solar collectors. • Pressured air is heated over 880 °C by a solar receiver. • The operation performance of solar air receiver is explored. • Dynamic model coupling heliostat field and receiver is developed. • The dynamic model is validated by the experimental data. • Two operation strategies of the solar air receiver are compared. [ABSTRACT FROM AUTHOR]

Solar Tower (ST) systems use heliostats to concentrate solar radiation onto a tower-mounted receiver. Optimizing the aiming strategy for these heliostats over the receiver remains a critical challenge due to the dynamic nature of solar radiation and the need to maximize energy capture while ensuring operational safety. This paper introduces a novel, model-free deep Reinforcement Learning (RL) approach to optimize heliostat aiming strategies, utilizing the Soft Actor–Critic (SAC) algorithm. This advanced RL method enhances the traditional Actor–Critic framework with two neural networks. The proposal dynamically adjusts the aiming points across the receiver surface in real time, trying to improve the overall performance of the ST plant. The strategy was simulated and evaluated over a full operational year and compared with traditional methods. The results show an increase of more than 8.8% in yearly absorbed power, a significant improvement that directly enhances performance and contributes to better economic outcomes for the technology. This technique also eliminates the need for constant human intervention and is applicable to both existing and future plants. • Novel RL-based aiming strategy for solar tower heliostats using Soft Actor–Critic (SAC). • Optimizes heliostat aiming in real-time without predefined points, enhancing efficiency. • Continuous receiver surface aiming adapts dynamically to sun and heliostat states. • Year-long validation shows improved energy output and reduced operational risks. • Comparative analysis of different aiming strategies reveals benefits of RL optimization. [ABSTRACT FROM AUTHOR]

For years, concentrated solar power (CSP) has been considered an emerging technology that could disrupt the energy production sector. The possibility to store the electricity generated during the sunny operating hours in the form of heat enhances energy dispatchability and gives CSP a unique value proposition that conventional renewable energies cannot provide cost-efficiently since it requires the integration of costly large-scale battery systems. CSP is a cleaner technology compared to photovoltaics, but photovoltaics currently has lower overall capital costs, making it more attractive to investors and stakeholders who want to spend less money upfront. This is one of the main reasons why CSP has never really led either the electricity market or the heating one, even if its combined generation capability (heat and electricity) is globally recognized as a great advantage for a renewable technology. In this study, we analyze the reasons why CSP is not as widespread as it could be; at the same time, we look at the opportunities and the enablers for a further deployment of this technology, focusing on the European region.

The efficiency of air-type solar towers influences the minimal cost of electricity/heat produced by them, which limits their use despite the widespread use of many forms of concentrated sun power plants. Nonetheless, the temperature potential of this kind of concentrated plant is the highest. To improve the efficiency of an air-type solar tower, a technique for reducing convective energy losses with return air is therefore suggested. In order to increase a cavity receiver's thermal efficiency, a little-known concept called vortex creation will be discussed in this work. The article models different ways of creating an air vortex inside the cavity receiver. Using the VoCoRec design as an example, cases are shown where the vortex increases and decreases the thermal efficiency of the receiver. The concept of Air Return Ratio (ARR) is used to determine the convective losses in a solar collector. This coefficient indicates the convective losses of the receiver due to buoyancy forces and has a direct proportional dependence on the convective efficiency coefficients of the receiver. The VoCoRec receiver, which incorporates the directional vortex inside the receiver, increased the air return coefficient by 4 % (at the same air mass flow rate). The dependence of the air return coefficient on different angles of the air outlet to the absorber plane, including in the radial direction, was also investigated. Increasing the angle of inclination of the air outlet to the main absorber increases the air return coefficient in all cases, but also increases the aerodynamic drag of the receiver (pressure drop). [ABSTRACT FROM AUTHOR]

This study utilizes decision tree algorithms to estimate the financial feasibility of concentrated solar power (CSP). The main focus of CSP is on solar tower (ST) technology combined with two backup systems, such as biomass boilers and thermal energy storage (TES). The main goal is to develop three decision tree algorithms to predict the power plant's profitability factor (P F) for each of the following three operational scenarios: solar tower-base case-no biomass (ST-BC-NB), solar tower-operation strategy 1-medium biomass (ST-OS1-MB), and solar tower-operation strategy 2-full biomass (ST-OS2-FB). P F was predicted according to main input parameters, including direct capital costs, biomass cost, annual escalation rate, hourly electricity price, annual escalation rate, and peaks and troughs for daily electricity prices. Thermal energy storage was in five different capacities: no-thermal energy storage (No-TES), 5 h, 10 h, 15 h, and 20 h. The decision tree models demonstrated accurate predictions with low errors, high confidence levels, and most data falling within the 95% confidence interval for the "No-TES" case. Solar power plants with biomass backup had a 30% reduction in generation costs compared to conventional plants. The configurations without thermal energy storage had the highest profitability, with a maximum P F of −0.014 USD/kWh and a 25% chance of achieving profitability. • Decision tree analysis evaluates economic feasibility of Concentrated Solar Power. • Solar tower modes (ST-BC-NB, ST-OS1-MB, ST-OS2-FB) predict P F. • Thermal energy storage capacities analyzed: No-TES, 5–20 h. • Accurate predictions, low errors, high confidence for "No-TES" case. • Solar thermal plants with biomass backup reduce generation costs by up to 30 %. [ABSTRACT FROM AUTHOR]

