Absorption Of Solar Energy Research Articles

Fabrication of black metal surface for high solar energy absorption by femtosecond laser hybrid technology

Metals are crucial for solar energy applications, but their highly reflective surfaces limit solar energy absorption. The difficulty in manufacturing an ideal light-absorbing structure limits the incorporation of anti-reflective characteristics in metals. In this study, a femtosecond laser method was introduced to form micro-nano structures in metals, enhancing absorption by the application of silver nanoparticles and resulting in solar absorption rates of 97.2%, 98.3%, and 98.9% for aluminum, titanium, and steel, respectively. The solar reflectance was reduced by 82.3%, 62.6%, and 79.2%, respectively, compared to bare metal. Photothermal conversion and deicing tests verified a more efficient photothermal conversion ability in the composite micro-nanostructure surface. Compared to bare metal, the structure has more than twice the solar absorption efficiency and improves the deicing efficiency by 132%. The resultant material exhibits high photothermal conversion and deicing efficiencies, enhancing its potential for solar energy applications, particularly in photothermal, photovoltaic, and thermal solar technologies.

Enhancing conical solar still performance using high conductive hollow cylindrical copper fins embedded by PCM

The present study aims to enhance the efficiency of the conical solar distiller in producing water during both day and night. This will be achieved through design enhancements, such as increasing the surface area of the distiller to maximize solar energy absorption and improve condensation rates. High thermal-conductivity cylindrical fins have been used, and their role will be investigated. These fins may be hollow and extended, with or without the inclusion of phase change material (PCM). Consequently, copper tubes are positioned at the base of the distiller basin, both with and without the inclusion of phase-changing paraffin wax material inside the hollow tubes. A comparison is made between the performance of three configurations: the first configuration is traditional, the second configuration includes fins without the incorporation of PCM, and the third configuration includes PCM-based fins. This comparison is crucial as it provides a clear understanding of the impact of each design enhancement on the distiller’s performance. The study findings indicated that the arrangement with hollow fins filled with PCM had the highest level of freshwater output. Furthermore, the results showed that the combined output of conical solar distillers equipped with fins made of copper tubes, both with and without PCM, were 7.50 and 6.75 L/m2/day, respectively. The cumulative production of conventional conical distillers is 4.85 L/m2/day. Freshwater output improved by 54.64 and 39.17 % when using hollow copper tubes with and without PCM within 24 h, compared with the conventional configuration. During night-time hours, it was observed that the freshwater output of distilled water from salt water significantly improved by 550 % when utilizing copper tubes loaded with PCM, compared to distillation using empty copper tubes. The maximum daily efficiency of conical distillers with fins with and without PCM were 73.6 % and 80.3 %, respectively. These results showed that conical distillers using copper tubes hollow filled with PCM represent good options for obtaining higher performance than distillation.

Experimental investigation of a nano coating efficiency for dust mitigation on photovoltaic panels in harsh climatic conditions

Dust accumulation on photovoltaic (PV) panels in arid regions diminishes solar energy absorption and panel efficiency. In this study, the effectiveness of a self-cleaning nano-coating thin film is evaluated in reducing dust accumulation and improving PV Panel efficiency. Surface morphology and elemental analysis of the nano-coating and dust are conducted. Continuous measurements of solar irradiances and ambient temperature have been recorded. SEM analysis of dust revealed irregularly shaped micron-sized particles with potential adhesive properties, causing shading effects on the PV panel surface. Conversely, the coating particles exhibited a uniform, spherical shape, suggesting effective prevention of dust adhesion. Solar irradiance ranged from 120 W/m² to a peak of 720 W/m² at noon. Application of the self-cleaning nano-coating thin film consistently increased short circuit current (Isc), with the coated panel averaging 2.8 A, which is 64.7% higher than the uncoated panel’s 1.7 A. The power output of the coated panel ranged from 7 W to 38 W, with an average of approximately 24.75 W, whereas the uncoated panel exhibited a power output between 3 W and 23 W, averaging around 14 W. These findings highlight the substantial potential of nano-coating for effective dust mitigation, particularly in dusty environments, thus enhancing PV system reliability.

