Concentrating solar power plants can store heat in large beds of hot particles, then release that heat on demand to run a supercritical CO2 power cycle. The hard part is the heat exchanger that transfers heat from the particles to the CO2: it has to deliver CO2 to the turbine above 700 °C at 20 MPa, and do it cheaply. Recent moving packed-bed and fluidized-bed designs have reached overall heat transfer coefficients below 400 W/m²K. At that performance, you need a lot of surface area made from expensive nickel-based alloys, which pushes cost above the targets set for next-generation CSP. Fluidized beds transfer heat from particles to walls better, but the particles mix back and forth along the flow direction (axial dispersion), which flattens the temperature profile, shrinks the log-mean temperature difference, and cuts the heat actually delivered to the CO2. This study shows that adding fins to the walls of a narrow fluidized-bed channel raises the effective bed-to-wall heat transfer coefficient and suppresses that axial mixing at the same time. A reduced-order model built on experimentally derived correlations explores what those gains mean for full heat exchanger designs. The result: overall heat transfer coefficients above 1000 W/m²K, suggesting a route to affordable particle-to-CO2 heat exchangers.
In parabolic trough solar power plants, flexible pipe connectors, specifically Rotation and Expansion Performing Assemblies (REPAs), are critical yet failure-prone components due to their exposure to thermal cycling, mechanical stress, and harsh environmental conditions. This study focuses on the Rotary Flex Hose Assembly (RFHA), one common REPA type. Unexpected RFHA malfunctions, such as leaks in swivel joints, can lead to costly downtime and safety hazards. Despite regular preventive maintenance, current strategies often fail to anticipate such failures early enough to prevent disruption. This study investigates whether vibration analysis, combined with machine learning, can provide early warnings of RFHA degradation. A convolutional neural network (CNN) was trained to detect pre-failure conditions using spectrogram comparisons derived from high-frequency vibration data collected during an accelerated life-cycle test campaign. Structural Similarity Index (SSIM) values were used to quantify differences between twin RFHA vibration patterns over time. The model successfully predicted failures up to 1,000 cycles in advance, equivalent to more than two years of lead time in field operation, achieving an overall accuracy of 0.93 and a precision of 1.0, indicating that all predicted failure events were correct and no false positive alarms were generated. These results demonstrate that SSIM-based vibration comparison and CNN classification can provide a robust foundation for predictive maintenance of RFHAs, offering a scalable solution for enhancing the reliability of CSP plant operation.
The integration of solar heat into industrial processes (SHIP) has become an essential step toward achieving decarbonization and improving energy efficiency in industrial sectors [1]. IDAE guide, developed by the Protermosolar association in collaboration with leading experts in the field of SHIP design [2], provides a comprehensive overview, showing current developments, highlighting key solar thermal technologies such as Linear Fresnel Reflectors (LFR), Parabolic Trough Collectors (PTC), and Solar Towers (ST), with a focus on their application in different temperature ranges and process heat requirements. Showing real cases and studies, at different temperatures, storage, applications. Jointly with hybridization potential analysis.
The overall performance of central receiver CSP plants highly depends on the design of the solar field and the receiver. The high computational cost of Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA) and raytracing simulations to evaluate the performance of these systems limits the feasibility of using such detailed simulations in coupled optimization schemes. As a result, coupled optimization approaches commonly use correlations and heuristic optimization methods instead of detailed, high-fidelity simulations for quick performance evaluations to enable an optimization loop and iteratively optimize the solar field and the receiver towards a coupled optimum. Although such correlations enable quick performance evaluations, they are often not very precise and only valid for a specific range of boundary conditions. Therefore, this study proposes the integration of Reduced-Order-Models (ROM) based on a limited set of high-fidelity training data points into the coupled optimization framework as an alternative to empirical correlations for receiver performance predictions. In this work, convective and radiative ROMs of a theoretical central tower cavity receiver have been successfully built, and a validation study showed very good estimation performance of 1,19% and 4,47% using the original data tensor consisting of 243 training data points. Theoretically reducing the training data set to 32 resulted in a noticeable increase of estimation error to 5,39% and 9,1%, but also a significant reduction in required training points. Once the ROM has been built, the performance evaluation of a single design point requires approximately tROM,i ≈ 0,06s, which is comparable to the time typically required using empirical correlations. Overall, the results demonstrate that data-driven ROMs provide a promising intermediate modeling approach between purely empirical correlations and fully resolved high-fidelity simulations.
