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Objectives: Impeded diffusion fraction (IDF) is a novel and promising diffusion-weighted imaging (DWI) technique that allows for the detection of various diffusion compartments, including macromolecular coordinated water, free diffusion, perfusion, and cellular free water. This study aims to investigate the clinical potential of IDF-DWI in detecting microvascular invasion (MVI) in hepatocellular carcinoma (HCC). Methods: 66 patients were prospectively included. Metrics derived from IDF-DWI and the apparent diffusion coefficient (ADC) were calculated. Multivariate logistic regression was employed to identify clinical risk factors. Diagnostic performance was evaluated using the area under the receiver operating characteristics curve (AUC-ROC), the area under the precision-recall curve (AUC-PR), and the calibration error (cal-error). Additionally, a power analysis was conducted to determine the required sample size. Results: The results suggested a significantly higher fraction of impeded diffusion (FID) originating from IDF-DWI in MVI-positive HCCs (p < 0.001). Moreover, the ADC was found to be significantly lower in MVI-positive HCCs (p = 0.019). Independent risk factors of MVI included larger tumor size and elevated alpha-fetoprotein (AFP) levels. The nomogram model incorporating ADC, FID, tumor size, and AFP level yielded the highest diagnostic accuracy for MVI (AUC-PR = 0.804, AUC-ROC = 0.783, cal-error = 0.044), followed by FID (AUC-PR = 0.693, AUC-ROC = 0.760, cal-error = 0.060) and ADC (AUC-PR = 0.570, AUC-ROC = 0.651, cal-error = 0.164). Conclusion: IDF-DWI shows great potential in noninvasively, accurately, and preoperatively detecting MVI in HCC and may offer clinical benefits for prognostic prediction and determination of treatment strategy. [ABSTRACT FROM AUTHOR]

This article introduces a novel analytical equation for computing the Nusselt number within the macroporous structures of channel absorbers utilized in high-temperature solar receivers. The equation incorporates heat and mass transfer processes occurring within boundary layers as fluid flows through complex-shaped macroporous absorber channels. The importance of accounting for the length of the thermodynamic boundary layer within channel-type macroporous media when calculating heat transfer coefficients using the Nusselt equation is demonstrated. By incorporating proposed indicators of porosity and flow characteristics, this method significantly enhances the accuracy of heat transfer coefficient calculations for such media. Discrepancies observed in existing calculation relationships and experiments are attributed to the omission of certain proposed values in the Nusselt number for macroporous media. To address this, empirical coefficients for the Nusselt number are derived using statistical methods. The resulting semi-empirical equation is applied to macroporous absorbers in solar receivers. The findings enable more accurate predictions of future absorber characteristics, enhancing their efficiency. The derived equation is successfully validated against numerical data across various geometric structures of absorbers in concentrated solar power plants. [ABSTRACT FROM AUTHOR]

In this paper, multi-objective optimization of the hydrogen production ( m ˙ H 2 ) of a solar-based cobalt-chlorine (Co–Cl) thermochemical cycle with grey relational analysis (GRA) has been performed. Monthly total irradiance averages (A), wind velocity (B), receiver height (C), receiver radius (D) and number of heliostats (E) are considered to achieve the highest the useful energy absorbed by the solar receiver ( Q ˙ a b s ), efficiency of the receiver (η r e c ), the overall efficiency of the system (η o v e r a l l) and hydrogen production ( m ˙ H 2 ). Orthogonal experimental design is planned according to L 18 orthogonal array created by Taguchi method. The percent contribution rates (PCR) on the Q ˙ a b s , η r e c , η o v e r a l l and m ˙ H 2 are determined with the help of ANOVA analysis. The optimal parameters are identified as monthly total irradiance average of 143.8 kW h (A 3), wind velocity of 5 m/s (B 2), receiver height of 8 m (C 1), receiver radius of 3 m (D 1) and number of heliostats of 850 (E 3), respectively. The highest Q ˙ a b s , η r e c , η o v e r a l l and m ˙ H 2 values corresponding to A 3 B 2 C 1 D 1 E 3 are obtained as 50.2 GW; 64.1%; 22.2% and 122.59 (tons/month), respectively. The PCR of the A, B, C, D and E parameters influencing the f-factor are determined to be 12.6 %, 1.92 %, 0.48 %, 15.03 %, and 53.20 %, respectively. Also, empirical equations are developed with regression analysis (RA) to estimate the Q ˙ a b s , η r e c , η o v e r a l l , m ˙ H 2 values. The statistical coefficients (R2-value) for training and testing data's are determined in the range of 0.771167–0.99608 for Q ˙ a b s , η r e c , η o v e r a l l and m ˙ H 2 , respectively. • Hydrogen production of a solar-based Co–Cl has been investigated. • Optimization of solar-based Co–Cl determined with Taguchi based GRA. • The η o v e r a l l of solar-based Co–Cl computed as 22.2%. [ABSTRACT FROM AUTHOR]

