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Graphical abstract Schematics of the PV/T system based on optical splitting film. Highlights: • Design and manufacture novel 2-axis tracking PV/T system with SiO 2 /TiO 2 thin film. • Design and fabricate SiO 2 /TiO 2 thin film with reflectance of 96.8% for PV bands. • Outdoor testing show PV cells with SiO 2 /TiO 2 thin film can decrease 3.0 K. • Power generation and efficiency of PV cells can be improved by 10% and 0.64%. • Energy and exergy efficiencies of PV/T can be improved by 4.94% and 1.03%. Abstract In a "thermally decoupled" PV/T system, photovoltaic and thermal absorbers are allowed to operate at different temperatures to utilize full-spectrum sunlight. In this study, a two-axis tracking PV/T system with a SiO 2 /TiO 2 interference thin film (irradiated by natural sunlight) was designed and fabricated initially. The SiO 2 /TiO 2 interference thin film designed by the authors achieved a high average reflectance (R ≥ 96.8%) for PV bands, with a high average transmittance (T ≥ 85%) at 1100–2500 nm. The photoelectric, photothermal, and overall efficiencies were tested and analyzed theoretically using the first and second laws of thermodynamics. Outdoor testing indicated that PV cells with SiO 2 /TiO 2 interference thin film can decrease by 3.0 K, and that the power generation and efficiency of the PV cells can be improved by 10% and 0.65%, respectively. The overall energy and exergy efficiency of the PV/T system based on SiO 2 /TiO 2 interference thin film can reach 22.72% and 18.81%, i.e., 4.94% and 1.03% higher than those without a SiO 2 /TiO 2 interference thin film, respectively. The calculated payback time was 17 years for this PV/T system. [ABSTRACT FROM AUTHOR]

Semi-transparent solar-cell-based SBS PV/T system is promising. However, traditional semi-transparent solar cell-based SBS PV/T system can only produce low-grade thermal energy because the semi-transparent solar cell cannot concentrate long-wavelength sunlight. Even if a concentrating system is used, the semi-transparent solar cell must be able to withstand high temperatures, which increases the costs of the solar cell, and an additional bracket is required for installing the concentrator. In this study, the idea of using a single piece of photovoltaic (PV) to regulate the radiative transfer of the full solar spectrum for realizing the co-generation of electricity and high-grade thermal energy is proposed. A semi-transparent solar cell with a serrated groove structure at its bottom was fabricated. The solar cell can convert 400–800 nm wavelength photons to electricity, and focus 800–2500 nm wavelength photons on a small spot to produce high-temperature thermal energy. Therefore, the transmitted irradiance can be improved with a simple structure in a semi-transparent solar cell-based SBS PV/T system. [Display omitted] • Semi-transparent solar cell with serrated groove structure for SBS is proposed. • Idea of using a single piece of PV to regulate full solar spectrum is proposed. • Semi-transparent solar cell-based SBS PV/CST system is experimentally studied. • Feasibility of such novel system is validated by indoor and outdoor experiments. • The utilization efficiency of the full-spectrum solar energy can reach 77%. Semi-transparent solar cells can be used for spectral beam splitting (SBS) in which short-wavelength photons are converted to electricity and long-wavelength photons are transmitted to thermal absorbers. However, these thermal absorbers can only produce low-grade thermal energy because the semi-transparent solar cell cannot concentrate long-wavelength photons. In this study, based on the idea of regulating the radiation field to match the energy conversion on-demand, the strategy to use a single piece of photovoltaic (PV) to regulate the photon capture of the full solar spectrum for realizing the co-generation of electricity and high-grade thermal energy is proposed. A semi-transparent solar cell with a serrated groove structure at the bottom is designed and fabricated. The cell can convert 400–800 nm wavelength photons to electricity, and focus 800–2500 nm wavelength photons to a small spot to produce high-temperature thermal energy. A novel α-Si thin-film semi-transparent solar cell-based SBS hybrid photovoltaic/concentrated solar thermal system is established. The feasibility of the system is validated through indoor and outdoor experiments. The utilization efficiency of the full-spectrum solar energy can reach 77%. The high average concentrated irradiance of up to 4.31 KW/m2 transmitted through the semi-transparent solar cells is sufficient for high-temperature thermal utilization. [ABSTRACT FROM AUTHOR]