Experimental investigation of distilled water production performance of conventional solar stills using CaCl2·6H2O phase change material reinforced with SrCl2·6H2O and graphene-based nanoparticles

This study aims to enhance the performance of conventional single-slope basin-type solar stills by integrating phase change materials (PCMs) and nanoparticles. Calcium chloride hexahydrate, known for its high heat storage capacity, was selected as the primary PCM. Strontium chloride hexahydrate was added as a nucleating agent to address the supercooling tendency. Additionally, graphene oxide (GO) and graphene nanoplatelets (GNP), which have not been previously used in solar stills or compared for their performance, were incorporated into the PCM to utilize their photothermal properties and enhance solar energy absorption. The integration of GO and GNP with the PCM-nucleating agent combination resulted in daily total distilled water productions of 5424ml/m2 and 5032 ml/m2, respectively. The integration of GO with the PCM-nucleating agent combination provided the most significant improvement in efficiency, with a 54.44 % increase compared to the standard still, a 15.4 % increase compared to the still using only the nucleating agent, and an 8 % increase compared to the still incorporating GNP.

Radiative cooling materials prepared by SiO2 aerogel microspheres@PVDF-HFP nanofilm for building cooling and thermal insulation

Radiative cooling is promising in meeting the current global demand for green sustainable development. However, the effective cooling of the existing radiant cooler will be limited due to the serious solar energy absorption and poor thermal insulation performance on the cold side. To addresss these issues, we propose herein a novel composite material of silicon dioxide (SiO2) aerogel microspheres combined with polyvinylidene fluoride-cohexafluoropropylene (PVDF-HFP) nanofiber membrane, in which SiO2 aerogel microspheres are firstly synthesized by sol-gel method and then incorporated into PVDF-HFP nanofiber membrane to give radiative cooling performance. As we expected, the molecular vibration characteristics of PVDF-HFP nanofiber membrane and the phonon polarization resonance of Si-O-Si bond in the transparent window can enhance the infrared emissivity of the membrane surface. In addition, the high porosity and the mesoporous structure formed by the interconnection of nano-network skeletons of SiO2 aerogel microspheres determine its excellent thermal insulation performance. The as-prepared material displays that the average solar reflectance of the composite membrane is 96.07 % and the average infrared emissivity of the atmospheric window is 94.95 %. Notably, when the average solar radiation intensity is 885.56 W•m−2, the passive radiative cooling temperature during the day can reach 11.2 °C. Furthermore, this material has excellent self-cleaning and thermal insulation performance, making it a potential radiant cooling candidate in many fields.

Carbon-intercalated halloysite-based aerogel efficiently encapsulating phase change materials with excellent photothermal conversion and energy storage

Latent heat storage systems based on organic phase change materials (PCMs) are considered to be an efficient solar energy utilization strategy, but leakage vulnerability and insensitivity to sunlight of PCMs limit their further application in energy storage. In this work, a new hierarchical porous aerogel was constructed with the carbon intercalated halloysite nanotubes (CHNTs) as the assembly units for PCMs encapsulation to improve the load weight, stability and sunlight absorption. The CHNTs were first successfully synthesized through intercalation and carbonization, with the aim of increasing their specific surface area and sunlight absorption.Subsequently, the CHNTs/polyvinyl alcohol (PVA) aerogels with 3D honeycomb structure were prepared by self-assembly using a freeze-drying method, which can significantly promote the encapsulation ratio of lauric acid (LA) in the pores of both aerogels and CHNTs. The CHNTs can not only improve compressive strength of the aerogels and shape stability of the composite PCMs, but also enhance light absorption ability of the composites compared to pristine HNTs. As a support material, CHNTs aerogel (CHNP) loaded more than 92 wt% PCM (LA@CHNP) and exhibited an extremely high latent heat capacity (170.9 J/g). The LA@CHNP had good structural and thermal stability in 300 cycles without visible leakage. Besides, solar energy absorption increased from 43 % to 98 %, and the solar-to-thermal energy conversion efficiency increased to 95.88 %, which could be attributed to 3D porousness and carbon nanolayers of the CHNTs. We have successfully synthesized an eco-friendly and facile composite LA@CHNP, which will contribute to the design of advanced composites with excellent solar energy storage properties, and provide a new direction for the application of carbonized materials.

