•An idea of dynamic management of solar and long-wave thermal radiations is proposed.•A dual-intelligent window based on this idea is demonstrated theoretically.•The novel window is accomplished by using a “common” material of VO2.•Property change of VO2 for both solar and long-wave thermal radiations is utilized.•The new window has a much better performance than traditional VO2 or low-e windows.Advanced energy-efficient windows have been widely investigated due to the special role of windows among building envelopes. Here, we propose an idea of dynamic management of both solar radiation and long-wave thermal radiation. A window based on this idea can be named as a dual-intelligent window, which blocks the solar radiation as well as emits little long-wave thermal radiation to the indoor side during hot daytime and cools the room by dissipating heat from the indoor side to the outdoor side through radiative heat transfer at cool nights. Based on the properties of thermochromic vanadium dioxide (VO2), it was found that a dual-intelligent window can be accomplished by pasting the VO2 film onto the indoor side of the window. The energy performance of this conceptual dual-intelligent window was numerically simulated and compared with low-emissivity window and traditional VO2 window where the VO2 film is on the outdoor side. The results show that the window with low emissivity cannot reduce the energy consumption for cooling due to the lack of the ability of regulating the long-wave thermal radiation. The dual-intelligent window surpasses the traditional intelligent VO2 windows due to the fact that the application of the dual-intelligent window can reduce cooling energy by 21.7% compared with the traditional intelligent window. This improvement of dual-intelligent window emphases the advantages of dynamically regulating solar and long-wave radiations simultaneously.

•A novel optical bionic membrane was proposed.•The absorption and scattering coefficients of the bionic membranes were deduced.•The reflection mechanism of the bionic membrane was elucidated.•The optimization of the optical bionic performance of the membrane was explored.Hyperspectral imaging is becoming an important detection method, which can identify the subtle differences between the reflection spectra of a target and its background. Considering that vegetation is one of the most important backgrounds, a bionic membrane containing hygroscopic material and chromium sesquioxide (Cr2O3) pigment was prepared to counter the hyperspectral detection through simulating the solar spectrum reflectance of natural leaf. The effects of water and Cr2O3 contents on the reflectance of the bionic membrane were discussed, and the absorption and scattering coefficients of the bionic membrane were calculated via a four-flux model to elucidate its reflection mechanism. Based on the obtained absorption and scattering coefficients, the reflectances of the bionic membranes (with a volume fraction of water in the range of 9.75–51.92% during the day time) containing different volume fraction of Cr2O3 (fc) were calculated through the four-flux model. Besides, a military specification of USA was used as the spectrum requirement of the bionic membrane in our work to determine an appropriate Cr2O3 content. It was found that when fc is 1.61%, the reflection spectra of the 3 mm thick bionic membranes can not only meet the military specification but also become opaque, which are capable to camouflage a target.

•Thermal conductivity (keff) of carbonized high silica/phenolic was measured.•An FE model was established to predict keff of carbonized high silica/phenolic.•Transverse thermal conductivity of the high silica fiber yarns was achieved.•Clayton model is suitable for predicting keff of carbonized high silica/phenolic.As a phenolic resin-based ablative material, high silica/phenolic composite is widely used in aerospace field. However, the effective thermal conductivity of carbonized ablative material formed during ablation process is rarely reported. In this work, carbonized sample of the high silica/phenolic ablative material was obtained by a carbonization process, and its effective thermal conductivity was measured from 100 to 970 °C. In addition, an analysis model of the effective thermal conductivity of the carbonized ablator consisting of fiber yarns and carbonized phenolic was established based on the result of structure analysis. The measured value of the effective thermal conductivity of the carbonized phenolic was used to inverse the transverse effective thermal conductivity of the fiber yarns. When the inversed values were adopted in different empirical models, it was found that the Clayton model is suitable for predicting the effective thermal conductivity of the carbonized high silica/phenolic.

