Coordinated event-based defocusing MPC for parabolic trough concentrated solar power plants in grid ancillary services

An intelligent framework for performance enhancement of a parabolic trough solar collector in solar aircraft using tangent hyperbolic hybrid nanofluid

Numerical investigation of the performance analysis of mono and hybrid nanofluids in a parabolic trough collector integrated with an Organic Rankine cycle

ABSTRACT Enhancing the thermal efficiency of parabolic trough solar collectors (PTCs) is vital for optimizing concentrated solar power systems and industrial solar thermal applications. Conventional receiver tubes often suffer from limited internal heat transfer and uneven solar flux distribution, reducing energy conversion efficiency. This study presents a comprehensive numerical investigation of PTC receivers with modified tube geometries ‐circular, elliptical, and hexagonal‐integrated with internal helical turbulators. Optical performance was evaluated using Monte Carlo Ray Tracing (MCRT) to determine solar flux distribution and identify optimal receiver eccentricities, while thermal–hydraulic behavior was assessed via computational fluid dynamics (CFD) simulations over Reynolds numbers from 3000 to 11,000. Optimal eccentricities were determined as −12, −8, and −12 mm for circular, elliptical, and hexagonal tubes, respectively. The elliptical tube achieved the highest optical interception, with an average intercept factor of 80.13%. The introduction of helical turbulators significantly enhanced heat transfer, increasing Nusselt numbers by 31%, 45%, and 46% for circular, elliptical, and hexagonal tubes, respectively. Corresponding friction factor ratios ranged from 1.6 to 2.0, highlighting the trade‐off between heat transfer improvement and flow resistance. Overall, the elliptical receiver with a small‐pitch helical turbulator delivered the best combined thermo‐optical performance.

Solar-integrated blue hydrogen production with optimized post-combustion carbon capture: A techno-economic and exergoeconomic assessment

A review on different profiles of absorber tube in parabolic trough solar collectors

Thermo-hydraulic assessment of flat-tube parabolic trough receivers under realistic non-uniform solar flux

Improving the performance of parabolic trough collectors using waste material-based turbulence enhancers and artificial intelligence-supported models

Thermal and exergy performance enhancement of a parabolic trough solar collector using twisted tape inserts

Parabolic Trough Collector (PTC) is one of the most widely used solar thermal technologies for harnessing solar energy efficiently. Heat transfer enhancement within PTCs is crucial to increase their overall thermal performance and energy conversion efficiency. This study presents a comprehensive bibliometric analysis of research on PTC enhancements, highlighting key trends, influential studies, and global contributions in this domain. The analysis identifies significant research clusters, collaborations, and the evolution of heat transfer improvement techniques over the years. Furthermore, this paper presents various passive and active techniques employed to enhance heat transfer in PTCs. Advanced active enhancement techniques for PTCs include integrating PV panels or thermoelectric generators for combined heat and power production, as well as using electromagnetic fields or ultrasonic waves to improve fluid flow and heat transfer. Additionally, forced circulation through pumps or mechanical stirring enhances thermal uniformity. Passive techniques, including inserts (wire coils, twisted tapes, and helical fins) and surface modifications (dimples, corrugations, and metal foams), are widely investigated for increasing turbulence and augmenting heat transfer rates. Additionally, different absorber tube geometries, such as U-shaped tubes, S-curved tubes, and cavity-based designs, have been explored to reduce thermal losses and enhance heat retention. Moreover, researchers have focused on hybrid techniques that combine multiple enhancement methods for superior performance. These include the integration of nanofluids with modified absorber tube geometries or the use of inserts alongside enhanced HTFs. Such combined approaches leverage the benefits of each individual technique to achieve greater efficiency improvements. Although several review papers exist on heat-transfer enhancement in PTCs, none of them provide a quantitative, data-driven overview of how research in this field has evolved. The rapid growth of publications on PTC enhancement techniques makes a structured bibliometric assessment necessary to identify trends, influential works, and global research dynamics. However, existing reviews do not provide a dedicated bibliometric assessment of heat-transfer enhancement methods in PTCs, leaving gaps in identifying research trends and underexplored techniques. The findings of this study provide a structured overview of past and current advancements in PTC heat transfer enhancement, offering valuable insights for future research directions. By analysing bibliometric data and reviewing enhancement techniques, this paper serves as a guideline for optimizing PTC designs to achieve higher thermal efficiency and energy output in solar thermal applications. However, existing reviews do not provide a dedicated bibliometric assessment of heat-transfer enhancement methods in PTCs, leaving gaps in identifying research trends and underexplored techniques. • A bibliometric analysis is conducted to map research trends in heat transfer enhancement for PTCs. • The paper provides a detailed evaluation of fins, inserts, nanofluids, and absorber tube geometry modifications for enhancing heat transfer in PTC • Combined methods show promising results in maximizing efficiency while managing pressure loss.

