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This paper presents three new methods for calculating the shading and blocking efficiency in Central Receiver Systems (CRSs). All of them are characterized by the calculation of multiple useful and total reflecting areas without the need to resort to parallel calculation in the CPU or GPU, and by low computation times and minimum errors. They are being specially designed for implementation in codes focused on heliostat field design and optimization in CRSs. The proposed methods have been compared against two outstanding "individual" methods (homology and Boolean operations), in addition to a reference case based on the Monte Carlo ray-tracing (MCRT) technique. The results indicate that one of the proposed methods presents reduced error values and high computational speed, even relaxing the restrictions on candidate filtering. At the same error level, the global method is up to 7.80 times faster than the fastest individual method (homology) and up to 194 times faster than the method based on the MCRT technique. The causes of the main errors of each method are also analyzed. [ABSTRACT FROM AUTHOR]

The central tower solar receiver system is comprised of a number of small tracing mirrors that focus the beam radiation onto a huge tower in the centre. The tracing mirrors are placed as well as adjusted in such a manner that the light is always reflected at the top of the tower. The major goal of this study is to carry out a mathematical assessment of the central tower solar receiver where solar load calculation and heat transfer analysis has been carried out. Solar load is calculated for the location of Pune, India. Mathematical modelling is performed for the solar central receiver system Results of the mathematical modelling reveal that the estimated average sunshine hour for the year ranges from 10.9 hours in the month of December to 12.9 hours in the month of July. The maximum incident beam radiation of 1050.9 w/m2 has been estimated in the month of April at 1200 hour. After computing the variables, the matrix equation can be generated and the system can calculate the energy under the first-order differential equation. The system's thermal efficiency can be computed once the maximum temperature of the heat transfer fluid, ambient air as well as copper tube is known. [ABSTRACT FROM AUTHOR]

This paper proposes a modern approach to a DC/DC converter based on silicon carbide metal–oxide–semiconductor field-effect transistors (SiC-MOSFET). In particular, SiC-based MOSFETs are designed and implemented as Class-E DC/DC converter. The converter is developed as part of a solar power tower (SPT) heliostat unit to supply DC motors under different operation loads. Simulations are presented to demonstrate the effectiveness of the drive system under various scenarios using MATLAB/Simulink. A prototype experimental setup has been built and tested for the proposed converter. The proposed system for SPT converter reduces switching losses that reflect on drive system efficiency without affecting working drive performance. An identical silicon isolated-gate bipolar junction transistor (Si-IGBT)-based converter is designed and implemented to compare the proposed converter based on SiC-MOSFET. The outcomes demonstrated that the proposed converter is more capable and efficient under high temperatures saving 12% power losses at high operating frequencies. Further, the proposed system's switching frequency is higher than the traditional Si-IGBT converter, leading to a greater reduction of power losses and improved efficiency. [ABSTRACT FROM AUTHOR]

The characteristics, distributions, and trends of the aerosol optical depth (AOD) and dust aerosol optical depth (DAOD) of three major concentrating solar power (CSP)-plant project areas (Hami, Turpan, and Ruoqiang) in Xinjiang, China were investigated and analyzed during 1980–2022 using the Modern-Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) reanalysis products. The monthly variation, seasonal variation, inter-annual variation, distributions of AOD and DAOD, and proportions of dust in the aerosols in these three CSP-plant project areas were computed and analyzed. Overall, the annual mean AOD at 550 nm in the Turpan project area was the highest (0.20–0.36), while Ruoqiang had the lowest annual mean AOD at 550 nm (0.13–0.30), and the annual mean AOD at 550 nm in Hami was distributed between 0.17 and 0.33. After 2010, the change in the rate of the annual mean AOD showed an overall downward trend in Hami and Ruoqiang, indicating that the atmospheric environmental changes in both areas were more favorable for the operation of CSP plants. In the project areas of Hami, Turpan, and Ruoqiang, more than 90% of the AOD values were mainly in ranges 0.10–0.30, 0.10–0.35, and 0.05–0.30, respectively. As expected, the AOD values in spring and summer were significantly higher than those in autumn and winter in the three study areas. In spring, the dust contents (i.e., ratios of DAOD to AOD) were the highest, accounting for 64% (Hami), 67% (Turpan), and 69% (Ruoqiang) of the total aerosol contents. In all three areas, the proportions of dust in aerosols in spring have shown an increasing trend since 2000, suggesting that the negative impact of the dust on the power generation efficiency in these areas has gradually been increasing. Therefore, it is recommended that the CSP plants in Hami, Turpan, and Ruoqiang develop a strategy for cleaning heliostats, especially in spring, to reduce the impact of dust adhesion on the efficiency of the CSP plants. [ABSTRACT FROM AUTHOR]

The heliostat is different from the ordinary low building because of the special shape of the heliostat. The wind tunnel pressure test is carried out the model of heliostats in the range of azimuth angles are between 0° to 180° and the range of elevation angles are between 0° to 90. The wind pressure time history of each measuring point on the mirror panel are obtained. On this basis, the mean wind pressure distribution of the mirror panel under typical working conditions is obtained, and then the maximum (minimum) value of the mean wind pressure under all working conditions and corresponding working conditions and measuring points are obtained. Then 10 representative measuring points are selected to study the variation law of wind pressure with wind direction angle and pitch angle respectively, and then the variation law of the mean wind pressure of 10 measuring points under all working conditions is obtained. Finally, the interference effect of the mean wind pressure of heliostats is studied, and the variation law of the interference effect of the mean wind pressure is obtained, and the maximum value, minimum value and corresponding working conditions of the interference effect are obtained. The results show that the maximum value of the mean wind pressure of heliostats under all working conditions is appeared at the measurement point of the lower edge of the mirror panel and on working condition 15-60 (wind direction angle - elevation angle), and the minimum value is appeared at the measurement point of the upper left corner of the mirror panel and on working condition 150-20. The variation law of the mean wind pressure of 10 measuring points under all working conditions is similar, and the position of measuring points has little effect on the variation law of the mean wind pressure under all working conditions. Only the working condition of the maximum value and minimum value are affected by the position of the measuring points. The mean wind pressure distribution under the most unfavorable working condition of heliostats is obtained, the maximum (minimum) value of the interference effect and corresponding working conditions are obtained. Which can be a reference for structural design and research. [ABSTRACT FROM AUTHOR]

Central tower concentrating solar power systems are moving to the forefront to become the technology of choice for generating renewable electricity, but their widespread implementation is limited by cost. Heliostats contribute almost 50% to the plant's cost and are thus the most significant element in central tower systems. For both large and small-area heliostats, the drive elements demonstrate the largest cost element in these systems. While large-area heliostats (>100 m2) have proven offer the best economy compared to other sizes, they require high-torque drives due to the heavy steel-based support structure. Heliostat costs could be reduced by decreasing the support structure's weight, avoiding large drive units and reducing energy consumption. However, the structure must be able to cope with the aerodynamic loads imposed upon them during operation. Although honeycomb sandwich composites have been widely used where high structural rigidity and low weight are desired, there is an absence of studies that rigorously investigated their suitability as the structure for heliostat mirror. Here, a fluid-structure interaction study investigated, for several loading conditions at various tilt and wind incidence angles, the aero-structural behavior characteristics of honeycomb sandwich composites used as a heliostat support structure. The honeycomb sandwich panel showed markedly different behavior characteristics at various operational conditions. The effect of tilt orientation on the sandwich panel's maximum deflection and stresses became more pronounced as wind velocity increased above 10 m/s, and increasing wind incidence angle reduced their magnitudes at different rates. The supporting components and torque tube had a noticeable wind-shielding effect, causing pronounced changes in the deflection and stresses experienced by the heliostat. The worst operational condition was at a tilt angle of 30° with wind flow of 20 m/s at 0° to the heliostat surface. However, the heliostat maintained its structural integrity according to relevant optical and material failure standards. [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]