•Phase change thermal control with under periodic ambient condition was studied.•Influences of PCM on thermal control effects were explored.•The simulated results agreed well with the experimental results.•Conditions of achieving the optimal thermal control effects were proposed.•An optimal phase change range can be obtained according to TMY data.Thermal control systems operating under periodic outdoor ambient conditions have numerous important applications in industrial fields. Reducing system energy consumption and enhancing temperature control effects are crucial to improving the performance of these systems. To this end, the application of phase change material (PCM) in the envelope of a thermal control system was investigated through experiment and simulation. A simulation model of an active ventilated thermal control system was constructed and verified with experimental results, and the influences of PCM incorporated in the envelope on the power consumption and temperature control effects were discussed in two time scales. The results for typical meteorological days indicate that excellent thermal control effects can be achieved when the phase change range of PCM brackets the temperature control setpoint and is consistent with the fluctuation range of the ambient temperature. The results for a typical meteorological year (TMY) demonstrate that an optimal phase change range can be determined according to TMY data to realize the optimal thermal control effects of PCM. When the required temperature control setpoint is not within the optimal phase change range, the phase change range bracketing the temperature control setpoint is recommended.

•The internal quantum efficiency (IQE) of epitaxial GaSb thin film cell was predicted.•The optimal thickness of the base region was obtained for the maximal IQE.•The optimal range of the bottom surface recombination velocity was obtained.•Increasing the hole Shockley–Read–Hall lifetime will greatly increase the IQE.As promising candidates for thermophotovoltaic energy conversion systems, epitaxial thin film III–V cells have gained increasing attention due to their potential for reduced weight. However, few studies have been done to date to enhance the performance of epitaxial single crystal GaSb thin film cells. In this work, the internal quantum efficiencies of epitaxial single crystal GaSb thin film cells with Zn-diffused and epitaxial p–n junctions were predicted with models verified using the corresponding experimental results. The results are the first to indicate that, for the former, when the base region thickness is approximately equal to minority carrier diffusion length, the maximal IQE can be obtained and it is notably higher than the IQE of GaSb bulk cell at wavelengths from 800 to 1700 nm. Reducing bottom surface recombination velocity and increasing hole Shockley–Read–Hall lifetime could also increase the IQE. While for the latter, the results demonstrated that the optimal base region thickness is also approximately equal to minority diffusion length, and reducing emitter region thickness will increase the IQE when the base region is optimized. The comparison of the two optimized GaSb thin film cells showed that the GaSb thin film cell with epitaxial p–n junction has a higher IQE.

•The lattice structure of metal phase VO2 does not change with temperature.•The influences of scales on the emission of a 2D VO2 PhC are discussed.•A 2D VO2 photonic crystal emitter matched well with InGaAs cell is designed.•The matched VO2 PhC emitter can highly improve the TPV system efficiency.The design and simulation of a two-dimensional (2D) photonic crystal (PhC) selective emitter made of vanadium dioxide (VO2), a type metal oxide with a high temperature resistance, are reported. Spectral emission characteristics of the 2D VO2 PhCs were investigated using the finite difference time domain (FDTD) method. The PhC consists of a periodic array of cylindrical air microcavities. The influences of the geometric characteristic parameters are discussed. The influences of the radius and depth on the emission of the 2D VO2 PhC can be explained based on the coupled-mode theory. The emissivities at wavelengths below the cut-off wavelength were enhanced by increasing the depth. When the depth was much larger than the radius, the cut-off wavelength increased with the radius. The effect of the period on the emissivity at wavelengths less than the period was highly influenced by the diffraction modes. The designed 2D VO2 PhC emitter exhibited a selective emission that was well-matched with InGaAs cells. The spectral emissivities within the convertible wavelength range of the InGaAs cells reached 0.95, and the emissivities for non-convertible wavelengths were less than 0.3.

•Zn diffusion in GaAs differs when Zn/Ga alloy is used instead of Zn/As alloy.•Ga atoms could suppress the high-concentration surface region of the Zn profile.•Photoluminescence analysis was used to identify the diffusion mechanisms.•Ga vacancies were found in the surface region of the kink-and-tail profile.•Ga vacancy was not found in the box profile and the tail of kink-and-tail profile.Most investigations on Zn diffusion in GaAs were processed using the Zn–As alloy sources to prevent the As atoms from escaping GaAs wafers, while we found that the Zn diffusion would change fundamentally if Zn–Ga alloy sources were used. The Ga atoms from the diffusion sources suppressed the formation of the high-concentration surface region in Zn profiles, thus converting a kink-and-tail profile into a box profile. The photoluminescence (PL) analysis was used to identify the diffusion mechanisms. The Ga vacancy defects were found in the surface region of the kink-and-tail profile, indicating that the dissociative mechanism dominated; the PL spectrum in the tail region of kink-and-tail profile and the main region of box profile showed the same signals, no Ga vacancy defects were found, thus the kick-out mechanism dominated.

