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• Transparent a-Si:H solar cells are developed using very thin back OMO electrodes. • Thin OMO electrode composed of Al-doped ZnO and Ag is 110 nm thick. • Cell efficiency and transmittance are experimentally and numerically studied. • Laser-patterning optimization is presented for thin OMO electrodes. • Transparent modules are optimally designed using equivalent-circuit model. Transparent hydrogenated amorphous silicon thin-film solar modules are fabricated using oxide-metal-oxide (OMO) electrodes as the back electrode for building-integrated photovoltaic applications. The outer aluminum-doped zinc oxide and inner silver layers constitute a thin OMO electrode (~110 nm thick), exhibiting a sheet resistance of 6.8 Ω/□ and an average transmittance of ~88% in the visible range of 400–800 nm. The external quantum efficiency and average transmittance of the cell were investigated for the absorber-layer thickness using the finite-difference time-domain method, and it was found that the optical loss in the cell was mainly due to the absorption of the front electrode in the ultra-violet region and free-carrier absorption of the OMO in the infrared region. Fabrication issues are introduced for a 532 nm short-pulse high-power laser patterning process for transparent modules with thin OMO electrodes. Optimization of the laser power for the P2 and P3 laser processes is demonstrated by observing the profiles and measuring the shunt resistance of the laser-patterned edges. Furthermore, the cell width is optimized based on an equivalent circuit model using PSpice simulation. The highest module efficiency and average transparency achieved in the range of 500–800 nm were 5.6% and 15.2%, respectively. The short-circuit current density, fill factor, and open-circuit voltage per cell of the module were found to be 10.8 mA/cm2, 62.7%, and 0.830 V, respectively. [ABSTRACT FROM AUTHOR]

• The energy performance of a D/M/D film in hot weather is elucidated. • The long-wave regulation of a D/M/D film proved to be important. • Suitable application mode of a D/M/D film is demonstrated. • A clear relationship between the Ag thickness and optical properties is presented. • Samples with highest T vis and T vis + R si are prepared for energy-efficient windows. A dielectric/metal/dielectric (D/M/D) film with a high visible (0.38–0.78 μm) transmittance and a high solar infrared (0.78–2.5 μm) reflectance can be applied on the outdoor surface of a window for energy saving in hot weather. However, in this kind of application with a D/M/D film, the regulation of long-wave (>3 μm) radiation is often neglected but proved to be significant in energy saving according to our previous work. For a ZnO/Ag/ZnO structure on flexible PET applied as a visible transparent solar infrared reflecting film with a low long-wave emittance, based on matrix formulation and a ray-tracing method, the influence of Ag layer thickness on visible transmittance (T vis), solar infrared reflectance (R si) and long-wave emittance (ε lw) are investigated. Two samples with the highest T vis and T vis + R si are prepared, respectively, with high visible transmittance, high solar infrared reflectance and low long-wave emittance, simultaneously. In hot weather, compared with a traditional silica glass, the exterior applied film consumes more energy, while the interior applied film saves 9.6% energy consumption for cooling. [ABSTRACT FROM AUTHOR]

• A normal distribution model for diffuse radiation is proposed. • The normal distribution is related to the incident angle of direct radiation. • Weather and season do not influence the normal distribution. • Weather only influences the value of diffuse radiation. • The normal distribution has higher accuracy than other models. Solar radiation is an important factor in the design and simulation of transparent systems. The angle-dependent optical properties of transparent systems are hard to predict because it is difficult to obtain the incidence angle of diffuse irradiance. In this paper, a normal distribution model is proposed for diffuse radiation. It is assumed that diffuse irradiance follows normal distribution. The expectation of the distribution is the incidence angle of direct radiation, while the variance is expressed as the isotropy index. Through the experimental results for a transparent double-glazing (DG) system, it is found that the values of isotropy index are related to the incidence angle of direct radiation. The normal distribution model is evaluated with the diffuse irradiance map given by the researchers in SRRL. And then the indoor diffuse irradiance through the DG system is calculated by the normal distribution model and other distribution models. The calculated results are compared with the experimental results. It is assumed that the outdoor diffuse irradiance incident on a DG system follows normal distribution. The diffuse irradiance and transmittance through a DG system are predicted by the interface energy-balance method. The predicted diffuse irradiance and transmittance by the model are compared with measured values and those predicted by other distribution models. The predicted indoor irradiance or transmittance for the proposed normal distribution model has better accuracies than the Perez and isotropic model. [ABSTRACT FROM AUTHOR]

• Highly transparent and conductive MGZO films are prepared for CZTSSe solar cells. • Correlation between transmittance and resistivity of TCO on the solar cells is studied. • A deviation of transmittance was caused by the thickness of MGZO in NIR-IR region. • Efficiency of the CZTSSe solar cell is up to 7.54% with the MGZO of 600 nm. The doping of Mg and Ga into ZnO is a method for obtaining excellent optical and electrical properties for a window layer in an inorganic solar cell. Because a tradeoff exists between the electrical and optical properties in the window layer, balancing them is important for enhancing the performance of the solar cells. From this viewpoint, the thickness change of the window layer affects the transmittance and the conductivity. In particular, it affects the transmittance in the NIR-IR region significantly, which can enhance the current collection but lead to poor conductivity when the transmittance of the window layer is increased. We examine the thickness effect of MGZO films for CZTSSe solar cells in order to determine the optimal conversion efficiency. The enhanced transmittance in the NIR-IR region with a thin MGZO layer contributed to a high current density, although the electrical resistivity was relatively high. An enhanced conversion efficiency of 7.54% was eventually recorded for an optimal thickness of the MGZO layer with an improved current density over 7 mA/cm2. [ABSTRACT FROM AUTHOR]

