Search Results (983)

Cu₂ZnSn(S,Se)₄ (CZTSSe) is a candidate thin-film photovoltaic material; however, its performance is restricted by innate defect-induced nonradiative recombination. Low-concentration Ge doping has been identified as an efficient way to mitigate these defects, but the selenization temperature remains an important process parameter that governs the structure and optoelectronic characteristics of CZTSSe absorbers. In the present work, low-concentration Ge-doped Cu₂ZnSn_0.95Ge_0.05S₄ (CZTGS) precursor films were synthesized through a green, n-butylammonium butyrate-based solution approach. The effects of the selenization temperature (530–570 °C) on the microstructure, composition, and photovoltaic performance of Cu₂ZnSn_0.95Ge_0.05(S,Se)₄ (CZTGSSe) films and devices were comprehensively investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectrometer (EDS), atomic force microscopy (AFM) were performed to comprehensively characterize the synthesized samples, and the results suggested that the selenization temperature dramatically altered the film grain growth, crystallinity, elemental retention and surface roughness. Specifically, the film that underwent selenization at 550 °C presented the best crystallinity, which was accompanied by large-scale even grains, efficient Ge⁴⁺ addition to the kesterite lattice and the lowest surface roughness. These better properties in terms of structure and composition resulted in the lowest carrier transport resistance (R_s = 8.6 Ω∙cm²), improved recombination resistance (R_j = 5.9 kΩ∙cm²), inhibited nonradiative recombination, and prolonged carrier lifetime (τ_EIS = 35.8 μs). Therefore, the resulting CZTGSSe thin-film solar cell had an 8.69% better power conversion efficiency (PCE), while its open-circuit voltage (V_OC) was 0.42 V, the fill factor (FF) was 55.51%, and the short-circuit current density (J_SC) was 37.71 mA·cm^–2. Our results elucidate the mechanism by which the selenization temperature regulates low-concentration Ge-doped kesterite devices and provide more insights into the optimization of processes for cost-effective, high-performance, and green thin-film solar cells. Full article

This study clarifies the catalytic role of chloride ions on the corrosion performance of SS316L alloy immersed in molten LiNaK carbonate salt at 700 °C. Accordingly, isothermal static immersion corrosion tests were systematically conducted under different experimental conditions. Our results revealed that the presence of Cl significantly accelerates the corrosion process: the rate constant of the corroded samples increased from 11.3 × 10⁻² mg/cm² to 13.8 × 10⁻² mg/cm² with the addition of Cl. Continuous migration of Cl₂ and volatile metal chlorides leads to the formation of obvious pores, transverse cracks along grain boundaries, surface wrinkles, and partial spalling of the oxide scale, thereby severely aggravating substrate degradation. Notably, no chlorine-containing compounds or chlorine-rich regions were detected in the corroded samples, confirming that chlorine is not consumed in the corrosion process, rather it acts as an autocatalyst through the cyclic process of “oxidation–diffusion–reaction–regeneration”. Full article

This study proposes an advanced short-term Direct Normal Irradiance (DNI) prediction model for Concentrated Solar Power (CSP) systems, integrating a convolutional neural network (CNN) with a fitted clear-sky DNI model. Leveraging all-sky images and historical DNI data, the model precisely identifies cloud motion patterns through dense optical flow analysis and forecasts DNI using a targeted region-of-interest (ROI) approach. When maximum cloud pixel velocity falls below 5 pixels per minute, the clear-sky DNI model or persistence model directly applies; for higher-velocity conditions, the CNN predicts the clear-sky index to dynamically adjust the forecast. Experimental validation across diverse weather conditions demonstrates superior accuracy, achieving significantly lower normalized Mean Absolute Errors (nMAEs) and normalized Root Mean Squared Errors (nRMSEs) for various forecast horizons under cloudy skies compared to recent state-of-the-art deep learning approaches. This work delivers a robust solution for preventing thermal shock in the receiver and improving the CSP operational stability. Full article