Fe3O4/Au@SiO2 nanocomposites with recyclable and wide spectral photo-thermal conversion for a direct absorption solar collector

The Fe3O4-based photothermal materials have been widely applied for the recycling of heavy metal nanoparticles to avoid secondary pollution in the utilization of solar energy owing to excellent magnetic properties. However, the narrow absorption band of Fe3O4 or metal nanoparticles limits their capacity for solar energy harvesting. In this paper, a recyclable and wide spectral photo-thermal conversion system (Fe3O4/Au@SiO2) based on Fe3O4 nanospheres and SiO2-modified Au nanorods (NRs) is prepared. Owing to the strong coupling effect between Fe3O4 and different Au NRs, the wide and strong absorption band from 400 nm to 1100 nm is obtained. Under the influence of magnetic field, the temperature change of nanofluids (NFs) at different positions can be controlled. When the concentration is 0.0467 vol%, the solar energy absorption fraction reaches 96.50 %. Besides, the photothermal performance of Fe3O4/Au@SiO2 NFs at different flow rates is investigated and the results show that temperature rise decreases as increasing flow rate. Finally, a water evaporator device based Fe3O4/Au@SiO2 NFs is developed. The maximum water evaporation rate of 2.6 kg m−2 h−1 can be reached and the movement of evaporator on water can be operated using magnetic field, showing great photothermal conversion performance and recovery potential in practical applications.

Stratospheric airship trajectory planning in wind field using deep reinforcement learning

Stratospheric airships, with their long endurance, high flight altitude, and large payload capacity, show promise in earth observation and mobile internet applications. However, challenges arise due to their low flight speed, limited maneuverability and energy constraints when planning trajectories in dynamic wind fields. This paper proposes a deep reinforcement learning-based method for trajectory planning of stratospheric airships. The model considers the motion characteristics of stratospheric airships and environmental factors like wind fields and solar radiation. The soft actor-critic (SAC) algorithm is utilized to assess the effectiveness of the method in various scenarios. A comparison between time-optimized and energy-optimized trajectories reveals that time-optimized trajectories are smoother with a higher speed, while energy-optimized trajectories can save up to 10% energy by utilizing wind fields and solar energy absorption. Overall, the deep reinforcement learning approach proves effective in trajectory planning for stratospheric airships in deterministic and dynamic wind fields, offering valuable insights for flight design and optimization.

Ultra-wideband polarization-independent nano-metamaterial-based solar energy absorber in infrared, visible and ultraviolet regimes

Ultra-wideband polarization-independent nano-metamaterial-based solar energy absorber in infrared, visible and ultraviolet regimes

Developing a novel sustainable and durable self-luminous pavement material with solar energy absorption capability

Self-luminous pavement materials can autonomously absorb solar energy and emit light at night, offering a novel approach to improving nighttime road visibility and reducing energy consumption. Despite their potential, current self-luminous pavement coatings face challenges related to insufficient durability and anti-skid properties. To address this, this paper aims to develop a novel sustainable and durable self-luminous pavement material and thin layer. The development involved optimizing high-transparency epoxy resin based on mechanical properties and ultraviolet aging resistance, as well as selecting long afterglow materials based on luminous performance. Subsequently, a novel self-luminous pavement thin layer, comprising an anti-skid layer, a bonding layer, a self-luminous layer, and a sub-bonding layer, was proposed and tested. The results indicate that this novel self-luminous thin layer maintains a brightness level of 4–6 mcd/m2 after 6 h of light emission, which is still a bright level for the human eye. Additionally, it shows robust performance against ultraviolet aging, water damage, and long-term abrasion. The material cost of this thin layer is approximately 32.00 USD/m2, offering an economic advantage over mixture and pouring-in type, and it also provides benefits such as energy savings, improved traffic safety, and enhanced aesthetic appeal of scenic roads. Future efforts should focus on analyzing the economic benefits of these functions to better understand the full lifecycle advantages of this innovative material. In general, the novel durable self-luminous thin layer proposed in this study provides a practical and sustainable solution for self-luminous pavements.

