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Building integrated photovoltaic (BIPV)-vacuum system is promising for advanced window application due to its ability to reduce heat transfer, control over admitted solar heat and generates environmentally benign electricity. In this work, numerically thermal comfort for an unfurnished room comprising of BIPV-vacuum glazing was evaluated for the United Kingdom (UK) climate. Required parameters to determine thermal comfort, one-dimensional heat transfer model was developed and validated for BIPV-vacuum glazing and results were compared with BIPV-double-pane glazing system. PV cell temperature difference between these two different types of glazing was 24 °C. For the UK climate, BIPV-vacuum glazing offered 26% higher room temperature at clear sunny day compared to BIPV-double system. BIPV–vacuum glazing system provided soothing or comfortable thermal comfort during mid-day period for a clear sunny day at temperate climate. In a combined BIPV-vacuum glazing, it was also predicted that vacuum glass facing external ambient is suitable for the UK climate whilst vacuum glass facing internal room ambient is applicable for Indian climate.

Semi-transparent ultrathin Cu(In,Ga)Se2 (CIGSe) solar cells offer many promising applications but their efficiencies are still limited. In this work, SiO2 point contact structures were prepared using nanosphere lithography on Sn:In2O3 (ITO) substrate and ultrathin CIGSe solar cells were fabricated on top. It was discovered that the SiO2 point contact structure at the CIGSe/ITO interface behaves significantly different from at the CIGSe/Mo interface and does not improve the rear interface reflectivity or short-circuit current density. However, the SiO2 point contact structure brings pronounced electrical benefits, arising from the joint effect of reduced back recombination and induced field effect by internal charges. Semi-transparent ultrathin CIGSe solar cells with an absorber thickness of 380 nm exhibited a significant increase in open circuit voltage of 26 mV and fill factor of 9.4% (absolute). Consequently, the efficiency is improved by 23% (from absolute 6.8%–8.4%).

In spite of enormous promise in a multitude of applications, semi-transparent organic photovoltaics (ST OPVs) relatively lag behind opaque OPVs in the efficiency, and further efforts are imperative to improve their performance while preserving their transparency and tunable color perceptivity. Here, we develop highly efficient ST OPVs based on quaternary blends (Q-blend) involving non-fullerene small molecules, and demonstrate their realistic application in four-terminal (4T) tandem PVs. The ST quaternary OPV (Q-OPV) exhibits superior power conversion efficiencies (PCEs) higher than those of the state-of-the-art ST OPVs under any irradiation conditions, while retaining high transparency and the possibility of implementing various colors. In particular, we achieve the first PCE value exceeding 15% (~15.46%) under indoor lighting among the ST OPVs reported to date. The 4T tandem configurations based on a ST Q-OPV with diverse opaque PVs demonstrate broadband photon harvesting, with aesthetic functions rendered from the color-codable ST Q-OPV. The benefits of the Q-blend platform, including efficient operation under any irradiation circumstance (both indoor and outdoor lighting) and device color codability via tuning the quaternary components, can further expand the applicability of the ST Q-OPV to various practical applications.

The energy performances of c-Si PV windows and a-Si PV windows have been investigated comprehensively worldwide. However, CdTe thin film PV windows which are supposed to achieve better performance due to its higher efficiency are rarely studied. This study evaluated the energy performance of semi-transparent CdTe thin film PV window applying on commercial buildings. The results show that CdTe PV windows have large energy saving potential in Hong Kong, and the annual energy generation of per unit CdTe PV windows is 52.3kWh/m 2 . Compared to the common window and a-Si PV window, the saving in net energy consumption is 19.6% and 15.3%, respectively.

Semi-transparent photovoltaic (STPV) glazing can beautify the architectural appearance, generate power in-place. However, few researches study the climate adaptability of monocrystalline silicon STPV glazing. For the STPV glazing system, this paper develops a multi-physics model including the solar radiation, optical, electrical, and thermal models to analyze its overall performance. The model is validated by experiment. The performance of the STPV glazing system with different solar cell coverage ratios (R) in various climate zones of China (Guangzhou, Changsha, Kunming, Lhasa, and Beijing) is also studied. Among the five cities, the energy output of the STPV glazing system is proportional to the R value, and all follow approximately the same trend as the incident solar radiation. However, the geographic latitude has a greater impact on the electrical performance of the STPV glazing system than solar radiation. The thermal performance is primarily affected by the ambient temperature. The STPV glazing system performs well in the temperate area, with low cooling demand and high annual energy output. Compared with the traditional single clear glazing, the overall performance of the STPV glazing system is better, especially when the large solar cell coverage ratio. This paper provides a research basis for application in different climate zones.