Over the past two decades, organic semiconductors have attracted significant research interest due to their advantageous features, including low-cost fabrication, lightweight properties, and portability, for photonic device applications. In this study, nickel sulfide doped with cobalt $(\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o})$ nanocomposites were successfully synthesized via a wet-chemical processing technique and used as a dopant in the active layer of thin-film organic solar cells (TFOSCs). The poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) blend was used as the active layer in this investigation. The devices were fabricated with $\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o}$ nanocomposites at 1 wt%, 2 wt%, and 3 wt% in the active layer to determine the optimal dopant concentration. However, the experimental evidence clearly showed that the solar cell’s performance depends on the concentration of the $\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o}$ nanocomposites. As a result, the highest power conversion efficiency (PCE) recorded in this experimental work was 6.11% at a 1% doping concentration, compared with 2.48% for the pristine reference device under AM 1.5G illumination (100 mW/cm²) in ambient conditions. The optical and electrical properties of the active layers are found to be strongly influenced by the inclusion of $\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o}$ nanocomposites in the medium. However, the device doped with 1 wt% $\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o}$ nanocomposite exhibits the highest absorption intensity, consistent with the better performance observed in this study, which can be attributed to the localized surface plasmon resonance (LSPR) effect. The optical and morphological characteristics of the synthesized $\mathrm{N}\mathrm{i}\mathrm{S}/\mathrm{C}\mathrm{o}$ nanocomposites were comprehensively analyzed using high-resolution transmission electron microscopy (HRTEM), high-resolution scanning electron microscopy (HRSEM), and additional complementary techniques. Full article

The increasing integration of renewable energy sources, such as solar photovoltaics, requires low-cost, scalable energy storage solutions suitable for decentralized systems. This work experimentally evaluates an iron chloride concentration redox flow battery (FeCl-CFB) coupled to a photovoltaic system. The battery, which employs the Fe²⁺/Fe³⁺ redox couple to store energy through a chemical concentration gradient, was electrochemically characterized using different carbon-based electrode materials and operated under solar charging for 25 charge–discharge cycles. A maximum power density of 6.3 W·m⁻² was achieved at the cell level, with stable cycling behavior under variable solar irradiance. Coulombic and energy efficiencies remained within ranges of 63–72% and 20–28%, respectively, throughout the cycles. Despite these moderate efficiencies, the system demonstrated a consistent and functional usable capacity. The main limitation identified was a decrease in maximum power after prolonged cycling, attributable to resistance and polarization losses rather than electrolyte instability. These preliminary results characterize the initial performance of the FeCl-CFB under solar-driven conditions, highlighting significant efficiency and stability challenges that must be addressed through further optimization to determine the future potential for decentralized energy storage. Full article

Thermal energy storage (TES) systems are widely employed in concentrated solar power (CSP) applications as a means of storing and dispatching energy. Typical thermal fluids used in TES systems include molten salts, such as solar salt (a KNO₃–NaNO₃ eutectic), as well as other inorganic salts currently under consideration. While these molten nitrate, chloride, sulfate, and carbonate salts offer favourable thermal properties, they can induce significant corrosion of metallic containment materials, leading to reduced system efficiency and component lifetime. Despite extensive post-exposure studies, in situ electrochemical understanding of corrosion mechanisms in molten solar salt remains limited, particularly for emerging alloys such as FeCrAl. In this study, the in situ corrosion behaviour of structural alloys in molten solar salt was investigated using electrochemical impedance spectroscopy (EIS). Complementary post-exposure characterization was performed using destructive techniques, including scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), to assess microstructural and chemical changes. The materials evaluated were stainless steel SS316 and comparatively underexplored Kanthal FeCrAl alloys, exposed to molten solar salt (40 wt% KNO₃–60 wt% NaNO₃) at 545 °C. The electrochemical and microstructural analyses indicate that FeCrAl exhibits superior corrosion resistance associated with the formation of a more stable and protective oxide scale, compared to SS316 under the investigated conditions. This study provides new electrochemical evidence supporting the suitability of FeCrAl alloys for TES applications, while also indicating that SS316 may develop improved corrosion resistance over extended exposure durations, highlighting the importance of long-term performance assessment. Full article