Neutral‐Colored Transparent Radiative Cooler by Tailoring Solar Absorption with Punctured Bragg Reflectors

Abstract Daytime radiative cooling (DRC) has emerged as a promising method for temperature reduction of surfaces exposed to sunlight, without energy consumption. Despite advancements in DRC design, existing reflector‐based methodologies often lack transparency because of visible reflection, hindering the widespread application of this technology using glass. Efforts to address this challenge have led to the development of transparent radiative cooling (TRC), although efficient cooling during daylight remains challenging because of the dominant solar energy absorption. This paper proposes a novel TRC design comprising a polydimethylsiloxane (PDMS) emitter atop a transparent dual‐reflector structure. An optimized Bragg reflector (OBR) and a 90 µm‐hole‐punctured Ag window screen reflector (WR) are used to reflect band A of the near‐infrared (NIR) spectrum (0.74 < λ < 1.4 µm) and the overall solar spectrum, respectively. During the daytime, the proposed TRC lowers the temperature by 22.1 °C through the transparent dual reflector system, compared to a PDMS‐coated glass. Thus, this approach optimizes the balance between solar reflection and visibility using a dual reflector, offering an optimal solution for applications requiring both cooling and transparency.

Thermal radiation characteristic parameters of biomass mixed feedstock for concentrating solar gasification reaction

Solar energy and biomass are both important renewable energy, and the studies on them contribute to current goal of global carbon neutral. The solar gasification process directly employs solar radiation to drive the conversion from biomass to syngas via endothermic gasification reactions. This process relies on the biomass feedstock absorbing incident solar irradiation to sustain these reactions. The thermal radiation characteristics of biomass materials, such as spectral emissivity and absorptivity, determine its capacity for solar energy absorption versus losses from self-emission. Thus, these parameters are critical inputs for accurate thermal-balance modeling of the solar reactor. In this study, the reflectance of 9 biomass samples were experimentally measured in the main solar spectrum range of 200–2500 nm. Based on measurement results, the refractive index (n) and extinction coefficient (k) of each biomass materials are obtained via Kramers-Kronig relations. Besides, the dielectric function of the 9 biomass samples are also modeled using a 5-th Lorentz oscillator model and the model parameters are determined. The results indicate that the 5-th Lorentz oscillator model adequately characterizes the thermal radiation properties of diverse biomass feedstocks over the measured spectrum. This work contributes important spectral property data to enable accurate modeling and optimization of solar thermochemical conversion based on biomass gasification processes.

High‐Performance Piezoelectric Nanogenerator and Self‐Charging Photo Power Cell Using Hexagonal Boron Nitride Nanoflakes and PVDF Composite

Two‐dimensional (2D) piezoelectric hexagonal boron nitride nanoflakes (h‐BN NFs) exhibit substantial potential for energy harvesting, electronics, and optoelectronics applications. Herein, a free‐standing PVDF/h‐BN NFs (Ph‐BN) composite film is synthesized for multi‐functional purposes. First and foremost, a piezoelectric nanogenerator (PENG) device is fabricated using free‐standing Ph‐BN composite films and the energy harvesting properties are performed. The nanogenerator, Ph‐BN‐7.5 PENG, exhibits the highest output voltage of 50 V and current of 250 nA with a maximum power of about 2 μW compared to other fabricated composite devices. Further, a photo power cell (PPC) is fabricated using PVA‐EY mixture dye as the photosensitive part or solar energy absorber, and Ph‐BN 7.5 film is utilized as the energy storage part. The PPC is self‐charged up to ≈1 V within 80 s under light illumination. The self‐charging mechanism for PPC is explained in detail. The Ph‐BN composite films demonstrate an innovative energy harvesting and storage approach, which can fulfill the energy prerequisite in the imminent future.

Design solutions and characterization of a small scale and very high concentration solar furnace using a Fresnel lens

The use of Fresnel lenses for solar energy concentration technology dates back to the 1950 s. These lenses feature a plano-convex optical design with a series of discontinuous convex grooves. Typically made from materials like polymethyl methacrylate, Fresnel lenses are lightweight, resistant to sunlight, thermally stable, and cost-effective.This study presents a novel Fresnel lens-based solar furnace configuration installed at the Eduardo Torroja Institute for Construction Science in Madrid, Spain. The novelty of this work lies in the exceptional performance and operability of the facility. Experimental characterization revealed a record peak irradiance over 7 MW m−2 for an incident target power exceeding 800 W. Comparison with ray tracing simulations shows good agreement with experimental results. This setup enables high temperature experiments up to 2000 °C with rapid execution times. A fixed receiver, a shutter system and a closed-loop heliostat tracking control system allow for flexible operation up to 5000 suns and straightforward maintenance. The concentrator element costs less than 300 USD (2022) m−2, offering an economical solution to solar-powered high concentration and temperature applications. This innovative design overcomes previous operational challenges, providing a robust and economical method for high-temperature material processing and other industrial applications.