• Algae-photobioreactors were installed as shading system in a real kindergarten. • The visible transmittance of the algae was determined through a 21 days monitoring. • The room daylighting and energy demand for lighting were simulated with Daysim. • Further simulations were run changing the site and the orientation of the room. • Performances with the algae shading system were compared to a venetian blind. • The lighting performances of algae and venetian blinds are comparable. A study on a novel photo-bio screen (PBS) used as a shading system in a real building is presented. The green microalgal culture (Scenedesmus obliquus) of the PBS allows a screening of the direct sunlight and a production of biomass containing bioactive compounds. The PBS was tested in a kindergarten classroom at Saint Marcel (Aosta Valley, north-west of Italy) and monitored for 3 weeks (June-July 2016). The visible transmittance T v of PBS was determined through in situ illuminance measurements, while the daylight amount in the room and the energy demand for lighting ED l were calculated through Diva-for-Rhino simulations (using the median measured T v as input). The analysis was split in two phases: (i) the real room (with south-facing windows and external obstructions); (ii) the same room without obstructions, analyzed parametrically by changing the site (Turin, Östersund, Athens, and Abu Dhabi) and the orientation (south, west, north, and east). For both phases, the results for PBSs were compared to what obtained applying a traditional venetian blind VB of comparable light transmission to the window. From the monitoring campaign, the T v of the PBS was found to have a quite high variation as a function of the dynamic boundary conditions, so an median value of 0.75 was identified as the reference T v. From simulations, it was found that the daylight amount and the ED l for PBS and the VB were comparable, with slightly better results for the PBS in Turin and Athens and slightly better results for the VB in Östersund and Abu Dhabi. [ABSTRACT FROM AUTHOR]

• The U-values of double/triple evacuated glazing with tempered glass were simulated. • Compared with the U-values of double/triple vacuum glazing with annealed glass. • the U-value of double evacuated glazing with tempered glass is reduced by 47.4%. • the U-value of triple evacuated glazing with tempered glass is reduced by 60.7%. • as tempered glass is 4 times stronger than annealed glass, less pillars are used. The application of tempered glass has made it possible to significantly reduce the support pillar number within evacuated glazing (EG) since tempered glass (T-glass) is four to ten times mechanically stronger than annealed glass (A-glass). The thermal transmittance (U-value) of 0.4 m by 0.4 m double evacuated glazing (DEG) with 4 mm thick T-glass and A-glass panes with emittance of 0.03 were determined to be 0.3 Wm−2K−1 and 0.57 Wm−2K−1, respectively (47.4% improvement) using previously experimentally validated finite volume model. The thermal transmittance (U-value) of 0.4 m by 0.4 m triple evacuated glazing (TEG) with 4 mm thick T-glass and A-glass panes with emittance of 0.03 were determined to be 0.11 Wm−2K−1 and 0.28 Wm−2K−1, respectively (60.7% improvement). The improvement in the U-value of EG with T-glass is due to a reduction in support pillar number, leading to reduction in heat conduction through pillar array. The impact of tempered glass on the thermal transmittance for TEG is greater than that of DEG since radiative heat transfer in TEG is much lower than that in DEG, thus the reduction in heat conduction resulted from the reduction of support pillar number in TEG is much larger than that in DEG. [ABSTRACT FROM AUTHOR]

Highlights • A solid concentrator photothermal/day lighting system was developed for greenhouse. • The maximum instantaneous thermal efficiency and power were 32.2% and 353 W/m2·s. • The area of the module was 0.09 m2, matching the size of the greenhouse roof panel. • The semi-transparency of the module allows co-production of crops and energy. Abstract Currently, the excess light above a light saturation point cannot be harnessed for plant growth in conventional greenhouse covers. In this study, we developed a solid compound parabolic concentrator (CPC) cover for use in greenhouses to convert excess light into heat. Optical simulation software was used to track the sunlight at different incident angles over time. We also conducted experiments to determine the transmittance and heating power of the solid CPC coating under real weather conditions. The maximum instantaneous thermal efficiency and thermal energy of a single solid CPC cover plate were 32.2% and 353 W/m2, respectively. The simulation results were in good agreement with the experimental output power and the trend of the actual transmittance of the covering material. The transmittance of the covering material was low when the midday sun was intense, and the transmittance was relatively high in the morning and afternoon. The variation of red and blue light in the greenhouse with the spectrum was analyzed at the same time. Studies have shown that this new greenhouse covering material can better adjust the brightness, make the illumination in the greenhouse more uniform, and thus improve the thermal environment in the greenhouse. The heat pipes converted excess light into heat, thereby achieving comprehensive utilization of solar light and heat. [ABSTRACT FROM AUTHOR]

Highlights • Various cases studied demonstrate the feasibility and capability of the new louver. • The louver harvests >50% solar energy and transmits >70% VIS for daylighting. • IR/UV absorption and VIS transmittance are high for both diffuse and direct radiation. • The louver performs well in all the locations studied of different AM models. • 7-band model is developed for accurate and efficient treatment of solar spectra. Abstract Water-filled prismatic glass louver was proposed to save energy consumptions in buildings because such innovative louvers can harvest solar energy as well as improve daylighting quality rather than "block" sunlight like traditional louvers. To enable this technology the effectiveness of ultraviolet (UV) and infrared (IR) energy harvest and visible (VIS) light transmittance was investigated via Monte Carlo simulations in this case study. The 7-band spectral model for glass and water was evaluated and adopted for several cases of solar spectra of different air mass (AM) coefficients with both direct and diffuse irradiation. Absorption and transmittance in different band regimes as well as in water and glass respectively were differentiated and compared. Practical solar data in Phoenix, Flagstaff, and Golden were utilized to demonstrate the performance of the proposed louver under different locations and realistic conditions. Results show that the device facing normally to direct sunlight can harvest around 51–54% of the total solar energy and transmit 74–76% VIS for daylighting in the range of AM1 to AM3. In particular for AM1.5, VIS transmittance reaches 76% for both direct and diffuse irradiation; UV absorption achieves 80% and 85% and IR absorption reaches 64% and 82% for diffuse and collimated irradiation, respectively. In all the three places tested, the device absorbs about 81% IR and 87% UV, and transmits about 76% VIS. [ABSTRACT FROM AUTHOR]