Italy’s abundant solar resources and its strategic Mediterranean location offer strong opportunities to accelerate the transition to a low-carbon energy system. This study presents a comparative techno-economic assessment of concentrating solar power (CSP) plants with 8 h of thermal energy storage (TES) and a 1 MW photovoltaic (PV) plant to evaluate their roles in exploiting Italy’s solar potential. The analysis covers four representative locations (Montalto, Val Basento, Ferrara, and Priolo) and examines solar availability, seasonal performance, capacity factor, electricity generation, land use, and levelized cost of electricity (LCOE). Both technologies show marked seasonal variability, with lower winter performance and summer peaks. Southern sites outperform the northern ones, with Priolo achieving the highest generation and Ferrara the lowest. CSP benefits from dispatchable operation enabled by TES, providing nearly constant rated output and summer capacity factors up to 78%, with annual production exceeding 4 GWh at the best site. In contrast, PV operates non-dispatchably, with capacity factors below 31% and annual generation between 1.47 and 1.72 GWh. The North–South performance gradient is stronger for CSP due to its dependence on direct normal irradiance. PV technology offers higher land use efficiency, producing over twice the energy per unit area compared to CSP technology, while CSP technology requires larger areas but ensures greater operational flexibility. Economically, PV technology achieves a lower LCOE, whereas CSP technology entails higher costs but adds value through dispatchability and improved grid integration. Overall, combining CSP and PV systems can enhance grid stability, reduce emissions, and strengthen Italy’s energy security, highlighting the importance of coordinated planning and investment in complementary solar technologies for decarbonization and for regions with similar climatic conditions. Full article

This review analyzes the catalytic routes for the Power-to-X (PtX) conversion of hydrogen to methane, methanol, ammonia, formic acid, and synthetic hydrocarbon fuels. The key reactive synthesis technologies and catalysts for each vector are described. Recent studies and pilot projects summarizing the reaction pathways of each vector and the associated catalyst technologies are also discussed. The analysis indicates that catalyst selection critically influences the efficiency and selectivity of these reactive systems. Some catalyst synthesis routes rely on expensive critical minerals (e.g., Ru and Rh), which raise technical and economic challenges for their industrial application. Catalyst deactivation and scale-up limitations are also relevant issues to be resolved. Emerging catalysts (e.g., Fe–Co or Co–Ni bimetallics, core–shell materials, metal-organic frameworks (MOFs), electrides, covalent-organic frameworks (COFs), and perovskites) are being explored to enhance stability, selectivity, and deactivation. Europe leads PtX development to consolidate the industrial production of hydrogen-based vectors with strong policy support, while the industrial initiatives in Latin America are limited (for instance, Chile’s green methanol and ammonia projects are examples) despite its great potential to generate renewable energy. In summary, Power-to-X can store renewable energy and close the carbon loop; however, its industrial consolidation demands catalyst innovation and supportive regulatory frameworks to overcome the challenges highlighted in this review. Full article

This study develops and optimizes a hybrid plant that couples a recompression sCO₂ Brayton cycle to a central-tower particle receiver with a bottoming Organic Rankine Cycle (ORC), including environmental and exergy balances. The two scenarios revealed Pareto points that raised the exergy efficiency to 0.65 in winter and reduced the fuel flow to 15 kg/s. Scenario number two achieves an overall thermal efficiency of 0.50 with total daily emissions of 2520 t CO₂ and 2850 kg NO_x, enabling nearly constant net power. Exergy destruction is concentrated in the high-temperature recuperator (HTR) and ORC turbines (27% each) and the ORC condenser (25%). Compared to a non-optimized baseline, the best solutions increased the ORC and Brayton efficiencies by 6.8–12.66% and 33.4–33.5%, respectively; cut gas-turbine power by 34% and ORC power to 10%; and lowered daily CO₂ and NO_x emissions by 52%. The gains stem from the coordinated adjustments of key levers: lower gas-turbine inlet temperature (about 10%), reduced Brayton mass flow (23%), and tuned ORC turbine inlet pressure. Full article

Local governments increasingly combine power purchase agreements (PPAs) with local retail power producers and suppliers (RPPSs) to pursue decarbonization and regional revitalization. However, there is limited municipal-scale evidence on how contractual design translates into regional multiplier and employment outcomes under structural uncertainty. Using a 38-sector municipal input–output table (2015) for Fukuchiyama City, Kyoto, Japan, we conduct scenario-based simulations to quantify the output and employment multipliers of on-site and off-site solar photovoltaic PPAs. We compare Type I multipliers (household exogenous) and Type II multipliers (household endogenous) across nine scenarios that combine three PPA arrangements—off-site sales to the local RPPS [A], off-site sales to a major utility [B], and on-site self-consumption [C]—with three interregional leakage scenarios (1)–(3). A systematic sensitivity analysis (±10–20% perturbation of structural coefficients) was implemented to provide results as conditional ranges rather than point estimates. Under baseline leakage (3), off-site PPAs sold to the local RPPS [A3] yield the largest short-term total effects (1.24 million USD/year). Crucially, the error bars confirm that the policy ranking of A > B > C remains robustly invariant across all leakage conditions. Endogenizing households increases total effects by approximately 22.9% without changing this ranking, with induced effects concentrated in consumption-related services. In contrast, on-site PPAs [C] yield significantly larger long-term cumulative multipliers through stable expenditure savings from avoided electricity purchases. These results provide a transferable evaluation protocol and identify policy levers—off-taker localization, local supply chain thickening, and localized O&M—that jointly determine whether PPAs deliver broad-based regional economic benefits. Full article