In a parabolic dish system, the heat losses from the cavity receiver significantly suppress the system's efficiency and may increase its overall cost. Several existing researches have numerically and experimentally developed the different cavity receiver models by modifying their inclinations, design geometrics, and structure. The conductive loss does not occur much in the cavity receivers compared to the convective loss. So, the analysis of convective loss is more critical in the cavity receivers; however, the accurate prediction of convection loss is quite complex due to the temperature distribution near the cavity. This prime aim of the paper is to comprehensively review the existing literature related to design configurations of cavity receivers and heat loss analysis to set a platform for performance improvement via design modifications. The study emphasizes the effect of geometric parameters like the structure of cavity receivers, shape and sizes, and angle of inclinations with the ground. Structural configurations, especially the hemispherical, cylindrical, conical, and trapezoidal cavity receivers utilized for the solar dish collector (SDC), are investigated between the years 1980 to 2022. A comparison is made based on heat loss models and research outcomes. Besides, the Nusselt correlation model used for predicting heat losses is also carried out in this review by varying the effects such as inclination, aperture ratio, wind effect, etc. This review supports the solar cavity designers for experimentally investigating and simulating a new modified solar cavity receiver with minimization and accurately predicting convective losses. [ABSTRACT FROM AUTHOR]

The development of a new generation of solid particle solar receivers (SPSRs) with high solar absorptivity (0.28–2.5 μm) and high infrared emissivity (1–22 μm) is crucial and has attracted much attention for the attainment of the goals of "peak carbon" and "carbon neutrality". To achieve the modulation of infrared emission and solar absorptivity, two types of medium- and high-entropy rare-earth hexaboride (ME/HEREB6) ceramics, (La0.25Sm0.25Ce0.25Eu0.25)B6 (MEREB6) and (La0.2Sm0.2Ce0.2Eu0.2Ba0.2)B6 (HEREB6), with severe lattice distortions were synthesized using a high-temperature solid-phase method. Compared to single-phase lanthanum hexaboride (LaB6), HEREB6 ceramics show an increase in solar absorptivity from 54.06% to 87.75% in the range of 0.28–2.5 μm and an increase in infrared emissivity from 76.19% to 89.96% in the 1–22 μm wavelength range. On the one hand, decreasing the free electron concentration and the plasma frequency reduces the reflection and ultimately increases the solar absorptivity. On the other hand, the lattice distortion induces changes in the B–B bond length, leading to significant changes in the Raman scattering spectrum, which affects the damping constant and ultimately increases the infrared emissivity. In conclusion, the multicomponent design can effectively improve the solar energy absorption and heat transfer capacity of ME/HEREB6, thus providing a new avenue for the development of solid particles. [ABSTRACT FROM AUTHOR]

A suggested absorption tube was designed for a thermosyphon solar water heating system (TSWHS) to enhanced the ability of the solar receiver to capture solar energy. The proposed design was based on overlapping and reversed flows, and its correctness was confirmed by conducting experimental simulations of the incident solar radiation and projecting heat flux on the proposed receiver tube models (Rt). Five receiver tube models were proposed as the standard, designed, and manufactured models which were tested under constant boundary conditions for all modeled flow rates (100, 150, 200, and 250 mL), flow directions (px and py), and constant heat flux. The most favorable thermal enhancement outcomes were achieved with the Rt4 model that exhibited a thermal efficiency of 70.5%, featuring an inner tube diameter of 12 mm and outer tube diameter of 35 mm, incorporating a py flow path. The selected model (Rt4) was employed, utilizing a py flow path for manufacturing the flat-plate collector (SRT2). The model was then compared with a normal model (SRT1) through Tests that were conducted for each model under similar weather conditions. The thermal gradient within the horizontal tank displayed an improvement by increasing 17% in heat transfer compared with the normal model. [ABSTRACT FROM AUTHOR]

