Efficient Utilization Of Solar Energy Research Articles

Additive Manufacturing: A Paradigm Shift in Revolutionizing Catalysis with 3D Printed Photocatalysts and Electrocatalysts Toward Environmental Sustainability.

Semiconductor-based materials utilized in photocatalysts and electrocatalysts present a sophisticated solution for efficient solar energy utilization and bias control, a field extensively explored for its potential in sustainable energy and environmental management. Recently, 3D printing has emerged as a transformative technology, offering rapid, cost-efficient, and highly customizable approaches to designing photocatalysts and electrocatalysts with precise structural control and tailored substrates. The adaptability and precision of printing facilitate seamless integration, loading, and blending of diverse photo(electro)catalytic materials during the printing process, significantly reducing material loss compared to traditional methods. Despite the evident advantages of 3D printing, a comprehensive compendium delineating its application in the realm of photocatalysis and electrocatalysis is conspicuously absent. This paper initiates by delving into the fundamental principles and mechanisms underpinning photocatalysts electrocatalysts and 3D printing. Subsequently, an exhaustive overview of the latest 3D printing techniques, underscoring their pivotal role in shaping the landscape of photocatalysts and electrocatalysts for energy and environmental applications. Furthermore, the paper examines various methodologies for seamlessly incorporating catalysts into 3D printed substrates, elucidating the consequential effects of catalyst deposition on catalytic properties. Finally, the paper thoroughly discusses the challenges that necessitate focused attention and resolution for future advancements in this domain.

Thermodynamic Analysis of a Cogeneration System Combined with Heat, Cold, and Electricity Based on the Supercritical CO2 Power Cycle

The supercritical CO2 power cycle driven by solar as a new generation of solar thermal power generation technology has drawn significant attention worldwide. In this paper, a cogeneration system derived from a supercritical CO2 recompression Brayton cycle is proposed, by considering the recovery of waste heat from the turbine outlet. The absorption refrigeration cycle is powered by the medium-temperature waste heat from the turbine outlet, while the low-temperature waste heat is employed for heating, achieving the cascaded utilization of the heat from the turbine outlet. As for the proposed combined cooling, heating, and power (CCHP) system, a dynamic model was built and verified in MATLAB R2021b/Simulink. Under design conditions, values for the energy utilization factor (EUF) and exergy efficiency of the cogeneration system were obtained. Moreover, the thermodynamic performances of the system were investigated in variable cooling/heating load and irradiation conditions. Compared with the reference system, it is indicated that the energy utilization factor (EUF) and exergy efficiency are 84.7% and 64.8%, which are improved by 11.5% and 10.3%. The proposed supercritical CO2 CCHP system offers an effective solution for the efficient utilization of solar energy.

Study on the photothermal conversion enhancement performance and application of the metal-polyphenol phase-change microcapsules modified by molybdenum disulfide

Aiming to improving photothermal conversion and heat storage efficiency, layered molybdenum disulfide (MoS2) was prepared with hydrothermal method, which was used as the thermally conductive and photothermal conversion material to modify metal-polyphenol (MPN) /paraffin (PA) microcapsules. The fabricated phase-change microcapsules (MoS2/MPN@PA-MEPCM) exhibits excellent thermal conductivity, photothermal conversion and heat storage performance. The effect of the additive amount of MoS2 on the leakage performance, microstructure, thermal conductivity, heat storage capacity, thermal stability and photothermal conversion performance of MoS2/MPN@PA-MEPCM was investigated. Furthermore, the enhancement mechanisms of the thermal conductivity and photothermal conversion were analyzed. The results show that when the additive amount of MoS2 is 10 wt%, the phase-change enthalpy of MoS2/MPN@PA-MEPCM reaches 127.1 J/g with an encapsulation ratio of 53.74 %. Compared to MPN@PA-MEPCM, the thermal conductivity of MoS2/MPN@PA-MEPCM increases by 88.45 % and the photothermal conversion and heat storage efficiency reaches 90.78 %. When the solar radiation intensity is 800 W/m2 and 1000 W/m2, the thermal efficiency of PFPSC is 57.17 % and 59.45 % respectively, which is higher than that of FPSC. The operation time of PFPSC is extended by 2435 s and 2750 s, respectively, improving the operational stability of flat plate solar water heaters. The developed microcapsules in this study demonstrate significant potential for highly efficient solar energy utilization and thermal energy storage in the fields of seawater desalination, solar water heating system and building heating.