The hydrothermal performance of Parabolic Trough Collector (PTC) system is strongly governed by the absorber-tube design. This study numerically optimizes geometrical features of an absorber tube to enhance conjugate heat transfer to the Heat Transfer Fluid (HTF) while limiting hydraulic losses. Rectangular fins are installed inside the absorber tube, and a novel axial sectioning concept is introduced in which the tube is divided into three equal-length sections. Taking the first section as a reference, the second and third sections are rotated by a sectional angular shift (γ) in the clockwise and counterclockwise directions, respectively, to promote controlled flow redistribution. The geometric design factors fin height (H), circumferential fin placement angle (β), and sectional angular shift (γ) are varied at four levels. A Taguchi L16 orthogonal array is employed to efficiently sample the design space. Thermal efficiency (η th ) and the Performance Enhancement Coefficient (PEC) are used to assess thermal and hydrothermal performances, respectively. Response Surface Methodology (RSM), supported by ANOVA and Pareto analysis, is applied to identify optimal configurations and statistically significant parameters. The fin height is identified as the most significant parameter, enhancing thermal performance through enhanced surface area, followed by the angular parameters β and γ, which contribute to improved flow mixing and mitigating local hot spots. Maximum thermal efficiency (68.28%) occurs at γ = 30°, β = 45°, and H = 20 mm, while the highest PEC (1.25) is obtained for the same geometry except β = 60°, yielding a 22.54% heat-loss reduction over the smooth tube.

• An open-source co-simulation framework (ASDELSOL) was applied to optimize retrofitted CSP/PV/eTES plant operation using real market pricess. • The techno-economic impact of PV ratio, electric heater capacity and auxiliary tank volume was quantified for three hybrid configurations. • Electric heaters and auxiliary storage enhance flexibility, but their CAPEX limits NPV gains within a 12-year horizon. This study evaluates the techno-economic viability of retrofitting Concentrated Solar Power (CSP) plants with Photovoltaics (PV) and Electric Thermal Energy Storage (eTES)—thermal storage charged via electric heaters—to enhance dispatchability and profitability under current market conditions. Using the dynamic tool ASDELSOL, a predictive control strategy combines daily solar-resource classification with hourly electricity-price segmentation. Three configurations are assessed: (1) CSP + PV; (2) CSP + PV with a direct electric heater to TES; and (3) CSP + PV with an electric heater feeding an auxiliary thermal tank. In Scenario 1, baseload operation is benchmarked against price-driven optimization; the latter raises Net Present Value (NPV) across all PV ratios, peaking at €36.86 M for 25% PV. Scenarios 2–3 are analyzed under economic optimization, quantifying the influence of heater sizing and auxiliary-tank volume. While these components increase operational flexibility, their added cost does not pay back within 12 years; extending the investment horizon shifts the optimum toward higher PV ratios and improves the appeal of more integrated layouts. Overall, CSP–PV retrofits operated with market-responsive control are cost-effective, and adding electric heaters plus auxiliary storage can yield additional value under favorable market and investment assumptions.

This work presents a numerical investigation of the thermo-hydraulic performance of a tube-bundle cavity (TB)receiver for parabolic trough collectors (PTCs). The proposed receiver replaces the conventional single absorbertube with multiple smaller tubes arranged in a circular bundle, forming a linear cavity that improves solar absorptionand reduces temperature non-uniformities on the absorber surface. A three-dimensional CFD model isdeveloped under real-scale operating conditions to assess several TB configurations through a two-stage optimizationprocedure. The designs are evaluated using thermal efficiency, pressure drop, and overall efficiencymetrics. The results indicate that, despite higher flow resistance, TB receivers significantly enhance thermalperformance compared to the conventional design. Hotspot temperature increases are reduced by up to 77%,while temperature uniformity increases by approximately 23%. Among the investigated configurations, the 12-tube design provides the best thermo-hydraulic compromise, achieving a maximum overall efficiency of 0.76 atan inlet temperature of 450 K, corresponding to a 7% improvement over the standard receiver. Additional analysesover inlet temperatures ranging from 400 to 550 K confirm the robustness of the optimized TB configurationin mitigating hotspot formation while maintaining superior overall performance.