Spectral beam splitting (SBS) hybrid PV/T system was a promising path for utilizing the full spectrum solar energy to cogenerate electricity and high-grade heat, with high conversion efficiency. To settle the balance between photoelectric and photothermal conversion performance for full spectrum solar energy utilization, the sunlight based on wavelength matching was divided into two or more parts at band-gap wavelength by a spectral beam splitter: sunlight with wavelength at and close to the band-gap of PV cell was directed to generate electricity, while the sunlight with rest wavelength was used for thermal output. SBS hybrid PV/T system can not only increase the overall efficiency, but can also decouple the photoelectric and photothermal conversion process in separated operation temperatures. The current state-of the-art review on the advancements of SBS hybrid PV/T system performed with the aid of nanofluids, nano-film and semitransparent PV cells was presented in this work, with emphasis on the latest developments during the last decade. Mechanisms of different SBS techniques, progress in system, thermodynamic and cost analyses of nanofluids, nano-film and semitransparent PV cell based SBS hybrid PV/T system were discussed in detail to give a comprehensive understanding of the nature of the full spectrum solar energy utilization and the factors impacting on the system efficiency. Though the cost increase can be offset by extra energy efficiency gain, the wavelength matching, optical losses and stability of SBS hybrid PV/T system needs to be solved for future industrial application. • Advancements of spectral beam splitting PV/T system was reviewed comprehensively. • Mechanisms of spectral beam splitting techniques was reviewed comprehensively. • Progress in system, thermodynamic and cost analyses were discussed in detail. • Problems of system needs to be solved for future application were discussed. [ABSTRACT FROM AUTHOR]

The mismatch between radiative intensity field and energy required for solar thermochemical reaction can cause serious heat waste and reduce energy conversion efficiency. To improve the energy conversion efficiency of solar to fuel, the radiative intensity regulation method to match energy conversion on demand in solar methane dry reforming is proposed in this study. The design of solar spots and biomimetic leaf hierarchical porous structures is investigated and optimized, which can realize a better radiative intensity field matching. The experimental and numerical studies show that, by using the method of regulating radiative intensity field to match energy conversion on-demand in solar thermochemical reactor, the methane conversion rate and solar thermochemical energy storage efficiency can be increased by 4.6% and 6.1%, respectively. The ideal synergy between real temperature field distribution and theoretical temperature requirement is perfectly achieved. [Display omitted] [ABSTRACT FROM AUTHOR]

Common glass without spectral regulation effect cannot offer an energy‐saving function, and radiative cooling technology without visible transparency cannot satisfy the illumination and esthetic demands. Herein, the concept of utilizing a biomimetic beetle cuticle structure, guided by principles of Chinese Taoist philosophy, is proposed to accomplish efficient radiative regulation. Subsequently, low‐cost biomimetic radiative cooling (Bio‐RC) glass is presented, which can reduce the temperature of buildings throughout daytime by blocking near‐infrared (NIR) radiation, conveying visible light, and emitting heat within the atmospheric window. Utilizing only three layers of thin films, Bio‐RC glass achieves multi‐band spectral regulation, avoids a complicated preparation process, and has the potential for large‐scale production. Spectrometry reveals that Bio‐RC glass exhibits an effective visible light transmissivity of 80.5%, a mean NIR transmissivity of 10.3%, and an effective emissivity of 94.8% within the atmospheric window. A one‐month rooftop test demonstrates that Bio‐RC glass achieves a maximum cavity temperature reduction of 18.1 °C compared with common glass. Energy consumption analysis indicates that Bio‐RC glass can conserve approximately 23.4% of the total energy consumption per year compared with common glass. The proposed Bio‐RC glass can lower the temperature during daylight while preserving transparency and esthetics, making it suitable for application in buildings and vehicles. [ABSTRACT FROM AUTHOR]