•The IQE of the box shaped Zn diffusion profile GaSb cells was calculated.•The effects of recombination velocity and lifetime of holes were discussed.•The effects of diffusion duration and etching depth were analyzed in-depth.•The results were elucidated by analyzing the behaviors of the minority carriers.Based on a GaSb thermophotovoltaic (TPV) cell with a box-shaped Zn diffusion profile, a theoretical model of the generation and drift of the photogenerated minority carriers in the cell was established, and the internal quantum efficiency (IQE) of the cell was predicted with the classical semiconductor theory. The calculated results agreed well with the measurements. It is determined that reducing the front surface recombination velocity (SnSn) could improve the IQE of the emitter region, whereas increasing the lifetime of holes (τhτh) could improve the IQE of the base region. The Zn diffusion duration has a large influence on the IQE at short wavelengths below 1200 nm. Compared with the IQE for the 5 h diffusion time, the IQE of the 2 h counterpart was improved dramatically. Front surface etching could increase the IQE at short wavelengths below 700 nm while there was a decrease in the IQE for wavelengths above 700 nm. Thus, front surface etching is not necessary for a cell with a box-shaped Zn diffusion profile because the IQE for the near infrared wavelengths are the most important. The calculated results were elucidated by analyzing the distribution of the minority carriers generated in the cell and their recombination processes.

●A novel zinc diffusion method was used to form p-type region in n-GaSb.●The surface high-concentration region was suppressed using this method.●The fabricated GaSb cells showed good performances without complex etching process.●The cost of cells is reduced since no protective gas is required during diffusion.This paper reports a novel zinc diffusion method for forming emitters in GaSb thermophotovoltaic cells. A closed quartz-tube diffusion system using Zn–Ga alloys as the diffusion source was designed to realize p-type doping in N-GaSb wafers. The surface diffusion region showing a high concentration of zinc was suppressed by this diffusion method, and the GaSb cells fabricated using this method showed good quantum efficiency in the near-infrared bands. Compared to that of the conventional pseudo-closed-box diffusion method, the controllability of the etch-back process after front-side metallization is significantly improved, and the cost of the cell fabrication is reduced because no protective gas is required during the diffusion process.

Low-density closed-cell aluminum foam is promising to be used as load-bearing and thermal insulation components. It is necessary to systematically study its thermal expansion performance. In this work, linear thermal expansion coefficient (LTEC) of the closed-cell aluminum foam of different density was measured in the temperature range of 100–500 °C. X-ray fluorescence was used to analyze elemental composition of the cell wall material. Phase transition characteristics were analyzed with X-ray diffraction and differential scanning calorimetry. LTEC of the closed-cell aluminum foam was found to be dominated by its cell wall property and independent of its density. Particularly, two anomalies were found and experimentally analyzed. Due to the release of the residual tensile stress, the LTEC declined and even exhibited negative values. After several thermal cycles, the residual stress vanished. With temperature higher than 300 °C, instantaneous LTEC showed hysteresis, which should result from the redistribution of some residual hydrogen in the Ti2Al20Ca lattice.

An Er2O3 coating-type selective emitter for themophotovoltaic application was prepared by plasma spray technology. The test results show that plasma spray technology could be used to prepare the Er2O3 coating-type selective emitter with good stability at 1400°C. Based on the measurements of the high temperature normal spectral emissivity and the spectral hemispherical emissivity of the samples at room temperature, the influence of the coating thickness was discussed, and the selective emission performance of the sample was evaluated using radiative efficiency as the criterion. The results demonstrate that the emission of substrate could not be neglected unless the coating thickness would be larger than the penetration depth, which is around 100 μm. The selective emission peak of the Er2O3 coating occurs at 1550 nm, matching well with the GaSb cells. However, the radiative efficiency is not larger than that of the SiC emitter, because the non-convertible emission of 1.725–5 μm accounts for a large proportion of the total radiation power, especially at high temperature. Effective suppression of this band emission is essential to the improvement of the radiation efficiency of the emitter.