Experimental study of electricity generation from solar energy using organic phase change materials and thermoelectric generator

The study investigates using edible oils (ostrich, mutton, beef, coconut) as natural phase change materials for solar energy absorption and storage. Exposed to 900 W/m2 direct radiation by a solar simulator, these materials harness captured energy at a specific depth to generate electricity through a thermoelectric device. The experimental results showed that coconut oil exhibits the highest thermal energy storage efficiency among others, measuring at 39 %, while mutton tallow shows the lowest performance at 16.59 %. Additionally, the performance of a system employing coconut oil as the best material, in combination with iron oxide nanoparticles and carbonized sawdust (CS) was experimentally evaluated at different mass fractions (0.3 %, 0.6 %, and 0.9 %) to enhance thermal conductivity and sunlight absorption. The carbonized sawdust and its nanoparticles increased the thermal energy storage efficiency of the system by 62 % and 53 %, respectively. Moreover, the stored exergy by the phase change materials indicates that coconut oil and beef tallow had the highest and lowest exergy efficiencies of 6.3 % and 3.3 %, respectively. The combination of coconut oil with iron oxide nanoparticles and carbonized sawdust leads to 10 % and 7.9 % increased exergy efficiencies respectively.

Examining the Application of Neural Networks in Predicting Temperature and Solar Cell Power

Cost-effective and efficient engineering of solar cells, in addition to creative design, necessitates a detailed examination of the physics involved in solar energy absorption. Solar energy does not operate at night without storage means such as batteries, and cloudy weather can render this technology unreliable during the day. Since solar cells are used to convert light into electricity, they must be composed of materials efficient in light absorption. Like any other power generation source, solar cells face challenges, including reduced output power with increasing cell surface temperature. With each degree rise in temperature, efficiency can decrease by up to 54.0%, highlighting the importance of addressing and implementing solutions to this issue. This study explores different specifications of solar cells after a general overview and modeling. It investigates methods for estimating solar cell temperature using ambient temperature and solar radiation, comparing them with a proposed neural network approach. If the neural network can achieve lower error rates than the desired thresholds, it would offer advantages over mathematical estimators mentioned in the literature. Additionally, this neural network demonstrates the capability to predict future solar cell temperatures, unlike instantaneous mathematical estimators for temperature and radiation. DOI: https://doi.org/10.52783/pst.558

Modelling and performance evaluation of a parabolic trough solar water heating system in various weather conditions in South Africa

In recent years, various energy sources and methods have been used to heat water in domestic and commercial buildings. Water heating methods for large households or commercial buildings include electrical heating elements, gas heaters, and solar energy (solar concentrators, flat plate collectors, evacuated tube collectors, etc.). In recent decades, the focus of water heating has shifted to solar energy, which is abundantly available in most African countries. The weather condition of a region has a huge impact on the system's performance. South Africa is characterised by four different weather seasons (winter, spring, summer, and autumn), unlike most African countries. Therefore, this study focuses on the impact of weather seasons on the system's performance for water heating through the combined use of solar energy and solar concentrator techniques. The system performance was modelled by using Matlab Simulink®, where historical weather data for Pretoria, South Africa, was fed into the model. Based on the weather data input, the system behaviour varied per season due to the change in solar intensity. The average outlet temperatures of the absorber, in the order of magnitude, were 333, 332, 328, and 325 K during the autumn, summer, spring, and winter seasons, respectively. Similarly, the average storage tank temperatures, in the order of magnitude, were 366, 364, 363, and 360 K in spring, summer, autumn, and winter, respectively. From this study, it is concluded that the different weather seasons in South Africa, have a direct impact on the performance of the system. Irrespective of the season, the system produced the required volume of hot water required throughout the year.