Due the energy resource comes from solar energy, resulting in a high working temperature, radiation field has a significant influence on the energy storage efficiency of the high temperature solar thermochemistry. In order to promote the solar energy conversion efficiency of solar driven steam methane reforming (SMR), the idea of regulate the radiation field to be in accordance with the energy conversion on-demand is proposed and the biomimetic leaf-type hierarchical porous structure solar thermochemical reactor is introduced, which can regulate the spatial distribution of solar radiation intensity and optimize the temperature field. Combined with thermochemical kinetics and Finite Volume Method (FVM), the numerical calculation model of the SMR reaction in a biomimetic solar thermochemical reactor is established to optimize the temperature field. The effects of different reaction conditions and reactor parameters on steam methane reforming hydrogen production are analyzed. The results show that methane conversion in the biomimetic leaf-type solar thermochemical reactor is increased by 4.5%. [Display omitted] • Methane reforming in solar reactor with biomimetic leaf-type hierarchical porous is studied. • The idea of biomimetic hierarchical porous is proposed to regulate radiation field. • Biomimetic leaf-type hierarchical porous structure can increase methane conversion by 4.5%. • The best combination of structural parameters is d 1 = 1.0 mm, d 2 = 3.0 mm and L 1 = 0.02 m. [ABSTRACT FROM AUTHOR]

Radiative cooling technology can emit infrared heat to the outer space through the "sky window" for cooling without consuming energy, which had drawn more and more attention. However, some researches reported that there was a significantly different cooling performance at different atmospheric total water vapor columns (TWC) conditions. In this study, taking a simple single-layer radiative cooling coating containing two kinds of particle mixture (SiO2, TiO2) as example, the spectral effective emissivity of the radiative cooling coating was proposed to evaluate the effect of the atmospheric water vapor on the cooling performance. The spectral effective emissivity of the coating was obtained through multiplying spectral emissivity of the coating by the atmospheric transmittivity, where the spectral emissivity was calculated by combining an algorithm for calculating radiative properties of the multi-particle system with the Monte Carlo ray-tracing method (MCRT). The effects of different atmospheric water vapor on the spectral effective emissivity of the simple single-layer radiative cooling coating containing different particles size, volume fraction and thickness were studied to improve the cooling performance of the coating. The results showed that with increasing TWC from 0 to 7000 atm-cm, the average effective emissivity of the simple single-layer coating decreased from 79.5% to 35.3%, with a decrease of 44.2%. The research results are of great significance to the further application development and the design criterion of radiative cooling materials in different atmospheric water vapor environments. [ABSTRACT FROM AUTHOR]

By exploiting the 3 K coldness of outer space as heat sink of terrestrial thermal radiation, passive daytime radiative cooling (PDRC) can achieve sub-ambient temperatures without any energy consumption, and thus exhibiting extraordinary application potentials. By pursuing the dual-band (solar and atmosphere window) optical properties to approach ideal 100 %, PDRC can maximize dissipating long wavelength infrared radiation to space and minimize absorbing sunlight simultaneously. PDRC technology can reach146 W/m2 theoretical cooling power and up to 120 W/m2 during application. This article focuses on the fundamental physics mechanism of radiative transfer and natural radiative cooling phenomena. Methodologies of infrared absorption functional group selection, optical band gap selection for solar reflection, photon and phonon enhanced resonance by micro-structure were discussed in detail to give a comprehensive instructing strategy of radiative cooling power improvement. Although PDRC technology can achieve sum-ambient temperature cooling without consuming any energy, its drawbacks such as single function of cooling and high whiteness requirement needed to hinder its large-scale application. This article also outlines the current primary applications of PDRC technology, along with summarizing the challenges and potential opportunities it encounters in practical implementation. This paper aims to provide a comprehensive overview on the fundamental physical mechanisms, methods for enhancing its power output, as well as the current state and future developments of PDRC applications, providing potential guidance for reducing greenhouse gas emissions and energy consumption. • Advancements of radiative cooling technology were reviewed comprehensively. • Fundamental physics of passive radiative cooling was reviewed comprehensively. • Material selection methodology and optical mechanism were discussed in detail. • The recent application of passive daytime radiative cooling was reviewed. • Some current challenges and potential applications were presented and discussed. [ABSTRACT FROM AUTHOR]