Based on the structure and dimensions of a vertical ZnO nanorod array (V-ZNA) sample, an ideal 2-D photonic crystal model was established. The optical properties of the V-ZNAs were analyzed with finite-difference time-domain (FDTD) method, and the influences of the geometry parameters, including the circumcircle diameters of the top and bottom surfaces (Dt and Db) and the height (H) of the nanorods, and the pitch between each column (L), were discussed. High transmittance and low reflectance in the waveband of 400–800 nm were proved, and the highest transmittance can be obtained with Dt<50 nm, H=200 nm, and Db/L=0.85, which was verified by Effective Index Method (EIM). The result indicates that V-ZNAs can be used as excellent light coupling element and antireflection material for solar energy applications.

•The VO2 glazing's application performance was demonstrated and simulated.•The demonstration was performed in a full-size room with a 1.65 m×1.65 m window.•The simulation was conducted with a software of high credibility.•The results showed the use of the VO2 glazing could save cooling consumption.As a typical thermochromic material, the vanadium dioxide (VO2) has a great potential for building energy efficiency development. In this study, the VO2 glazing's application performance was first demonstrated in full-size, and simulated with a software of high credibility. For a 2.9 m×1.8 m×1.8 m low-mass room whose window's size is 1.65 m×1.65 m, the measured results showed that the room with the VO2 glazing saved 10.2–19.9% cumulative cooling load than that with an ordinary glazing during the demonstration. The application performance to a conventional residential room in the hot summer and warm winter zone was simulated in BuildingEnergy, a simulation software developed by the authors. The simulated results showed that the use of the VO2 glazing could save ∼9.4% electricity consumption. The effects of the window's orientation and the area ratio of window to wall were also discussed in this study.

The experimental I–V characteristics of a Si cell module in a thermophotovoltaic (TPV) system were investigated using SiC or Yb2O3 radiator. The results demonstrate that the short-circuit current increases while the open-circuit voltage, along with the fill factor, decreases with the cell temperature when the radiator temperature increases from 1273 to 1573 K, leading to a suppressed increase of the output power of the system. The maximum output power density of the cell module is 0.05 W/cm2 when the temperature of the SiC radiator is 1573 K, while the electrical efficiency of the system is only 0.22%. The efficiency is 1.3% with a Yb2O3 radiator at the same temperature, however, the maximum output power density drops to 0.03 W/cm2. The values of the open-circuit voltage and the maximum output power obtained from the theoretical model conform to the experimental ones. But the theoretical short-circuit current is higher because of the existence of the contact resistance inside the cell module. In addition, the performance and cost of TPV cogeneration systems with the SiC or Yb2O3 radiator using industrial high-temperature waste heat were analyzed. The system electrical efficiency could reach 3.1% with a Yb2O3 radiator at 1573 K. The system cost and investment recovery period are 6732 EUR/kWel and 14 years, respectively.

The influence of the period of rotation on the effectiveness of the thermophotovoltaic (TPV) rotary regenerator was theoretically and experimentally investigated. It was found that the deviations of the theoretical results from the experimental ones decrease with the increase of the period of rotation. To the TPV system of 10 kW combustion power, the deviation is 3.5% when the rotation period is 3 s; while the deviation decreases to 1.5% when the rotation period increases to 15 s. The deviation could be mainly attributed to the cold and hot fluids carryover loss which was not considered in the model. With a new model taking account of the carryover loss established, the predicted results were greatly improved. Based on the modified model, the influence of geometrical parameters of rotary regenerator on the effectiveness was analyzed for TPV systems of various combustion power. The results demonstrate that the effectiveness increases with the increase of the rotary regenerator diameter and height, while fluid carryover loss increases at the same time, which weakens the impact of geometrical parameters.