Highlights • Highly transparent and conducting ZnO thin films have been optimized by Al doping. • Prepared films exhibit good optical transmittance ∼90–95% in the visible energies. • High conductivity (0.26 mho cm−1) and low resistivity (3.8 Ω cm) has been found in 2 wt% AZO film. • Solar cell configuration with SLG/Mo/CuInS 2 /CdS/iZnO/2 wt% AZO/Ag is delivered, 2.20% PCE. • This is superior to all other cells and especially 53% higher than that of the pristine ZnO. Abstract ZnO thin film with flake-like surface morphology has been optimized by Al doping via the home-built chemical spray pyrolysis technique at substrate temperature 250 °C. Then, its performance as an anti-reflecting as well as highly transparent and conducting window layer in CuInS 2 based solid-state solar cell is explored here. The solid-state properties of the pristine and Al-doped ZnO (AZO) thin films have been studied to determine its potential for use in photovoltaic applications. First, it substantiates that the Zn, O and Al atoms are mainly involved for the growth of hexagonal wurtzite crystal structure by EDAX, XPS and XRD studies. All the films exhibit good optical transmittance nearly ∼90–95% in the visible energy region. Further, the 2 wt% AZO film shows low reflection loss in the same region. The decreased electron forbidden gap size is noticed in Al doped ZnO as compared to pure ZnO film. The good electrical parameters i.e., high conductivity (0.26 mho cm−1) and low resistivity (3.8 Ω cm) are found in the 2 wt% AZO film. Wettability test confirms the 2 wt% AZO flake-like surface morphology exhibited hydrophobic nature. Eventually, the 2 wt% Al-doped ZnO flake-like morphology thin film utilized as a window layer in CuInS 2 based solid-state solar cell which exhibits a pronounced photocurrent density result in 2.20% power conversion efficiency (PCE) is achieved. This efficiency is superior to all others and 53% higher than that of pristine ZnO window layer based photovoltaic cell. [ABSTRACT FROM AUTHOR]

Highlights • The transmittance was determined by the atmosphere and the emitted energy. • The method of coupling analysis was established in the paper. • Materials with a greater distribution of energy should be priority considerations. Abstract This paper established a mathematical model to explore the characteristics of infrared energy of 8–14 μm emitted from an urban surface and analyzed the atmospheric transmittance under actual weather conditions. Then, the amount of infrared energy that penetrated the atmospheric infrared window was determined, based on the coupling analysis of urban radiation energy and atmospheric transmittance. Six typical urban surface materials were researched in this case study. The results showed that the transmittance was changed under different weather conditions and different urban surface materials had different infrared energy penetration of the atmospheric infrared window, which indicated different urban surface materials may have potentially different effects on the urban thermal environment. The results also indicated that the transmittance for different materials was affected not only by atmospheric transmittance but also by the distribution of emitted infrared energy along wavelengths, which provides a new perspective for related researchers to understand the phenomenon. [ABSTRACT FROM AUTHOR]

Dust deposition on photovoltaic (PV) modules is related to environmental and weather conditions and results in a reduction in power generation efficiency over time. The effects of films on the transmittance can be obtained by testing sample glasses coated with silicon and fluorine super-hydrophobic films with a spectrophotometer. Red soil particles with a diameter of 25 μm were selected to simulate the process of natural dust deposition on PV module samples, and an incubator of constant temperature and humidity was used to simulate the condensation process. PV module samples were irradiated by a solar simulator after the aforementioned simulation process, and the effects of different amounts of sediment in unit areas on the photovoltaic properties and spectral characteristics were determined. The experimental results indicate that the influence of dust on the power generation efficiency of PV modules coated with fluorine super-hydrophobic film is smaller than that for PV modules coated with silicon super-hydrophobic film and that the super-hydrophobic films can not only greatly reduce the dust accumulation on the surface of PV modules but also increase the generating efficiency. [ABSTRACT FROM AUTHOR]

Clear-sky Direct Normal Irradiance (DNI) is the solar power received at ground level per unit of area, at a specific location, under cloud-free conditions. Regarding Concentrating Solar Power (CSP) technologies, such conditions mean that there is no cloud between the Sun and the observer, i.e. the solar field. Since clear sky defines the nominal operating conditions of CSP plants, real-time estimates and forecasts of clear-sky DNI are key information for power plant operators tasked with the management of those plants. So, the present paper focuses first on a new algorithm for the real-time detection of clear-sky situations from DNI measurements. This algorithm makes use of the last-known clear-sky situation and requires the maximum speed at which the atmosphere becomes opaque to be evaluated. The paper also focuses on an efficient approach to the real-time assessment of clear-sky DNI. This approach combines the model developed by Ineichen and Perez with a persistence of atmospheric turbidity, taking advantage of the fact that changes in this quantity are relatively small throughout the day in comparison to changes in DNI, even when the sky is free of clouds. Performance is evaluated via a comparative study, in which empirical models are included, using one-minute data from two sites (Golden, USA, and Perpignan, France). MAE and RMSE are lower than 10 W m - 2 and 21 W m - 2 , respectively. The same approach is capable of providing accurate intraday forecasts of clear-sky DNI. It has proven to be the best compromise between accuracy and complexity (reference is a persistence of DNI) among the considered approaches, including neuro-fuzzy approaches. For a forecast horizon of 5 h,MAE ≃ 30 W m - 2 and RMSE ≃ 37 W m - 2 . [ABSTRACT FROM AUTHOR]