This paper is a summary of the last ten years of work on the study of parabolic trough collectors (PTCs) and compound parabolic collectors (CPCs) coupled to photovoltaic and thermal solar receiver collectors (SCR-PVTs). While reviewing the state of the art, numerous review papers were found that focused on conventional solar receiver collector (SRC) technology for solar thermal generation. However, there is a lack of review papers summarizing SRC-PVT hybrid technology for solar electric/thermal generation, which would be beneficial for researchers interested in this area of research. This paper provides a review of SRC-PVT hybrid technologies. The theoretical foundations for analyzing and modeling PTC and CPC concentrators coupled to SRC-PVT are described, with an emphasis on modeling through thermal resistances and energy balances. Additionally, this section provides a concise overview of previous studies that have addressed the modeling of PTC and CPC collectors coupled to SCR-PVT, as well as experimental information useful for the validation of new mathematical models of SRC-PVT. [ABSTRACT FROM AUTHOR]

Significant high-quality heat is wasted in the vacuum thermionic generator (VTIG), which can be efficiently utilized as a prime mover of a bottoming system for cogeneration applications. For this purpose, a new environmental-friendly hybrid system composed of a heliostat solar field, VTIG, and looped multi-stage thermoacoustically driven cryocooler (LMTC) is established, in which the high-temperature heat source of the solar receiver runs the VTIG to generate power, and the LMTC recovers the waste heat of the VTIG to produce a cooling load. Thermodynamic, economic, and environmental analyses of the system are carried out based on exergy and emergy concepts. Moreover, a parametric study is performed to assess the effect of design parameters on the system's thermodynamic, economic, and environmental criteria. Finally, the multi-criteria salp swarm optimization algorithm and decision-making procedures are conducted to improve the exergetic performance and decrease the system's cost and monetary emergy rates along with the environmental impact and ecological emergy rate. Findings depict that at the reliable, optimal operation of the system, the exergetic efficiency can reach 29.36% with a maximum power of 17.2 MW and cooling load of 0.260 MW. The system's cost and monetary emergy rate can be reduced to 0.059 $/s and 5.94 × 1010 seJ/s, with 10.6% and 10% reductions, respectively. Moreover, the environmental impact and ecological emergy rates decline by 6% and 7.4%, respectively. The theoretical findings may offer guidance for the optimum designing and practical running of such a solar solid-state cogeneration system. [ABSTRACT FROM AUTHOR]

Energy transformation requires replacing power plants based on fossil raw materials with renewable energy. Energy harvesting plays an important, although not fully appreciated, role here. Distributed, local power supply systems for small receivers, based on various sources which previously dissipated energy, may contribute to changing the current energy paradigm. This article presents an overview of energy harvesting technologies and various energy sources used in this process. Particular attention was paid to sources of a less conventional nature. The aim of this article is to encourage and direct scientists with the potential to explore this topic to look for new, previously unexploited energy sources and innovative and effective methods of obtaining useful energy in the harvesting process. [ABSTRACT FROM AUTHOR]

Geological structures have been shown by studies to have influence on the occurrence, storage and transportation of groundwater. Understanding the structural network of an area unearths a deep insight into the groundwater dynamics of the area. A geological structural analysis was carried out to reveal the geological structural network of Ghana's Voltaian basin. Using aeromagnetic data, structural density models were generated using the Center for Exploration Targeting grid analysis technique for two depth ranges (that is up to 100 m and 300 m) over the Voltaian basin. The total length of geological structures (lineaments) delineated at depths up to 100 m and 300 m were more than 5000 km and more than 8000 km, respectively. Given this, the study area was observed to be structurally dense at each of the aforementioned depths. The structural density models were discretized into five classes (very low, low, moderate, moderately high and very high regions), each of which was evaluated to determine their spatial association with known locations of groundwater occurrences within the study area using the frequency ratio technique. Frequency ratio results for both structural density models derived at 100 m and 300 m depths show the existence of a strong correlation between high structural density model classes and the known groundwater occurrences. The structural density models were further evaluated using the receiver operating characteristics curve. The area under the receiver operating characteristics curve scores indicates that, although both structural density models showed very good performance (with receiver operating characteristics scores greater than 0.7), the 300‐m depth structural density model performed better than the structural density model generated at a depth of 100 m (with their receiver operating characteristics scores being 0.721 and 0.715, respectively). The obtained results corroborate with literature assertion that groundwater occurrence within the Voltaian basin is mainly associated with structural features. It is expected that the outputs of this study would guide future groundwater exploration programmes within the study area. [ABSTRACT FROM AUTHOR]

