Solar Conversion Research Articles

Construction of MXene-enhanced rigid polyurethane foam/polyethylene glycol phase change composites for solar thermal conversion and storage

In this study, various rigid polyurethanes foams (PUFs) with different morphologies were prepared and subsequently used for encapsulating the phase change material, polyethylene glycol (PEG). To address the low photothermal conversion efficiency of polyurethane-based phase change materials, MXene was successfully synthesized via an in-situ hydrofluoric acid (HF) etching method and incorporated into the PEG to obtain MXene@PEG composite material. Finally, a series of innovative MXene@PEG-PUF phase change composites were successfully fabricated by utilizing PUFs as the supporting matrix and the MXene@PEG composite as the phase change component through a vacuum impregnation technique, and their thermophysical properties and photothermal conversion performance were systematically studied. The results show that PUF is the ideal capsulation material for PEG. And MXene@PEG-PUF demonstrates a high PCM loading rate (>80 wt%) and a high latent heat storage enthalpy (>140 J/g) with a relative enthalpy efficiency of 99.5%, maintaining excellent shape stability and relative enthalpy efficiency of 95.58% after 150 thermal cycles. This highlights its superior thermal reliability, making it suitable for practical building energy-saving applications. Most importantly, the incorporation of MXene into PUF@PEG significantly enhances solar-to-thermal conversion capability, attributed to the exceptional photothermal characteristics of MXene.

Crystal phase-dependent optical properties of CoMn-based spinel oxides for solar thermal conversion

This work reveals the intrinsic correlation of the crystal phase of CoMnO-based spinel oxides with its optical properties and solar thermal conversion efficiency.

Novel dual spectral conversion via Eu2+, Cu+-coactivated core–shell-structured CaS@CaZnOS phosphors for efficient photosynthesis of plants

Core–shell-structured CaS:Eu2+,Cu+@CaZnOS:Cu+ phosphor with excellent dual-excitation and dual-emission performance can efficiently convert solar energy and enhance the photosynthesis efficiency of crops in facility agriculture.

Atomically precise metal nanoclusters combine with MXene towards solar CO2 conversion.

Atomically precise metal nanoclusters (NCs) have been deemed a new generation of photosensitizers for light harvesting on account of their quantum confinement effect, peculiar atom-stacking mode, and enriched catalytic active sites. Nonetheless, to date, precise charge modulation over metal NCs has still been challenging considering their ultra-short carrier lifetime and poor stability. In this work, we conceptually demonstrate the integration of metal NCs with MXene in transition metal chalcogenide (TMC) photosystems via a progressive, exquisite, and elegant interface design to trigger tunable, precise and high-efficiency charge motion over metal NCs, stimulating a directional carrier transport pathway. In this customized ternary heterostructured photosystem, metal NCs function as light-harvesting antennas, MXene serves as a terminal electron reservoir, and the TMC substrate provides suitable energy level alignment for retracting photocarriers of metal NCs, giving rise to a spatial cascade charge transport route and markedly boosting charge separation efficiency. The interface configuration and energy level alignment engineering synergistically contribute to the considerably enhanced visible-light-driven photocatalytic CO2-to-CO reduction performance of the metal NCs/TMCs/MXene heterostructure. The intermediate active species during the photocatalytic CO2 reduction are unambiguously determined, based on which the photocatalytic mechanism is elucidated. Our work will provide an inspiring idea to bridge the gap between atomically precise metal NCs and MXene in terms of controllable charge migration for solar-to-fuel conversion.

High-throughput screening of stable sulfide semiconductors for solar cell conversion

Based on stability, band gap, carrier effective masses, defect tolerance, and optical absorption coefficients, RE3CoCrS7 (RE = La, Y) is identified as a high-performance sulfide semiconductor for solar cell conversion in A3BB′S7 family.

Boron nanosheets boosting solar thermal water evaporation.

Hydrogel-based solar vapour generators (SVGs) are promising for wastewater treatment and desalination. The performance of SVG systems is governed by solar thermal conversion and water management. Progress has been made in achieving high energy conversion efficiency, but the water evaporation rates are still unsatisfactory under 1 sun irradiation. This study introduced novel two-dimensional (2D) boron nanosheets as additives into hydrogel-based SVGs. The resulting SVGs exhibit an outstanding evaporation rate of 4.03 kg m-2 h-1 under 1 sun irradiation. This significant improvement is attributed to the 2D boron nanosheets, which leads to the formation of a higher content of intermediate water and reduced water evaporation enthalpy to 845.11 kJ kg-1. The SVGs into which boron nanosheets were incorporated also showed high salt resistance and durability, demonstrating their great potential for desalination applications.

