Efficient Utilization Of Solar Energy Research Articles

Facile synthesis of heterostructured g-C3N4/Ag -TiO2 photocatalysts with enhanced visible-light photocatalytic performance

In this study, the g-C3N4/Ag-TiO2 composite photocatalysts were prepared to enhance the efficient utilization of solar energy. The g-C3N4 was synthesized by facile heat treatment of urea at 600℃ for 4 h, and 0.05 wt% to 3 wt% Ag-TiO2 were obtained through the chemical reduction method. The composite photocatalysts were prepared by mixing the g-C3N4 and Ag-TiO2 with a weight ratio of 50:50 at room temperature. The photocatalytic efficiency was carried out by using 0.05 g of photocatalysts with 10 mg·L-1 of rhodamine B 120 mL under 60 min of visible light irradiation. The experimental results indicated that a sample with 0.1 wt% Ag-TiO2 could degrade rhodamine B up to 21.21%. The g-C3N4/(0.1 wt% Ag-TiO2) and g-C3N4 showed rhodamine B degradation efficiency up to 100%, which was 10.4 times and 4.7 times of pure TiO2 and 0.1 wt% Ag-TiO2, respectively. It can be suggested that the Ag deposited on TiO2 played an important role in the absorption capability under the visible light through the surface plasmon resonance effect. In addition, heterojunction between g-C3N4 and TiO2 could reduce the recombination of electron-hole pairs.

Energy production features of rooftop hybrid photovoltaic–wind system and matching analysis with building energy use

Rooftop photovoltaic (PV)–wind hybrid systems serve as a promising energy supply source to mitigate environmental concerns and satisfy high energy demands. Most of energy matching studies focused on the matching capability of photovoltaic generation with building load, and the application of wind power to complement PV was rarely considered. In the context, this study explored the production aspects of PV–wind turbine (WT) hybrid systems and their potential to meet building energy use demands in densely built urban areas. Both solar and wind resources in 18 cities in eastern China were classified into three energy output levels, and Hangzhou was selected as a representative city for analysis of the complementarity of the two resources. Based on the modeling of hybrid PV–wind system generation, a PV/WT production feature curve was generated by k-means clustering. The matching between renewable energy production and building energy use and the influences of different wind resources and building heights were analyzed for rooftop hybrid systems in two typical residential buildings. The results reveal that the wind and solar resources in Hangzhou are partly complementary in terms of time sequence and power output. For the multi-story and high-rise residential building considered, a rooftop hybrid PV–WT system was concluded to be beneficial in improving energy generation, reliability, and load matching performance in a limited space. The technical performance for the high-rise case was inferior to that for the multi-story case considered. In the case of residential buildings, the matching between on-site supply and load is influenced by the local wind resources and building height. The richer the urban wind resource, the greater the load cover ratio and the self-sufficiency of the installed rooftop hybrid system. However, the load matching performance declines with increasing building height. The proposed general method for analyzing rooftop hybrid PV–WT systems can enable widespread and efficient solar and wind energy utilization in densely populated and built urban areas.

Towards single‐atom photocatalysts for future carbon‐neutral application

AbstractThe implementation of carbon neutrality to achieve the goal of controlling global warming in the Paris Climate Agreement is currently the most important international climate issue. Efficient utilization of solar energy through photocatalysts is of great significance to the adjustment of energy structure. Single‐atom photocatalysts have excellent catalytic activity and selectivity in a variety of applications, including sustainable energy conversion, chemical synthesis, CO2 reduction, environmental remediation, and other areas, owing to their unique electronic structure and high atom usage. Here, we elaborated on the content and implementation direction of the carbon neutrality policy and demonstrated the design principles of single‐atom photocatalysts. Recent single‐atom synthesis strategies are summarized, and representative characterization methods have been shown to further reveal the structure–performance relationship. Then, we focus on the application of single‐atom photocatalysts in CO2 reduction, sustainable energy conversion, and environmental remediation. Finally, the opportunities and challenges in the application of single‐atom photocatalysts were discussed based on its current development.