The successful operation of solar thermal plants requires a distributed control system (DCS) that is built with a combination of controls expertise and input from subject matter experts to define requirements that the control system must satisfy. This work describes the distributed control system for the Generation 3 Particle Pilot Plant (G3P3) at Sandia National Laboratories and the procedure used to design and achieve the associated control requirements. Automation and supervisory control logic plays an integral role in the G3P3 DCS due to the high number of controllable components and feedback signals that indicate the systems state-of-health at any moment. The implementation and testing of these key components will be shown and discussed in detail in this work.
Achieving full decarbonization of the energy sector — in which approximately two thirds of total demand corresponds to thermal energy and one third to electricity — constitutes one of the most complex yet imperative challenges facing contemporary society. Concentrated Solar Thermal (CST) technologies have demonstrated a well-established capacity to deliver both clean thermal energy and electricity with high efficiency, while also showing considerable potential to complement other renewable energy sources in a cost-effective manner. In light of this, a sustainable energy future that does not incorporate a substantial contribution from CST systems appears highly unlikely. The application of CST systems to supply the industrial sector with clean thermal energy — internationally referred to as Solar Heat for Industrial Processes (SHIP) — has already reached a competitive standing relative to conventional energy sources in numerous regions worldwide. This growing competitiveness is driving significant expansion of SHIP installations, particularly in countries endowed with favorable solar resources. SolarPACES international conferences stand as the foremost global forums for the dissemination and discussion of advances in CST- related research and technology. A community that I am proud to belong to because we have a long-standing tradition of fostering excellent relationships among its members, regardless of culture, politics, or religion. With 43 years of activity since its inauguration in 1982, the conference has become the world's reference event for the CST community, consistently proving highly effective in convening stakeholders from across the sector — including researchers, industry representatives, and policy makers — to share experiences, exchange knowledge, showcase cutting-edge innovations, and foster collaborative research initiatives aimed at enhancing the competitiveness and broader deployment of CST technologies. In view of the current state of CST commercialization, this year's edition proved to be of considerable relevance to the field, as participants gathered in Almería to contribute innovative perspectives on cost reduction strategies, performance optimization, and the extension of operational lifespans. The SolarPACES 2025 International Conference took place from 23 to 26 September 2025 in Almería, Spain. On this occasion, more than 520 experts and delegates from 40 countries convened at the Palacio de Congresos y Exposiciones of Almería. The Conference featured a rich and diverse technical programme comprising 4 plenary sessions with 10 keynote presentations and 3 roundtable discussions, 44 technical sessions encompassing 215 oral presentations, and 292 poster contributions. The scientific programme was further complemented by two technical visits: one to the commercial CSP plant Andasol-3 (Marquesado Solar) and another to the facilities of the Plataforma Solar de Almería, the world's largest public research and development center dedicated to CST technologies. The participants were welcomed during the opening session by distinguished authorities, among whom were the Spanish Secretary General for Research of the Ministry of Science, Innovation and Universities, Eva Ortega Paíno, and the Policy Officer at the Directorate-General for Research and Innovation of the European Commission, Marina Montero Carrero, both of whom underscored the crucial role of CST among the key energy technologies identified by the European Union in pursuit of its ambitious climate objective of achieving carbon neutrality by 2050. This volume compiles the full papers submitted upon being presented at the conference, and successfully completed the review process for the SolarPACES 2025 Conference Proceedings. The contributions span across all 17 conference topics, collectively addressing a broad and comprehensive range of current issues in the field of CST technologies. Among these, the topics that attracted the greatest number of contributions were, “Thermal Energy Storage Materials, Media, and Systems”, “Analysis and Simulation of CSP Systems”, and “Measurement Systems, Devices, and Procedures”. This distribution clearly reflects the primary research trajectories that the CST community has been pursuing in recent years, and points to the directions in which the technology is expected to evolve in the coming decades. The papers gathered in this volume represent a meaningful step forward in advancing the technological and economic performance of CST technologies, and are expected to contribute actively to their further development and wider deployment across the energy sector. Each contribution reflects the dedication and expertise of its authors, whose work is essential to the continued progress of this field. I wish to extend my sincere and deepest appreciation to all of them, as well as to the members of the organizing committee, whose efforts and commitment were instrumental in bringing this Conference to fruition. My gratitude equally extends to all participants, whose engagement and valuable contributions made this event a truly enriching scientific and professional experience.