Low visibility events at King Khalid airport in Riyadh, Saudi Arabia, are investigated using hourly time series of meteorological and air pollution data from April 2015 to December 2017. The analysis of binary classification is based on two machine learning classifiers (random forest (RF) and K-nearest neighbors (KNN)). Six models based on the feature selection methods of RF feature importance and Pearson correlation matrix are presented. The classification tasks include two resampling approaches (random oversampling and random undersampling) to address the problem of an imbalanced dataset of the visibility event classes. An important finding is that oversampling outperforms undersampling for the evaluated classifiers and achieves higher scores in terms of accuracy and F1 score metrics. The RF classifier has a better performance compared to the KNN in both sampling approaches. The RF classifier with oversampling approach provides the best overall performance in terms of accuracy, F1 score, and area under the receiver operating characteristics (AUROC). The best model has scores above 0.95 based on all the evaluation metrics considered in the study. Air temperature and dewpoint temperature have minimal impact on the performance, whereas the particulate matter with aerodynamic diameter <10 μm (PM10) has a profound impact on the performance. It is found that the PM10 has the highest importance (52%) for the low visibility events based on the analysis of RF feature importance. Other pollutants and meteorological variables show relative importance between 5 and 10% for low visibility events. Overall, the best model is found when all variables, except temperature and dewpoint temperature, are employed to predict the visibility classes. [ABSTRACT FROM AUTHOR]

This study examined the performance of a concentrating solar collector with an asymmetric reflector. Two receivers were investigated, differing in the presence of photovoltaic cells. The first one was equipped with cells on both sides while the other was without cells. The analysis was performed using a numerical model that integrates a combination of three-dimensional optical and thermal analyses developed in COMSOL. The investigation included studying the influence of CuO/water and CuO/Syltherm 800 nanofluids on the thermal performance for the receiver without photovoltaic elements, as well as on both thermal and electrical efficiencies for the hybrid receiver. Two volumetric concentrations of CuO in water and Syltherm 800, 3% and 5%, were explored with varying inlet temperatures, ranging from 20 °C to 80 °C for the hybrid solar unit and from 20 °C to 140 °C for the thermal solar unit. The outcomes of the examination were compared between the nanofluids and the pure base fluid. Properly pressurized water was considered in the case without photovoltaic elements. [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]

Hydropower facilities are often remotely monitored or controlled from a centralized remote control room. Additionally, major component manufacturers monitor the performance of installed components, increasingly via public communication infrastructures. While these communications enable efficiencies and increased reliability, they also expand the cyber-attack surface. Communications may use the internet to remote control a facility's control systems, or it may involve sending control commands over a network from a control room to a machine. The content could be encrypted and decrypted using a public key to protect the communicated information. These cryptographic encoding and decoding schemes become vulnerable as more advances are made in computer technologies, such as quantum computing. In contrast, quantum key distribution (QKD) and other quantum cryptographic protocols are not based upon a computational problem, and offer an alternative to symmetric cryptography in some scenarios. Although the underlying mechanism of quantum cryptogrpahic protocols such as QKD ensure that any attempt by an adversary to observe the quantum part of the protocol will result in a detectable signature as an increased error rate, potentially even preventing key generation, it serves as a warning for further investigation. In QKD, when the error rate is low enough and enough photons have been detected, a shared private key can be generated known only to the sender and receiver. We describe how this novel technology and its several modalities could benefit the critical infrastructures of dams or hydropower facilities. The presented discussions may be viewed as a precursor to a quantum cybersecurity roadmap for the identification of relevant threats and mitigation. [ABSTRACT FROM AUTHOR]

Evaluating the heat losses of linear Fresnel concentrator (LFC) receivers is crucial for determining plant efficiency and managing the flow rate in solar lines. This becomes particularly significant when operating in direct steam generation to manage the steam quality at the line outlet. In general, the LFC receiver heat losses are determined experimentally on prototype systems to control the inlet condition or numerically using 3D computational fluid dynamics models or 1D mathematical models. The originality of this work is in reporting the study of heat losses of a commercial 9 MWe solar Fresnel power plant without impacting its electricity production. The experimentally measured receiver's linear heat losses were found to be well represented by a second-degree polynomial function of the difference between the inlet/outlet fluid temperature average and the ambient temperature. Finally, to express the strong influence of wind speed on the receiver heat losses, a 1D single-phase model was developed and adapted to include the current receiver degradation. To conclude, the model was validated by comparing the experimental and theoretical results. Based on this comparison, it can be concluded that the model accurately predicts experimental heat losses with an acceptable uncertainty of ±30%, regardless of the wind velocity. [ABSTRACT FROM AUTHOR]