Thermal energy storage cement mortar containing encapsulated hydrated salt/fly ash cenosphere phase change material: Thermo-mechanical properties and energy saving analysis

Solar passive house equipped with thermal energy storage cement mortar (TESCM) containing encapsulated phase change material (PCM) has showed great potential in terms of energy saving. However, TESCMs are universally behaved as deteriorated mechanical strength and high cost, limiting their applications. This study developed a novel TESCM by integrating cement mortar with polyethylene glycol@SiO2-coated eutectic hydrated salt/fly ash cenosphere encapsulated PCM, in order to improve the mechanical property and cost-effectiveness. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and attenuated total reflection Fourier transform infrared (ATR-FTIR) results showed that the synthetic encapsulated PCM possessed satisfying encapsulation ability, latent heat and chemical compatibility. The encapsulated PCM was incorporated into cement mortar by partial replacement of sand. It turned out that the prepared TESCM containing 20% encapsulated PCM exhibited 28d compressive and flexural strengths of 36.5 MPa and 6.2 MPa, merely presenting slight decreases of mechanical strengths compared to the control cement mortar. Moreover, X-ray diffraction (XRD), thermal gravimetric (TG) and backscattered electron (BSE) were conducted on TESCM to analyze the hydration products, hydration degree and interface transition zone between cement matrix and the encapsulated PCM, and the influence on mechanical strength was deeply analyzed. Besides, thermal performance test confirmed that the prepared TESCMs had good heat storage capacity. In the heating test, the peak temperature in the test chamber equipped with TESCM was reduced by 3.1 °C when 20% encapsulated PCM was contained in TESCM. Furthermore, economic evaluation indicated the low cost and prominent energy saving performance of the prepared TESCM. This work provides insights into the developing structural-functional building materials with high mechanical strength and thermal energy storage for efficient solar energy utilization in passive buildings.

SCL, Encoding a Chloroplast Signal Recognition Particle Receptor, Affects Chlorophyll Synthesis and Chloroplast Development in Rice

Crop yield is largely determined by the solar energy utilization efficiency of photosynthesis; plants with long stay-green periods have greater total photosynthetic production levels and crop yields. Here, a novel seedling chlorosis and lethality (scl) mutant exhibiting a yellow leaf and seedling-lethal phenotype was identified in rice (Oryza sativa L.). The mutant had deformed chloroplasts and almost no protein complexes in thylakoid membranes. The expression levels of photosynthesis-associated genes were significantly down-regulated in scl compared with the wild-type (WT). Positive transgenic lines generated by Agrobacterium tumefaciens-mediated transformation of the scl mutant with a complementation vector harboring SCL cDNA exhibited the normal green leaf phenotype, whereas the scl seedling harboring the empty vector displayed the yellow leaf phenotype, indicating that SCL is LOC_Os01g72800. A fusion protein expressing SCL with green fluorescent protein revealed the fluorescence signal localized to chloroplasts. The expression patterns of chloroplast development and chlorophyll biosynthesis and degradation-related genes were disordered in scl mutant, possibly resulting in the yellow leaf phenotype. These results indicated that the SCL loss of function impaired chloroplast development, chlorophyll biosynthesis, and light-harvesting chlorophyll-binding protein transportation in rice.

Design of a novel photoelectrochemical enzymatic biofuel cell with high power output under visible light

• A novel PEBFC with high enough power output under visible light was designed. • GR-CdS QDs/TiO 2 NRAs photoanode could catalyze the oxidation of AA excellently. • The reduction of oxygen was highly efficient at the 3D GR-SWCNTs-laccase biocathode. • Two PEBFCs connected in series could light the red LED successfully. Photoelectrochemical enzymatic biofuel cell (PEBFC) shows the obvious advantages in the renewable energy conversion field. However, because of the low utilization efficiency of solar energy and the unendurable power output, PEBFC cannot satisfy the demand of practical applications. Herein, a novel PEBFC prototype is designed. Taking a TiO 2 nanorod arrays (NRAs) decorated graphene–cadmium sulfide quantum dots (GR–CdS QDs) hybrid at fluorine-doped tin oxide (FTO) glass electrode as the photoanode, it can catalyze the oxidation of ascorbic acid (AA) effectively, with the oxidation current being as high as –137.8 μA cm −2 , and the anodic open circuit potential ( E a O C P ) reaching approximately –0.52 V; using a laccase–bound three–dimensional graphene–single walled carbon nanotubes (3D GR–SWCNTs–laccase) hybrid electrode as the biocathode, along with 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), the biocathode can catalyze the reduction of oxygen remarkably, and the cathodic open circuit potential ( E c OCP ) is as high as 0.54 V. Under optimal conditions, such PEBFC can obtain sufficient high open circuit voltage (V oc ) of 1.05 V and maximum power output density (P max ) of 227.5 μW cm −2 , respectively. Two PEBFCs connected in series can light a red light-emitting diode (LED) successfully.