Green hydrogen is recognized as a critical energy carrier for deep decarbonization, yet many production pathways remain reliant on fossil fuels or conventional photovoltaic electrolysis. This study presents a comparative performance assessment of a solar thermal-driven hydrogen production system integrating an organic Rankine cycle (ORC) with an alkaline electrolyzer. The proposed configuration comprises solar thermal collectors, a pressurized sensible heat storage tank, an ORC power unit, and an electrolyzer. A dynamic MATLAB-based simulation framework was developed to evaluate eight system configurations under identical meteorological conditions over a full year of hourly operation. The investigated scenarios examined the combined effects of collector technology (evacuated tube vs. parabolic trough), ORC working fluids (R245fa and n-pentane), and system sizing parameters. Performance was assessed based on annual hydrogen yield, overall solar-to-hydrogen efficiency, and productivity per unit collector area. The optimal configuration—employing parabolic trough collectors, an R245fa working fluid, a 180 m 2 collector field, and an 8 m 3 storage tank—achieved an annual hydrogen production of 752.8 kg·year − 1 (4.705 kg·m − 2 ·year − 1 ), corresponding to 25,094 kWh·year − 1 of hydrogen energy output. The overall solar-to-hydrogen efficiency reached 7.03%, with a solar-to-ORC efficiency of 10.2%. Results underscore the critical role of thermal availability and storage stability in enhancing ORC operating hours and hydrogen yield, demonstrating the viability of solar thermal ORC–electrolyzer systems for sustainable hydrogen production in high-insolation regions.

Parabolic trough solar collectors (PTSCs) are a mature concentrating solar technology, but their performance is limited by solar intermittency. Integration with phase change materials (PCMs) can mitigate this limitation, yet conventional PCMs suffer from low thermal conductivity. Nano-enhanced PCMs (NePCMs) offer improved heat transfer, but most existing studies rely on simplified transient models and lack comprehensive annual performance assessment under realistic climatic conditions. To address this gap, this study develops a fully transient optical–thermal–phase-change model to investigate the annual performance of a PTSC integrated with NePCM. The coupled governing equations are discretized using a semi-implicit finite-difference scheme, while the melting and solidification processes are captured via a Stefan moving-boundary formulation and solved iteratively using a Gauss–Seidel algorithm. Hourly climatic data for Yazd (8760 h) are applied to resolve seasonal and diurnal variations. The results show that adding aluminum oxide (Al 2 O 3 ) nanoparticles significantly enhances system performance: at 1 wt% concentration, the annual thermal efficiency increases by 10% (to 52%) compared to pure paraffin, and the annual exergy efficiency reaches 31% (an improvement of 15% over the baseline). Monthly useful energy output rises to 440 kWh, and the levelized cost of heat is reduced to 0.085 $/kWh th , yielding the minimum payback period of about 5.2 years. Although the 3 wt% case achieves the highest instantaneous and monthly energy output (up to 470 kWh/month) and Carbon Dioxide (CO 2 ) avoidance (peaking at 120 kg/month), its economic performance deteriorates due to higher material costs. Overall, the results demonstrate that a 1 wt% nanoparticle loading offers the most favorable balance between thermodynamic performance, environmental benefit, and economic feasibility.

In humid climates, effective moisture control is essential for thermal comfort and reducing building cooling loads. This study experimentally evaluates a solar-regenerated solid desiccant cooling system integrated with an indirect liquid-to-air heat exchanger. The system uses a parabolic trough collector and a modified evacuated tube receiver for regeneration. Performance was analyzed under varying regeneration temperatures (60–90 °C), cooling water flow rates (50–125 liters/hour), desiccant wheel speeds (5–25 revolutions/hour), and ambient conditions. Results show that increasing regeneration temperature enhanced dehumidification by 27%, reducing humidity ratio from 18.5 to 13.5 g/kg, but also raised desiccant exit air temperature from 44 °C to 50 °C. Higher water flow maintains supply air temperatures 8–13 °C lower than at lower flow. Faster wheel speeds improved moisture removal (20.3 to 15 g/kg) but increased supply air temperature by 5.7 °C at 80 °C. Coefficient of performance (COP) improved with regeneration temperature and wheel speed, though exergy efficiency declined by 41% at high speeds. Optimal performance occurred at 80 °C regeneration, 100–125 liters/hour cooling flow, and 15–20 revolutions/hour wheel speed, achieving 0.67 COP and 31% exergy efficiency. Further, the potential of passive desiccant cooling was also confirmed through energy and exergy analysis, demonstrating the system’s viability as an energy-efficient solution for hot-humid regions, aligning with sustainable cooling demands.