Enhanced optical properties of BiVO4 photoanode with subwavelength moth-eye structure fabricated via e-beam evaporation and direct printing

Photoelectrochemical (PEC) water splitting, which harnesses solar radiation (an infinite energy source) for clean hydrogen production without carbon-dioxide emissions, is an ideal eco-friendly energy technology. The core reactions in PEC water splitting, involving the oxidation and reduction of water, are driven by electron–hole pairs generated through solar energy absorption. Consequently, the light-absorption efficiency emerges as a critical parameter in PEC devices. Conventional thin-film-type photoanodes, however, grapple with limited absorption due to their high reflectance, hindering absorption and carrier separation efficiency. Conversely, moth-eye-structured photoanodes exhibit an anti-reflection effect stemming from their subwavelength structure, markedly enhancing light-absorption efficiency. In this study, we present the design and fabrication of a densely packed moth-eye-structured bismuth vanadate (BiVO4) (M-BVO) photoanode, which is engineered to possess superior light absorption properties. The photoanode was fabricated via direct printing, electron-beam evaporation, and Vanadium calcination processes. The light absorption of the resulting M-BVO photoanode increased to approximately 92 % within the 300–500 nm wavelength range, with the absorption efficiency (ηabs) surging to 82.9 %. This represents a 23.5 % enhancement compared to its flat BiVO4 counterparts. Impressively, the photocurrent density of M-BVO reached 2.98 mA cm−2 at 1.23 VRHE, 37.6 % higher than that of flat BiVO4. These results indicate that the PEC efficiency can be significantly increased through moth-eye structuring, emphasizing the indispensable role of nanostructure research in the manufacture of high-efficiency photoanodes.

Latent heat type nanofluid based on MXene and MoS2 modified hierarchical structured phase change nanocapsules for sustainable and efficient light-heat conversion

Recently, solar energy has garnered widespread attention due to its clean, pollution-free, and renewable characteristics. Among them, latent heat nanofluids (LHNF) are extensively employed in direct absorption solar collectors (DASC) because of their high heat storage density and efficient heat transfer efficiency. In this study, a novel LHNF was prepared through electrostatic interaction between phase change nanocapsules modified with MXene-MoS2 (hereafter named “n-22@SiO2-Ti3C2Tx-MoS2 MEPCN”) and ionic liquid, aiming at sustainable light-heat conversion. Phase change nanocapsules are obtained by encapsulating docosane (n-22) within an inorganic SiO2 shell and modifying it with Ti3C2Tx and MoS2 to improve the absorption of solar energy across the full spectrum. Research indicates that LHNF possesses high thermal stability, low viscosity, and high thermal conductivity. Furthermore, LHNF contains 4 % n-22@SiO2-Ti3C2Tx-MoS2 can achieve full spectral absorption at an optical path length of 0.005 m. The equilibrium temperature of LHNF-10 % under 1 Sun irradiation can reach 76.3 °C, with a light-heat conversion efficiency of 85.62 %. Its energy storage performance remains relatively stable under cycling conditions. In addition, the water evaporation rate of the fiber fabric coated with LHNF-10 % increased by 94.42 % compared to the untreated fabric, and this increase persisted even after sunlight was turned off. Its outstanding light-heat conversion performance is anticipated to confer application advantage in intermittent solar energy utilization, wearable fabrics, and biomedical materials.

Ultra-broadband absorber based on algorithmic optimization of MgF2–Fe stacked structure

Broadband absorbers possess a wide array of potential applications, including electromagnetic cloaking, solar energy harvesting, and solar power generation. However, achieving excellent ultra-broadband absorption with plasma-metal materials remains challenging due to their inherently narrow bandwidth. To tackle this issue, we propose an ultra-broadband absorber, free from lithography, composed of a multilayer stack of magnesium-iron fluoride (MgF2–Fe). In this study, we optimized the structural parameters of the absorber using a particle swarm optimization algorithm to achieve theoretically optimal absorptivity. Numerical simulations revealed that the absorber achieved an impressive theoretical average absorption of 98.4% across a broad wavelength range from ultraviolet to near-infrared (321–1800 nm). Importantly, it exhibited stable absorption performance at large incidence angles (0–70°), while maintaining high absorption efficiency. Furthermore, it demonstrated polarization independence at perpendicular incidence angles. Subsequently, experimental preparations and tests were conducted on absorber samples to evaluate their solar energy absorption capacity. Both experimental and theoretical comparisons underscored the promising potential of this structure for applications in solar energy collection, conversion, and solar power generation.