Two-dimensional polar materials for photocatalytic water splitting

<p indent="0mm">As one of the most charming and attractive technologies, photocatalytic overall water-splitting using solar energy is known as a feasible and efficient route to alleviate energy crisis and environmental pollution. Since the seminal work of photocatalytic decomposition of H₂O into H₂ and O₂ on a Pt/TiO₂ electrode by Fujishima and Honda in 1972, photocatalytic water splitting has been persistently investigated, achieving many remarkable advancements. In principle, photocatalytic water splitting reaction mainly involves the following fundamental processes: Absorption of photons induces electron transition and forms electron-hole pairs; then the photogenerated electron-hole pairs separate and migrate to the surface of the photocatalyst; finally, redox reaction occurs on the surface. Therefore, to develop high-performance photocatalysts, several criteria must be fulfilled, including a moderate band gap that should be larger than <sc>1.23 eV</sc> but lower than <sc>3.0 eV</sc> to maximize absorption and utilization solar light, the ability of rapid separation and transfer of carriers, and the suitable band edge alignment to straddle the redox potentials of water. To this end, numerous efforts have been devoted to searching for photocatalytic candidates. In recent years, two-dimensional (2D) materials, e.g., g-C₃N₄, phosphorene and transition-metal dichalcogenides, have been identified as the potential photocatalysts candidates for water splitting. Compared with the bulk materials, 2D materials hold excellent ability of optical adsorption, short carrier migration distance, high carrier mobility, large specific surface area, and abundant active sites. Therefore, the 2D materials are desirable for high-performance photocatalysts. Nevertheless, most of the 2D photocatalysts for water splitting have the structural symmetry along the out-of-plane direction, which mainly harvests the ultraviolet light and limits the efficiency of solar energy utilization. Some new materials and mechanisms for photocatalytic water-splitting are urgently needed. Interestingly, the asymmetric 2D materials with the intrinsic dipole moment, termed as 2D polar materials, show exciting prospects for the photocatalytic applications with high efficiency. The intrinsic dipole moment in 2D polar materials not only accelerates the separation of photogenerated carriers but also is good for relieving the conventional restriction of <sc>1.23 eV</sc> for band gap of photocatalysts, leading to a widened light absorption region (from visible to near-infrared light). Thus, the solar energy utilization efficiency will be substantially enhanced. Motivated by this mechanism, some 2D polar photocatalysts are proposed, such as MXY (M=W, Mo, Cr, Pt; X, Y=S, Se, Te, X<x content-type="symbol">¹</x>Y), M₂XY (M=Ga, In; X, Y=S, Se, Te, X<x content-type="symbol">¹</x>Y), and M₂X₃(M=Al, Ga, In; X=S, Se, Te). In this review, we outline the recent progress in material discovery and photocatalytic characteristics of the different types of 2D polar photocatalysts, including Janus materials and ferroelectrics. The underlying mechanisms for polarization-promoted photocatalysis are discussed to better understand the role of 2D polar materials in photocatalysis. After the presentation of the experimental efforts on 2D polar materials, we conclude with a discussion of the emerging challenges and new perspective for future research and development on 2D polar photocatalysts. We hope that this review, with a specific focus on 2D polar photocatalysts, would help readers gain deep understandings on 2D polar material-based photocatalysts and in turn stimulate further both theoretical and experimental efforts.

Theoretical design of two-dimensional visible light-driven photocatalysts for overall water splitting

Hydrogen production from water via photocatalytic water splitting has attracted great interest due to the increasing challenge from energy and environment. The light harvest, electron–hole separation, and catalytic activity are keys to enhance the efficiency of solar energy utilization, which stimulates the development of high-performance photocatalysts. In recent years, two-dimensional (2D) materials have attracted much attention due to their extremely large specific surface area, shortened carrier migration path, and excellent optical properties, but it is still a challenge to realize overall water splitting under visible light with 2D material photocatalysts experimentally. Density functional theory-based first-principles calculations provide a quicker and lower cost approach in material design than experimental exploration. In this review, recent advances in design of 2D material photocatalysts, including metal-containing, metal-free, and heterojunction materials, for photocatalytic water splitting are presented from a theoretical perspective. Future opportunities and challenges in theoretical design of 2D material photocatalysts toward overall water splitting are also included.