Ultra-thin Cu(In,Ga)Se2 (CIGSe) is a promising absorber for thin-film solar cells, as it combines the advantages of low raw material consumption and high conversion efficiency. In addition, ultra-thin absorbers on transparent back contacts bring the advantage of semitransparency, which is essential for e.g. tandem or bifacial solar cells. This work optimizes ultra-thin CIGSe on In2O3:Sn (ITO) for application in bifacial semi-transparent ultra-thin (BSTUT) CIGSe solar cells. Firstly, 100–400 nm ITO were coated onto glass substrates, and it was revealed that the thickness of ITO influences its optical bandgap Eg due to the Burstein-Moss (B-M) shift. The band gap of 400 nm ITO increased by 0.14 eV compared to the 100 nm thick ITO, and the Voc of the related BSTUT CIGSe solar cells raised by 0.043 V as a result of the diminished Schottky barrier Φ b at the ITO/CIGSe interface. Secondly, 0–8 mg of NaF used for post deposition treatment (PDT) of the CIGSe were applied to the BSTUT solar cells. Compared to the reference without NaF, 8 mg NaF PDT enhanced the carrier density NA from 2 × 1015cm−3 to 1.2 × 1016cm−3 and diminished the ITO/CIGSe Schottky barrier Φ b by 0.21 eV. In conclusion, we found that NaF PDT can tune the carrier density of ultra-thin CIGSe on ITO, and both thicker ITO and higher NaF PDT dose can reduce the ITO/CIGSe Schottky barrier. These discoveries enable future optimization of BSTUT CIGSe solar cells.

Electric glue plays a key role in laminating top electrodes for organic and perovskite thin-film solar cells. However, there has been seldom reported for chemically reactive low–work function electrode yet. In this paper, polyethyleneimine (PEI) was developed as transparent top electrode adhesive, surface modifier for air-stable low–work function, and barrier to suppress the chemical corrosion of metal electrode in perovskite solar cells. The lamination was finished under room temperature with a pressure as low as 8 MPa, which is a very mild condition for device fabrication. The solar cells with transparent top electrode laminated for 10min had the best performances, in which the average value of PEI thickness between silver nanowires and the adjacent layer was found to play a key role in adjusting the performance of solar cells.

Open-cell foams have been accepted as one of the most promising substrates in immobilized photoreactors due to high mass transfer efficiency and large specific area but did not show a significant advantage over other substrates. A real-geometry-based computational fluid dynamic model of the photoreactor packed with idealized restructured β-SiC foams for the gas-phase photodegradation of methylethylketone (MEK) using the rutile TiO2 thick film is proposed to clarify the unanticipated inferior performance quantitatively. The difference in transparency of the substrate is demonstrated as the origin of inferior performance that the MEK conversion ratio with glass foams is 30.5% and 25.98% higher than those with opaque foams and with glass Raschig rings, respectively. Moreover, the semi-transparent substrate breaks through the limitation of the photoactivity with the foams of high cell density, that the MEK conversion could reach 11.1% when ρc = 45 ppi, improved by approximately 183% when compared to the opaque samples.

Use of ventilated semi-transparent photovoltaic (STPV) module integrated window systems offer energy saving vis-a-vis heating/cooling requirement along with energy generation. The present work investigates the net potential outcomes of the STPV window system in a composite climate of India. Consideration of effect of Angle of Incidence (AOI) on energy generation is another pivotal aspect of the study. Detail analysis of variation in the generation and net energy consumption with design cum installation parameters and Opto-thermal characteristics of STPV module have been presented. The analysis has been carried using both experimental and simulation data. The application of high efficient cadmium telluride (CdTe) STPV module resulted in more energy generation from the window systems. The maximum energy generation of the highest efficient module was found to be 119.6 kWh/m2/yr. A window as per the recommendation of the energy conservation building code of India was considered as reference case to analyze the energy-saving potential of the STPV systems. Compared to the reference window, the saving in net energy consumption was found to be as high as 60.4%. The findings of the research indicate that the considered STPV technology based window system has great potential in the daytime used buildings of the studied location.