A spectral splitting CPV/T hybrid system based on wave-selecting filter coated compound parabolic concentrator and linear Fresnel reflector concentrator

Efficient full-spectrum solar energy utilization shows great potential to improve solar energy conversion efficiency. In this paper, a spectral splitting concentrated photovoltaic/thermal hybrid system based on a wave-selecting filter-coated compound parabolic concentrator and linear Fresnel reflector mirror field is developed. Optical models to simulate the linear Fresnel reflector have been developed and validated. With the wave-selecting filter coated compound parabolic concentrator, the visible and near infrared spectra transmit onto the photovoltaic cells, while the rest are reflected to the receiver tube. Furthermore, a simplified receiver indoor test prototype is designed to investigate the characteristic of solar photovoltaic module with the spectral filter in the context of the compound parabolic concentrator. The measured I–V curves are compared with the modeled results. Additionally, the thermodynamic performance of the system is analyzed. Parametric studies are performed to investigate the effect of key design parameters including the mirror width, focal length and the radius of the receiver tube on the solar flux density and the exergy efficiency. An exergy efficiency of 35.51% and an optical efficiency of 94.78% are achieved. With a preliminary techno-economic analysis, the levelized cost of the electricity of the system is $0.209/kWh with a payback period of 10 years.

Electronic Sunflower Design

Solar energy is known as the most primitive source of energy; it's clean, renewable, abundant, and widely distributed, offering a very broad prospect for utilization. However, the low efficiency of solar energy utilization has always been affecting and hindering the popularization of solar energy technology. The design of a solar tracking system offers a new approach to solving this problem, thereby greatly improving the efficiency of solar energy utilization. This design employs a photoelectric tracking method, using a stepper motor driven by photoelectric sensors, which generate feedback signals to a microprocessor based on the intensity of incident light. The microprocessor runs the program and controls the tracking mechanism to adjust the angle of the solar panels to track the sun. A single-chip microcontroller-implemented solar tracking system can effectively improve the photoelectric conversion efficiency of solar panels and has a broad application prospect.

Solar demulsification: Towards the oil-water interface broken of solar photo-thermo-electro coupling

The stability of the emulsified oil/water mixture depends on the strength and tightness of the interface, which is closely related to the adsorption and close packing of the active components on the interface. The core task of demulsification is to change the interface properties to enhance efficient oil-water separation. In this study, a coupling model of photo field, thermo field, and electro field was constructed to focus on fully considering the particularity of the demulsification, while improving the utilization efficiency of solar energy by presetting and matching a variety of energy flows and sub-processes. Taking oil/water emulsion from the ASP flooding as an example, the oil removal rate of 82.27% can be obtained, and efficient energy modes, namely high-intensity thermo field, uniform photo field and low-intensity electro field, are established. At the same time, the results show that the photo-thermo-electro field changes the properties of the oil-water interface, such as the interfacial tension, zeta potential and modulus. The mechanism of solar demulsification is that the solar thermal effect changes the motion state of the molecules at the interface, the coupling electro effect drives the migration of charged droplets and the stretching or deformation of the polymer chain, which combined with the photo field to degrade the polymer at the interface. Solar demulsification not only enables innovation in the form of energy and promotes its sustainable development, but also provides a green process in which solar thermo, photo, and electro are synergistically combined to achieve demulsification.