A solar power tower plant includes a solar tower and tens of thousands of heliostats, with the latter accounting for 40–50% of the total cost. To reduce heliostat costs, a new type of heliostat support structure (HSS) is proposed, consisting of a prestressed high-strength concrete pipe pile and cast-in-place concrete. With the performance and applicability of this structure unknown, full-scale field load testing of the proposed HSS on coarse gravel, subjected to lateral loads or torsion–lateral combined loads, was conducted. The results indicated that lateral load amplifies the rotation under torque and the proposed HSS for mirror arrays can provide sufficient rigidity to limit structural deformations within tolerable values under severe wind loading. Together with three-dimensional modelling, the performance of the proposed HSS was thoroughly investigated to facilitate the development of modified prediction methods for its lateral and torsional load responses. A detailed design procedure is proposed for the new structure, considering foundation deformations, bearing capacity and survival requirements. This study proved that the proposed HSS can improve the economic performance of solar power tower plants. [ABSTRACT FROM AUTHOR]

Generating electric power using solar thermal systems is effective, particularly for countries with high solar potential. In order to decide on a relevant location to implement the solar tower plant and develop the mathematical model of a no-blocking heliostat field, a meteorological assessment was discussed in this paper. In addition, a parametric study was examined to evaluate the effect of the designed parameters (heliostat size, heliostat height from the ground, tower height, receiver aperture, and the minimum radius) on the solar field's performance. The preliminary solar field was then compared to the final design using the optimal design parameters. The obtained results showed that "Tamanrasset City" satisfied the necessary conditions for implementing a solar tower plant. According to preliminary solar field generation, no heliostat blocked its neighbor with a blocking efficiency of 100%. An analysis of its performance revealed that the optimized solar field would be capable of producing 15, 6571 MW, operating at an optical efficiency of 76.95%, and the enhancement rate of both efficiency and power output was 8.1%. [ABSTRACT FROM AUTHOR]

Wind-induced tracking deviations of heliostats can be analyzed through numerical simulations or experimental studies on a full-scale heliostat. However, these methods are relatively costly and often, simpler estimations are necessary and sufficient. One simpler approach is to use an analytical model that describes the wind-induced tracking deviations and which requires only a few input parameters that can be determined through straightforward measurements at the full-scale heliostat. Therefore, this paper presents the derivation of an analytical model and describes the development process in a detailed way to clarify the necessary assumptions and simplifications. For verification purposes, the developed model is furthermore applied to measurement data of a field study. It is shown that the results of the model application agree well with the expectations and that the measured heliostat response matches the predicted response well, provided the underlying assumptions of the model fully apply to the investigated heliostat. Overall, no unexplainable inconsistencies are identified and the results support the model well. Thus, a method is provided which allows the estimation and prediction of wind-induced tracking deviations with comparatively little effort. In addition, the developed model helps to identify and analyze those parameters that have the greatest impact on the wind-induced tracking deviations of different types of heliostats. • Estimation of wind-induced tracking deviations of heliostats with little effort. • Only few and easy-to-determine input parameters for analytical model required. • Model developed for T-type and Stellio type heliostats, further applications possible. • Model confirmed through measurement data of a full-scale field study. [ABSTRACT FROM AUTHOR]

Weather conditions have significant impacts on the solar concentration processes of the heliostat fields in solar tower power plants. The cloud shadow movements may cause varying solar irradiance levels received by each heliostat. Hence, fixed aiming strategies may not be able to guarantee the solar concentrating performance. Dynamic aiming strategies are able to optimize the aiming strategy based on real-time shadowing conditions and short-term forecast, and, therefore, provide much more robust solar concentration performance compared to fixed strategies. In this work, a model predictive control approach for s heliostat field power regulatory aiming strategy was proposed to regulate the total concentrated solar flux on the central receiver. The model predictive control method obtains the aiming strategy, leveraging real-time and forecast shadowing conditions based on the solar concentration model of the heliostat field. The allowable flux density of the receiver and the aiming angle adjustment limits are also considered as soft and hard constraints in the aiming strategy optimization. A Noor III-like heliostat field sector was studied with a range of shadow-passing scenarios, and the results demonstrated the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Optical optimizations for a Concentrated Solar Power (CSP) system are currently limited largely to gradient-free methods, since the gradient is hard to obtain by using the existing numerical optics tools available in the community. This article aims to build new algorithms of the Monte-Carlo type, which numerically estimate the gradient of power impacting the receiver with respect to the geometric parameters that characterize the geometric status of the heliostats in the heliostats field, for a Solar Power Tower (SPT) system. Physical models will be built for the specific intensity and also for its derivatives to the geometric parameters of the heliostats, also called geometric sensitivities of intensity. Similar to the intensity but with their own models, they are regarded as physical quantities emitted, absorbed and reflected in the system. They carry the perturbations of intensity as information, corresponding to the relations between the geometric parameters and the physical events in the SPT system: blocking, spillage, shadowing, etc. These relations will be distinguished and discussed. Finally, not only the gradient but also the contributions of physical events (blocking, spillage, shadowing, etc.) to the gradient can be estimated for further sensitivity analysis and optimization processes. • A Monte-Carlo algorithm estimates the geometric gradient for Solar Power Towers. • Evaluate physical contributions to gradient for analysis and optimization. • Significantly more efficient than finite difference method for big heliostat fields. [ABSTRACT FROM AUTHOR]

A thermodynamic analysis was performed on a newly developed concentrated solar power (CSP) technology known as the Cross-Linear (CL), which addresses the issue of cosine loss in conventional CSP technology. The analytical model has been developed and validated using experimental data collected at the experimental site situated in Bhopal, India. The analysis was performed under direct normal irradiance of 775 W/m2 with the key objective to determine the optimum inlet condition of the heat transfer fluid (HTF) considering three optimization parameters: HTF outlet temperature, energy, and exergy efficiency of the receiver. Also, the exergy of the solar field is investigated depending on the available solar irradiation throughout the day for three different configurations of the heliostat field. After a comprehensive analysis of the results, the optimal air inlet temperature range was observed to be between 373 and 423 K, and the optimal air mass flow rate was overserved to be 0.0925 kg/s (333 kg/h), which provides energy and exergy efficiency values within 50% to 60% and 28% to 34%, respectively. The maximum electrical exergy efficiency for 30 kW plant capacity is observed to be around 70% at solar noon with a cosine factor of around 0.9 for 4-hour duration. [ABSTRACT FROM AUTHOR]