We propose a flexible proximity sensor to detect sub-centimeter distance with an ultra-high displacement resolution. The proximity sensor is realized by integrating a semi-transparent organic photo detector with a transparent top electrode and a finger-type bottom electrode. By placing the semi-transparent finger-type photodetector on a light source, such as a light-emitting diode (LED), the photodetector can detect the light reflected from an object on top of the sensor. With the highly compact structure, the detecting range is from 1 mm to 30 mm. From 1 mm to 10 mm, the sensor is particularly sensitive and delivers a resolution of 1 mm. The air-stable photodetector can also be fabricated on a flexible substrate without encapsulation, enabling the integration with arbitrary light sources. After 1000 times bending, the flexible photodetector shows no obvious degradation.

Currently, certified lab scale organic photovoltaic (OPV) cells reach efficiencies of more than 12% and life times of 10 years. For commercialization, it is necessary to understand which performance can be reached in fully printed large scale products. Our investigations show that large area, semi-transparent organic photovoltaic modules based on industrially available materials can achieve power conversion efficiencies of more than 4.8% on rigid substrates and 4.3% on flexible ones. The modules processed with a combination of large area coating and laser patterning with an active area of 68.76 cm 2 for flexible modules and a total area of 197.4 cm 2 for glass modules offer exceptionally high geometric fill factors of more than 94% and a transparency of more than 10%. The processing recipe and the layout of the modules are based on indications of optical and electrical simulations which allow to produce devices with only negligible losses in comparison to small single cell devices. Losses due to imperfect coating or patterning are identified by thermal imaging.

Semi-transparent PV (STPV) windows can provide daylight illuminance and electricity generation simultaneously. The performance of semi-transparent PV in saving cooling energy has been proved in previous studies. This study presents the heating performance of STPV window in winter in Hong Kong. The passive heating effect of STPV was investigated experimentally. The results indicated that space heating is not needed for the room equipped with STPV in work time on sunny days. The SHGC and U-value of the STPV were also calculated. The average values of SHGC and U-value are 0.2 and 5.58 W/(m2 K), respectively.

Semi-transparent solar cells have been well developed in recent years, and can potentially be applied in many areas. Sb2Se3 has also received an increasing amount of attention because of its excellent optoelectronic properties. In order to combine these advantages, we attempted to fabricate a semi-transparent thin-film Sb2Se3 solar cell which meanwhile maintains the high efficiency. The effect of thickness of Sb2Se3 thin film on the optical and electrical properties were investigated. The optical absorption and power conversion efficiency were improved for Sb2Se3 thin film solar cells as the increase of the thickness of Sb2Se3 thin film, however, the obtained 120-nm-thick Sb2Se3 film was completely opaque. The optimized device was achieved with the thickness of 80 nm which exhibits the semi-transparent property and almost the same efficiency as the 120 nm Sb2Se3 thin film solar cell. This work demonstrates that the fabricated device has potential for applications in small wearable devices and may be extended to large-area glass-face applications.

The reported semi-transparent organic solar cells (ST-OSCs) are commonly based on a middle bandgap donor and narrow bandgap acceptor blend, for example, the PTB7-Th:Y6 blend. However, the strong absorption of PTB7-Th in the visible region hinders the further improvement of average visible transmission (AVT) for the ST-OSCs. Here we report a new kind of all-small-molecule ST-OSCs based on TAPC:Y6 blend. The used donor TAPC has little absorption in the visible region, which is beneficial for attaining high transparency. The optimized ST-OSCs based on TAPC:Y6 blend realize a power conversion efficiency of 3.01%. Importantly, a high AVT of 47.99% is achieved for this kind of ST-OSCs, much higher than those of reported ST-OSCs. The proposed TAPC:Y6 ST-OSCs also have a good color perception, whose CIE 1931 coordinates are (0.292,0.313) and color rendering index is 94.5.