Lead-free perovskite solar cells have become attractive as they are more environmentally friendly than their lead-based counterparts. Among these lead-free perovskite materials is MASnI₂Br, which has attracted considerable attention due to its environmentally friendly advantages and beneficial optoelectronic properties. However, further enhancement is required in order to improve the power conversion efficiencies. In this study, an MASnI₂Br-based perovsdkite solar cell is designed and optimized using SCAPS-1D simulations. An extensive iterative simulation approach is carried out to optimize critical parameters such as electron affinity, energy bandgap, layer thickness and doping concentration for both transport layers. In addition, the thickness of the MASnI₂Br absorbing layer is optimized. With the improved device setup, the maximum achievable power conversion efficiency is 24%. Furthermore, by matching the optimized electronic structure with realistic transport materials, CBTS and TiO₂ are identified as suitable hole and electron transport layers, respectively. The proposed TiO₂/MASnI₂Br/CBTS perovskite solar cell has a power conversion efficiency of about 23.6%. Full article

A considerable proportion of perishable goods, including fruits and vegetables, deteriorate prior to reaching customers. Inadequate refrigeration infrastructure, particularly in developing nations with arid climates and markets distant from agricultural sources, accounts for most of these losses. A food cold chain has three primary phases: pre-cooling, cold storage, and refrigerated transportation. All phases of the cold chain rely fundamentally on refrigeration to preserve perishable products at designated temperatures, relative humidity, and CO₂ concentrations, thus prolonging their shelf life. Solar-driven or aided refrigeration systems use solar energy to power cooling systems and preserve the food in the cold chain. These systems are especially beneficial in off-grid or developing areas for preserving perishable goods such as fruits, vegetables, and other food items, mitigating postharvest losses that can exceed 30–50% in areas with inconsistent energy supplies. Despite progress in efficiency and scalability, numerous research gaps remain across technological, economic, social, policy, and regional dimensions, including technical aspects, optimization, and integration. There is a need to enhance energy-efficient designs, particularly by managing solar intermittency to address non-uniform cooling, which leads to inconsistent ripening and spoilage, and by integrating sustainable refrigerants to mitigate environmental impact. Further development is necessary for micro-scale, transportable, or decentralized systems designed for small farms, while economic and financing obstacles include high upfront costs and limited financial accessibility. Substantial deficiencies exist in creating affordable models and funding channels for small-scale agriculturalists. Addressing these deficiencies could expedite adoption, thereby reducing global food loss and waste (accounting for 8–10% of GHG emissions) while improving food security. Future research must emphasize multidisciplinary methodologies that amalgamate engineering, economics, and social sciences to provide comprehensive solutions. Full article