Wind loads on heliostats are often investigated through experimental wind tunnel studies or numerical simulations. However, these approaches cannot consider the full-scale conditions but require a reproduction and simulation of both the heliostat structure and the wind conditions. Complementary full-scale investigations are therefore crucial but are at the same time relatively costly, as it is cumbersome to set up large heliostats with measurement devices. This paper introduces a new pressure measurement system which is easy-to-apply to a real-scale heliostat and enables full-scale investigations with minimized effort. The results of a first field study are presented during which wind and pressure measurements were taken simultaneously over periods of 10 min at a 48.5 m2 pentagonal Stellio heliostat. The non-dimensional pressure distributions are investigated and it is shown that the mean c p -values are very consistent amongst the measurement periods and reach values between 2.2 and 2.6. These values, in turn, are found to agree well with results of a wind tunnel study. Moreover, the behavior of the load coefficients with varying angles of attack is studied and the aerodynamic admittance functions are evaluated which give in-depth insight into the generation of aerodynamic loads. The admittance functions are found to start decreasing at a non-dimensional frequency of approximately 0.2. This finding indicates that eddies which are about the size of the heliostat or larger are fully effective in generating aerodynamic loads while the effectiveness of smaller eddies is reduced. • New pressure measurement system developed with maximum sampling frequency of 50 Hz. • Full-scale wind and pressure measurements conducted over several 10-minute periods. • Mean pressure distributions found to reach consistent cp-values between 2.2 and 2.6. • Aerodynamic admittance gives insight into wind load generation. • Eddies smaller than the heliostat are not fully effective in generating loads. [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]

In solar power tower plants, knowing the optical quality of heliostats makes it possible to predict relevant information on the receiver surface, such as the irradiance concentration factor and spillage. However, there are no standardized routines for optical characterization in commercial facilities because the process is challenging, multidisciplinary, and time-demanding. This article revises the traditional optical characterization methodology followed at the Solar Platform of Almería (PSA). The process starts with the acquisition of the image of the studied optical system. After that, the picture must be fitted to an analytical model, which requires finding the variables that best reproduce the reality. The traditional method for accomplishing this task is iterative, semi-automatic, and contains trial-and-error components. This work studies how to replace this part with heuristic optimizers and considers using the state-of-the-art methods TLBO, UEGO, and Multi-Start Interior-Point (MSIP). Their effectiveness has been compared to the results manually achieved by an expert with three different heliostat facets. According to the results obtained, the parameter sets found by TLBO and UEGO outperform those obtained through the traditional method. • Support for optical characterization campaigns at solar power tower plants. • Revision of the methodology followed at the Plataforma Solar de Almería (PSA). • Process enhancement with global optimizers to minimize expert intervention. • Experimentation and method validation with three heliostat facets at the PSA. • The optimizers TLBO and UEGO achieve similar results to the traditional method. [ABSTRACT FROM AUTHOR]

Solar Power Tower technology requires accurate techniques to ensure the optical performance of the heliostats both in commissioning and operation phases. This paper presents a technique based on target reflection to detect and correct canting errors in heliostat facets. A camera mounted on the back of a target heliostat sees an object heliostat and the target facets in reflection. The pixels difference between detected and theoretical borders determines the canting errors. Experiments in a lab scale testbed show that canting errors can be corrected up to an average value of around as low as 0.15 mrad. Experiments were also performed on a real heliostat at Plataforma Solar de Almería. As a result, canting errors (up to 5 mrad) have been reduced below 0.75 mrad. Mirror slope errors, which can be noticeable in large facets, becomes the largest source of inaccuracy in the presented method. [Display omitted] [ABSTRACT FROM AUTHOR]

An important part of future global energy depends on the development of the solar industry. To date, we have noticed the shift from fossil fuels energy towards renewable energy. The past decade has shown significant progress in computer science and CAD is increasingly used for design and development. Visualization of the data generated from the models in the CAD program plays an important role in the creation of state-of-the-art designs. An important limitation during the design phase is the visualization of three-dimensional geometry. This article attempts to illustrate the use of VR technologies in solar thermal power plant development. This article analyzes various strategies and methods for the visualization of CAD models in virtual reality. Android phone interfaces with a desktop computer, as well as head movement control strategies, are discussed. It is concluded that VR technologies can help with visualization, as well as in the development of the field of solar thermal power plants, having minimal design-related issues. [ABSTRACT FROM AUTHOR]

• Shading and blocking efficiency of a heliostat field is essential to be estimated. • A method is proposed with higher accuracy and reduced computational cost. • Double counting error is eliminated, and edge-to-centre checking is implemented. • Parallel neighbor assumption for finding shading/blocking efficiency is discarded. • Precise Pre-selection of potential shader/blocker reduces non-essential computation. Evaluation of optical efficiency of a heliostat field is essential for central receiver tower plants. In the present study, an improved method is demonstrated to eliminate drawbacks of existing methods for evaluating shading and blocking efficiency. The proposed method obviates the parallel plane assumption with the immediate neighbours; hence improves accuracy. Moreover, the lack of flexibility introduced due to such simplifying assumptions in terms of altered field configuration is removed. The family of ray-tracing methods often provides accurate result only at the cost of large computational expense. The current method renders similar degree of accuracy at significantly lower cost by eliminating inefficiencies of a brute-force approach. At first, it identifies potential shader (blocker) neighbours through a two-level filtering. Secondly, the grids on a heliostat are checked from-edge-to-centre instead of a random order. Moreover, the grids already found to be shaded (blocked) by one neighbor are excluded from further checks. Such systematic approach reduces nonessential checking for shading (blocking) and hence improves computational efficiency. Furthermore, such approach also discards any possibility of double counting. Finally, the degree of accuracy as obtained through computationally expensive ray-tracing methods is achieved by the present method with far less number of grid points. [ABSTRACT FROM AUTHOR]

The efficiency of heliostat fields is analyzed in terms of mirror density. It is shown that it is possible to estimate the blocking and shadowing losses without ray tracing or polygon clipping. The calculations are based on general geometric properties and provide a kind of upper limit for heliostats with various mirror shapes and tracking systems. The use of mirror density allows to skip a multiparametric optimization of heliostat coordinates and to describe heliostat fields as if they had an ideal layout. The optimal distribution of mirror density is found by solving a variational problem, which assures that the transfer of heliostats from a region of low efficiency to a region of high efficiency does not change the overall efficiency of the field. The gains from the transfer are compensated exactly by the losses from the additional blocking and shadowing. It is shown how to design heliostat fields with a balanced mirror density, and the advantages of the balanced layout are compared with a more conventional nonblocking layout. The analysis also includes an economic model, which helps to estimate the price of solar heat and to distribute the investment costs properly between the heliostat field and other components of power plant. [Display omitted] • The blocking and shadowing of heliostats are described in terms of mirror density. • The efficiency of heliostat field is maximized through a variation of mirror density. • A balanced distribution of mirror density corresponds to ideal heliostat field. • The balancing derivative shows how close a heliostat field is to the ideal one. • The balanced efficiency shows the optimal cost ratio of heliostat field and receiver. [ABSTRACT FROM AUTHOR]

The growing need to increase environmental and energy sustainability in buildings (housing, offices, warehouses, etc.) requires the use of solar radiation as a renewable source of energy that can help to lower carbon footprint, making buildings more efficient and thereby contributing to a more sustainable planet, while enhancing the health and wellbeing of its occupants. One of the technologies deployed in the use of solar energy in buildings is heliostats. In this context, this paper presents an analysis of the performance of a heliostat illuminator to improve illumination in a classroom at the Campus of Rabanales of the University of Cordoba (Spain). A design of a system in charge of monitoring and measuring daylighting variables using Arduino hardware technology and free software is shown. This equipment develops the communications, programming and collection of lighting data. In parallel, installation of an artificial lighting system complementary to the natural lighting system is implemented. Finally, an analysis of the impact of the proposed solution on the improvement of energy efficiency is presented. Specifically, it is estimated that up to 64% of savings in artificial lighting can be achieved in spaces with heliostatic illuminators compared to those without them. [ABSTRACT FROM AUTHOR]