The Semi-Transparent Photovoltaic (STPV) Window is a new form of building integrated photovoltaics (BIPV), which not only can generate electricity, but also improve indoor light and thermal environment. The STPV window was designed, manufactured and applied on a test building. Energy and environmental benefits were studied. The research site is located in an area with solar radiation diversification. The parameters of the life cycle assessment (LCA) model are derived from the database, experimental data and the electricity simulation model. The two important indicators, energy payback time (EPBT) and greenhouse gas payback time (GPBT), are selected to analysis this system, and another seven environmental indicators are considered for different aspects. According to the research findings, the EPBT of the STPV window is 13.8 years, and the GPBT 10.4 years, which are both less than the preset service life of 25 years. The results show that the STPV window can reduce pollution and the waste of non-renewable resources. The optimization analysis connected with the LCA study was carried out based on the critical parameters of the STPV window application in buildings. Optimal directions and preferable locations can result in the STPV window being more economical and sustainable. With increase of the window-to-wall ratio (WWR) and the coverage ratio of PV cells, the EPBT and GPBT gradually become shorter. Following to the research findings, suggestions are put forward to effectively reduce the life cycle cost of BIPV systems.

This study evaluated the energy performance of an a-Si semi-transparent PV insulating glass unit (IGU) via numerical simulation and experimental tests. Combined with the measured optical and electrical characteristics of the PV laminate, an integrated model was developed to simulate the overall energy performance of the PV IGU in EnergyPlus. Outdoor experiments were conducted to validate the accuracy of the simulation model. The proper consistency between the simulation results and the experimental data indicated that the simulation model was reliable for predicting the overall energy performance of PV IGU. With the validated model, a sensitivity analysis was conducted to investigate the influences of air gap depth and rear side glass, and an optimal design scheme was proposed to maximize the energy efficiency of PV IGU in Hong Kong. Finally, the energy saving potential of the optimized PV IGU compared to the other commonly used window systems was evaluated. It was found that the energy saving potential of the optimized PV IGU was 25.3% and 10.7%, respectively, compared to the single clear glass window and the Low-E glass window. The methodology developed in this study is expected to provide a useful reference for simulating the energy performance of PV IGU.

The use of semi-transparent photovoltaics (STPV) as a greenhouse cladding material can serve to transmit daylight while providing some shading and solar electricity generation. This paper experimentally validates an energy model of a greenhouse concept employing STPV. The model is then used to compare the energy performance of a full-scale greenhouse and a vertical farm concept, with both employing STPV. Simulation results for Montreal indicate that the vertical farm generates 49% less solar electricity and consumes up to 31% less heating than the greenhouse, whereas their cooling energy demand is approximately equal. This research evaluates promising design concepts for year-round urban agriculture and renewable energy generation.

Transparent conductive composites can be achieved from PVDF–MWCNT at very low concentration of MWCNT. These composites show different degree of UV–Visible radiation absorption depending on MWCNT concentration in composites. The composition dependent dielectric properties and AC conductivity were also measured for these composites. Properties like AC conductivity, dielectric constant and loss are increasing with filler concentration. The variations of DC conductivity against composition and temperature are also reported. The electrical hysteresis and electrical set are observed for PVDF–MWCNT composites when subjected to heating–cooling cycle. The validity of different theoretical models depicting percolation threshold with respect to DC conductivity was tested for these composites.

The installation of semi-transparent tension structures in the entrance portal of road tunnels leads to significant energy savings. These savings can be maximized when the tensions structures are designed in such a way that their material and shape contribute to their optimal photometric and mechanical performance. In this research, a graphic design software in the field of light simulation has been used and combined with the ESTS equation, developed in a previous study, to simulate tension structures with three different shapes and three different materials. Nine possible combinations were thus tested. The results obtained show that this new method is a quick, inexpensive, and safe way to optimize the material and shape of the tension structure installed at the entrance portal of a road tunnel, regardless of its orientation and location.

A semi-transparent Cu thin film with a thickness of 40 nm and a tensile strength of 36 MPa onto the glass substrate deposited through a solution-based process, by heat-treating the spin-coated precursor film at 350 °C with Ar gas flowing at a rate of 1.5 L min−1. The Cu thin film is more than ca. 30% transparent in the visible region and exhibits 40−100% reflectance in the infrared region. The electrical resistivity of the Cu thin film is 4.7(6)×10−5 Ω cm.