Preliminary thermal performance characterization of a flexible separate heat pipe used for the tracking-type photovoltaic/thermal system

In the solar heating field, the separate heat pipe-based photovoltaic/thermal technology can improve the comprehensive utilization efficiency of solar energy and reduce the maintenance difficulty in long-term outdoor operation by preventing freezing and scaling problems. Its promotion and application are of great significance for reducing fossil energy consumption and carbon emissions, and thus have attracted much attention. However, the performance of conventional photovoltaic/thermal modules is limited by their frame shadow due to the insulation demand, which leaves plenty of room for overall efficiency gains. To solve this problem, a novel separate heat pipe-based photovoltaic/thermal system is proposed by introducing a dual-axis tracking method through a flexible separate heat pipe and side-altitude inclination. To preliminarily characterize the thermal performance of the flexible separate heat pipe in dual-axis tracking conditions, an indoor experimental platform of the flexible separate heat pipe using the solar collector and finned-tube heat exchanger in the water tank as the evaporator and condenser was set up. The effects of side inclination angle, altitude angle of the solar collector and solar irradiance on the thermal efficiency, mass flow rate, and thermal resistance of the system are investigated in detail. The experimental results show the system can generally maintain effective heat transfer in side inclination states, with thermal efficiency mostly ranging from 44.68% to 86.12%. The proposed flexible separate heat pipe is qualified for the dual-axis tracking of photovoltaic/thermal system and shows great potential in improving the utilization of solar energy.

Thermal performance and energy flow analysis of a PV/T coupled ground source heat pump system

Ground source heat pump (GSHP) system in cold regions will lead to a decrease in soil source temperature over the years after a long period of operation, and if no timely measures are taken, the system performance will get worse and worse, and even face the risk of shut down. The PV/T (photovoltaic/thermal) is an integrated energy supply system that can both improve the efficiency of solar energy utilization and weaken the soil temperature imbalance. In this paper, the thermal performance and year-round energy flow of the system are analyzed by the simulation model, and the effects of different soil thermal storage control strategies on the thermal storage performance in the transition season are explored. The results show that the coefficient of performance of the heat pump unit can reach 3.99 and 3.96 in the heating and cooling periods. The soil temperature only increases by 0.09 °C and 0.11 °C compared with the initial temperature after five and ten years of long-term system operation, respectively. In addition, after a comprehensive comparison of the thermal storage performance of different control strategies in the transition season, this study found that the temperature difference control strategy was superior to the time control strategy. Ultimately, the annual energy supply of the simulation system produces an additional 391.8 kWh of electricity in addition to meeting the energy demand for cooling, heating and power supply of the building, which realizes the zero-energy operation of the building.

Enhancing Solar Thermal Efficiency: PCM Integration for Compact Energy Storage Systems

The optimal utilization of solar energy presents a challenge in meeting round-the-clock hot water demands while accommodating limited space in modern architectural designs. Solar collectors, operating solely during daylight hours and weather-dependent, necessitate efficient energy storage to meet evening and morning peak hot water consumption in households. Current architectural trends, marked by smaller boiler rooms, further compound the challenge of integrating conventional solar tanks, emphasizing the critical need for compact energy storage solutions. Addressing this challenge, this paper proposes a ground-breaking solution: a solar tank infused with phase change material (PCM). This innovative tank design not only boasts smaller dimensions but also significantly higher heat capacity compared to conventional counterparts. Crucially, the PCM solar tank enables solar collectors to operate at lower temperatures, potentially elevating the overall efficiency of the solar collector system. The proposed storage system comprises two synergistic heat-absorbing units: a solar water heater and a PCM-based heat storage unit. While the solar water heater fulfills the daytime hot water supply, the PCM storage unit accumulates and retains heat throughout the day, ensuring continuous hot water availability during night hours and overcast periods. Leveraging small cylinders filled with paraffin, serving as the PCM, integrated with solar collectors maximizes solar energy absorption and storage. This paper meticulously compares the performance of the PCM-based thermal energy storage system with conventional sensible heat storage systems, presenting insightful conclusions derived from the comparative analysis. The findings underscore the remarkable efficiency and efficacy of the PCM-based solution in meeting the challenges posed by solar energy intermittency and limited space constraints, offering a promising avenue for sustainable and efficient solar energy utilization in residential settings.