This paper explains the energy mix of China's overseas electricity investments across Belt and Road Initiative (BRI) recipient countries. We focus on Indonesia and Pakistan. Our research is based on both newly gathered project-level data and in-depth interviews with stakeholders of Chinese-backed power plants in Indonesia and Pakistan. We examine (1) why Chinese actors are involved in renewable power generation in Pakistan and not in Indonesia, and (2) why Chinese-backed coal-fired projects in Pakistan are cleaner than in Indonesia. We argue that variations along the three dimensions – scope, governance regime, and issue linkage – lead to different energy mixes in Chinese-invested power plants across BRI countries. This framework specifies how supply and demand factors interact across multiple levels regarding the formulation and implementation of China's overseas electricity projects. Our findings shed new light on the environmental implications of BRI projects and the dynamics of renewable energy development in emerging markets. [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]

Several researchers have shown that the heat transfer performance of solar parabolic trough (SPT) receivers may be improved by increasing their surface area or by adding internal fins to the tubes. Unfortunately, the manufacture of internally finned tubes involves complex processes, resulting in significant cost increases. On the other hand, the addition of external fins to tubes is more technically and economically feasible in a low-resource setting. This study investigates the potential benefits of integrating external fins on the receiver tubes of a low-cost SPT collector system. Experiments were conducted using an SPT system with a focal length of 300 mm and a collector length of 5.1 m, and they were positioned by an automated Sun tracking system. Tests were undertaken using both smooth and externally finned receiver tubes operating at five different water flow rates. The solar receiver with a finned tube was able to provide a maximum water temperature of 59.34 °C compared with that of 56.52 °C for a smooth tube at a flow rate of 0.5 L per minute. The externally finned absorber tube was also found to have a maximum efficiency of 18.20% at an average daily solar intensity of 834.61 W/m2, which is approximately 48% more efficient than the smooth tube. The calculations indicate that the experimental SPT system using finned tubes potentially avoids 0.2726 metric tons of CO2e per year, with finned tubes outperforming smooth tubes by up to 44%. The results show that using externally finned receiver tubes can significantly enhance the thermal performance of SPT collector systems. [ABSTRACT FROM AUTHOR]

This study sought to determine an optimal scenario concerning multiple climatic parameters to maximize the performance of a solar system. A molten salt energy storage unit was used to enable round-the-clock power generation and maximize the system's reliability. A solar concentrator with heliostats and a solar receiver was employed to absorb solar energy, and a modified steam Rankine cycle was utilized to generate power. A total of 12 scenarios were evaluated based on three climatic parameters (ambient temperature, sunshine duration, and wind speed) and one techno-economic parameter (number of heliostats). Sankey analysis, which is a novel technique used to determine the optimal scenarios in the literature, revealed that Scenario 8 was optimal. This scenario showed the maximum exergy rate, minimum exergy destruction, and lowest cost rate. This scenario considered the sunshine duration of 11 h, ambient temperature of 16 °C, wind speed of 3 m/s, and 300 heliostats, resulting in output energy of 1582 kWh and exergy destruction of 34250 kWh. The parametric analysis showed that the turbine and superheater temperatures had the greatest effects on the system performance. The exergy analysis of the system demonstrated that the heliostats and solar receivers accounted for the largest portions of exergy destruction. Multi-objective optimization via response surface method yielded the optimal exergy round-trip efficiency of 11.5% and optimal cost rate of 229.2 $/h. The economic analysis of the system revealed that the solar subsystem had the highest cost rate. In terms of efficiency and production power, this system will perform differently in different parts of the world and under different weather conditions. To this end, it is important to find out where this particular system will be more efficient and powerful. Six different scenarios have been defined for the parametric analysis of the proposed system in order to achieve reliable results. For the case study, Los Angeles and San Diego were selected as the regions with the highest similarity to the optimal scenario in terms of sunshine duration, ambient temperature, and wind speed, whereas Paris and Toronto were randomly selected. The performance of the system showed that the system can produce 2612.3 megawatts of electricity in the city of San Diego and 2472.4 megawatts of electricity in the city of Los Angeles. Also, by setting up this system, it is possible to provide electricity for 51 to 54 residential units. The proposed system performed better in regions with climatic parameters similar to those in the optimal scenario. [ABSTRACT FROM AUTHOR]