Resume Dans cette etude, nous avons etabli par la methode des elements finis en trois dimensions une approche simplifiee pour analyser l'evolution de la temperature au sein d'une membrane semi-transparente de type polyethylene terephtalate (PET) amorphe, exposees a une source radiative. En se basant sur le comportement optique du PET, un transfert radiatif monodirectionnel, suivant l'epaisseur de la membrane est considere. Des simulations numeriques ont permis de confronter et de valider les resultats obtenus vis-a-vis des resultats analytiques et experimentaux. Comme application, nous avons etudie le chauffage d'une feuille thermoplastique en PET exposee a une source radiative infrarouge.

In this paper, we solve numerically the coupled conduction–radiation heat transfer problem in semi-transparent orthotropic materials. Both the conduction and the radiation problems are solved with finite-volumes. The numerical solution obtained here is validated with results available in the literature. Results are presented for test cases involving the non-uniform heating of bodies at high-temperatures.

The kernel substitution method permits to find an analytical expression of the temperature within a semi-transparent medium. But a question still remains: which coefficients must be used in the substitute kernel? This paper presents a synthesis to answer this question. A study presents several methods on a test case to determine the coefficients. The values obtained are then compared with those commonly used in the literature.

The aim of this theoretical and experimental study is to provide a complete methodology to estimate the intrinsic diffusivity of semi-transparent media from flash method experiments. A semi-analytical model describes the coupled conductive–radiative transient heat transfer in a slab. The relevance of the model used for the inversion is then investigated. Experimental results are presented for several semi-transparent samples: float glass, SiO 2 and ZnSe. Measurements of rear face temperature are obtained by optical way (infrared detection) for a wide temperature range (293–700 K), for several radiation boundary conditions (black or gold coatings). The results are compared with those obtained through an other set-up and an other experimental procedure.

The effect of physical parameters and geometrical configurations on the interface shape in semi-transparent BaF 2 crystals grown by the vertical Bridgman process are studied both experimentally and numerically. Values of thermo-physical parameters are suggested in the case of BaF 2 .

The directional emission intensities emerging from a parallel plane slab or semi-transparent media in which is imposed a variable spatial refractive index, have been determined by a curved ray-tracing method determining the trajectories of radiation propagation and integrating the radiative transfer equation on each of these trajectories. Cases of linear and sinusoidal refractive indexes are examined, for both isothermal and non-isothermal situations, which display significant differences from the case of a constant refractive index.

The dual reciprocity boundary element method (DRBEM) has been developed to solve unsteady heat transfer problems with phase change moving interface and non-linear thermophysical properties. Numerical simulation of the heat transfer in Bridgman growth process of semi-transparent crystals has been made. Some results of transient temperature fields and time marching solid-liquid phase-change moving interface in the crystal growth are presented in this paper.

Using a radiative and conductive heat transfer model for shaped semi-transparent crystals, the influence of various growth conditions on the stress field, namely the von Mises stress, has been studied in sapphire crystals obtained by the EFG method.

The effect of some thermal and geometrical-size configurations on the interface shape and on the temperature distribution in semi-transparent fluoride-type crystals grown by the vertical Bridgman method are studied by finite-element analysis.

A method of simultaneous measurement of the thermal conductivity and absorption coefficient of radiation by arbitrary heating is proposed for semi-transparent liquids and non-scattering of radiation. These properties were determined by a numerical analysis of the combined transfer of conduction and radiation in the specimen system on the basis of the measured data of the temperature changes with time. This method was applied to some kinds of liquid. The determined values of both properties agree with the available data obtained separately by using the existing methods.

This study's aim is to appreciate real site surface temperature error values obtained using a thermocouple on semi-transparent materials and to determine a method of correction. Using an efficient measurement system, an experimental study was carried out under a number of climatic conditions. The results show that high values for solar radiation and wind speed have a significant influence on thermocouple measurement. The authors, therefore, decided to validate and develop a corrective model for the measurement errors of these two parameters. The conclusion also provides data on the model's relative drawbacks and current limitations.

It is believed that the use of transparent insulation materials (TIM) is prospective in the fields of solar energy and architecture engineering. Semi-transparent films are the basic constituents of some TIM, e.g., honeycomb structure. Two most important characteristics of semi-transparent films are their transmittance for solar radiation and emittance for long wave thermal radiation. In this paper, a technique for determining the optical constants of these films is presented. The thermal radiation properties of several semi-transparent films are reported.