Abstract Radiative cooling, as a passive cooling method, is an effective way to save energy and reduce emissions by dissipating heat into space through the "sky window," without consuming any additional energy. The actual particles in the radiative-cooling coating constitute a particle cloud with non-uniform size distribution and the cooling effect is greatly affected by the spectral reflectance of the actual substrate. Herein, the radiative transfer of actual SiO 2 particles doped with a radiative-cooling coating was initially studied. Monte Carlo ray-tracing method, combined with Mie theory, was used to analyze the influence of particle size, volume fraction of particles, coating thickness, and different substrate reflectances on the spectral radiative characteristics of the radiative-cooling coating. The particles size distribution and spectral substrate reflectance were considered. The numerical results show that the maximum spectral reflectance difference between a coating with a uniform-size-distribution particle cloud and a coating with a non-uniform-size-distribution particle cloud can reach 27.3%. Furthermore, the influence of particle parameters and reflectance of the substrate on the radiative characteristics of the radiative-cooling coating is mainly concentrated in the 10–12 μm band. At 8–10 μm and 12–13 μm, the radiative-cooling coating emissivity varies little with the change of particle parameters and the reflectance of substrate, which is induced by the strong absorption of SiO 2 particles. [ABSTRACT FROM AUTHOR]

Hydrogen production from water using a catalyst and solar energy was an ideal future fue l source. In this study, an elaborate experimental test rig of hydrogen production from solar water splitting was designed and established with self-controlled temperature system. The effects of light intensity on the reaction rate of hydrogen production from solar water splitting were experimentally investigated with the consideration of optical losses, reaction temperature, and photo-catalysts powder cluster. Besides, a revised expression of full-spectrum solar-to-hydrogen energy conversion efficiency with the consideration of optical losses was also put forward, which can be more accurate to evaluate the full-spectrum solar-to-hydrogen energy of photo-catalysts powders. The results indicated that optical losses of solar water splitting reactor increased with the increase of the incoming light intensity, and the hydrogen production rate increased linearly with the increase of effective light intensity even at higher light intensity region when the optical losses of solar water splitting reactor were considered. [ABSTRACT FROM AUTHOR]

Low-Cost and Large-Scale Producible Biomimetic Radiative Cooling Glass with Multiband Radiative Regulation Performance (Advanced Optical Materials 23/2022) Keywords: biomimetic; esthetics preservation; radiative transfer; radiative cooling; solar energy EN biomimetic esthetics preservation radiative transfer radiative cooling solar energy 1 1 1 12/07/22 20221201 NES 221201 In article number 2202031, Xinping Zhang, Fuqiang Wang, and co-workers propose and achieve a low-cost and large-scale producible radiative cooling glass with multiband radiative regulation performance. Biomimetic, radiative transfer, radiative cooling, solar energy, esthetics preservation. [Extracted from the article]

• Idea of using biomimetic structures to control solar irradiation was proposed. • The optical performance of energy-efficient glass was examined using FDTD method. • The τ e = ∼ 82 % and ρ N I R = ∼ 90 % of energy-efficient glass were higher than that of low-E glass. • Energy-efficient glass could save about 20% total electrical consumption per year. Solar irradiation is the main factor contributing to ultra-high energy demand in buildings, and windows are crucial elements with a significant effect on the energy demand in indoor spaces, affecting the cooling, heating, and artificial lighting requirements. Inspired by hercules beetle utilizing the refractive index difference of spongy multilayer structure for infrared reflection and moth-eye using the continuous refractive index change of microscopic convex structure for anti-reflection, this study proposes a visibly transparent and infrared-reflective energy-efficient glass using biomimetic structures to save energy in buildings, based on the idea of regulating the radiation to match the energy utilization on-demand. The selected materials for the proposed biomimetic energy-efficient (BE) glass are SiO 2 , Al 2 O 3 , and Ag based on the idea of using the difference in refractive index of multilayer media for radiation regulating. The transmissivity and reflectivity of BE glass are examined adopting the finite-difference time-domain (FDTD) method. The numerical analysis results demonstrate that BE glass covered with a cone-shaped biomimetic moth-eye structure and a biomimetic multilayer structure exhibits visible light transmissivity of 82.37%, in addition to an infrared light reflectivity of over 90%, which is higher than that of the currently employed low-E glasses. The proposed BE glass offers excellent energy-saving features in both hot and cold weather and the energy consumption analysis indicates that comparing with conventional common glass, it could save about 20% total electrical consumption (43.5 kWh/m2) per year [Display omitted] [ABSTRACT FROM AUTHOR]