Heliostat tracking is a critical component of the solar field of concentrating solar power tower (SPT) systems and can be the source of significant losses in power and profit when it lacks the necessary accuracy. This paper presents an advanced heliostat drive system for the SPT generation plant. An integrated model for the heliostat drive system based on dual axes tracking is proposed using an inexpensive angle sensor. The mathematical model of the integrated drive system is developed, including the solar, tower, and heliostat models. The matlab simulation model for the proposed integrated drive system is developed and evaluated. An experimental prototype for a dual-axis heliostat is built using Class-E direct current choppers and an inexpensive Gyro angle sensor. The prototype is tested and considered in the Dhahran region in Saudi Arabia under different operating conditions. A comparative study between simulation and experimental results is conducted to assess the efficacy and accuracy of the proposed controller drive system and validate the developed integrated model. Both simulation and experimental results demonstrate the effectiveness of the proposed dual-axis trackers to follow the sunbeams throughout the year. [ABSTRACT FROM AUTHOR]

• An improved biomimetic heliostat field layout is proposed to reduce the energy loss. • Two novel time-saving methods are developed for annual optical process simulation. • The highest optical efficiency is achieved by using the square hexagonal heliostats. • The improved biomimetic field layout achieves the best optical and thermal efficiency. • Stress failure is prone to more likely occur to the receiver at noon of winter solstice. Designing and optimizing heliostat field layout is an important prerequisite for solving higher energy demand and safety issue of the concentrating and collecting subsystem (CCS) in the next-generation solar power tower (SPT). This paper proposed an improved biomimetic heliostat field layout to improve the optical efficiency and reduce the energy loss of CCSs. Then, the random photon trial method and the emission position limitation method were developed to speed up the optical process simulation, which shortened the computational time by 63.36% in one year. Furthermore, the improved biomimetic heliostat field layout, the related biomimetic heliostat field layout and the radial staggered heliostat field layout were optimized for the highest optical efficiency in conjunction with the rectangular, the square quadrilateral, the square pentagonal and the square hexagonal heliostats. Finally, the effects of these three field layouts on the thermal performance and safety of CCSs under different conditions were investigated. The results show that the proposed improved biomimetic heliostat field layout can obtain the highest annual weighted optical efficiency using the square hexagonal heliostats and the receiver efficiency is improved by the improved biomimetic heliostat field layout by homogenizing the solar heat flux distribution. It is also reveals that the receiver is more prone to stress failure at noon of winter solstice due to the most inhomogeneous solar heat flux and the highest peak equivalent thermal stress, which may be improved through novel heliostats aiming strategies, more advanced field layouts and receiver structure optimizations. This study provides an efficient heliostat field layout and design guidance for the CCS in the next-generation SPT. [ABSTRACT FROM AUTHOR]

[Display omitted] • Theoretical and run-test evaluation of the 50 MW beam-down power plant is conducted. • The variation in heliostat efficiency, flux density, and power generation is analyzed. • The average outlet temperature of the molten salt was up to 559℃ for 50 min. • The flux density of hyperboloid mirror on four typical days is 10.2/11.2/10.9/9 kW/m2. • The flux density of receiver on four typical days is 353.6/399.1/381.7/314.2 kW/m2. The beam-down concentrating solar power plant has the advantages of high concentrating ratio, low installation and maintenance requirements, and low pump consumption. To conduct further theoretical and run-test evaluations of the optical and thermal performance of the beam-down concentrating solar power system, the Yumen Xinneng 50 MW beam-down power plant is analyzed in this research. The variation of the heliostat field efficiency, hyperboloid mirror flux density, receiver flux density, and annual power generation under various operating parameters is discussed. The run-test results from June 12th indicated an average outlet temperature of molten salt reached 559°C between 13:07 and 13:56 under an average direct normal irradiation of 739.7 W/m2. The corresponding inlet temperature increased from 302.3°C to 307.6°C due to the rewarming effect caused by the increase in hot molten salt. Regarding the simulation results, the recommended design parameters for the vertex ratio of the hyperboloid mirror are between 0.775 and 0.8 to mitigate the contradiction between initial investment and optical efficiency. The maximum values of cosine efficiency, shading and blocking efficiency, shading efficiency of the hyperboloid mirror, and attenuation efficiency for the heliostat field are 85.56%, 99.96%, 99.35%, and 97.46% on June 1st for the maximum solar elevation angle of 70.72°. Consequently, the maximum values of the average hyperboloid mirror flux density and receiver flux density are 11.2 kW/m2 and 399.1 kW/m2 on June 1st. The maximum power generation for a 7-day period is 4674.22 MWe in June with a duration time of 100 hours. This paper can further expand research on the comprehensive performance of beam-down power plants. [ABSTRACT FROM AUTHOR]

• Reflection from beds of spherical and diffuse particles is modelled as incidence angle - dependent. • Reflection characteristics are determined via Bidirectional Reflection Distribution Function (BRDF). • Solar irradiation to solar particle receivers is modelled to reduce the computation time. In this study, a novel reflection model for particle beds formed by diffuse, gray, opaque and spherical particles is developed, and applied to the Centrifugal Solar Particle Receiver (CentRec). The reflection from particle beds comprised of diffuse reflecting particles are neither diffuse nor specular but incidence angle dependent due to the spherical surface of the particles forming the particle bed. The reflection characteristics of a particle bed being representative for the CentRec application is derived for a wide range of incidence angles of the incoming rays (0° ≤ γ gen ≤ 85°). Later, the derived characteristics are imported to the in-house ray tracing tool SPRAY. A realistic ray distribution is generated by taking the heliostat configuration into account. The absorbed power distribution on the particle film surface in the CentRec is found after several reflections inside the CentRec cavity. The model results are compared with resolved MCRT results for typical CentRec operating conditions. Very high accuracy in terms of reflection loss through the aperture and absorbed power distribution in the receiver is achieved with the developed reflection model. The required computational time to model the solar irradiation in the CentRec is reduced significantly and there is still room for improvement. [ABSTRACT FROM AUTHOR]

In the current work, a solar-based energy plant that includes an organic Rankine cycle, an NH 3 − LiNO 3 operated refrigeration system, reverse osmosis desalination, and hydrogen production device are integrated, modeled, and optimized. A parametric examination is designed with Matlab software to show the impact of varying primary system variables on outputs like system total energy, exergy efficiency, and total exergy output. All processes have been carried out for different working fluids, namely iso-butane, Propane, n-octane, and the results are compared. Parametric analysis reveals that at solar radiation of 800 W/m2, which is reasonable for the sun in most of the Middle East, selecting n-Octane as a working media results in an increase in the hydrogen production rate of about 150%. This also confirms the importance of selecting the right working fluid for the ORC unit. Moreover, the influence of substantial decision variables on the hydrogen production, net out pout power, exergy efficiency indicated that multi-criteria optimization is necessary. The multi-objective optimization strategy suggests the TIP = 1753 kPa, T oil = 99 °C , η i s t u r = 0.9, η i s p u m p = 0.87, and A Heliostat = 2800 m2, for the optimum state of the studied system. Additionally, the scatter distribution and sensitivity analysis for optimum point introduced by multi-criteria optimization utilized for better understanding the optimization process. • Design a heliostat field solar system to drive a multi-output system. • Exergy-based analysis and economic optimization of proposed system. • n-octane in the ORC with solar radiation 800 W/m2 shows the best performance. • Optimization suggests exergy efficiency of 30% with 205.5$/h for developed system. [ABSTRACT FROM AUTHOR]