Assessing the potential of TOPCon solar cells architecture using industrial n-type cast-mono silicon material

Cast-mono silicon material is interesting for its lower carbon footprint compared to Czochralski (Cz) monocrystalline silicon. However, solar cells fabricated using cast-mono (CM) silicon show lower performances. In this work, two routes to make cast-mono silicon advantageous over Cz silicon are considered. The first route is to further reduce carbon footprint of cast-mono silicon, by using Upgraded Metallurgical Grade silicon (UMG-Si) feedstock instead of Solar Grade silicon (SoG-Si) feedstock. TOPCon solar cells are fabricated using both feedstocks, and cast-mono growth technology, using industrial-type furnaces. Laboratory studies show that UMG-Si can result in efficiencies higher than solar cells made of SoG-Si when feeding the material to a CM crystallization process. But when compared to Cz, CM-UMG-Si TOPCon solar cells conversion efficiency values are still 0.5%abs lower. The second route is to take advantage of the TOPCon passivation layer (e.g., poly-Si) ability to getter metallic impurities, and thus improve the quality of cast-mono material. Several TOPCon sequences are tested and their effect on the carrier recombination properties of the device are studied. In the end, solar cells are fabricated and again, UMG-Si solar cells show better results than SoG-Si solar cells, with efficiency up to 22.65%, independently confirmed.

Au-decorated Sb2Se3 photocathodes for solar-driven CO2 reduction.

Photoelectrodes with FTO/Au/Sb2Se3/TiO2/Au architecture were studied in photoelectrochemical CO2 reduction reaction (PEC CO2RR). The preparation is based on a simple spin coating technique, where nanorod-like structures were obtained for Sb2Se3, as confirmed by SEM images. A thin conformal layer of TiO2 was coated on the Sb2Se3 nanorods via ALD, which acted as both an electron transfer layer and a protective coating. Au nanoparticles were deposited as co-catalysts via photo-assisted electrodeposition at different applied potentials to control their growth and morphology. The use of such architectures has not been explored in CO2RR yet. The photoelectrochemical performance for CO2RR was investigated with different Au catalyst loadings. A photocurrent density of ∼7.5 mA cm-2 at -0.57 V vs. RHE for syngas generation was achieved, with an average Faradaic efficiency of 25 ± 6% for CO and 63 ± 12% for H2. The presented results point toward the use of Sb2Se3-based photoelectrodes in solar CO2 conversion applications.

A Ni@C nanowire-enabled photothermal membrane for highly efficient solar-driven interfacial water purification.

Ni@C nanowires were in situ grown with about 5 nm nickel particles uniformly distributed along the one-dimensional framework. By assembling into a membrane, Ni@C exhibited 95.7% solar spectral absorption and a high water interfacial evaporation rate of 2.38 kg m-2 h-1 under one sun. Superhydrophobic modification further enabled long-term stable saline water evaporation. This work demonstrates the promising potential of non-precious Ni for solar photothermal conversion applications.

Betanin dye extracted from ayrampo (Opuntia soehrensii) seeds to develop dye-sensitized solar cells.

Pigments extracted from ayrampo seeds of the Peruvian-native prickly pear (Opuntia soehrensii) were used in dye-sensitized solar cells with promising efficiencies. The performance of the solar cells was then improved via the addition of citric acid to stabilise the photosensitive dye, and an efficiency of 1.41% was achieved with current output remaining stable after 7 days. Upon testing in low-light conditions, the solar conversion efficiency of devices increased to 4%. This paper not only highlights the potential of natural sensitizers in DSSCs but also shows that simple extraction and gentle handling methods can contribute to the device performance.

Spatially ordered NiOOH-ZnS/CdS heterostructures with an efficient photo-carrier transmission channel for markedly improved H2 production.

Spatially-ordered 1D nanocrystal-based semiconductor nanostructures possess distinct merits for photocatalytic reaction, including large surface area, fast carrier separation, and enhanced light scattering and absorption. Nevertheless, establishing a valid photo-carrier transmission channel is still crucial yet challenging for semiconductor heterostructures to realize efficient photocatalysis. In this work, spatially ordered NiOOH-ZnS/CdS heterostructures were constructed by sequential ZnS coating and NiOOH photo-deposition on multi-armed CdS, which consists of {112̄0}-faceted wurtzite nanorods grown epitaxially on {111}-faceted zinc blende core. Intriguingly, the surface photovoltage spectroscopy and PbO2 photo-deposition results suggest that the photogenerated holes of CdS were first transferred to the Zn-vacancy level of ZnS and then to NiOOH, as driven by the built-in electric field between ZnS and CdS and the hole-extracting effect of the NiOOH cocatalyst, leading to the efficient charge separation of NiOOH-ZnS/CdS. With visible-light (λ > 420 nm) irradiation, NiOOH-ZnS/CdS exhibited a distinguished H2-evolution rate of 152.20 mmol g-1 h-1 (apparent quantum efficiency of 40.9% at 420 nm), approximately 18 folds that of 3 wt% Pt-loaded CdS and much higher than that of ZnS/CdS and NiOOH-CdS counterparts as well as the most reported CdS-containing photocatalysts. Moreover, the cycling and long-term H2 generation tests manifested the outstanding photocatalyst stability of NiOOH-ZnS/CdS. The study results presented here may propel the controllable design of highly-active nanomaterials for solar conversion and utilization.