Zinc diffusion process in N-GaSb was studied with excessive, appropriate and insufficient quantity of diffusion source (zinc pellets). Kink-and-tail type zinc concentration profiles obtained with appropriate zinc pellets quantity were successfully simulated using the assumption that the vacancy mechanism mediated by VGa0 and kick-out mechanism mediated by IGa+ take effect at the same time. It is found out that for diffusion temperature from 460°C to 500°C, the zinc surface concentration of the diffused samples has nearly no change and the logarithmic value of the zinc surface diffusion coefficient is linear with the reciprocal value of diffusion temperature; when the diffusion temperature is constant, both the zinc surface concentration and diffusion coefficient do not change with diffusion time.

Infrared false target is an important mean to induce the infrared-guided weapons, and the key issue is how to keep the surface temperature of the infrared false target to be the same as that of the object to be protected. One-dimensional heat transfer models of a metal plate and imitative material were established to explore the influences of the thermophysical properties of imitative material on the surface temperature difference (STD) between the metal plate and imitative material which were subjected to periodical ambient conditions. It is elucidated that the STD is determined by the imitative material's dimensionless thickness (dim*) and the thermal inertia (Pim). When dim* is above 1.0, the STD is invariable as long as Pim is a constant. And if the dimensionless thickness of metal plate (dm*) is also larger than 1.0, the STD approaches to zero as long as Pim is the same as the thermal inertia of metal plate (Pm). When dim* is between 0.08 and 1, the STD varies irregularly with Pim and dim*. However, if dm* is also in the range of 0.08–1, the STD approaches to zero on condition that Pim=Pm and dim*=dm*. If dim* is below 0.08, the STD is unchanged when Pimdim* is a constant. And if dm* is also less than 0.08, the STD approaches to zero as long as Pimdim*=Pmdm*. Furthermore, an application-oriented discussion indicates that the imitative material can be both light and thin via the application of the phase change material with a preset STD because of its high specific heat capacity during the phase transition process.

●A novel zinc diffusion method was used to form p-type region in n-GaSb.●The surface high-concentration region was suppressed using this method.●The fabricated GaSb cells showed good performances without complex etching process.●The cost of cells is reduced since no protective gas is required during diffusion.This paper reports a novel zinc diffusion method for forming emitters in GaSb thermophotovoltaic cells. A closed quartz-tube diffusion system using Zn–Ga alloys as the diffusion source was designed to realize p-type doping in N-GaSb wafers. The surface diffusion region showing a high concentration of zinc was suppressed by this diffusion method, and the GaSb cells fabricated using this method showed good quantum efficiency in the near-infrared bands. Compared to that of the conventional pseudo-closed-box diffusion method, the controllability of the etch-back process after front-side metallization is significantly improved, and the cost of the cell fabrication is reduced because no protective gas is required during the diffusion process.

•The IQE of the box shaped Zn diffusion profile GaSb cells was calculated.•The effects of recombination velocity and lifetime of holes were discussed.•The effects of diffusion duration and etching depth were analyzed in-depth.•The results were elucidated by analyzing the behaviors of the minority carriers.Based on a GaSb thermophotovoltaic (TPV) cell with a box-shaped Zn diffusion profile, a theoretical model of the generation and drift of the photogenerated minority carriers in the cell was established, and the internal quantum efficiency (IQE) of the cell was predicted with the classical semiconductor theory. The calculated results agreed well with the measurements. It is determined that reducing the front surface recombination velocity (Sn) could improve the IQE of the emitter region, whereas increasing the lifetime of holes (τh) could improve the IQE of the base region. The Zn diffusion duration has a large influence on the IQE at short wavelengths below 1200 nm. Compared with the IQE for the 5 h diffusion time, the IQE of the 2 h counterpart was improved dramatically. Front surface etching could increase the IQE at short wavelengths below 700 nm while there was a decrease in the IQE for wavelengths above 700 nm. Thus, front surface etching is not necessary for a cell with a box-shaped Zn diffusion profile because the IQE for the near infrared wavelengths are the most important. The calculated results were elucidated by analyzing the distribution of the minority carriers generated in the cell and their recombination processes.