• • A detailed analysis of the rear geometry influence on heliostat's aerodynamic load coefficients is reported. • • A maximum difference of 219% is found when comparing box cavity vs. torque tube geometries. • • An explanation of the results is given in terms of pressure fields and air flow patterns. The study of heliostat load coefficients in stow position has become more extensive because of the importance of this scenario in the design process and cost estimation of an entire Concentrating Solar Thermal Power Tower plant. When in stow position, in the presence of high-velocity wind flow, heliostats behavior can be compared to an airfoil; as the air flows at different velocities over the upper and lower sections, significant pressure imbalances need to be considered. This paper presents a Large Eddy Simulation study of how four different geometries in the rear area of a squared heliostat at a horizontal inclination affect the magnitudes of the hinge moment (C MHy), drag (C Fx), lift (C Fz) and overturning (C My) coefficients. Results show maximum differences of more than 128% for peak C Fx when comparing type A and B geometries at the same 45° wind orientations. Also, for types A and B at β = 180°, peak C My and C MHy presented differences of 47% and 36%, respectively, between heliostat models. Also, considering force's change in direction (i.e. lift vs downforce), a 219% maximum difference was observed for peak C Fz between type A and type D models at β = 45°. The results show how the differences in shapes and size proportions between the front and rear heliostat sections affect the stow position's aerodynamic load coefficients (ALC). It was also observed that the ratio of the chord length to the maximum vertical distance from the rear mirror surface to the farthest point of structure geometry of the heliostat is directly correlated with ALC variations for analyzed heliostats. [ABSTRACT FROM AUTHOR]

Off-axis incidence is inherent to sun tracking mirrors, named heliostats. Moreover, heliostat defocus takes place, provided that the focal length of the mirrors usually differs from their distance to the target. Defocus, along with high incidence angles, lead to astigmatic aberrations, that are overlooked by analytic functions based on convolution. This paper presents an analytic function on the image plane that reproduces these aberrations. As the reflection of the heliostat axes is non-orthogonal with defocus, the identification of the reflected axes plays a key role in the resulting model. In comparison with Monte Carlo Ray-Tracing, the model shows correlation coefficients above 90%, except at the tangential and sagittal foci, where the analytic function is indeterminate. An astigmatic parameter is provided to assess the model validity, which is complementary to UNIZAR at high incidence angles. • Analytic function that reproduces astigmatic aberrations in defocused heliostats. • Accounts for non-orthogonality of heliostat reflected axes under defocus. • Flux spot lines up along the sagittal axis at the tangential focus, and viceversa. • Indeterminate analytic function at the astigmatic foci. • Appropriate for 1 − cos ω L H / f > 0.005, complementing UNIZAR. [ABSTRACT FROM AUTHOR]

• Perimeter mesh fence reduces heliostat wind loads by up to 50%. • Wind load reduction increases linearly with decreasing mesh fence porosity. • Edge-mounted mesh devices reduce stow and operating wind loads. • Mid-porosity mesh devices reduce operating drag by 15% and lift by 30% • Mesh devices can increase stow drag and operating lift. This study examines the effectiveness of mesh grids in heliostat field perimeter fences and edge-mounted devices for heliostat wind load reduction. Two experimental studies were conducted: (1) the effect of mesh porosity and non-dimensional longitudinal distance of a perimeter fence upstream on the forces on a heliostat, and (2) the effect of mesh porosity and non-dimensional height-chord ratio of a heliostat edge-mounted mesh device on the heliostat loads. The experiments were conducted using an instrumented heliostat model positioned in the atmospheric test section of the Adelaide Wind Tunnel. It was found that perimeter mesh fences reduce peak loads by up to 50% and edge-mounted porous mesh devices reduce peak loads by up to 30% at the expense of increasing loads at different elevation angles. The porosity and height-chord ratio of an edge-mounted mesh were found to be important parameters influencing the maximum drag and lift reductions in operating and stow positions. The results of this work show the potential of mesh grids for reducing wind load on heliostats, and the importance of conducting a detailed techno-economic analysis on mesh grids throughout a heliostat field. The application of mesh grids on commercial-scale heliostats requires a further evaluation of the reduction of heliostat wind loads and thus cost of a field through mitigation of the incoming ABL turbulence and wake-induced turbulence from upstream heliostats. [ABSTRACT FROM AUTHOR]

Third-generation concentrating solar-thermal power (CSP) systems are proposed which aim to halve the cost of electricity from CSP. This work demonstrates that a transition from state-of-the-art cylindrical molten nitrate salt receivers with a peak concentrated solar flux of 1 MW/m2 and a heliostat field optical error of 3 mrad to future cylindrical sodium receivers with a peak flux of 1.8 MW/m2 and a heliostat field optical error of 1 mrad could enable the exergy output of CSP receivers to be increased significantly, by 25% at design point, while keeping the general system design very similar. This comparison is conducted on a large dataset established with a detailed field and receiver energy balance model considering field aiming, peak receiver flux and hydrodynamics. It is based on design point simulations, and is independent from cost considerations. At high temperatures, the optimal configurations achieve their gains only with very accurate heliostats and when the peak flux is increased, while at low temperatures, there is nothing to be gained from very high peak flux limits on external tubular receivers. This underscores the critical importance of high heliostat accuracy for high-temperature CSP systems design. For the third-generation, high-temperature (740 °C) sodium receiver configuration considered, it is found that the upper limit to thermal–optical efficiency of optimised receivers at design-point is around 88 %. • An extensive thermo-optical parametric study of tower CSP systems is performed. • Performance limits, independent of cost considerations, are analysed in detail. • Liquid sodium receivers can enable a 25% exergy gain over molten salt systems. • Performance is strongly affected by field optical error and peak design flux values. • High accuracy heliostats appear critical for the next generation of CSP systems. [ABSTRACT FROM AUTHOR]

Concentrating solar power central-receiver plants use thousands of sun-tracking mirrors, i.e., heliostats, to reflect sunlight to a central receiver, which collects and uses the heat to generate electricity. Over time, soiling reduces the reflectivity of the heliostats and, therefore, the efficiency of the system. Current industry practice sends vehicles to wash heliostats in an ad hoc fashion. We present a mixed-integer nonlinear program that determines wash vehicle fleet size, mix, and assignment of wash crews to heliostats to minimize the sum of (i) the revenues lost due to heliostat soiling, (ii) the costs of hiring wash crews and operating the vehicles, and (iii) the costs of purchasing wash vehicles. We establish conditions for convexity of the objective function, and then propose a decomposition method that enables near-optimal solutions to the wash vehicle fleet sizing and assignment problem on the order of a couple of minutes. These solutions yield hundreds of thousands of dollars in savings per year over current industry practices. [ABSTRACT FROM AUTHOR]