Preparation and characterization of chitosan/ZnO-Ag composite microcapsules and their applications in solar energy harvesting and electromagnetic interference shielding

Phase change microcapsules are known for their latent heat storage capability. However, the efficient absorption and utilization of solar energy by these microcapsules remains a significant challenge. In this study, we successfully prepared composite phase change microcapsules containing ZnO-Ag nanospheres, chitosan, and paraffin. These microcapsules demonstrated remarkable photothermal conversion efficiency. ZnO was found to effectively absorb ultraviolet light, while the plasmonic resonance of Ag was utilized to absorb and make use of light energy in the visible region. Moreover, due to the synergistic absorption and reflection of electromagnetic waves by ZnO-Ag nanoparticles and graphene, the well-dispersed chitosan/ZnO-Ag composite microcapsules and graphene in the fabric coating demonstrated exceptional electromagnetic shielding performance. In addition, the coated fabric based on composite microcapsules exhibited excellent antibacterial properties, effectively inhibiting the growth of bacteria such as S. aureus and E. coli. This antibacterial performance adds to their potential applications in various fields. These multifunctional phase change microcapsules offer vast potential for the effective utilization of solar energy, serving as efficient photothermal conversion and energy storage materials.

Thermal Stability and Weather Resistance of a Bionic Lotus Multiscale Micro-Nanostructure TiC/TiN-Ni/Mo Spectral Selective Absorber Based on Laser Cladding-Induced Melt Foaming.

As the core of a solar collector, a solar selective absorbing coating has become the key material for efficient utilization and development of solar energy. In order to overcome the core scientific problem of poor high-temperature stability of optical properties caused by atomic diffusion between layers in the high-temperature environment of traditional multilayer solar absorption coatings, the multiscale lotus bionic porous structure was constructed by using a TiC/TiN-Ni/Mo material system with excellent intrinsic absorption performance. The melt foam method and laser cladding technology were combined to deposit the multiscale bionic porous structure solar selective absorption coating in situ by a laser-induced melt foaming strategy. It was found that the bubbles in the molten pool were affected by Marangoni force, gravity, buoyancy, and surface tension. The unescaped bubbles formed pores near the surface of the coating and showed a bimodal distribution. For the multiscale addition of 1.8 and 0.4 μm pore-forming agents with a mass fraction of 15 wt %, the multiscale pores enhance the scattering and secondary absorption of light and reduce the amplitude of electromagnetic wave to electron vibration; at the same time, the small-size conductor effect formed by the hole increases the surface electron concentration, strengthens the absorption of light, and enhances the magnetic field strength at the hole, and the structural absorbing effect is significant. The coating absorptivity α reaches 85%, and the temperature stability is excellent. Compared with the substrate, the coating has a smaller corrosion current density, larger polarization resistance, and strong corrosion resistance. The research shows that the laser-induced multiscale bionic porous structure coating obtains the intrinsic absorption-structural absorption composite absorption mechanism and realizes the integration of flexible design and efficient manufacturing of high-temperature solar absorption coatings.

Experimental study and performance enhancement of micro heat pipe PV/T system

The integration of photovoltaic/thermal (PV/T) systems, which enable the simultaneous conversion of solar energy into both electricity and thermal energy, holds great promise in the solar-rich northwest region of China. This study aims to assess the performance of a micro heat pipe (MHP) PV/T system through comprehensive experiments conducted over the four seasons in Lanzhou. The experimental setup involved the measurement of various parameters including environmental temperature, surface temperature of the PV/T panel, back temperature of the PV/T panel, and water temperature, as well as the determination of the power collection efficiency (PCE) and thermal conversion efficiency (TCE). The PV/T system was installed at a tilt angle of 45°, resulting in an average PCE of 12.42 % and TCE of 34.7 %. To further understand the system performance, a two-dimensional mathematical model was developed and validated using the experimental data, demonstrating good agreement between the simulated and actual results. The simulation provided valuable insights into the temperature distribution across different components of the PV/T module, such as the glass cover, solar cell, and single shell of the MHP. The findings revealed that increasing the number of MHPs from 12 to 20 led to a modest improvement of 0.21 % and 2.72 % in the PCE and TCE, respectively. Similarly, raising the flow rate from 0.108 L/s to 0.128 L/s resulted in a corresponding increase of 0.25 % and 3.01 % in the PCE and TCE, respectively. These experimental investigations and numerical simulations established a solid scientific foundation and offered practical guidance for the implementation of MHP-PV/T systems, thereby facilitating the efficient utilization of solar energy in future applications.