Hierarchical microencapsulation of phase change material with carbon-nanotubes/polydopamine/silica shell for synergistic enhancement of solar photothermal conversion and storage

Aiming at improving the utilization efficiency of solar photothermal energy, this study focuses on a novel phase-change microcapsule system based on an n-docosane core and a carbon-nanotubes (CNTs)/polydopamine (PDA)/silica hierarchical shell. The system was fabricated by encapsulating n-docosane in a silica shell and then depositing a PDA layer on the shell surface, followed by conglutinating CNTs onto the PDA layer. The resultant microcapsule system shows a regular spherical morphology together with desired core-shell hierarchical microstructure and chemical compositions. The presence of CNTs/PDA coating layer can impart an efficient solar light-to-heat energy conversion capability to the microcapsule system through photon capture and sunlight absorption. The microcapsule system not only shows a good latent heat-storage capability with satisfactory phase-change enthalpies of over 130 J/g but also exhibits an optimal photothermal conversion efficiency of 90.1%. The microcapsule system also exhibits good leakage-prevention performance, high thermal cycle stability, excellent thermal impact resistance, and good shape/form stability to deal with a wide range of solar photothermal energy applications. Through integrating CNTs and PDA into a phase-change microcapsule system, this work provides a promising approach for the development of PCMs-based functional materials with enhanced solar light-to-heat energy conversion and storage performance for efficient utilization of solar energy.

An Air Convection Wall with a Hollow Structure in Chinese Solar Greenhouses: Thermal Performance and Effects on Microclimate

A Chinese solar greenhouse (CSG) is a horticultural facility that uses solar energy to promote a growth environment for crops and provides high-efficiency thermal storage performance to meet the demand of vegetables’ growth in winter. Besides being an important load-bearing structure in CSGs, the north wall is a heat sink, storing during the day in order to act as a heat source during the night. At times, the night temperature is lower than the minimum growth temperature requirement of vegetables, and the additional heating is needed. Therefore, optimizing the heat storage and release performance of the north wall in a CSG is an important approach for improving growth environment and reducing consumption of fossil fuel. This study proposes a heat storage north wall with a hollow layer on the basis of air convection, aiming to optimize the utilization of solar energy in CSGs. By the air convection effects, the hollow layer collects and stores surplus solar energy in the air during the day and transfers it to the cultivation space for heating at night. Additionally, field tests were conducted to compare the natural and forced convection strategies via airflow and heat transfer efficiency. The final effect on the indoor temperature ensured that the lowest temperatures at night were above 5 °C under both the natural and forced convection strategies during the winter in the Beijing suburbs where the average minimum temperature is below −10.8 °C during the experimental period. The hollow structure improves the utilization efficiency of solar energy in CSGs and ensures winter production efficiency in northern China.

Three-dimensional directional cellulose-based carbon aerogels composite phase change materials with enhanced broadband absorption for light-thermal-electric conversion

Energy shortage, environmental and ecological issues have prompted a focus on effective solar energy utilization. Using composite phase change materials (PCMs) as an energy storage medium is an important method to achieve efficient solar energy conversion. Biomass materials are highly desirable for solar applications due to their wide range of sources, low cost, environment-friendly, and natural porous structure. In this study, cellulose is selected as a carbon source precursor. Three-dimensional (3D) directional cellulose-based carbon aerogels (CBCA) are constructed through an immersion expansion, orientation, freeze-drying, and carbonization process. Taking tert-butanol/ deionized water as co-solvent, the aerogel shows high specific surface and productivity as well as low structural shrinkage. 3D directional graphitized porous network and graphene guarantee excellent broadband absorption, efficient heat transfer pathways, and effective thermal storage ability. Stearic acid (SA) and graphene are melt blending, followed by a vacuum-impregnating process for the formation of 3D composite PCMs. The thermal storage capability of PCMs is greater than 96%, accompanied by the highest thermal conductivity of 1.17 W/(m·K) with 0.5 wt% graphene. Moreover, the highest light-thermal conversion efficiency can reach 90.3%. It also has a maximum light-thermal-electric energy conversion output power of 1.80 mW. This work provides a feasible, economical strategy for highly efficient solar energy storage and thermal energy utilization.