The growing use of plastic film coverings in agriculture is due to the possibility of increasing the air temperature around the plants, reducing radiative and convective energy losses, protecting fruit trees from adverse weather conditions, reducing fungal diseases, assuring less reliance on herbicides and pesticides, better protection of food products and more efficient water conservation. Low-density polyethylene (LD-PE) is one of the most widely used plastic films for greenhouse coverings, low and medium tunnels and soil mulching. In this paper, we present radiometric properties of a new and old (used for more than five years) LD-PE film, experimentally investigated using different methodological approaches for different wavelength bands, especially at medium IR. Experimental measurements in the IR wavelength spectrum, included the Near (0.78–3 μm), i.e. N-IR-A (0.78–1.4 μm) and N-IR-B (1.4–3 μm) and Medium (3–50 μm) in accordance with ISO 20473 (E) 2007 were carried out. Experimental results obtained are in agreement with those in the literature and show that the aging effects are minimal in the plastic film used for five years. This finding is crucial for greenhouse design. Referring to practical applications, energy balance of an ordinary agricultural greenhouse was also evaluated. The authors believe that this research results on all the optical properties in a wide spectral range of LD-PE will be useful not only in agriculture, but also for any other solar engineering application. [ABSTRACT FROM AUTHOR]

A wind tunnel protocol is presented that allows to study the efficiency of anti-soiling and anti-reflective coatings under dry soiling conditions. Anti-soiling coatings are intended to reduce the accumulation of dust on photovoltaic modules and other surfaces. Dust accumulation is the combined result of sedimentation (or deposition) and syngenetic or post-genetic removal. In the field, the amount of dust present on a photovoltaic surface is always the result of accumulation. The protocol allows one to study the effects of anti-soiling and anti-reflective coatings on the processes of dust deposition and dust removal separately so that the specific operation of the coatings in comparison to uncoated glass can be better understood. Using an aeolian dust wind tunnel, dust deposition and dust removal measurements were performed under quasi-natural conditions on surfaces with and surfaces without an anti-soiling coating. Optical transmittance measurements were performed to determine the impact of anti-soiling and anti-reflective coatings on the amount of light passing through dust-polluted surfaces. We illustrate the protocol by comparing anti-soiling and anti-reflective coated surfaces with identical uncoated surfaces. The anti-soiling coating that was tested in this study has a dual functionality as it has both anti-soiling and anti-reflective properties. Results showed that the tested coatings did not affect the sedimentation of dust, but they did have a significant effect on dust removal, which started at a lower wind speed and cleaned the surface more rapidly compared to the uncoated surface. Additionally, the anti-soiling coating outperformed the anti-reflective coating regarding the wind speed at which dust removal started, indicating that dust adhesion forces on the anti-soiling coating are lower. Transmittance was always higher for the coated surfaces than for the uncoated surface, but the benefit of the coatings (higher transmittance) decreased as the glass surfaces became more polluted with dust. [ABSTRACT FROM AUTHOR]

Self-cleaning of optically transmitting surfaces is important to improve the performance of solar harvesting devices in harsh environments such as dust and humid ambient. Non-wetting characteristics of surfaces can create self-cleaning effects while lowering efforts required to remove dust from surfaces. Non-wetting, in which the texture has been filled with some lubricant, have robust self-cleaning characteristics than surfaces with air pockets trapped between the textures. Consequently, non-wetting surface in which the textures are impregnated with silicone oil is examined in relation to solar energy harvesting applications. In this case, a hierarchal texture is generated first onto the transparent glasses by the convective assembly of silica particles. The resulting textures are characterized incorporating scanning electron and atomic force microscopes. The textures are then impregnated with silicone oil after functionalization with OTS (Octadecyltrichlorosilane). Non-wetting behavior, film thickness and transmittance of the resulting surface are assessed using contact angle goniometer, ellipsometer, and UV–Visible spectrophotometer. The resulting surfaces are tested in outdoor environments and transmittance reduction of UV–visible spectrum is assessed. It is found that silicon oil impregnation improves water droplet mobility at the surface; however, optical transmittance reduces significantly over the time due to dust particles settlement at the silicon oil film interface. [ABSTRACT FROM AUTHOR]

We report hydrophobic modification of a high-performance broadband antireflective (AR) film comprising mesoporous MgF 2 nanoparticles. The MgF 2 film demonstrates high transmission, >99% (400–800 nm) and >97% (300–1500 nm) and is hydrophilic with a water contact angle of 27°. Hydrophobic modification with a fluorosilane containing silica sol by a simple dip coating process increases the water contact angle to 130° without affecting transmittance. Hence, this hybrid layer exhibits excellent anti-reflection in a broad wavelength range (98.8% (400–800 nm) and 97.03% (300–1500 nm)), along with good water-repellence. Moreover, the layer is also environmentally and mechanically stable indicating its suitability for solar and optical applications. [ABSTRACT FROM AUTHOR]