This paper proposes a novel 4 × 10 Gb/s underwater optical wireless communication system based on orbital angular momentum (OAM) multiplexed beams. The proposed transmission uses four OAM beams based on Laguerre-Gaussian profiles, each transporting data at 10 Gb/s at 532 nm operating wavelength. The system performance is evaluated for five different types of water environments, i.e., pure sea (PS), clear ocean (CO), coastal ocean (CS), harbor I (HI), and harbor II (HII) by measuring the received optical power (ROP), underwater transmission distance, bit error rate, beam divergence angle, eye-diagrams, and receiver aperture diameter. The obtained results show that the PS has the longest underwater propagation distance of 10 m, while HII has the shortest range of 2.62 m due to high attenuation at ROP of approximately −18 dBm. The underwater span achieved at the same ROP value for CO, CS, and HI are 8 m, 6.1 m, and 3.85 m, respectively. [ABSTRACT FROM AUTHOR]

As the solar energy utilization technology for renewable clean energy, actual parabolic trough receivers are subject to tracking errors and absorber tube installation errors, and the bellows and Kovar ring under these errors have a significant impact on the receiver's safety. Based on the MCRT-FVM-FEM principles in this paper, a receiver's optical-thermal-stress mathematical model is modeled and the thermal-stress performance and safety of the receiver's key components under two errors are evaluated. The correlation between the bellows and Kovar ring's performance and the two errors is analyzed. The results demonstrate that the lower tracking errors and larger installation errors markedly increment the absorber's deformation and have a negative impact on the receiver safety. Bellows and Kovar ring's asymmetrical temperature distribution causes variable swell and uneven stress under tracking and installation errors. Temperature gradient variation of bellows is more sensitive under errors than Kovar rings. Kovar ring's compressive stress rises substantially as the Y-directional installation error varied from −15 mm to 15 mm compared to other errors. With tracking errors exceeding 8 mrad, bellows' tensile stress and Kovar ring's compressive stress diminish under installation error. Thus, larger tracking errors significantly reduce the threat to the receiver when installation errors exist. [ABSTRACT FROM AUTHOR]

Solar co-generation, i.e., the generation of electricity and heat in a single device by concentrating the sunbeams, has the potential to significantly increase the overall system performance. The main challenge is related to the cooling of solar cells. In order to do so, it is essential to reduce the thermal resistance between the cell and heat transfer fluid. This paper features the optimization procedure of a low-cost custom concentrated photovoltaic thermal (CPV-T) receiver for a parabolic trough collector using silicon solar cells. A finite volume model for the thermal process has been developed. Hence, a fluid dynamic thermal simulation of the receiver is presented. The optimized heat sink tube geometries have been manufactured and tested in a lab environment, allowing for a comparison between modelling and experimental test results. Three possible heat sink geometries have been designed and compared regarding their overall heat transfer coefficient with respect to the non-dimensional pumping power, i.e. the ratio between the overall transferred heat and the energy required for pumping. The overall heat transfer coefficient for a finned heat sink has been increased up to 60% with respect to a baseline case without fins under similar conditions. • Concentrated Photovoltaic Thermal Receiver for Solar Co-Generation applications. • CPV-T 3D conjugate heat transfer numerical modelling. • CPV-T solar collector receiver experimental setup. • CPV-T heat sink geometry numerical and experimental analysis. • Thermal and fluid dynamic CPV-T heat sink geometry study including fins analysis. [ABSTRACT FROM AUTHOR]

• A new dimensionless number Z should aid in the design phase of volumetric receivers. • Z indicates the slope of the solid-phase temperature profile in direction of gas flow. • The volumetric effect's occurrence depends on flux density and outlet temperature. • The volumetric effect is a necessary but not sufficient condition for high efficiency. • High flux densities are only interesting for very high receiver operating temperatures. This work introduces a new dimensionless number Z that should aid in the design phase of volumetric receivers. The number Z is able to indicate whether the volumetric effect is achievable for a specific combination of absorber geometry and thermal boundary conditions. It can be seen as an indicator of the slope of the solid-phase temperature profile in direction of gas flow. The volumetric effect is expected to occur at values of Z smaller than 1, when the convective plus radiative cooling (P c) outweighs the absorbed solar power (P a). An experimentally validated numerical model is used for a parametric simulation study, which sheds light on the absorber's operating conditions (incident solar flux density and operating temperature) that favor the ideal temperature profile. [ABSTRACT FROM AUTHOR]