In-situ Synthesis of the Thinnest In2 Se3 /In2 S3 /In2 Se3 Sandwich-Like Heterojunction for Photoelectrocatalytic Water Splitting.

The efficient utilization of solar energy for photoelectrocatalytic (PEC) water splitting is a feasible solution for developing clean energy and alleviating environmental issues. However, as the core of PEC technology, the existing photoanode catalysts have disadvantages such as poor photoelectrocatalytic conversion efficiency, low conductivity of photogenerated carriers, and instability. Here, we report the ultrathin two-dimensional sandwich-like (SW) heterojunction of In2 Se3 /In2 S3 /In2 Se3 (SW In2 S3 @In2 Se3 ) for the first time for PEC water splitting. Our findings identify the efficient separation of electrons and holes by constructing SW In2 S3 @In2 Se3 heterojunction. The in situ synthesis of ultrathin nanosheet arrays by using surface substitution of Se atom to epitaxially grow cell In2 Se3 maximizes the contact area of heterogeneous interface and accelerates the transmission of charge carrier. Benefitting from the unique structure and composition characteristic, SW In2 S3 @In2 Se3 displays excellent performance in PEC water splitting. The photocurrent density of SW In2 S3 @In2 Se3 reaches 8.43 mA cm-2 at 1.23 VRHE . Compared with In2 S3 , the SW In2 S3 @In2 Se3 photoanode has nearly 12 times higher PEC performance, which represents the best performance among the In2 S3 -based photoanode heterojunction reported so far. The evolution rate of O2 reaches 78.8 μmol cm-2 h-1 , and the photocurrent has no apparent variety within 24 h.

Experimental Assessment of the Influence of the Design on the Performance of Novel Evaporators with Latent Energy Storage Ability

This study was carried out within the HYBUILD project, as part of the task aimed at developing novel evaporators for compact and direct integration of phase-change materials (PCM) into air-conditioning systems for efficient utilization of solar energy. To achieve this, novel evaporators were designed to contain PCM between refrigerant and heat transfer fluid (HTF) channels, allowing a three-media heat exchange mechanism. This paper experimentally assesses the influence of the configuration/arrangement of the channels on the performance of the evaporators, using three different lab-scale prototypes. Key performance indicators (KPI) relevant for thermal energy storage (TES) and heat exchangers (HEX) were used to study the influence of the design on the performance of the different designs of the novel evaporators. The results show that the change in the PCM, refrigerant, and HTF channel configuration affects the performance of the novel evaporators independently. The coefficient of performance (COP) of the refrigeration system and the energy storage density of the modules are the least affected KPIs (less than 16%), whereas the state of charge (SOC) at thermal equilibrium is the most affected KPI (about 44%). A discussion on how these effects provide unique strength for specific applications is included.

Development of photoluminescence phase-change microcapsules for comfort thermal regulation and fluorescent recognition applications in advanced textiles

To expand the application range of microencapsulated phase change materials into advanced textiles, we designed and developed a type of photoluminescence phase-change microcapsule system based on an n-eicosane core and a Eu3+-doped CaCO3/Fe3O4 composite shell. This type of functionalized phase-change microcapsules was fabricated by encapsulating n-eicosane in the CaCO3/Fe3O4 composite shell through in-situ precipitation in a Pickering emulsion-templating system, followed by doping Eu3+ on the surface of the CaCO3/Fe3O4 composite shell. The resultant microcapsules show a well-defined core–shell microstructure and regular spherical morphology with a rough surface due to the presence of Eu3+. Introducing Fe3O4 nanoparticles as a light absorber into the CaCO3 shell enhanced the utilization efficiency of solar photothermal energy for the phase-change microcapsules. The fabricated microcapsules not only exhibited a satisfactory thermal regulation capability under a latent heat capacity of over 125 J/g, but also achieved a high photothermal conversion efficiency of 67.6%. Doping Eu3+ into the CaCO3/Fe3O4 composite shell imparted a photoluminescence function to the phase-change microcapsules, resulting in a fluorescence emission at an excitation wavelength of 394 nm. An application investigation of the phase-change microcapsules in advanced textiles was carried out to confirm their contributions to the thermal comfort of human body together with high recognition under the extreme conditions. With excellent solar photothermal conversion, latent heat storage, and photoluminescence performance, the phase-change microcapsules developed by this study exhibit great potential for bifunctional applications of comfort thermal regulation and fluorescent recognition in advanced textiles.