SOLARPILOT is a software package that generates solar field layouts and characterizes the optical performance of concentrating solar power (CSP) tower systems. SOLARPILOT was developed by the National Renewable Energy Laboratory (NREL) as a stand-alone desktop application but has also been incorporated into NREL's System Advisor Model (SAM) in a simplified format. Prior means for user interaction with SOLARPILOT have included the application's graphical interface, the SAM routines with limited configurability, and through a built-in scripting language called "LK." This article presents a new, full-featured, PYTHON-based application programmable interface (API) for SOLARPILOT, which we hereafter refer to as CoPylot. CoPylot enables PYTHON users to perform detailed CSP tower analysis utilizing either the Hermite expansion technique (analytical) or the SolTrace ray-tracing engine. CoPylot's enables CSP researchers to perform analysis that was previously not possible through SOLARPILOT'S existing interfaces. This article discusses the capabilities of CoPylot and presents a use case wherein we populate a model that obtains optimal solar field aiming strategies. [ABSTRACT FROM AUTHOR]

A comparative analysis has been carried out between eight metaheuristic algorithms, namely; genetic algorithm (GA), differential evolution (DE), particle swarm optimization (PSO), grey wolf optimization (GWO), improved grey wolf optimization (IGWO), artificial bee colony (ABC), grasshopper optimization algorithm (GOA), and a proposed hybrid genetic-grasshopper (GA-GOA) to optimize the staggered heliostat field of the PS10 plant. The annual weighted efficiency is taken as the objective function for field layout optimization. In addition, the investigated algorithms have been assessed in terms of best energy yield, levelized cost of energy (LCOE), land use factor (LUF), and computational cost. It has been found that evolutionary algorithms outperform swarm intelligence algorithms in terms of efficiency, whereas GOA and GWO converge faster. To get high efficiency with low computational cost, a hybrid GA-GOA algorithm has been proposed. This study found that the hybrid GA-GOA algorithm does indeed deliver improved performance, with an optimum weighted efficiency boosted by 1.45% at a computation cost of ∼63.7 h. In addition, it provides the best optimum LCOE of 26.22 c€/kWh and successfully enhances LUF by 11.2% compared to the PS10 reference plant. Based on these results, the authors can conclude that the proposed hybrid GA-GOA algorithm represents a suitable tool to cost-effectively optimize the design of heliostat field layouts and reduce their land footprint. [ABSTRACT FROM AUTHOR]

• Comparison of optimized spiral and staggered layouts for different heliostat shapes. • The GOA algorithm is used for the first time to optimize the heliostat layout. • A circular heliostat shape reduces the land area by 25.9% & 28.4% for both layouts. • A circular heliostat shape improves the efficiency to 71% & 71.1% for both layouts. During the design and characterization of Solar Power Tower (SPT) systems, the selection and optimization of the heliostat field distribution are critical. Additionally, selecting the appropriate heliostat shape is an important factor to consider because of the optical losses linked to the heliostat shape. In the current study, the optimization and comparison between biomimetic spiral and Campo radial-staggered layout are carried out by considering various heliostat shapes. The optimization is carried out for the PS10 plant installed in Spain. The Grasshopper Optimization Algorithm (GOA) approach is used, and the heliostat field efficiency is assessed. The optimized heliostat field showed that the Campo radial-staggered layout provides better efficiency and the lowest land area when compared to the biomimetic spiral layout. In addition, using a circular heliostat shape for the original PS10 field, the land area could be reduced by 25.86% (about 113,538 m2) and 28.39% (about 124,633 m2) for the biomimetic spiral and staggered fields, respectively. On the other hand, for the circular heliostat, the yearly efficiency is improved to ∼ 71 and ∼ 71.1% for biomimetic spiral and staggered fields, respectively, compared to the conventional rectangular heliostat with an efficiency equal to ∼ 69.3%. Indeed, the registered gains in land area and yearly efficiency will reduce the Levelized cost of energy. [ABSTRACT FROM AUTHOR]

Heliostats are prone to be destroyed under the action of thunderstorm and hail in the wild. Many studies on heliostat mainly focused on the effect of wind load, while it is a lack of in-depth understanding on the dynamic responses of heliostats under hail impacting. This study performs the dynamic response of heliostat under hail impacting in Tibetan Plateau of China by numerical simulation. A hail dynamic constitutive model considering strain rate effect and brittle fracture behavior was established and verified based on historical hail statistics, and the effects of hail impacting position, hail size, elevation angle and thickness of heliostat on the dynamic response characteristics were analyzed. The research results demonstrate that the impact position has a significant influence on the displacement of heliostat, but a little effect on the maximum stress. The stress and displacement of the heliostat increase with the increase of hail size, while decrease with the increase of the elevation angle and thickness of heliostat. When the hail diameter increases to 30 mm, the maximum principal stress of heliostat exceed its tensile strength. The results are useful and interesting to researchers who can reference the obtained results to predict the heliostat safety under hail impacting. [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]

As part of the research for techniques to control the final energy reaching the receivers of central solar power plants, this work combines two contrasting methods in a novel way as a first step towards integrating such systems in solar plants. To determine the effective power reaching the receiver, the direct normal irradiance was predicted at ground level using a total sky camera, TSI-880 model. Subsequently, these DNI values were used as the inputs for a heliostat model (Fiat-Lux) to trace the sunlight's path according to the mirror features. The predicted valuex of flux, obtained from these simulations, differ of less than 20% from the real values. This represents a significant advance in integrating different technologies to quantify the losses produced in the path from the heliostats to the central receiver, which are normally caused by the presence of atmospheric attenuation factors. [ABSTRACT FROM AUTHOR]

This study presents an analysis of the theoretical upper limits to the mean annual optical efficiency of the Light Collection and Concentration (LCC) subsystem of a solar tower system, which is the subsystem composed of the heliostat field and the active surfaces of the receiver that capture the concentrated solar radiation sent by the heliostat field to transform it into thermal energy. The "ideal" LCC subsystem is modelled gradually, by incrementally introducing into the model factors that limit the mean annual optical efficiency of any LCC subsystem and whose influence in the optical efficiency cannot be reduced to zero, starting with the cosine factor, followed by the atmospheric transmittance, and then by the product of the receiver intercept factor and a factor related to the shading of the heliostat field by the receiver. At each degree of complexity of the ideal LCC subsystem model, the optimal configuration of the "ideal" LCC subsystem that achieves the highest mean annual optical efficiency in terms of heliostat field shape and receiver size is identified for a selected range of latitudes, tower heights and heliostat field sizes or total mirror areas. Thus, the upper-limits of the mean annual optical efficiency of the LCC subsystem of solar towers are obtained as a function of the specified parameters. The results obtained show that at a latitude of 30° North, for tower heights between 200 and 300 meters and heliostat fields with mirror areas between 1.3 km2 and 2.5 km2, the upper limit of the mean annual optical efficiencies vary between 79.2% and 74.7%, with the highest upper limit corresponding to the combinations of the tallest towers and smallest heliostat fields. This strongly indicates that the mean annual optical efficiency of actual solar mono-tower systems of commercially realistic heliostat field sizes and tower heights will hardly reach 70% at any location on Earth. • Upper limits as a function of optical factors. • Factors considered: Cosine, Transmittance, Receiver Intercept and Shading. • Influence of latitude, field and receiver size and tower height on upper limits. [ABSTRACT FROM AUTHOR]