Improvements in the geometry of solar towers are explained in this study. Both computational and experimental studies are carried out. Three different solar towers of 1:60, 1:70, and 1:122 scale ratios are taken for the study. All the studies are carried out in an open atmosphere, where a hot wire anemometer is used to measure the peak velocity at the collector–tower junction. The collector geometry is kept flat, inclined, and semi-divergent. The tower geometry is modified from the straight tower into semi-divergent and fully divergent towers. The fully divergent tower with a semi-convergent collector achieves the highest power output among the other two models. The area convergence is the prime factor for an increase in peak velocity. The divergent tower with a semi-convergent collector achieves 54% more power output than a cylindrical tower with a flat collector. [ABSTRACT FROM AUTHOR]

This study presents a sensitivity analysis of the levelized cost of electricity (LCOE) for a particle-based system with the costs of the most current components. New models for the primary heat exchanger, thermal energy storage, and tower are presented and used to establish lower and upper bounds for these three components. The rest of component costs such as particle cost, cavity cost, and lift cost are set to lower and upper bounds estimating an uncertainty between 25% and 50%. Other relevant parameters related to lift and storage performance are also included in the analysis with the same uncertainty. This study also includes an upgrade to the receiver model by including the wind effect in the efficiency, which was not included in previous publications and may have a big impact in the system design. A parametric analysis shows the optimum values of solar multiple, storage hours, tower height, and concentration ratio, and a probabilistic analysis provides a cumulative distribution function for a range of LCOE values. The results show that the LCOE could be below $0.06/kWh with a probability of between 80% and 90%, where the costs of primary heat exchanger, particles, and lifts have largest contribution to the variance of the LCOE. [ABSTRACT FROM AUTHOR]

Particle solar receivers promise economical and operational advantages compared to the molten salt-based solar receivers. In this study, an experiment is designed to observe the particle flow characteristics in the Centrifugal Particle Solar Receiver. A set of experiments for various receiver rotational speeds and particle mass flowrates is conducted, and experimentally obtained raw results are post-processed by means of an Image Processing Routine based on 4BestEstimate algorithm. The axial advance of the particles in one receiver rotation, the particle film thickness, and the ratio of the length of the stationary zone to the receiver circumference is measured to be later used in the validation study of the discrete element method-based numerical model. [ABSTRACT FROM AUTHOR]

This article explores the patents of solar energy technologies in the organic Rankine cycle (ORC) applications. The conversion of low-quality thermal energy into electricity is one of the main characteristics of an ORC, making efficient and viable technologies available today. However, only a few and outdated articles that analyze patents that use solar energy technologies in ORC applications exist. This leads to a lack of updated information regarding the number of published patents, International Patent Classification (IPC) codes associated with them, technology life cycle status, and the most relevant patented developments. Thus, this article conducts a current investigation of patents published between January 2010 and May 2022 using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology and keywords. One thousand two hundred ninety-nine patents were obtained as part of the study and classified in F and Y groups of the IPC. The time-lapse analyzed was between January 2010 and May 2022. In 2014 and 2015, a peak of published patents was observed. China (CN) was the country that published the most significant number of patents worldwide. However, the European Patent Office (EP), the World Intellectual Property Organization (WO), and the United States (US) publish the patents with the highest number of patent citations. Furthermore, the possible trend regarding the development of patents for each technology is presented. A high-performance theoretical ORC plant based on the patent information analyzed by this article is introduced. Finally, exploration of IPC revealed 17 codes related to solar energy technologies in ORC applications not indexed in the main search. [ABSTRACT FROM AUTHOR]

Spinning-elevation (SE) tracking system produces a decent image on the receiver surface; however, it is subjected to large variations in tracking speed. In this research, a graphical ray tracing (GRT) model for center-oriented spinning-elevation (COSE) tracking method is developed to evaluate tracking angles. Instead of a target, a heliostat is pointed toward the on-field center point of the tower. Therefore, a spinning-axis of rotation is a line joining a heliostat, and a center of the tower and elevation-axis is perpendicular to it. This aiming strategy has shown a substantial reduction in rotations of spinning-motor. In contrast, the elevation-motor runs at slightly higher rotations than the target-oriented SE method for the same application. Also, COSE tracking method obtains better shape of the reflected image with less aberration on the receiver surface as compared with SE and the traditional Azimuth-elevation (AE) method. [ABSTRACT FROM AUTHOR]