Performance optimization of photovoltaic systems: Reassessment of political optimization with a quantum Nelder-mead functionality

Evaluating the PV system parameters is crucial for the more efficient utilization of sustainable solar energy. Due to PV systems' nonlinear and multimodal nature, efficient evaluation of PV system parameters is still a very challenging task. This paper proposes an improved political optimization algorithm, namely the QNMPO algorithm, which combines quantum rotation gate and Nelder-Mead simplex (NMs). It can be used to evaluate unknown parameters of PV systems and solar cells efficiently. In QNMPO, the quantum rotation gate method can rotate the population of agents to a more favorable position for finding the optimal solution, making the individuals in the middle of the population communicate more frequently and enhancing the population's diversity. In addition, the NMs method can improve the solution quality by better searching the neighborhoods near the optimal solution and then strengthen the advantage of local development of the algorithm so that it can converge to the global optimal solution faster. The developed QNMPO algorithm extracts the unknown parameters for single diode, double diode, triple diode and photovoltaic modules in this study. It is compared with some other representative algorithms. The experimental results show that QNMPO outperforms similar algorithms in convergence speed, solution accuracy, and better solution performance. QNMPO was then used to successfully extract the best parameter values for three real PV models (three commercial PV models (thin-film ST40, monocrystalline SM55, and multi crystalline KC200GT)) at different temperatures and different irradiance levels. The results also show that QNMPO performs consistently and accurately enough under varying temperatures and irradiation. Therefore, the QNMPO algorithm proposed in this paper can be a promising parameter extraction method for solar PV systems with good performance.

Enhancing the heat transfer and photothermal conversion of salt hydrate phase change material for efficient solar energy utilization

Solar energy is intermittent, resulting in a discrepancy between the solar energy supply and building energy demand. Salt hydrate phase change material (PCM) is a promising material for use as an energy storage medium, but it suffers from a high supercooling degree, low thermal conductivity, and insufficient photothermal conversion efficiency. In this work, a novel sodium acetate trihydrate (SAT) composite was developed by synergistically using nano SiO2 (NS) as the nucleating agent, silicon carbide (SiC) foam as the thermal conductivity enhancer, and carbon nanotubes (CNT) as the photothermal enhancer. The supercooling degree of the modified SAT composite was only 1.4 °C, whereas the thermal conductivity and photothermal conversion efficiency could be increased to 1.54 W/(m•K) and 94.2 %, respectively. Most importantly, the payback period for applying the modified SAT composite in solar energy storage for domestic hot water supply is only 3.1 years, and the carbon dioxide emission could be reduced by approximately 1379.1 kg CO2-eq/year for a typical four-person family. Overall, the modified SAT composite with stable and excellent thermophysical properties offers great potential for the storage of solar thermal energy.

Energy performance of a reversible window integrated with photovoltaic blinds in Harbin

A reversible window integrated with photovoltaic blinds (RW-PVB) has the potential to achieve higher solar energy utilization efficiency and reduce net electricity consumption (NEC) of building when compared with conventional photovoltaic window (CPVW). However, research on the overall energy performance of RW-PVB is still required to provide methods for exploiting the energy saving potential of RW-PVB and optimizing its design. To this end, this study developed a comprehensive model of RW-PVB to evaluate and balance its thermal, electrical and daylighting performance by considering different types of PV glazing, window to wall ratios (WWRs) and orientations. The results showed that the four types of RW-PVBs selected, including amorphous silicon (a-Si), cadmium telluride (CdTe), dye-sensitized solar cell (DSSC), and perovskite solar cell (PSC) ones, all performed better in reducing NEC when compared with the corresponding CPVW in Harbin, a representative heating dominated city in China. The net energy saving ratios ranged from 2.16 to 13.10% varying with the type of RW-PVB. The three orientations studied, namely the southwest, south and southeast ones, did not have a significant impact on the near optimal WWR which were about 0.3, 0.6, 0.3 and 0.5 for a-Si, CdTe, DSSC and PSC RW-PVBs, respectively. The south orientation was the most beneficial to the installation of RW-PVB for NEC reduction among the three orientations selected.