In order to evaluate the energy saving performance of various windows on a common basis, three conceptual window models are presented, and an energy consumption index is defined as the ratio of the energy consumption of a given window to the corresponding value of the perfect window. A building energy analysis program, “BuildingEnergy”, was used to evaluate the energy consumption value of different window models. The following results are obtained: the energy saving potential of regulating the emissivity of the window is greater than that of regulating the solar transmissivity, the optimized phase transition temperature of the ideal near infrared solar spectrum regulating window is between 16 and 21 °C, and due to the high absorptivity in the metal state, the single vanadium dioxide (VO2) glazing discussed here behaves differently than the ideal near infrared solar spectrum regulating window, and it shows no obvious solar control advantage in energy savings over the ordinary window, and the phase transition process has no contribution to the energy saving effect of the single VO2 glazing in the summer.Highlights► Perfect and ideal window models are defined to set the technical ceilings (limitation) for different window technologies. ► The energy saving potential of regulating long wave thermal radiation property of the window is greater than that of regulating the solar spectrum transmissivity. ► The regulating capacity of the current VO2 glass to solar radiation is limited, and the high solar spectrum absorptivity in the metal state leads to higher energy consumption than in semiconductor state. ► The energy saving effect of the current VO2 single glass in summer is because of low transmittance due to high absorption rather than reflection, and the phase transition process has no contribution to its energy saving effect.

A novel thin film organic bionic leaf was prepared by a solution-casting method to simulate the thermal effect of transpiration and solar spectrum reflection characteristics of plant leaves. The main components of the bionic leaf are polyvinyl alcohol (PVA), lithium chloride (LiCl) and chromium sesquioxide (Cr2O3). The thin film was modified by chemical cross-linking, and its surface was modified by alkylsilane to prevent excessive swelling. The thin film can simulate the thermal effect of natural leaf transpiration because that the hygroscopic PVA and LiCl can absorb and desorb water due to the high and low humidity of the ambient air at night and day, respectively. The thin film has the similar solar spectrum reflection characteristics to those of plant leaves due to the Cr2O3 and the water content of the hygroscopic materials. The measured diurnal maximum radiation temperature difference between the organic bionic leaf and the Osmanthus fragrans leaf was only 0.55 °C. In addition, the solar spectrum reflection measurements revealed that the organic bionic leaf could precisely simulate the key solar spectrum reflection characteristics of plant leaves.

We proposed a kind of bionic leaf to simulate the thermal effect of leaf transpiration. The bionic leaf was firstly designed to be composed of a green coating, a water holding layer, a Composite Adsorbent (CS) layer and an adsorption-desorption rate controlling layer. A thermophysical model was established for the bionic leaf, and the dynamic simulation results reveal that the water holding layer is not necessary; a CS of high thermal conductivity should be selected as the CS layer; the adsorption-desorption rate controlling layer could be removed due to the low adsorption-desorption rate of the CS; and when CaCl2 mass fraction of the CS reaches 40%; the bionic leaf could simulate the dynamic thermal behavior of the natural leaf. Based on the simulation results, we prepared bionic leaves with different CaCl2 content. The thermographies of the bionic leaf and the natural leaf were shot using the Infrared Thermal Imager. The measured average radiative temperature difference between the bionic and natural leaves is less than 1.0 °C.

Understanding the heat and mass transfer processes of plant leaves is essential for plant bionic engineering. A general thermophysical model was established for a plant leaf with particular emphasis on the transpiration process. The model was verified by the field measured stomatal resistance and temperature of a camphor leaf. A dynamical simulation revealed that diurnal transpiration water consumption is dominated by the solar irradiance and the day-average temperature of the leaf is dominated by the ambient air temperature; transpiration plays an important role in the cooling of the leaf, in average it could dissipate around 32.9% of the total solar energy absorbed by the leaf in summer. To imitate the thermal infared characteristic of the real leaf, the up surface of the bionic leaf must have emissivity and solar absorptivity close to those of a real leaf and its shape and surface roughness must be similar to those of the real leaf. The key point is that the bionic leaf must be able to evaporate water to simulate the transpiration of a plant leaf, appropriate adsorbent can be used to realize this function.