Summary: Solar tower power plant technology is based on the principle of concentrating incident solar irradiation on a receiving surface located at the top of the tower via a mirror field. The heliostat field consists of a significant number of reflective mirrors; each heliostat tracks the Sun individually and reflects the Sun's incident rays at a focal point. Therefore, the heliostat position plays a major role in the global system efficiency and must be carefully chosen to minimize optical losses. In this paper, a mathematical model was proposed for the analysis of the optical efficiency of the solar tower power plant. Detailed optical losses are mainly losses by blockage, shading, spillage, and atmospheric mitigation. During this study, the approach was oriented toward the optical study of the solar thermal power plant: a new method for calculating the blocked and shaded surface has been developed. This new method was then validated basing on the database of the marketed solar power plant PS10 installation with a north heliostat field configuration geometry, as well as a validation was elaborated based on a surrounding heliostat field configuration geometry. Obtained results show that the individual heliostat efficiency is in the range of 0.824; based on published papers, the calculation error factor is in the order of 0.01%. Numerical results of the shading and blocking efficiencies prove the reliability of the developed model. In the first hand, the model is valid whatever the heliostat parameter (its row, heliostat orientation, its position according to their neighbor, etc). On the other hand, the developed model is applicable in all heliostat field configurations; it is valid in both surrounding and north configurations. [ABSTRACT FROM AUTHOR]

This article deals with the potential assessment of tower type solar thermal power system. An algorithm was developed to employ sun-tracking method, which provides the characteristic angles of the heliostats such that the incoming beams of sun rays are reflected to the receiver. A suite of MATLAB code was developed to implement the mathematical models for a quick evaluation of solar energy potential in a radially staggered heliostat field for the capital city of Kingdom of Saudi Arabia, Riyadh. An existing clear-sky model in the literature was used to compute hourly insolation. Optical efficiencies and heat collected by the receiver (from individual heliostat in the field on hourly basis) were computed and the monthly-averaged daily results were presented zone-wise and for the complete heliostat field. It was observed that the optical efficiency of the heliostat decreases with increasing distance from the receiver tower; this was due to increasing spillage of the reflected rays and decreasing cosine efficiency with increasing distance of the heliostat from the receiver tower. Results showed that annual average optical efficiency of the field is nearly forty-nine percent. [ABSTRACT FROM AUTHOR]

Solar central receivers have inherently large time constants and time delays caused by their thermal inertia are due to the transport of the heat transfer fluid alongside the panels. This problem is even accentuated if these systems are continuously exposed to direct normal irradiance (DNI) fluctuations. Ensuring an adequate operation of this kind of process implies the adaptation of control strategies. This paper proposes a strategy that couples the temperature control of the outlet fluid while considering the heliostats' aiming points location to maintain the receiver operating below its design limit and simulates its performance under several scenarios. These tests are carried out on a non-steady-state solar plant model that considers its optical and thermal characteristics. The structure of the proposed control system is based on using intermediate flow valves along the heating flow path to reduce time delay. Hence, it renders the control system more responsive to either a DNI variation affecting the solar field or moving its operation from one state to another. The control strategy structure contains feedback and feedforward loops to determine the near-future process response to DNI measurements. It allows adding more information to the loop used to maintain the system's desired steady-state operation. The overall strategy can take the process to a steady-state operation regardless of the hour or day of operation. It produces a low variation of the outlet temperature, with a standard deviation of 3 °C, while the receiver is under a transient DNI and maintains the heliostats aimed toward the receiver without exceeding its heat flux limits. Results indicate that the proposed strategy achieves over 80% improvement based on the integral absolute error (IAE) performance index compared to conventional single-loop temperature control. Besides the simulated numerical results, this research also presents the advantages of considering intermediate mass-flow valves for control purposes of the receiver. This work should be considered a step towards improving multivariable control algorithms for the safe operation of solar central receivers. [ABSTRACT FROM AUTHOR]

Concentrated solar power (CSP) is a cutting-edge method of conserving renewable energy. The concentrated solar power is utilized as a heating source to increase the temperature of heat transfer fluid circulating in the piping of the central solar receiver. The solar central receiver is the most crucial part in solar tower power plants. In this study, a Computational Fluid Dynamics (CFD) framework was developed for analyzing four designs of the central tower receiver, namely, a conventional uniform tube diameter solar receiver (UTD), vertical variable tube diameter solar receiver (VTD), a circular solar variable tube diameter (CVTD) receiver and a leaf type circular solar receiver (LTSR). This analysis studied the solar radiation heat transfer efficiency, temperature distribution, and fluid outlet temperature; pressure and velocity distributions for the designs using CFD. It was found that the CVTD design helped achieve a higher rise in temperature of the heat transfer fluid (HTF) when the mass flow rate was in the range of 0.1 to 0.2 liter per minute. The CVTD and LSTR models of receiver were more efficient heat transfer receiver designs compared with other designs for same surface area and strength of beam radiations. [ABSTRACT FROM AUTHOR]

Methane pyrolysis has emerged as a promising low-carbon hydrogen production method, serving as a bridge from conventional fossil fuels to renewable energies (REs). A recent technique for sustainable hydrogen production involves the process of methane pyrolysis in molten salt. To better understand the potential of sustainable turquoise hydrogen production, this paper presents a techno-economic assessment of methane pyrolysis in molten salt combined with a high-temperature heliostat solar field. In addition, a high-temperature thermal energy storage (HTES) unit is utilized to ensure uninterrupted hydrogen production during periods of solar unavailability, thereby contributing to the economic viability of the overall system. The proposed system can produce about 9 tons of H 2 /day and 27 tons of solid carbon/day with a round-trip efficiency of 49.8 % and a levelized cost of hydrogen (LCOH) of 1.93 $/kg. To further decarbonize the process, the feasibility of utilizing REs as the source of electricity for the HTES was analyzed, yielding a synergistic achievement of clean and economic hydrogen production. This configuration resulted in a LCOH of 1.25 $/kg, after including the United States (US) clean hydrogen production tax incentives. The proposed system shows the potential to achieve the US Department of Energy target of 1 $/kg of hydrogen with a 20 % reduction in the cost of RE infrastructure. • Proposing a novel design for methane pyrolysis in molten salt based on heliostat solar field. • Utilizing high-temperature thermal energy storage for continuous hydrogen production. • Performing a comprehensive techno-economic analysis by including clean hydrogen tax incentives. • Reaching a hydrogen cost of 1.25 $/kg by incorporating the US clean hydrogen tax incentives. • Achieving the target of hydrogen shot (1 $/kg of H 2) through a 20 % reduction in the cost of RE infrastructure. [ABSTRACT FROM AUTHOR]

• •Development of an enhanced hybrid model for multi-hour ahead DNI forecasting. • •Comprehensive performance analysis using four different DNI databases. • •Implementation of the GA-GOA Algorithm for CSP Optimization. • •Assessment of electricity generation from CSP plants for multi-hour ahead forecasting. This study addresses the critical need for precise Direct Normal Irradiation forecasting in concentrating solar power systems to enhance performance and manage power generation intermittency. We propose a novel hybrid model that combines Variation Mode Decomposition, Swarm Decomposition Algorithm, Random Forest for feature selection, and Deep Convolutional Neural Networks, aiming to improve the forecasting accuracy. This model covers the entire process from Direct Normal Irradiation forecasting to heliostat field optimization and electricity generation. We validated the model across four globally diverse regions, taking into account their distinct climates and meteorological conditions. The results show that our model aligns closely with actual measurements and outperforms existing forecasting methods in terms of precision and stability. The forecasting performance was assessed using normalized Root Mean Square Error, with results ranging from 0.75% to 3.4% across different regions. This demonstrates the model's potential for real-world application in concentrating solar power systems, optimizing heliostat field effectiveness, and reliably forecasting electricity production for grid management. [ABSTRACT FROM AUTHOR]