Molten salts are essential heat transfer and storage media in high-temperature applications such as Concentrated Solar Power (CSP), owing to their high boiling points, low vapor pressures, and excellent thermal stability. The overall performance of such systems is largely governed by the convective heat transfer characteristics of molten salt fluids. This review systematically synthesizes recent advances over the past five years in enhancing the thermophysical properties and convective heat transfer of molten salts, focusing on two primary strategies: improving the intrinsic properties of molten salts through nanoparticle doping, and optimizing the structural design of heat exchangers. The enhancement of thermophysical properties is mainly achieved by preparing molten salt-based nanofluids. Dispersing low concentrations (typically 0.1–1.0 wt.%) of nanoparticles such as SiO₂, Al₂O₃, and carbon nanotubes (CNTs) can yield significant improvements—thermal conductivity increases of up to ~100% (e.g., 0.5 wt% SiO₂ in NaNO₃-KNO₃) and specific heat capacity enhancements of 20–30% (e.g., 1.0 wt% Al₂O₃ in carbonates). Multiscale simulations, particularly molecular dynamics (MD), have revealed key enhancement mechanisms, including the formation of ordered ionic layers on nanoparticle surfaces that create efficient nanoscale heat conduction pathways, and the modulation of ion–ion interactions. Concurrently, significant heat transfer enhancement can be achieved through structural optimization. Single-method technologies, such as enhanced heat transfer tubes, improve performance by disrupting the thermal boundary layer. For instance, spirally grooved tubes can increase the Nusselt number (Nu) by 19% for Re > 25,000, while twisted tape inserts can enhance laminar flow heat transfer by up to 8.6 times. Composite strategies that couple nanofluids with enhanced geometries demonstrate superior overall performance, with Performance Evaluation Criterion (PEC) values reaching up to 1.48 for converging–diverging tubes with SiO₂ nanofluids and 1.21 for trefoil-shaped U-tubes with Cu-based nanofluids. Compact heat exchangers (CHEs) offer high efficiency, achieving PEC values of 1.07–1.4 in optimized designs, but face challenges such as clogging risks in large-scale applications. Future research directions include the development of advanced composite molten salts, the application of artificial intelligence and multiscale simulations for mechanistic analysis and design optimization, the fabrication of novel heat exchanger structures via additive manufacturing, and cross-disciplinary integration for full-chain system optimization. These concerted efforts are essential for realizing efficient, cost-effective, and reliable molten salt-based energy systems. Full article

The global clean energy transition is essential for limiting the global temperature rise to 1.5 °C and achieving net-zero greenhouse gas (GHG) emissions by 2050. This review synthesizes evidence from peer-reviewed studies, policy reports and industry benchmarks, addressing the three interrelated pillars of the clean energy transition: clean energy technologies, critical material scarcity, and operational challenges. This study highlights that although clean energy technologies, particularly solar photovoltaics and wind power, have achieved cost parity with fossil fuels, their widespread deployment is still hindered by technical, material, and system-level challenges. The demand for critical minerals, essential for renewable energy technologies, is growing faster than mining supply chains can respond, exacerbated by high geographical concentration, price volatility, and low recycling rates. Furthermore, lifecycle and operational challenges, including premature asset retirement and grid integration issues, continue to hinder progress. To address these challenges, this review identifies four priority research areas: reducing material intensity through low-scarcity technologies, improving recycling and reuse systems for critical materials, optimizing smart grid frameworks, and promoting coordinated policy frameworks for fair cost allocation and mineral supply chain governance. This review offers a unified analytical framework to inform technology selection, infrastructure investment, and policy design, contributing to a resource-secure, sustainable clean energy transition. Full article

Small-scale concentrated solar power (CSP) systems coupled with micro gas turbines (MGTs) offer a promising solution for decentralised and sustainable power generation. However, CSP–MGT systems are subject to pronounced transient behaviour during start-up and operation due to fluctuating solar irradiance, making accurate transient modelling essential. This work introduces a fully coupled transient electro-thermo-mechanical model of a CSP-driven micro gas turbine, explicitly linking thermal transients and heat soakage effects to electrical performance during start-up. Unlike existing models, the proposed approach captures the interaction between turbomachinery thermal inertia, shaft dynamics, and detailed electrical machine and power converter losses under real-world transient operating conditions. The model integrates thermodynamic, mechanical, electrical, and control subsystems within a unified framework using a lumped-volume formulation suitable for real-time-capable simulations. To improve prediction accuracy at low rotational speeds, a dedicated interpolation strategy for turbomachinery performance maps is implemented. The model is validated at both component and system levels using experimental data from a 6 kWe CSP–MGT test facility. The results show good agreement with measurements, with maximum deviations of approximately 8% in receiver outlet temperature and less than 6% in air mass flow rate. The findings demonstrate that accounting for heat soakage is critical for a realistic prediction of thermal and electrical transients, as neglecting thermal inertia leads to an underestimation of the start-up electrical energy consumption by up to 140%, highlighting the dominant role of thermal mass effects in small-scale micro gas turbines compared to larger systems. The proposed model provides a robust tool for analysing start-up behaviour and supports improved control and operational strategy development for CSP–MGT systems under variable solar conditions. Full article