Heliostats are frequently exposed to wind loads during operation, and specific pitch–azimuth angle combinations can critically affect structural stability, tracking accuracy, and power generation efficiency. This study investigates the aerodynamic characteristics of a single heliostat under various pitch–azimuth configurations through wind tunnel experiments. The mean values and probability distributions of drag, lift, and hinge moment coefficients were analyzed, distinguishing Gaussian from non-Gaussian regions. Results show that heliostat wind loads strongly depend on pitch–azimuth combinations, with certain attitudes amplifying aerodynamic forces. The rear support structure enhances turbulence, leading to pronounced non-Gaussian behavior under low pitch–high azimuth and high pitch–low azimuth conditions. Aerodynamic coefficients exhibit kurtosis-dominated non-Gaussian distributions at extreme azimuth angles, while hinge moment coefficients transition to kurtosis- and skewness-dominated distributions under high azimuth. These findings highlight that unfavorable pitch–azimuth configurations significantly increase the probability of extreme loads. To ensure accurate peak load estimation in heliostat wind-resistant design, it is essential to account for these adverse aerodynamic conditions in structural evaluation.
This study presents a numerical and economic evaluation of a novel structured thermal energy storage (TES) system using recycled ceramic structured material with internal flow channels. The performance of this system is compared with a conventional packed-bed configuration composed of natural rocks and sand. An unsteady one-dimensional numerical model is developed to simulate heat transfer and fluid flow, with varying design parameters such as the tank aspect ratio and the channel diameter in the structured configuration. All cases assume a fixed bed tank volume of 18,380m³. Results show that low aspect ratios enhance energy accumulation in structured configurations due to the larger tank diameter, which reduces the fluid velocity inside the channels and increases residence time, thereby improving heat transfer and thermocline thickness. Structured TES configurations with small channel diameters (typically 5 mm) further improve performance, even surpassing packed beds in some cases. However, low aspect ratios penalise economic performance, as the fixed-size buffer and sump regions occupy a larger fraction of the tank volume, increasing the capacity cost (in $/kWh). Packed beds benefit from higher aspect ratios, which improve thermal stratification and reduce capacity cost. The study concludes that ceramic structured TES can achieve competitive or superior capacity costs compared to packed beds when the geometry is properly optimised. Furthermore, structured systems offer the potential to mitigate issues such as thermal ratcheting. Future work will focus on optimising additional parameters such as the void fraction and the charging and discharging cutoff temperature, as well as on experimental validation and system-level cost integration.
The work consists of the design and study of an air-molten salt heat exchanger using different numerical models. The heat exchanger will be built and used on a lab-scale unit that studies the behavior of a lab scale thermal energy storage system. The thermal storage experimental unit is a prototype designed to mimic the behavior of a CSP (Concentrated Solar Power) plants.
This paper presents the development and implementation of a novel approach to spillage recovery devices (SRDs) for high-temperature air-based solar thermal receivers by Odqa Renewable Energy Technologies Ltd. As concentrated solar thermal systems push towards higher operating temperatures to improve efficiency, spillage becomes a significant technical challenge, increasing both in flux and overall fraction of the incident power. Odqa’s air-based receiver design however, leverages heat recovery and regeneration, allowing spillage to be repurposed rather than wasted. This paper investigates the impact of SRDs on some key CST parameters such as aperture size. The first section explores the sensitivity of receiver performance to SRD integration, while the second details Odqa’s approach to developing such a system for a 100kW receiver prototype. The optimized SRD design, tailored to distinct operational conditions, demonstrates the feasibility of such an approach and their potential use as mechanism to increase the overall performance of CST systems cost.