Theoretical investigation of heat exchange in a model (system) consisting of a shaped cylindrical semi-transparent crystal with a set of screens surrounding the crystal and an outer heater is considered. It is shown that the temperature field in the crystal is very sensitive to the temperature distribution along the surface of the heater and to a lesser extent depends on the parameters of the set of screens. Solutions to direct and inverse problems are obtained. In the first case, the temperature of the heater is given and the crystal temperature is found. In the second case, in contrast, the temperature of the heater which will ensure the wanted temperature in the crystal is sought. Special attention is given to the case when the linear temperature distribution in the crystal is needed.

The effects of the heat transfer on the melt-solid interface shape and on the temperature distribution in shaped semi-transparent crystals grown by EFG method are studied by finite-element analysis.

The spectral directional emission intensities of axisymmetric, semi-transparent materials have been determined by a ray-tracing method using differential geometry and the geometrical approximation. As an example, the emission mapping of a semi-transparent paraboloid is examined, both for isothermal and non-isothermal cases, which display unusual emission properties.

Because of the lack of theory and methods of measuring the ambient radiation in real situations, it is impossible to quantify the self-radiation properties of a target. Our earlier paper, (13) proposed a theory, “Equivalent Blackbody Radiation Theory,” and a design method for infrared systems that can measure quantitatively the ambient radiation and self-radiating properties of opaque targets. We now extend our treatment to the more general case which includes opaque, semi-transparent and transparent objects. As examples, the ambient radiation in different situations, the self-radiation properties of an opaque metal plate and a semi-transparent crystal, and the true temperature difference of human breath during inspiration and exhalation are measured quantitatively and successfully.

Criteria for the selection of molecular metals as the active components of conducting bi-layer composite films are presented and discussed. It is shown that two-dimensional (2D) organic metals with halide or trihalides anions have some advantages over other molecular metals for the conducting bi-layer composite film preparation.

The energy absorbed by a fluid confined within a circular-cylindrical cover is calculated. Energy losses due to reflection on both sides of the inner and outer surfaces of the cover as well as the energy absorption of the cover are considered. Formation of ray cascades are taken into account. A ray tracing computer simulation was performed for various cover thicknesses, coefficients of extinction, cover diameters, and concentrations. A comparison of the energy absorbed for the circular geometry and of a flat surface geometry was also done. Optimization of the fluid diameter with respect to the amount of energy absorbed by the fluid per unit aperture was obtained.

Theoretical analysis of the interaction between concentrated solar radiation and a honeycomb matrix or a bed of particles cooled by a gas is presented. The computation and the experimental results show evidence of overheating of the solid near the irradiated surface. To prevent the upper surface from this phenomenon and to reduce the radiative heat losses, we propose to use selective semi-transparent porous absorbers. The first results about coatings on silica are presented.

The effects of anisotropic scattering of radiation on the melting (solidification) of a semi-infinite, semi-transparent medium at melting temperature is investigated. The model allows for the penetration of radiation deep into the isothermal region causing local melting, hence generating a two-phase zone between the purely liquid and purely solid regions. The results show that anisotropic scattering has significant effects on the rate of propagation of the melt (solidification) front. Backward scattering retards the melting, while forward scattering enhances it. The more forward the scattering, the faster the rate of melting (solidification) of the medium.

A theoretical study has been made to investigate the dependence of the two-point resolution by an aberration free, semi-transparent and φ-phase annular aperture, on the real part of the complex degree of coherence. Rayleigh's criterion in its modified version has been used for the partially coherent optical systems and a comparison between Rayleigh and Sparrow resolution has been made. In order to reveal important information concerning the characteristics of the image, the intensity distribution from two mutually partially coherent point sources has also been evaluated.

If a material is either inhomogeneous or has an uneven surface, a portion of the direct insolation incident upon it becomes diffuse. A methodology is proposed for determining such forward scattering of the direct beam. Results for a number of translucent, translucent, and net plastic materials are reported.

A class of apodisation functions for use in coherently illuminated systems is applied to the imagery of semi-transparent phase edge objects. It is shown that the image intensity distribution is either a monotonic function or at most has a single minimum.

A straightforward transient analysis for the heating of a fluid through a semi-transparent plate is presented in this note. It is concluded that the present theory also validates the experimental results of Lumsdaine.