The principles of design for two types of prismatic elements have been studied. The theoretical approach has been used for design of the glass prisms to optimize their function for given application and geographic location. The two manufactured prismatic glass elements have been applied in triple glazed window samples with a low emissivity coating and experimentally tested to determine the realistic angular selective optical properties. A specific test stand for glass prism transmittance measurement has been developed and applied. The results have been compared with conventional triple glazing with clear glass panes and triple glazing with solar control pane applied, both alternatives with the identical low emissivity coating. Significant advantages of transmittance selectivity (low transmittance for high solar altitude – summer condition, high transmittance for low solar altitude – winter condition) have been proved especially for triple glazing with reverse symmetrical prism. The results open the possible application of the prismatic structures in modern façade envelopes, e.g. curtain walling facades or greenhouse walls as low-cost alternative to other types of shading devices. [ABSTRACT FROM AUTHOR]

A nanocomposite film based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) modified with dual additives of carbon black (CB) and dimethyl sulfoxide (DMSO) was developed as a hole transport layer (HTL) in inverted planar perovskite solar cells (PSCs) for the first time. Taking advantage of the cooperative effect of CB and DMSO, the co-modified film of CB-DMSO-PEDOT:PSS shows superior capabilities to collect and transport the charge induced by reduced sheet resistance and to assist the growth of perovskite light harvest layer with enlarged grains in micron scale on its surface when compared with the single-modified films of CB-PEDOT:PSS and DMSO-PEDOT:PSS as well as the pristine film of PEDOT:PSS. Meanwhile, the co-modified film still preserves high transparency in the visible range with a transmittance of 89.8% at 550 nm and do not alter the transparency of the pristine film greatly. As a result, the PSCs made on the co-modified film as a HTL possess higher short-circuit photocurrent density and open-circuit voltage than the devices based on the single-modified and pristine films, leading to a remarkable enhancement in the power conversion efficiency. [ABSTRACT FROM AUTHOR]

The study of radiation property of particles is of great significance in the field of solar thermo-chemistry. In this study the randomly dispersed particle system is obtained by the KBr tablet method, and the transmittance of activated carbon particle systems in 0.4–25 μm wavelength are measured by the spectrophotometer and FTIR to obtain their radiation property. The extinction coefficient of the particle systems and the efficiency factor for extinction of single particle are calculated through experimental data. The results show that the activated carbon particles have higher absorption ability in the visible light spectrum. Above investigation will not only be beneficial to the simulation of solar thermo-chemistry hydrogen production process, but also provide an experimental basis for inverse calculation of optical constants of the activated carbon particles. [ABSTRACT FROM AUTHOR]

Nowadays, the urgent need to replace fossil fuels with renewable energy is no secret. Therefore, researching in this area and developing the infrastructures necessary for the optimized utilization of these types of energy, are rising sharply. Among different kinds of renewable energy, due to easy access, solar energy has received special attention and extensive studies have been done, in order to increase the efficiency of the solar collectors and PV panels. One of the prime problems of solar systems in arid regions is the accumulation of dust on transparent surfaces, followed by an intensive drop in the transmission coefficient. In the present study, in a 70-day test period, up to 22% transmission coefficient loss, caused by the accumulation of dust on the surface, was observed. Thus, in order to solve this problem, Nanocoatings were deposited on glass samples to create self-cleaning property. A nanospray was used to create a hydrophobic film on the surface and TiO 2 was coated in three different thickness to create a hydrophilic film on sample surfaces. Test results showed that these surface modifications have a significant impact in the reduction of dust accumulation and the loss of the transmission coefficient. Although there was no rain during the test, for samples with surface modification, the transmission coefficient drops were noticeably reduced. After rain simulation, the results indicate that transmission loss reduced from 22% to 0.5% and dust settlement problem was almost completely solved. [ABSTRACT FROM AUTHOR]

This paper presents the results of an experimental study to measure and verify on-site global solar transmittance as a function of varying angles of incidence for glazing samples under natural clear-sky conditions, including: single-pane clear, double-pane clear, and double-pane low-e glazing. Field measurements were implemented using a silicon photodiode sensor and two thermopile-type pyranometers based on an easily-assembled test box with sample glazing. Measurement results were then compared to the published data (i.e., Tsol values in the WINDOW libraries). The results indicate that silicon photodiode sensors can be used to measure and verify direct solar transmittance within an acceptable range of accuracy. However, the global (i.e., direct and diffuse) solar transmittance measured by the thermopile-type sensors was significantly higher than the Tsol values from the WINDOW program. As a result, it is recommended that such field measurements could be used to verify the on-site direct and global solar transmittance of as-built glazing since the WINDOW program currently only accounts for direct (i.e., beam) solar radiation in the reference solar spectrum (i.e., ASTM E891 ). [ABSTRACT FROM AUTHOR]

A methodology to classify days as a function of the state of the sky for Concentrated Solar Power (CSP) plant operation is proposed. For this purpose, three indexes are used to characterize the energy, variability and time distribution of the DNI and to define the type of days by means of clustering techniques. Two sets of indexes are tested and compared. The energy of days is represented by the transmittance index, k b . Two indexes are used to characterize the variability of the DNI: persistence index of the instantaneous k b values (POP D ) and Variability Index (VI). Equivalent indexes have been previously used to classify the types of days using Global Horizontal Irradiation (GHI). A novel index to define the time distribution of the DNI daily energy is introduced. Clustering analysis is applied to thirteen years (2000–2012) of 10-min DNI measurements recorded in Seville (37.40°N, 6.01°W) by the Group of Thermodynamics and Renewable Energy (GTER) at the University of Seville. The k-medoids algorithm is used for cluster analysis. Through the use of well-known internal validity indexes and with the help of the L-method, the optimum number of clusters (types of days) is found to be 10. The results are compared with the assessment carried out by five experts on a reference set composed of DNI daily curves from two years (2010 and 2011). This comparison reveals a better coincidence when the clustering is performed using VI . [ABSTRACT FROM AUTHOR]