A key aspect for the development of solar thermal technology is to improve cost-competitiveness without compromising efficiency. One of the more expensive items in a solar thermal power plant is the heliostat field, which accounts for 40-50% of the total plant investment. One way to decrease this cost is to reduce the size of the field by improving the efficiency in the thermal exploitation of this concentrated solar radiation. This work presents a novel radial solar receiver design based on compact structures, which allows solar radiation to be absorbed more efficiently by reducing the absorber area and shaping a macroscopic sun trap geometry to reduce heat losses. These compact structures are specially designed to work with pressurised gases, so their coupling to supercritical CO2 power cycles is straightforward. Specifically, the direct coupling to a novel sCO2 cycle is considered, where the heat is supplied in the low-pressure line of the cycle and the CO2 is compressed at low temperature, which reduces the auxiliary consumption, increasing the net efficiency. The advantages of the microchannel radial receiver have been highlighted by a thermo-economic comparison between this receiver and a conventional external receiver, resulting in a significantly lower total plant investment (171 Mio.$ vs. 195 Mio.$). This difference is due to the smaller heliostat field required, due to the improved thermal performance of the novel receiver design compared to the more conventional one.
This paper conducts a numerical investigation of the performance improvement of a Parabolic Trough Collector (PTC) receiver using Computational Fluid Dynamics (CFD) simulations performed in ANSYS Fluent. The study aims to evaluate novel receiver configurations by comparing a conventional receiver (Case 1) with three innovative configurations (Cases 2, 3, and 4), using liquid sodium as the heat transfer fluid (HTF). The model’s accuracy is validated against experimental data and theoretical expressions from the literature. Simulations are performed across various mass flow rates to assess key parameters, including the Nusselt number, friction coefficient, thermal efficiency, and circumferential temperature difference. The results indicate that Case 3 demonstrates the highest thermal performance among the configurations. Specifically, the novel receiver configurations consistently outperformed the conventional receiver. The Nusselt number increased by 29.84%, 126.1%, and 10%; the friction factor rose by 178%, 305%, and 17%; the thermal efficiency improved by 3.6%, 4%, and 3.4%; and the temperature difference decreased by 4.05%, 13.2%, and 1.31% for Confs 2, 3, and 4, respectively. Additionally, liquid sodium significantly enhanced the thermal performance of the PTC due to its superior thermal properties. These findings underscore the effectiveness of the proposed receiver configurations and the advantages of using liquid sodium as the HTF, offering a promising approach to improving PTC efficiency.
Supercritical CO2 power cycles emerge as the next-generation standard for Concentrated Solar Power technology mainly due to their high efficiency and reduced footprint. This study investigates the role of the S-CO2 turbomachinery in an Integrated Solar Combined Cycle, and performs the design and optimization of the geometries to maximize their efficiency using mean-line models. Centrifugal compressors, axial-flow and radial-inflow turbines have been considered. Various geometries are identified to achieve similar high efficiencies, highlighting the need for additional criteria in selecting the optimal design. For this particular combined cycle, the results also reveal that variations in turbomachinery efficiency have a relatively minor impact on overall cycle efficiency, with turbine efficiency exerting a more decisive influence than compressor efficiency.
The use of solid particles in concentrated solar power (CSP) technologies enables operation at elevated temperatures (approximately 1000°C), resulting in improved thermal efficiencies and reduced costs for CSP applications. However, achieving high-temperature operation in particle-based systems presents significant challenges, as all key components must be rigorously evaluated under elevated temperature conditions. In a particle-based CSP system, a substantial amount of heat loss occurs during the handling of particles. Furthermore, as the system's capacity increases, the height of the tower also rises, leading to prolonged travel times for the particles and consequently greater heat loss. King Saud University and Sandia National Laboratories are collaborating on the design, testing, and risk mitigation of a cost-effective particle lift system (PLS) suitable for high-temperature applications. This paper outlines the design basis, sizing methodology, scaling considerations, and ground testing of two different PLS scales.
Concentrating solar power plants are considered an important contributor to renewable energy supply due to their high efficiency and cost-effective storage. Solar tower systems using solid particles as a heat transfer and storage medium, in combination with concentrating photovoltaics (CPV), promise to reduce the levelized cost of energy. This study evaluates the cost potential from hybridizing solar power plants with CPV modules integrated into the radiation shield of a particle receiver, to capture spillage radiation that is otherwise lost. Simulation results for a commercial configuration case show that the annual electricity production could be increased by up to 12%, with levelized cost of electricity from the CPV part ranging from 0.02 to 0.024 €/kWh. The electric components of the CPV subsystem have by far the highest single component cost contribution, the cooling water loop adds a minor contribution. Further improvement options exist and are discussed briefly. A demonstration test in a real receiver application is currently under preparation in DLR’s solar tower test facility. Six CPV modules will be integrated into the radiation shield of a particle receiver. Solar testing will validate the performance and also provide information about potential dust contamination problems.