Bio‐based lamb tail fat phase change material with enhanced thermal properties by incorporation of cyclophosphazene additives

AbstractAmong organic phase‐change materials (PCM), paraffin is commonly used, but it is not environmentally friendly due to its petrochemical origin. For efficient utilization of solar or thermal energy, new PCM are needed, or it is necessary to improve the thermal properties of existing materials. Therefore, the utilization of renewable alternatives such as lamb's tail fat as a latent heat storage material is of particular importance for the evaluation of bio‐based waste oils. In this study, new PCM were developed by using different concentrations of cyclophosphazene derivatives as an additive to the starting lamb tail fat (LTF) material. According to the results, doping the LTF with 1% and 2% hexa(N,N‐dibutyl‐4‐aminophenoxy)cyclotriphosphazene (HBACP) the heat of fusion is significantly improved, while the 1% hexa(2‐ethylhexyloxy)cyclotriphosphazene (HEHCP) doping decreased the heat of fusion. In a comparison of various doped PCM, it was found that the tail fat doped with 1% HBACP had a heat of fusion of 166.6 kJ/kg, but a lower specific heat capacity and thermal conductivity than that doped with 2% HBACP. On the other hand, 1% HEHCP had the lowest thermal conductivity but a higher specific heat capacity than 1% HBACP. In addition, it was found that the PCM developed by incorporating HBACP could be operated as a cooling fluid for photovoltaic modules or as a working fluid in concentrated solar energy systems due to the higher heat of fusion value of 1% HBACP and the higher specific heat capacity of 2% HBACP, which consists of lamb's tail fat.

Performance investigation of a V-trough concentrating agrivoltaic system based on spectral splitting

Abstract In order to improve the comprehensive utilization efficiency of solar energy, a V-trough concentrating and splitting agrivoltaic hybrid system (VCSPVA system) is proposed in this paper, which transmits the red and blue spectral bands to crop field for photosynthesis conversion and concentrates the other bands to the solar panels for photoelectric conversion. Then, the power generation is completed with sustaining the crop growth, while the overall utilization efficiency of solar energy is improved significantly. The influence of key parameters is studied in detail. Results show that by adjusting trough angles, more reflected radiation can be received by the solar panels, minimizing the energy loss of the system. Through mathematical model establishment, the energy, economic and carbon emission evaluations of the proposed system are carried out. Consequently, the VCSPVA system has the highest annual efficiency of 16.96%, which is 39.15% and 45.93% higher than that of the traditional agrivoltaic system and photovoltaic-only system, respectively. Meanwhile, the net present value and carbon emission mitigation are $758680.99 and 0.25 t·m−2·a−1, respectively, which demonstrates a competitive option for dual land use and a significant role in reducing greenhouse gas emissions.

Innovative cinque rib-roughened stimulators on performance improvement in triangular channel solar air heater

