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[Display omitted] • The spectral reshaping intermediate structure on silicon substrate with simple fabrication process. • The hierarchical Si NW absorber exhibits an excellent optical absorption performance from 220 nm to 1100 nm and a lower emittance above 1100 nm. • The Si-W-SiN/SiNO multilayer emitter shows a selective narrowband absorption (i.e., emission) peak in the target wavelength and low thermal radiation loss in long wave range. • The overall efficiency of the whole STPV system is precisely optimized by varying emitter parameters and system parameters. • At achievable light concentration intensity of 1000, the STPV system efficiency can exceed 29% using this integrated silicon-based intermediate structure. Solar thermophotovoltaics (STPV) system is a technique that uses absorber and emitter to remold wide-band solar radiation into narrowband infrared emission and then convert it into electric energy in order to get high energy conversion efficiency. In this study, we fabricated an integrated silicon-based intermediate structure to enable the spectral reshaping. The absorber is a hierarchical Si NW structure, which exhibits excellent absorption performance of over 95 % in the spectral range of 220–1100 nm and a low heat loss in the long-wavelength band. The emitter is planar Si-W-SiN/SiNO structure, exhibiting a selective narrowband absorption (i.e., emission) peak in the target wavelength. When the emission peak of emitter is at 1800 nm, the overall efficiency of the STPV system based on this silicon-based intermediate structure can theoretically exceed 29 % with an achievable solar concentration of 1000 and an emitter-to-absorber area ratio of 4. We also test the prepared spectral reshaping intermediate structures on real systems and discuss further optimizations. [ABSTRACT FROM AUTHOR]

• A novel design of plated volumetric cavity receiver is proposed. • Numerical modelling of molten salt flow inside cells and air flow in the cavity. • Numerical analysis of molten salt flow at different velocities. • Estimated the heat losses from the plated receiver numerically. • Flow circulations observed to be significantly high at very low velocities. The article mainly focuses on the study of thermal performance of liquid volumetric plated cavity receiver which includes the flow characteristics of heat transfer fluid and estimation of heat losses. Due to higher heat capacity, liquids are considered more suitable heat transfer fluid than air. However, it is difficult to use liquid as heat transfer fluid (HTF) in the conventional air volumetric receivers, therefore a plated volumetric receiver is proposed, as it can heat the fluid within the volume of the receiver. The plated receiver consists of a parallel arrangement of rectangular cells suspended in an enclosure. Each cell is enclosed by two large rectangular metallic plates joined together, creating a hollow space between them with inlet and outlet nozzles. The incoming solar radiation is absorbed by outer surface of the cell and transferred to the HTF. Large absorbing surface area and large contact area between the plates and HTF is the key feature for avoiding hot spots on the cell's surfaces. Numerical analysis is carried out for molten salt flow inside the cells and air flow in the cavity. The results show a uniform distribution of flow (with Re = 212) resulting into no hotspots on the receiver surface. Local heat transfer coefficient is estimated to be maximum and minimum in the high and low flux regions, respectively. The thermal efficiency of the receiver is calculated as 90.76 %. The cell thickness and plate size of the receiver is 6 mm and 100 mm × 50 mm, respectively. [ABSTRACT FROM AUTHOR]

• A silica aerogel-based photovoltaic/thermal (PV/T) collector is proposed. • The aerogel-based PV/T collector significantly suppress radiation heat loss. • The thermal performance of the aerogel-based PV/T collector is enhanced by 46%. • The performance of aerogel-based PV/T is equivalent to that of spectrally selective PV/T with a thermal emissivity of 0.1. • The exergy efficiency of the aerogel-based PV/T collector is increased by16.2%. Photovoltaic/thermal (PV/T) collector can convert incident sunlight into electrical and heat energy simultaneously. However, compared with the solar thermal collector, the radiative heat loss of the PV/T absorber is larger since the spectrally selective PV/T absorber is difficult to design and fabricate after introducing PV cells, which leads to lower thermal efficiency. Thus, an approach that can reduce the radiative heat loss of the PV/T collector without the requirement for spectrally selective PV/T absorber is emergently needed. Here, a novel aerogel-based PV/T collector is proposed to suppress radiative heat loss and improve efficiency by introducing the silica aerogel that is highly transparent to sunlight and opaque to infrared light, as well as ultra-low effective thermal conductive into the PV/T collector. A numerical model is established to evaluate the performance of the aerogel-based PV/T collector, and the results present that the heat loss of the PV/T collector at the operating temperature of 70°C can be dramatically reduced by approximately 75% after using the silica aerogel and the thermal efficiency can also be increased by 46%. Moreover, a parametric study is conducted to investigate the influence of solar radiation, ambient temperature, and emissivity of the PV/T absorber on the performance of the aerogel-based PV/T collector. This study is devoted to exploring a new method to suppress the radiative heat loss of the PV/T collector and enhance its solar harvesting performance correspondingly, which gives a reference for the design of high-performance PV/T utilization. [ABSTRACT FROM AUTHOR]

• A concept of modified shape coefficient of building was proposed. • The shape coefficient of building was modified based on solar radiation factors. • The modified shape coefficient of building was experimentally proved. • The shape coefficient of building was reduced by 32.4% in this present case. • The restriction on shape coefficient of building could be liberalized moderately. The shape coefficient of building (SCB) is a measure of correlating a building's shape and its energy consumption. However, strictly adhering to restrictions the SCB may not be conducive to reducing energy consumption, as it disregards the potential benefits of solar radiation. To address this, a novel concept and method for determining the modified shape coefficient of building (MSCB) have been introduced in considerations of heat loss and solar heat gain. Field measurements were conducted in western Sichuan to establish a comprehensive understanding of the factors influencing indoor thermal environments, involving collecting indoor air temperature data for model buildings under natural and heating conditions, including solar radiation, building orientations, and U-values. Results demonstrated that maintaining an identical SCB did not consistently ensure similar indoor thermal environments. The indoor thermal environments were significantly influenced by building orientations, U-values, and solar radiation, highlighting the limitations of relying solely on SCB. A simulation method validated through experiments was utilized to predict the dynamic heating load of an actual building. The influence of building orientations on the MSCB across different time scales and actual climatic conditions was investigated. Results illustrated a potential reduction of the SCB by up to 32.4% in the specific case. This reduction correlated with trends observed in the monthly correction factors and heat consumption, suggesting that moderate relaxation of SCB restrictions could be viable even in scenarios with high heating demands. This research contributes valuable insights into the realm of energy-efficient building design. [ABSTRACT FROM AUTHOR]