A durable hydrophobic photothermal membrane based on a honeycomb structure MXene for stable and efficient solar desalination.

Solar powered water evaporation is a green and environmentally friendly water treatment technology, which is a hot research topic for water purification at present. Advanced structural design and hydrophilic photothermal materials have achieved efficient solar evaporation of pure water, but the long-term stability of high salinity desalination has become a problem that cannot be ignored in practical applications. In order to solve this problem, a hydrophobic honeycomb structure MXene/AuNFs composite membrane was proposed in this paper, which used the three-dimensional highly porous microstructure of MXene and multibranched structure of gold nanoflowers particles to improve the light absorption and photothermal conversion efficiency of MXene/AuNFs. At the same time, the surface of the composite membrane was modified with hydrophobic fluorosilane 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFTE). The hydrophobic layer can prevent the accumulation of salt particles on the surface of the membrane, so that the composite film can continue to produce water vapor in a high salt environment. With high utilization rate of light energy, multiple-level geometrical structures of MXene for rapid water transport on the filter membrane and salt barrier on the membrane good stability, the hydrophobic MXene/AuNFs achieves solar evaporation rate of 1.59 kg m-2 h-1 and solar conversion efficiency is 97.8%, and stable operation under simulated sea water conditions under one sun irradiation over more than 10 cycles. The hydrophobic MXene/AuNFs membrane proved to be an efficient and stable photothermal material for solar desalination.

A dye sensitized photosynthesis cell for stable water oxidation mediated by photo-generated bromine.

The critical step of a dye-sensitized photoelectrochemical cell (DSPEC) is water oxidation. The photoanodes suffer rapid surface carrier recombination due to slow water oxidation kinetics and this results in low solar conversion efficiency and poor stability. Here, we design a novel sensitization-oxidation photo-anode, where the [Ru(4,4'-PO3H2-bpy)(bpy)2]2+ (RuP2+, bpy = 2,2'-bipyridine) chromophore and [Ru(bda)(pic)2] (pic = picoline, bda = 2,2'-bipyridine-6,6'-dicarboxylate) water oxidation catalyst (WOC) are immobilized separately on the surface of a mesoporous semiconductor thin film. The electrode creates a mobile and strong Br3- oxidant generated by the dye-sensitized electrode, which initiates water oxidation at a remote catalytic site. Under 100 mW cm-2 illumination in pH 4.65 in 0.1 M acetate buffer solution, the photoanode could perform a stable photoelectrochemical water oxidation for 6 hours with a photocurrent density of around 0.25 mA cm-2. This dual electrode could open a new door by utilizing an electron transfer mediator to design highly stable photoelectrochemical cells.

A multifunctional binder capable of harvesting light, electronic transport, and photocharging a lithium-ion photobattery

Poly(perylenediimide-alt-ethylene oxide) was prepared as a multifunctional lithium-ion battery binder. Upon light harvesting, the binder oxidized LiFePO4 and subsequently injected an electron into the circuit for potential solar conversion and storage.

Numerical analysis of double-diffusive natural convective flow of Ostwald-de Waele fluid in an irregular enclosure with a circular obstacle

PurposeThe current study aims to enhance the double diffusive natural convection in an Ostwald-de Waele fluid filled in a hexagonal enclosures using non-uniform magnetic field embedded with circular obstacle. The upper wall has maximum temperature Th∗ and concentration (Ch∗) whereas the lower wall is kept at minimum temperature Tc∗ and concentration Cc∗. The parameters that play a significant role in the heat and mass transfer are evaluated, including Hartmann number, power law index, Rayleigh number and buoyancy ratio. Design/Methodology/approachIn two-dimensions, the governing formulation is written as a set of balancing equations for velocities, pressures, energies and concentrations. The nonlinear governing PDEs are solved using numerical approach based on Finite Element Method (FEM). The discretization is performed using the stable finite element pair ℘2/℘1. Code validation and results are ensured by conducting a grid convergence and comparison test respectively. FindingsThe influence of flow on velocity, isotherms and iso-concentration field is examined by analyzing a broad variety of variables such as power-law index 0.7≤n≤1.2, Hartmann number 0≤Ha≤50, Rayleigh number 104≤Ra≤106, inclination angle 0°≤γ≤90° and buoyancy ratio -2≤N≤2. The findings are displayed graphically, including the flow, temperature and concentration fields. Heat and mass transfer rates are maximum for shear thinning fluids while for shear thickening fluids it reduces, whereas it is maximum for concentration dominated assistant flow and minimum for concentration dominant counter flow. ApplicationThe novel aspects of the research include its thorough examination of solar thermal power conversion and its inventive energy deficiency devices and a wide range of electrical design applications.