Abstract Present study investigates application of cinque-faced rib roughening to improve the efficiency of solar air heaters (SAHs). Research focuses on a novel design, the cinque-faced rib-roughened triangular channel SAH (CFRTCSAH), which incorporates five-faced wire ribs on the absorber plate’s underside. By breaking down the laminar sublayer and enhancing flow separation and reattachment, - ribs significantly enhance heat transfer. It establishes a comprehensive theoretical model to analyze the thermal and hydraulic performance of the CFRTCSAH. The study considers the influence of parameters such as relative roughness pitch (P/e) and relative roughness height (e/Dh) on thermal efficiency and heat removal factor. The results demonstrate that the CFRTCSAH achieves remarkable thermal efficiency, reaching up to 80.7% under optimal roughness parameters (P/e = 12, e/Dh = 0.05). It is found that an increase in mass flow rates positively impacts thermal efficiency but should not exceed 0.09 kg/s for maximum effective efficiency. Additionally, it has observed that the CFRTCSAH performs most effectively when the relative roughness pitch ratio (P/e) is set to 12. A higher relative roughness height (e/Dh) promotes convective heat transfer, enhancing thermal performance, especially at lower mass flow rates. Conclusion presents a novel approach to improving the thermal performance of SAHs by introducing cinque-faced rib roughening. The CFRTCSAH design exhibits significant potential for achieving high thermal efficiency and can contribute to more efficient solar energy utilization in various applications. These findings offer valuable insights for the development of SAHs, promoting sustainable and energy-efficient technologies.

Single-atom iron cocatalyst for highly enhancing TiO2 photocatalytic degradation of antibiotics and antibiotic-resistant genes

The efficient and sustainable utilization of solar energy and biomass resources through photocatalysis is important for achieving a carbon–neutral energy cycle. Here, we report an efficient photocatalyst SA-Fe@TiO2, where single-atom Fe sites are anchored to nitrogen-doped biochar and coupled with anatase TiO2. This innovative biochar-supported single-atom catalyst serves as a novel cocatalyst that can facilitate charge carrier separation and transfer. SA-Fe@TiO2 achieves an increase of 4.3 times in apparent rate constant for the degradation of the antibiotic sulfamethoxazole (SMX) and exhibits superior capacity for inactivating antibiotic-resistant genes compared with pure TiO2. Experimental evidence reveals the remarkable resistance of SA-Fe@TiO2 against environmental interferences, unveiling the involvement of three primary reactive species (h+, •OH, and •O2−) in SMX photodegradation. In addition, we fabricate immobilized SA-Fe@TiO2 films that effectively degrade five distinct antibiotics within 20 min. This study presents a new method for developing single-atom photocatalysts for highly efficient environmental remediation in the context of carbon neutrality.

Mathematical Modelling and Statistical Analysis of Improved Grey Wolf Optimized Maximum Tracking for Solar Photovoltaic Energy System Under Non Linear Operational Conditions

IAs the utilization of solar photovoltaic (PV) energy systems continues to expand, the efficient extraction of energy under non-linear operational conditions becomes paramount. This research focuses on the development and enhancement of a Maximum Power Point Tracking (MPPT) algorithm, specifically tailored for solar PV systems, through the integration of Improved Grey Wolf Optimization (IGWO) techniques. The study utilizes mathematical modeling and statistical analysis to evaluate the performance of the proposed IGWO-based MPPT algorithm. This research, we first establish a comprehensive mathematical model of a solar PV energy system that accurately represents its non-linear operational characteristics, taking into account factors such as temperature variations, shading effects, and changing environmental conditions. Subsequently, we introduce the Improved Grey Wolf Optimization algorithm to optimize the MPPT process, aiming to enhance energy extraction efficiency by dynamically adapting to varying conditions. The statistical analysis includes the comparison of the IGWO-based MPPT algorithm with conventional MPPT methods, such as Perturb and Observe (P&O) and Incremental Conductance (IncCond), under various non-linear operational scenarios. Key performance metrics, including energy conversion efficiency, response time, and tracking accuracy, are thoroughly evaluated to assess the algorithm's effectiveness in real-world conditions. The results of this study demonstrate the superior performance of the IGWO-based MPPT algorithm in enhancing the energy harvesting capabilities of solar PV systems under non-linear operational conditions. The proposed approach not only improves the overall energy conversion efficiency but also reduces the adverse effects of environmental variables on the system's performance. In conclusion, the integration of Improved Grey Wolf Optimization into the MPPT process represents a promising advancement in the field of solar photovoltaic energy systems. The mathematical modeling and statistical analysis conducted in this research provide valuable insights into the practical benefits of this approach, paving the way for more efficient and reliable solar energy utilization in the future.