• A gap between heliostat facets increases load coefficients. • Heliostat facet aspect ratio increases the effect of gap spacing on coefficients. • Facet gap spacing changes the centre of pressure. • Maximum coefficients shift within CSP operating ranges as gap spacing increases. • Gap effects should be considered in heliostat design, and experimental modelling. Multi-facet heliostats are more versatile and advantageous in design compared to single facet heliostats, while generating new design challenges. Multi-facet designs can reduce manufacturing costs, allow for decentralisation of power supply, and bring the option of face down stow. Addition of a gap between two facets, changes the flow structure around the heliostat. The effect of gap between two heliostat facets is therefore investigated on wind loads through experimental investigation in a large wind tunnel. A heliostat model was placed in a simulated atmospheric boundary layer at The University of Adelaide wind tunnel. The investigation covered gap ratios between two panels (gap spacing/facet width) from 0 to 2, and panel aspect ratios (facet width/chord length) of 0.35 to 0.65, forming a complete heliostat aspect ratio of 0.7 to 1.3 with no gap. Wind load coefficients were determined using load cell measurements at the base, and application of differential pressure sensors on the surface, of the heliostat model. Findings indicate the presence of a gap, in general, increases the wind load on the heliostat, with facet aspect ratio exacerbating the results. The maximum load cases shift further into the operating range of heliostats where a change in centre of pressure, due to a change in gap ratio, shifts maximum coefficients from an elevation angle of 30° to 45° for lift force and hinge moment, and 90° to 75° for azimuthal moment. Increasing loads on elevation and azimuth drives potentially increases tracking deviations and beam misalignment, reducing concentrated solar power plant performance. [ABSTRACT FROM AUTHOR]

• The receiver aperture of the SPT system is idealized to be the outer surface of a cone. • Spatial distribution of the optically feasible region of the field for an SPT system. • Incremental change in the optical performance with latitude. • A simplified methodology for preliminary estimation of annual optical efficiency of solar tower system. The proper prediction of the optical performance of the Solar Power Tower (SPT) system is a critical requirement. In this study, the heliostats are assumed to be negligibly small in dimension compared to the inter-heliostat distance, and the receiver aperture is idealized to be the outer surface of a cone. The receiver aperture is represented using the tilt angle. The interception efficiency of a heliostat could be predicted with the help of the ratio of the receiver aperture slant height to the heliostat characteristic diameter and the tilt angle of the receiver aperture. The cosine and the attenuation efficiency factors have also been estimated, but, the shading and blocking factors have not been considered. The outcome of the numerical analysis showed that the optical performance potential of a field location is strongly dependent on the tilt angle of the receiver aperture. The optimum value of the tilt angle of the receiver aperture was seen to vary with the latitude and the tower height. In general, the optical performance of the heliostat field improved with the increase in the tower height and an increase in the ratio of receiver aperture slant height to heliostat characteristic diameter. But, the results also indicated that the degree of improvement in the optical performance due to a tall tower is a strong function of the latitude. Also, increasing the receiver aperture slant height relative to the heliostat characteristic diameter beyond a certain limit failed to enhance the optical performance by any significant extent. [ABSTRACT FROM AUTHOR]

• The effects of heliostat aspect ratio and ground clearance ratio on the wind loads were investigated. • The results show that the heliostat aspect ratio does not significantly affect drag/lift coefficients. • The results show that increasing the ground creance ratio causes an increase in the overturning/hinge moment coefficient. The impact of heliostat aspect ratio (AR) and ground clearance ratio (GR) on static wind load coefficients has been studied in this article. Wind tunnel experiments were undertaken at Thebarton wind tunnel at the University of Adelaide. A high-frequency load cell was used to measure the forces and moments on heliostat models with five AR ranging from 1 to 2, four different pylon hinge heights (0.1 ≤ GR ≤ 1) and elevation angles from 0° to 90° at a constant azimuth angle of zero degrees. The results show that increasing AR does not have a significant impact on drag and lift coefficients, but increases hinge moment, and the overturning moment coefficient by up to 55 % compared with a square heliostat. The results also indicate that for an approximately constant GR, increasing AR causes a reduction in drag and overturning moment coefficients, and lift coefficients for AR ≤ 1.5. The effects of GR show that drag coefficient is approximately constant with GR while the lift coefficient increases slightly. It also indicates that increasing GR causes increased overturning moments coefficient and hinge moment coefficients by up to 40 % and 30 %, respectively. Finally, increasing the hinge height of heliostat result in increase in lift coefficient, overturning moment and hinge moment coefficients. [ABSTRACT FROM AUTHOR]

In this study, two wind-solar-based polygeneration systems namely CES-1 and CES-2 are developed, modeled, and analyzed thermodynamically. CES-1 hybridizes a heliostat based CSP system with wind turbines while CES-2 integrates heliostat-based CPVT with wind turbines. This study aims to compare the production and thermodynamics performance of two heliostat based concentrated solar power technologies when hybridized with wind turbines. The systems have been modeled to produce, freshwater, hot water, electricity, hydrogen, and cooling with different cycles/subsystems. While the overall objective of the study is to model two polygeneration systems with improved energy and exergy performances, the performances of two solar technologies are compared. The wind turbine system integrated with the comprehensive energy systems will produce 1.14 MW of electricity and it has 72.2% energy and exergy efficiency. Also, based on the same solar energy input, the performance of the heliostat integrated CPVT system (CES-2) is found to be better than that of the CSP based system (CES-1). The polygeneration thermal and exergy efficiencies for the two systems respectively are 48.08% and 31.67% for CES-1; 59.7% and 43.91% for CES-2. Also, the electric power produced by CES-2 is 280 kW higher in comparison to CES-1. • Design of two comprehensive energy system to achieve better energy and exergy performance. • Thermodynamic modeling of two systems for hydrogen, hot water, electricity, and cooling production. • Comparison of heliostat CPVT and CSP system performance with the same input solar energy. [ABSTRACT FROM AUTHOR]

• 3 novel biomimetic surrounding heliostat field layouts are proposed for solar tower. • Parameters of new layouts are optimized, and optimal results are obtained. • Biomimetic layout with linear increasing factor has the best optical performance. • Receiver's annual incident energy is raised by 1.5% compared with staggered layout. • Receiver's peak heat flux and stress are decreased by 4.2% and 4.3%, respectively. Three gradually sparse biomimetic (GSB) heliostat field layouts, which gradually extend from the inside to the outside, are proposed herein. Annual optical performance is compared with the standard biomimetic (SB) layout and the widely used staggered layout. In the end, the receiver's optical-thermal–mechanical performance is analyzed with the above five heliostat fields for the next-generation solar power tower (SPT) with the receiver's outlet temperature at 720 °C. The results show that the GSB layout with a linear increasing factor (Linear-GSB) has the best optical performance. Compared with the staggered layout and the SB layout, the Linear-GSB layout can increase the annual intercepted energy (E ann) by 1.5% and 1.3% under the same heliostat number, respectively. Moreover, GSB layouts can simultaneously reduce the receiver's maximum heat flux (q max), maximum thermal stress (σ w,max) and improve its heat flux distribution homogeneity. Compared with the staggered layout, q max , σ w,max , and heat flux maldistribution index of the receiver under the Linear-GSB layout at noon of spring equinox are decreased by 4.2%, 4.3%, and 19.8%, respectively. Meanwhile, the Linear-GSB layout can achieve slightly higher receiver efficiency compared with the staggered layout. [ABSTRACT FROM AUTHOR]