The study aims to evaluate thermal performance of newly developed spectrally selective coated glazing (SS) which has very low near infrared (NIR) transmittance and fairly high visible (VIS) transmittance. The performance of SS was first tested in full scale mock-up test cells and then compared with three types of conventional glazing systems (single low-e, triple low-e and clear). The comparative field test without air conditioning showed that solar gain of SS was less than or similar to the conventional glazing systems due to the low NIR transmittance, which present a potential of cooling energy saving in building application. Based on the field test, the thermal performance of SS was predicted using a building energy simulation. The simulation result showed that SS reduce 21% and 33% of total energy consumption as compared to the glazing with low-e coating and the glazing without coating respectively. The study concluded that SS can achieve lighting energy reduction with high VIS transmittance and cooling energy reduction with both high NIR transmittance and high U-value. Ultimately, SS will be highly applicable in cooling-dominated buildings or climate zone. [ABSTRACT FROM AUTHOR]

ITO/Ag/ITO (IAI) multilayer coatings were designed for spectral beam splitter applications and these coatings were deposited on glass substrates by magnetron sputtering method. The thicknesses of the component layers, namely, Ag and ITO were varied to achieve high visible transmittance, high NIR-IR reflectance and optimum cut-off wavelength. The optimized ITO/Ag/ITO exhibits high visible transmittance (∼88%) and high NIR-IR reflectance (>90%) with an optimum cut-off wavelength (∼900 nm). A novel chemical etching method was used to improve the transmittance of the plain glass substrate. The optimized IAI multilayer coating deposited on single side etched glass substrate resulted in increase in transmittance (∼91%), which is due to the nano-porous morphology of the etched glass substrate. The angular and polarization dependence studies of IAI multilayer coatings were also studied in detail. [ABSTRACT FROM AUTHOR]

In daylight and energy simulations, fenestration products are characterized by their visible transmittance (VT) and solar heat gain coefficient (SHGC) that are both dependant on the angle of incidence, as well as by their U-value. In this work, 18 typical fenestration products suitable for the Canadian context were chosen and correlations between their actual properties were developed. First, it is shown that variations from a “standard” angular dependency curve for VT and SHGC are relatively small in such a way that the angular dependency can be approximated either by an average relation for all fenestration types, or by more precise correlations involving a linear combination of solutions with the use of a weigh coefficients. Then, relationships between values of normal VT, U-value and normal SHGC are established. In the end, it was possible to deduce the detailed behavior of all insulated glazing units (IGU) from only one continuous variable. A more precise approach with three continuous variables was also developed. A test case is presented to illustrate how to use the correlations to generate different types of IGUs in simulations. [ABSTRACT FROM AUTHOR]

Dust depositions on photovoltaic (PV) modules reduce the transmittance of PV glazing, resulting in the degradation of efficiency. The primary source of dust is wind-blown sand and soil particles from the ground. The coarse dust particles have a diameter larger than 2 μm. Photochemical reactions of gaseous pollutants in the atmosphere and dried droplets of seawater forming salt particles form most of the fine particles smaller than 2 μm in diameter. The physical properties of dust, such as specific gravity, particle shape, surface properties, moisture content, plastic and liquid limits, and particular grain size, vary from location to another all over the world. These differences are due to the topographic, geological, and environmental conditions of each region. The weight and shape of dust particles have a significant effect on their deposition behaviour and PV performance. In this paper, an investigation of energy losses caused by dust deposition on PV modules in Oman is presented. Six dust samples collected over three months from six locations in Northern Oman were investigated to evaluate their physical properties. Most of the dust particles (64%) diameters size ranged from 2 to 63 μm. The dust deposition on PV modules was found to vary from one location to another. The results indicated that there is no significant energy-yield loss caused by the low surface mass concentration of dust (<1 g/m 2 ) on the PV module. The maximum daily efficiency loss was measured and compared with that from the literature, revealing that the efficiency loss was 0.05%, which is small compared to those of neighbouring countries. However, the results show a decline in the productivity of the PV module up to 35–40% after exposure to the weather conditions for more than three months, indicating that the advisable cleaning period, is every three months. Therefore, establishing PV systems at these sites is a reasonable option. [ABSTRACT FROM AUTHOR]

Spray deposition of molybdenum trioxide (MoO 3 ) hole transport layer under a DC voltage (500 V and 1000 V) applied to the nozzle yielded orthorhombic phase of MoO 3 (α-MoO 3 ) with no other phases present. The films had uniform, compact surface morphology with reduced roughness, increased transmittance and band gap as compared to those for spray deposited MoO 3 layer deposited without applying the DC voltage. In addition an increase in the work function was also observed possibly due to the change in the nanostructures formed on the surface. XPS result showed that the application of DC voltage during spray deposition reduced the oxygen vacancies. The reduced potential barrier height between MoO 3 and P3HT layer can be useful in organic bulk-heterojunction solar cell (ITO/MoO 3 /P3HT:PCBM/Al). This was indeed proven by organic bulk-heterojunction solar cell fabricated using the electric field assisted spray deposited MoO 3 layer yielding 2.71% power conversion efficiency with short circuit current density (J SC ) of 10.0 mA cm −2 , open circuit voltage (V OC ) of 0.57 V and fill factor (FF) of 47.4%. The organic solar cell fabricated using electric field assisted spray deposited MoO 3 layer showed an improved performance as compared to the standard spin coated solar cell. [ABSTRACT FROM AUTHOR]