Construction of a 2D/2D Crystalline Porous Materials Based S‐Scheme Heterojunction for Efficient Photocatalytic H2 Production

AbstractGenerally, the low electron–hole separation efficiency of covalent organic frameworks (COFs) prevents their catalytic performance from reaching satisfactory results. For this reason, the creation of heterojunctions is considered an effective strategy but usually suffers from dimensional mismatch of the integrated material, even at the expense of its redox capacity. To overcome these difficulties, a novel 2D/2D S‐scheme heterojunction between H2N–Cu–MOF (NCM) and TpPa–1–COF (TP1C) is successfully constructed for efficient photocatalytic H2 production. The matching dimensions of two crystalline porous materials enables the integrated materials with abundant surface reactive sites, strong interaction and optimized electronic structure. Moreover, the combination of two crystalline porous materials can also form a S–scheme heterojunction, which can not only promote the separation of electron–hole pair, but also preserve the redox ability, thus remarkably boosting the catalytic competence. Consequently, the rate of optimal 20% NCM/TP1C in photocatalytic H2 production reaches 4.19 mmol g−1 h−1, which is 46.5 times higher than that of bare NCM, and 22.1 folds over that of pure TP1C. This research offers an innovative perspective for the formation of S–scheme heterojunctions based on porous crystal materials for efficient solar energy utilization.

Thermal performance of two evacuated tube solar collectors with flat heat pipes

To promote the transition to clean heating methods in rural areas and improve solar energy utilization efficiency, two new types of solar water collectors with evacuated tubes, namely finned and finless collectors, are constructed with multi-channel flat tubes and flat micro-heat pipe arrays, and comparison experiments are conducted. By integrating with multi-channel flat tubes, the micro-heat pipe arrays, which function as the central heat transfer component, are capable of attaining effective thermal transmission. The multi-channel flat tubes have a substantial surface area available for heat transfer with the thermal fluid, while the evacuated tubes exhibit superior thermal insulation performance. The structural discrepancy between the two collectors lies in the presence or absence of louvered fins attached to the flat heat pipes inside the evacuated tubes. The comparative analysis of the two collectors includes time constant, thermal resistance analysis, distribution of temperature, normalized temperature difference, pressure drop, and actual operation effect under different conditions. The average thermal efficiency of the finless collector (59.4 %) is lower than that of the finned collector (78.2 %) on a typical experimental day. Then, further investigations are conducted to explore the effects of heat transfer fluid volume flow rate and inlet temperature on the thermal performance of finned solar water collector. With the heat transfer fluid volume flow rate of 120 L/h and the inlet temperature at 15 °C, the finned collector can achieve its maximum thermal efficiency of 86.4 %.

Dodecahedral hollow multi-shelled Co3O4/Ag:ZnIn2S4 photocatalyst for enhancing solar energy utilization efficiency.

Employing semiconductor photocatalysts featuring a hollow multi-shelled (HoMs) structure to establish a heterojunction is an effective approach to addressing the issues of low light energy utilization and severe recombination of photogenerated charge carriers. To take advantage of these key factors in semiconductor photocatalysis, here, a dodecahedral HoMs Co3O4/Ag:ZnIn2S4 photocatalyst (denoted as Co3O4/AZIS) was firstly synthesized by coupling Ag+-doped ZnIn2S4 (AZIS) nanosheets with dodecahedral HoMs Co3O4. The unique HoMs structure of the photocatalyst can not only effectively promote the separation and transfer of photo-induced charge, but also improve the utilization rate of visible light, exposing rich active sites for the photocatalytic redox reaction. The photocatalytic experiment results showed that the Co3O4/90.0 wt% AZIS photocatalyst has a high hydrogen (H2) production rate (695.0 μmol h-1 g-1) and high methyl orange (MO) degradation rate (0.4243 min-1). This work provides a feasible strategy for the development of HoMs heterojunction photocatalysts with enhanced H2 production and degradation properties of organic dyes.