In a solar power plant, the circular central solar receiver aids in the segregation of electricity output. Because the geometry of the receiver has different diameters in existing approaches, which determines the exact reaction of the fluid on a whole is quite challenging. The mathematical design and modeling of a solar central receiver with a variable diameter header are discussed in this research paper. Hence, a novel Thermo-Mechanical Joint Behavior Analyzing CFD model is employed to solve large-scale transient fluctuation activities directly, while a sub-grid-scale model is used to compute small-scale motions implicitly using Navier-Stokes equations. Moreover, the joints are very vital influences for losses and creation of pressure so there is a high need to analyze the joint efficiently. Consequently, the joints are an essential part of the header which influences more to the performance of the solar receiver, thereby the experimentation is carried out for measurement of pressure difference, turbulence, velocity distribution due to the movement of a Nano-fluid medium in the solar convergent-divergent header configuration precisely. [ABSTRACT FROM AUTHOR]

A non-tubular prototype cavity receiver absorber with extended internal surfaces (fins) is proposed to enhance heat transfer in Stirling engine-based Concentrated Solar Power systems. There is limited research on the realization of downsized absorbers in terms of their design and manufacturing. The objective of the absorber solution proposed in this paper is to address the issue of inadequate comprehension regarding the impacts of the geometric and flow parameters on thermohydraulic efficiency. These impacts are numerically investigated in a 100 mm long heat transfer channel with a 10 mm × 10 mm section. The prototype absorber is fabricated using a wire electrode-discharging manufacturing approach, and is experimentally investigated using the enthalpy method. Numerical results indicate that heat transfer to the working fluid in the novel absorber can reach 482 W at the reasonable cost of 0.391% pressure drop per 100 mm (air flow at 0.0015 kg/s and 5 bar). In the experimental investigation, the prototype realizes a 1113.033 W heat transfer rate at 8 bar and 12 kg/h. This implies that a non-tubular design with extended internal surfaces can increase the internal surface area to enhance heat transfer while downsizing the volume to reduce heat loss. [ABSTRACT FROM AUTHOR]

In solar thermal technology, solar receiver materials with high solar absorptivity and photocatalytic efficiency have recently become a mandatory requirement for promoting and maximizing the released thermal and electrical energy. This paper presents a detailed study of the optical performance and thermal stress durability of the promising solar receiver material, black Al 2 O 3 /CuO ceramics. Different Al 2 O 3 /CuO ceramics with different CuO content (10–40 wt%) were obtained by the pressureless sintering method. Optical properties such as solar absorbance and reflectance, band gap energy and photoluminescence are inclusively investigated. The thermal stress resistance of the obtained ceramic receivers is simulated using the finite element modeling (FEM) method at different temperatures. Results indicated that adding and increasing the content of CuO to Al 2 O 3 has a significant role in transforming alumina from a non-solar light-absorbed material to a solar absorber material with high absorptivity in the Ultraviolet–Visible-Near Infrared (UV-VIS-NIR) spectrum. Composite with 40 wt% CuO has recorded the maximum absorbance of 75% in the visible light region. Moreover, Al 2 O 3 /CuO ceramics gave multiple graded band-gaps in the range of (1.6–5 eV). Composites with high wt% of CuO have the most increased photocatalytic activity and light emissivity efficiency. Thermal stress analysis of the different ceramics showed outstanding stress durability with uniform heat distribution. Hence, black Al 2 O 3 /CuO ceramics can be considered ideal solar absorber materials with high sustainability and durability at high temperatures. [Display omitted] [ABSTRACT FROM AUTHOR]

A recuperated solar-dish Brayton cycle using an off-the-shelf turbocharger as a micro-turbine and a rectangular cavity receiver with integrated thermal storage is considered in this study. Due to the high temperatures that these solar receivers operate at, a considerable amount of heat is lost to the environment through the aperture, decreasing the solar-to-mechanical efficiency of the cycle. In this work, the heat losses from the solar receiver were reduced by utilising a novel glass channel on the inside of the cavity receiver, running parallel to the receiver walls and cooled by the working fluid (air) flowing from the compressor. The objective of this conceptual study was to investigate the impact of the novel air-cooled window on the performance of the cycle at steady state. An entropy generation minimisation technique combined with a SolTrace analysis was used. Results showed that the maximum solar-to-mechanical efficiencies were on average between 41% and 45% lower than for the cycle without the window. However, it was found that the exhaust temperature of the cycle with the window was higher. Therefore, a higher energy utilisation factor of between 9% and 11% was found when cogeneration was included. [ABSTRACT FROM AUTHOR]