Soiling is one of the main problems that cause power losses in photovoltaic plants. This article presents a method to determine dirt in a photovoltaic plant using three digital cameras and analyzing the average (Red, Green and Blue) RGB values obtained from each of them. The study also incorporates inclined, global, direct and diffuse irradiance data, as well as suspended particle data PM10, PM2.5 and PM1, where the number indicates the size of the particle in µm. In this investigation, three digital cameras were strategically placed to capture images of the panels at regular intervals. From these images, average RGB values were calculated to quantify the level of dirt on the panels. These values were correlated with solar radiation data, the photovoltaic power of the plant and the concentrations of suspended particles. The results demonstrate that analysis of mean RGB values provides a reliable and non-intrusive method for monitoring fouling in PV plants, contributing to more efficient maintenance strategies and an increase in energy production.
In the joint European project Thermal Energy Storage for On-demand Solar Trigeneration (TES4Trig), an innovative solar driven CCHP (Combined Cycle Heat and Power) system was investigated. The main components of the CCHP system are an Organic Rankine Cycle (ORC) coupled with an Ejector Cooling Cycle (ECC), a solid-state thermal energy storage (TES) syfstem as well as a parabolic trough collector (PTC) field. The system will be demonstrated on-site at the Lavrio Technological and Cultural Park (LTCP) in Attica, Greece [1]. Simulation results of the system for supplying energy to the administrative building of the LTCP are presented. Furthermore, a simulation for a scaled-up system was carried out for a hospital in Heraklion. The results show that the scaled-up system can deliver 10 % of the electricity demand and 39 % of the heat demand with the ORC cycle. The ECC cycle covers 15 % of the cooling requirement. By that, a load factor of 81.4 % over a year is achieved. This can be further optimized by considering other PTC field variables and TES capacities. From an energy perspective, it can be concluded from the results that a TES4Trig system for large electricity, heating and cooling consumers such as a hospital has great potential for the future. It is preferable that the consumer has a continuous energy consumption to maximize system utilization.
It has been demonstrated that heat fluxes greater than 4 MW/m2 can occur at high-flux concentrated solar power (CSP) receivers. In the present paper, a receiver design for additive manufacturing processing is proposed using sodium as heat transfer medium. The proposed design incorporates helical structures within the ducts, which facilitate the swirling motion of the sodium and promote the transportation of the colder coolant towards the heated wall. The objective of this configuration is twofold: first, to enhance heat transfer, and second, to mitigate local overheating at the liquid-solid interface of the receiver. The effectiveness of design variations is substantiated by CFD (Computational Fluid Dynamics) investigations.
This study analyses the integration of concentrating solar energy with a liquid metal reactor for methane pyrolysis, configured as a vertical column. It compares two irradiation strategies: distributing radiation along the entire column height versus focusing it on the middle section. Parameters such as irradiance, total power, methane mass flow, and residence time are assessed. Both configurations present advantages and disadvantages, but designs achieving very high temperatures are preferred over those prioritizing thermal homogeneity. The findings provide insights for optimizing solar reactors for efficient hydrogen production.
This study investigates the integration of third-generation (Gen3) Concentrated Solar Power (CSP) systems with Solid Oxide Electrolysis Cells (SOEC) for green hydrogen (gH2) production in the Atacama Desert, Chile. A 100 MW CSP plant coupled with SOEC systems of varying capacities is modeled to optimize hydrogen production using thermal storage particles at 780°C. The analysis focuses on the techno-economic performance, highlighting the importance of Thermal Energy Storage (TES) capacity. Results indicate that optimal gH2 production occurs with around 10 hours of TES, beyond which additional storage offers minimal benefits. The findings demonstrate that asymmetrical capacity integration between CSP and SOEC systems is economically advantageous, particularly when maintaining a capacity ratio (CR) between 0.01 and 0.2. This integration can potentially exceed the energy demands of the region’s copper mining industry, contributing to significant reductions in fossil fuel reliance and promoting the commercialization of surplus hydrogen.