This investigation involves a numerical simulated combined Monte Carlo Ray Tracing (MCRT) method and Computational Fluid Dynamics (CFD) modeling within a modified parabolic trough solar collector, incorporating a novel design of inserted fins in the absorber tube. The primary objective behind integrating these fins into the absorber tube is to enhance the efficiency of the heat transfer process. Tri-dimensional simulations are conducted to thoroughly analyze fluid dynamics, model the physical process and especially analyze the effect of varying geometric and operating conditions. The proposed innovative configurations offer better temperature distribution than the smooth absorber tube where the inserted fins ensure adequate fluid flow mixing between the hot tube wall (exposed to concentrated heat flux) and the lower temperature tube (face exposed only to direct irradiation). The effect of the inserted fins spacing on the thermal performance of the Parabolic trough collector (PTC) is deeply studied and results are compared to that of conventional PTC’s tube. After identifying the optimal configuration and determining the appropriate fins spacing value, the corresponding configuration was retained and a new approach was applied. Indeed, various fin arrangements were examined and the better configuration, that presents lower pressure losses, was evaluated. This parametric study clearly shows the advantage of the use of internal fins in the region where the flow is fully developed. PTC system studied (a) and different designs of the fins equipped receiver (b).

This study presents an experimental analysis of thermal energy storage (TES) system at high temperatures combined with a parabolic trough solar collector. The system utilizes solar salt (NaNO₃–KNO₃ eutectic) for thermal storage and a graphene–TiO₂/ethylene glycol hybrid nanofluid as the heat transfer medium. The main aim is to assess the impact of the hybrid nanofluid on the charging and discharging performance in outdoor solar operating conditions. A 100-L TES tank with 360 sealed solar saltmodules was charged with an average thermal input of 2.3 kW provided by the solar collector. The temperature changes along the axis during charging and discharging were tracked with several thermocouples. The findings demonstrate enhanced heat transfer during charging, decreased thermal layering close to the melting point of solar salt, and prolonged heat-release time during discharging with the application of the hybrid nanofluid. The system's charging efficiency, discharging efficiency, and round-trip efficiency were 48.6%, 81.6%, and 39.6%, respectively. The results indicate the capability of hybrid nanofluid-assisted heat transfer to improve the thermal performance of molten-salt-based TES systems used in concentrated solar powerapplications.

• Techno-economic analysis of an air-fed PTC solar system for industrial process. • Innovative dual rock bed thermal energy storage for continuous heat supply. • Parametric analysis of concentrated solar thermal system for a real case-study. • Lowest LCOH of 4.5c€/kWh, competitive with industrial natural gas costs. • Sustainable energy solutions supporting industrial decarbonization. Parabolic trough collectors are a mature and reliable technology for integrating solar energy into industrial heat supply. The proposed system combines an air-fed parabolic trough collectors solar field with a thermal energy storage composed of two parallel rock beds. This configuration is an innovative solution that ensures continuity in both solar energy collection and thermal load delivery. A dedicated control strategy is designed to efficiently manage the charging and discharging phases of the two tanks. Due to the variability of solar energy, a long-term dynamic analysis was performed to accurately assess system performance. The plant was evaluated through a dynamic energy analysis and an economic assessment based on a case study of an air-based pasta drying plant with a nominal thermal load of 120 kW th . A parametric study was carried out by varying the solar field size and layout, as well as the storage capacity, in order to determine their influence on energy performance and the Levelized Cost of Heat (LCOH). The results indicate a maximum solar fraction of 86.71%, while the lowest LCOH obtained is 5.0 c€/kWh, corresponding to an energy saving of 48.6%. A sensitivity analysis complemented the outcomes. The study demonstrates the strong energy and economic potential of this innovative solar thermal system.

Off-design modeling of radial turbines and system-level optimization for transcritical CO2-based mixture power cycles in parabolic trough CSP plants