• Start-up duration of a tubular receiver filled with nickel foam is predicted. • Preheating performances are compared by operating synergy electric heater and solar simulator. • Transient temperature and thermal stress distribution of solar receiver is obtained. • The maximum difference of duration is 11 min between cold and hot start-up strategy. A cylindrical tubular receiver filled with nickel foam (CTRNF) appears to be a promising receiver concept due to its capability to provide temperatures over 900 °C at a high pressure. Nevertheless, CTRNF is challenged by the unsteadiness and high intensity of radiant flux may cause inaccurate start-up time predictions, providing unrealistic and unstable outlet temperatures. In this article, these matters are addressed by a numerical model coupling the Monte Carlo ray tracing (MCRT) method and discrete coordinate (DO) radiative transfer model. The model considers the cold, semi-cold, semi-hot, and hot start-up strategies on the CTRNF using N 2 and Ar as the working medium. Three preheating methods and their influence on the thermal characteristic of the CTRNF are proposed. Temperature and equivalent stress distribution of internal heat absorber is simulated and analyzed. The results indicate that the duration for four start-up strategies takes 1711 s, 2189 s, 1212 s and 1032 s as the outlet temperature reaches to 1200 K, respectively, when Ar is used as the working medium (10 g/s) and radiative power of 10.5 kW incidents on the solar receiver. Compared with the 68.44 kg Ar consumption of cold start-up strategy, the Ar working medium consumption decrease by 24.44 kg, 51.68 kg, and 63.16 kg for semi-cold start-up, semi-hot start-up, and hot start-up strategy. However, the maximum equivalent stress of the CTRNF under the hot start-up strategy is 100 MPa higher than under the cold start-up strategy, which requires accurate monitoring of the cavity temperature in solar receiver. [ABSTRACT FROM AUTHOR]

Performance comparison of basic organic Rankine cycle (ORC) and parallel double evaporator ORC (PDORC) integrated with solar power tower (SPT) driven intercooled cascade sCO2 (supercritical carbon dioxide) cycle was carried out in present study. The intercooled cascade sCO2 cycle/ORC (configuration-1) and the intercooled cascade sCO2 cycle/PDORC (configuration-2) were considered for comparison on basis of parametric analysis. The effects of SPT design parameters such as solar irradiation, solar receiver emittance, and concentration ratio on system performance were investigated. It was concluded that the addition of basic ORC and PDORC to the intercooled cascade sCO2 cycle improved the thermal efficiency by 2.26% and 6.66% respectively at solar irradiation of 950 W/m². In the case of basic ORC and PDORC, the waste heat recovery ratios were 0.1197 and 0.1775, respectively. It was also discovered that configuration-2 performed better than configuration-1 in terms of waste heat recovery. The combined cycle's performance can be improved even more by lowering solar emittance and increasing the concentration ratio. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new concept for using liquid metals in solar cavity receivers is proposed. • Directly irradiated liquid film used for safe operation under high radiative fluxes. • A quasi-steady-state analytical model is used to evaluate the energy efficiency. • Sensitivity of receiver performance to the internal optical properties are studied. • Concept showed a more promising potential when coupled with absorptive cavity walls. Solar thermal energy has the theoretical potential to deliver heat at ultra-high temperatures (>1300 K), which can enable integration with state-of-the-art thermal energy storage systems and unlock new applications, including advanced power cycles and thermal processes. Liquid metals are prospective heat transfer fluids for such systems, given their favourable thermo-physical properties, while their aggressive corrosiveness is shown to be mitigated using compatible refractory containment materials. The conventional approach of collecting concentrated solar energy typically involves intermediate solid absorbers, in form of tubes or porous structures, which are prone to thermomechanical and chemical failure under high solar radiation. This paper investigates the use of directly irradiated liquid metal (tin) film, operating between 800 and 1673 K, in two possible cavity configurations: A 'reflective cavity' and an 'absorptive cavity'. The former employs cavity walls as internal reflectors to entrap radiation by secondary reflections until directly absorbed by the liquid metal. In the latter, the directly irradiated film is used to moderate the initial shot of concentrated solar radiation before diffusively reflecting them to the absorptive cavity walls, which perform as a radiative heat exchanger used to preheat the liquid metal. The concept performance is evaluated using an approximate quasi-steady-state energy model of the receiver. The reflective cavity performance is found strongly dependent on the optical properties of its internal surfaces, which resulted in poor efficiencies (<40 %) without special treatments. The absorptive cavity demonstrated higher efficiencies (>70 %) with greater insensitivity to the optical properties, hence, promoting its consideration in future developments of this concept. [ABSTRACT FROM AUTHOR]