Up-conversion fluorescent carbon quantum dots decorated covalent triazine frameworks as efficient metal-free photocatalyst for hydrogen evolution

Photocatalytic hydrogen production holds great promise for alleviating the energy shortage through effective photo-to-chemical conversion, and the development of visible-light responsive, low-cost and sustainable photocatalysts remains key priority. In this study, carbon quantum dots/covalent triazine-based framework (CQDs/CTF) non-metallic photocatalyst was constructed through a simple impregnation method for photocatalytic H 2 evolution. Upon 0.24% CQDs loading, a three-fold enhanced H 2 production activity of 102 μmol∙g −1 ∙h −1 was achieved compared with pristine CTF-1 (34.5 μmol∙g −1 ∙h −1 ). Photoluminescence and photoelectrochemical study revealed carbon quantum dots served as the electron libraries, which was conducive to facilitate electron capture and promote the separation of photoinduced electron-hole pairs in CTF-1. Notably, the excitation-independent up-conversion fluorescent characteristics of CQDs endowed the catalysts broadened visible-light response range and higher solar energy utilization efficiency. This study deepens insights into the mechanism of CQDs modification and paves a trustworthy strategy for harvesting visible-light-driven metal-free photocatalyst with highly-active and robust performance. • A highly active and stable metal-free photocatalyst based on CTFs was constructed. • The fluorescent behavior of CQDs under different wavelength ranges were studied. • The lights emitted by CQDs could be efficiently utilized to stimulate CTFs. • The photocatalytic process and mechanism were systematically studied.

Experimental investigation of the comprehensive heat transfer performance of PCMs filled with CMF in a heat storage device

Phase-change materials (PCMs) can overcome the low energy density and utilization efficiency of solar energy. However, the low thermal conductivity of PCMs significantly affects the thermal efficiency of solar devices; thus, improving the thermal conductivity of PCMs has been the focus of many recent studies. In this study, copper metal foam (CMF) composite PCMs were prepared using paraffin wax and high-pore-density CMF. The effect of the CMF proportion on heat transfer enhancement in the PCM melting process was analyzed using experimental equipment for heat storage visualization. Comprehensive heat transfer coefficients of CMF composite PCMs were obtained. The experimental results showed that as the CMF proportion increased from 0 to 2.15%, the melting time of the CMF composite PCMs and their heat storage capacity first increased and then decreased, whereas the heat storage rate and comprehensive heat transfer coefficient first decreased and then increased. The minimum temperature gradient of 8.09 K was reached when the CMF proportion was 2.15%. More importantly, as the proportion of CMF increased from 0.43 to 2.15%, the proportion of natural convection decreased from 87.90 to 17.69%, and natural convection was the major heat transfer mechanism in the melting process of composite PCMs with a low CMF proportion. The composite PCMs with a CMF proportion of 0.86% has the best heat storage performance when the heat storage capacity and heat storage rate were both considered.

Diradical-Featured Organic Small-Molecule Photothermal Material with High-Spin State in Dimers for Ultra-Broadband Solar Energy Harvesting.

Organic materials with radical characteristics are gaining increasing attention, due to their potential implications in highly efficient utilization of solar energy. Manipulating intermolecular interactions is crucial for tuning radical properties, as well as regulating their absorption bands, and thus improving the photothermal conversion efficiency. Herein, a diradical-featured organic small-molecule croconium derivative, CR-DPA-T, is reported for highly efficient utilization of solar energy. Upon aggregation, CR-DPA-T exists in dimer form, stabilized by the strong intermolecular π-π interactions, and exhibits a rarely reported high-spin state. Benefiting from the synergic effects of radical characteristics and strong intermolecular π-π interactions, CR-DPA-T powder absorbs broadly from 300 to 2000nm. In-depth investigations with transient absorption analysis reveal that the strong intermolecular π-π interactions can promote nonradiative relaxation by accelerating internal conversion and facilitating intermolecular charge transfer (ICT) between dimeric molecules to open up faster internal conversion pathways. Remarkably, CR-DPA-T powder demonstrates a high photothermal efficiency of 79.5% under 808nm laser irradiation. By employing CR-DPA-T as a solar harvester, a CR-DPA-T-loaded flexible self-healing poly(dimethylsiloxane) (H-PDMS) film, named as H-PDMS/CR-DPA-T self-healing film, is fabricated and employed for solar-thermal applications. These findings provide a feasible guideline for developing highly efficient diradical-featured organic photothermal materials.