Transparent conductive oxides (TCOs) have been used in a wide variety of applications as sensors and electronic displays and for solar harvesting for the past decades. TCOs are made of conductive materials such as metals. Many studies have been conducted to improve the properties of materials for TCOs. The properties that make a TCO effective are high transmittance and low resistivity. The current commercialized TCO is indium tin oxide (ITO), which has excellent transmittance and lower resistivity than other TCOs such as zinc oxide. Indium is expensive as its availability is becoming more limited over time. As such, studies to find an alternative material to ITO are continuing. Perovskite-structure materials are a candidate material with acceptable optoelectric properties. Perovskites have a wide band gap of ∼3.0 eV and high transmittance along with exceptionally low resistance. The first part of this paper mainly discusses the progress and development of perovskite-structured TCO as well as materials modification by doping. [ABSTRACT FROM AUTHOR]

Parabolic trough is the most extended solar thermoelectric technology. Solar radiation is converted into heat and transferred to the heat transfer fluid in the solar receiver tubes. The thermal energy obtained feeds a conventional Rankine power cycle. The performance of the receiver tube can be broken down into three single components: the optical transmittance of the outer glass envelope or capability in transmitting the radiant energy; the optical absorptance of the metal tube or capability to absorb the radiation; and heat losses of the tube or capability to retain the heat which depends of inner tube coating emissivity and the vacuum between both tubes. In this paper a novel test bench implementing both thermal and optical measurement systems is described and compared with other systems referred in the literature. The results obtained from the evaluation of three different solar receivers with different diameters are presented. Optical measurements of transmittance and absorptance parameters are carried out in the wavelength range of 300–2500 nm. Optical evaluation of trough receivers at operating temperatures up to 450 °C is feasible. The receivers can be heated using a high intensity electric current flowing through the internal tube. Uniform Joule heating results a reliable heat losses measurement method at temperatures up to 650 °C. [ABSTRACT FROM AUTHOR]

The performance of parabolic trough receiver tubes has a direct impact on concentrated solar power plant production and thus must be maintained at as high a level as possible during the life cycle of the plant. In this paper, in-the-field degradation of commercial plant receiver transmittance and absorptance is studied after four years of operation. Since no records of similar measurements were available regarding the reception of the receivers, the results are compared with both the manufacturer’s technical specifications and with the guaranteed values. For this purpose, the Mini Incus portable spectrophotometer developed by Abengoa is used to measure the optical properties of an 80-receiver sample. This sample is built up considering the two main factors most likely involved in transmittance and absorptance degradation: interactions with external agents and operating temperature. Therefore, receivers from different locations both in the field and within loops are chosen. A statistical study is performed on the data collected in order to obtain representative values for the whole population of evaluated receivers as well as for every group differentiated. The results reveal no significant degradation of the absorptance or transmittance of the receivers, with measured average transmittance and absorptance values of 96.6 ± 0.2% and 95.9 ± 0.2%, respectively, higher than the 96% and 95% indicated in the technical specification for new first generation receivers. Receiver location in the field and position within the loop does not influence optical property degradation, since the appreciated differences fall within the uncertainty of the measurement device. The obtained results are then compared with the technical specification values and with those guaranteed by the manufacturer after 4 years of operation, and the suitability of the guarantee in matching the reality experienced by the receivers in the field is discussed. [ABSTRACT FROM AUTHOR]

Here, we present research addressing one of the main challenges facing the efficient production of solar energy in arid regions where solar insolation is at its highest, but where the significant challenges of pervasive dust, sand storms and insufficient rain can dramatically alter the feasibility of harvesting solar energy. In this study, the impact of dust on the light transmittance through low iron glass was assessed for different periods of time. Additionally, different cleaning mechanisms were briefly reviewed including the promising technique of dry cleaning using robotic systems. This paper explores the effect of dry cleaning for the removal of dust particles settled down on glass and the impact of brushing on the transmission of the glass. It was demonstrated that dry cleaning using Nylon brushes does not have a significant, permanent effect on the optical characteristics of the glass surface, even when the brush is used to clean a dusty surface. Significantly, the process of brushing dusty samples does improve transmittance over the un-brushed state. However, the cleaning efficiency of the nylon brushes is not as high as cleaning using water and delicate wipers. The glass samples showed some changes in the surface of the glass after brushing, however, this was shown not to have a permanent effect on the optical characteristics of the glass after the simulated equivalent of 20 years of cleaning. Therefore, the data presented in this paper demonstrates the need for careful testing in the development and assessment of dry cleaning dust mitigation solutions. It also offers an indication of the technology’s positive potential and elucidates some of the most important obstacles that need to be overcome. [ABSTRACT FROM AUTHOR]

The optical properties of the immersion dielectric liquids are highly important for concentrating photovoltaic (CPV) systems with direct liquid-immersion cooling applications. A method for experimentally determining the optical transmittance of immersion dielectric liquids was proposed, based on the spectrophotometer measurement and photometry correction. Through the method, the optical transmittance of five candidate immersion dielectric liquids, both before and after long term stability test, was determined. Further, normalized photocurrent density ( J np ) was introduced to evaluate the effect of transmittance loss on CPV solar cells photocurrent. Results show that all the selected liquids exhibit much higher transmittance than that of EVA and silicone encapsulants in the spectrum range of 300–1100 nm. De-ionized water is shown to be the strongest absorber in the longer wavelength range and thus it is not suitable for immersing multi-junction CPV solar cells. With the other four initial organic liquids presence, the bottom subcell J np of the specified three-junction solar cells decreased. In fact, this is a beneficial property, especially for dimethyl silicon oil and ethyl acetate. In addition, results from the long term stability test show that the most stable liquid for CPV immersion cooling applications was observed to be dimethyl silicon oil. This is because no degradation in its optical transmittance was detected after immersion tabbed CPV solar cells for 180 days. [ABSTRACT FROM AUTHOR]