Potential Study of Using Hybrid Renewable Energy Systems for Power Supply of Tourism Camp in Mongolia

Due to the increase in the number of tourists coming from abroad, tourism camps have become interested in offering distinctive experiences, such as being close to nature and eco-friendly. Therefore, utilizing a hybrid renewable energy system for power supply becomes an attractive, nature-friendly, and reliable option for users located in remote areas disconnected from the central network. This article evaluates the electricity demand and associated costs for tourist camps using three different types of hybrid systems consisting of solar photovoltaic systems, wind turbines, diesel generators, battery storage, and converters. PV/wind systems will cost twice as much as PV/wind/battery systems. Additionally, they are not environmentally suitable due to the large number of batteries. PV/wind/battery systems, comprising a 3 kW capacity PV, a 5 kW capacity wind turbine, and batteries, could offer greater flexibility for tourist camps. This system is estimated to generate 19,303 kWh/year of electricity while not emitting greenhouse gases, despite being more expensive than a PV/wind/diesel hybrid system. The HOMER Pro software is used in this paper for optimization and techno-economic analysis.

Converting bio-waste rice into ultralight hierarchical porous carbon to pack polyethylene glycol for multifunctional applications: Experiment and molecular dynamics simulations

A structural-functional integrated shape-stabilized composite phase change material (PCM) was synthesized by converting biowaste rice into ultralight (0.08 g/cm3) hierarchical porous carbon (CNR) to pack polyethylene glycol (PEG) PCM. The thermal property and corresponding mechanism were analyzed. The results show that the composite PCM exhibits excellent thermal storage efficiency (93.3 %), considerable solar photothermal conversion efficiency and superior thermal stability. The interfacial thermal resistance (ITR) of PEG/CNR is 73 % lower than graphene foam-based composite PCM thus a fast transient temperature response. Particularly, the package of PEG endowed composite PCM with elastic characteristic thereby an enhanced compressive strength. Furthermore, covering PEG/CNR results in a delay of approximately 1.3 times in reaching the peak temperature on the surface of electronic components, and a delay of 5 times in cooling time. This study presents solid guidelines for societal development that is sustainable and makes some recommendations for construction of composite PCMs combining multifunctional applications.

Spectrally Selective Ultra‐Broadband Solar Absorber Based on Pyramidal Structure

Here, a spectrally selective solar absorber is explored and an ultra‐broadband solar absorber is proposed based on pyramidal structure. The finite‐difference in time domain (FDTD) software is used to model the spectral characteristics and magnetic absorption patterns of this absorber. The emissivity of the absorber is less than 20% in the far‐infrared band over 6000 nm, showing good selectivity, and the total solar thermal conversion efficiency is very close to that of an ideal truncated selective solar absorber by analyzing the performance of our proposed absorber‐related indexes. By studying the high absorption band of the absorber, the selectivity can be better investigated in depth. Here, 200–4000 nm is chosed as the depth study band. The absorber possesses an ultra‐wide bandwidth of 3554 nm and an average absorption of over 97.4%, and in the 200–3754 nm band, the absorber has an ultra‐high absorption rate of more than 98.3%, and its thermal emitter has a high emission efficiency of 94% at a temperature of 1000 K. Notably, the weighted average absorption in the 280–4000 nm band at AM1.5 is as high as 98.86%, with a loss of only 1.14%. The ultra‐broadband absorption property of this solar absorber is mainly a joint effect of surface plasmon resonance coupling.

Ultraviolet-wavelength driven solar spectral converter for photovoltaic cell application

Ultraviolet-wavelength driven solar spectral converter for photovoltaic cell application

The effect of space charge neutralization on the parametric design of photon enhanced thermionic solar converters

Photon-enhanced thermionic emission (PETE) is a promising method for increasing current density at relatively low cathode temperatures, but is susceptible to the space charge effect. In this study, we propose a novel PETE device model in which the space-charge barrier is relaxed by photon-excited cesium ions. The decrease in maximum efficiency with interelectrode gap is more gradual compared to previous studies. We investigate the effects of cathode materials properties (band gap and electron affinity) and operating conditions (cathode temperature and interelectrode gap) on PETE performance, and identify optimal performance conditions. Our findings show that the optimal gap range exceeds 5 μm and near field radiation loss can be minimized, providing an important opportunity for designing PETE device with larger interelectrode gaps and higher solar flux concentrations.