Photovoltaic–thermal (PVT) collectors are hybrid collectors which make, in principle, optimal use of the solar resource by co-generating electricity and heat in a single module. Spectrally selective but transparent low-emissivity (low-e) coatings are a suitable measure to reduce thermal losses. In this paper the development of PVT collectors with low-e coatings by means of experiment and simulation is presented. A highly transparent low-e coating based on silver, specifically optimized for the application in PVT collectors, is developed. By combining layers of low-refractive SiO 2 and high-refractive TiO 2 a low emissivity of ɛ 373K = 0.13 is achieved while maintaining high solar transmittance of τ AM1.5 = 0.79. This coating is applied in a glazed, flat plate, liquid-type PVT collector. Thermal and electrical performance were tested and compared to a PVT collector with the same design yet without low-e coating. A numerical model of the PVT collector is presented showing good agreement of simulation and experiment. With this model the impact of low-e coatings on thermal and electrical performance is analysed and discussed. The newly developed low-e coating reduces the collector heat losses by 82% while the electrical efficiency drops by only 3%. [ABSTRACT FROM AUTHOR]

A mathematical model is proposed for calculating the solar gains through the multi-glazing facades (MGFs) with venetian blinds considering specular reflection. Net radiation method is used to establish the solar radiation energy balance equations in the overall MGFs layers. Then, a mixed method combines ray tracing and radiosity methods is used to determine the optical properties of the venetian blind in this system. Numerical results are compared with the optical properties of venetian blind calculated by the radiosity method and the experimental results. The comparisons show that the proposed model results fit better with the experimental results. Some important impact factors on the total solar transmittance of the MGFs are analyzed including the venetian blind geometric dimension W/S ratio, the slat reflectance, the slat shining factor, the slat angle, and the sun profile angle. Moreover, the effect of the proportion of the beam radiation on the total solar transmittance is also considered. The impact of the W/S ratio, the slat reflectance, and the slat angle are not limitless, when the solar profile angle is greater than (90°- φ ), the impact of them are not significant. Meanwhile, the impact of the shining factor and the proportion of the beam radiation depend on their intersection point. Before the slat angle intersection points, the higher the shining factor, the smaller the transmittance, but it is opposite for the proportion of the beam radiation. [ABSTRACT FROM AUTHOR]

In this paper, we present a simple method to fabricate the antireflective porous surface on sodalime glass using a single step HF-vapor phase etching method. Under optimal conditions, both-sides etched glass substrate exhibited a broadband enhancement in the transmittance with maximum transmittance as high as 99.2% at ∼500 nm with extremely low diffusive scattering. The measured transmittance exceeds by ∼7.6% as compared to plain glass (91.6%). X-ray photoelectron spectroscopy results confirmed the formation of a fluoride layer comprising of NaF and CaF 2 on sodalime glass substrate after etching. Field emission scanning electron microscopy results showed the formation of porous structure with randomly distributed pores of size <150 nm. The refractive index of the porous fluoride layer was found to be 1.28 and lowest reflectance of 0.6% has been achieved. Moreover, reflection (measured at 500 nm) remains below 1.5% over a range of incident angles (8–48°), which is ascribed to the fact that refractive index follows a gradual change in the nanoporous surface. The theoretical transmittance of the optimized etched glass determined by finite difference time domain simulation shows a good agreement with the experimental results. The silicon solar cell covered with both-sides optimized etched glass showed a relative increase of ∼4% in power conversion efficiency as compared to a solar cell covered with a plain glass. [ABSTRACT FROM AUTHOR]

This study is to determine the range of incidence angles for a required transmittance of elementary prisms in a curved Fresnel lens and hence to determine the curvature of the lens. The p - polarized light and s-polarized light is considered separately. Calculations indicated that the transmittance of s-polarized light is always lower than p-polarized light and the total transmittance generally decreases with the increase of incidence angle monotonously according to the Fresnel equations, and therefore the transmittance of s-polarized light was recommended as the target for a lens’ design. Stokes’ reversible relation was derived by Fresnel formulas, which illustrates the reflectivity on both sides of the interface is equivalent when light goes through two media along with a certain path no matter which direction it is transmitted. It is found there is the optimal transmittance condition of prism (OTCP) when the incidence angle changes for a given refractive index bases on Stokes’ reversible relation. According to OTCP, the transmittance of a curved Fresnel lens can be calculated for a given curvature and focus and therefore the shape of lens can be optimized. The incidence angles for the required transmittance values of 0.95, 0.90, 0.85, 0.80 and 0.75, respectively, are given for different refractive indices. For example, for the refractive index n 21 = 1.49 (a value for the common PMMA), the range of incidence angle of s-polarized light is 0–22° if the required transmittance is 0.90; it becomes 0–48° when the required transmittance is reduced to 0.80. [ABSTRACT FROM AUTHOR]

This work deeply investigated the effect of water in terpineol-based TiO 2 screen-printing inks, commonly used for the deposition of photoanodes for dye-sensitized solar cells. The study involved all the different phases necessary for the photoanode production and the final device characterization. Firstly, inks modified with different amounts of water were produced and analyzed considering particle dispersion (DLS) and rheological behavior, while the deposited layers were analyzed in terms of morphology (FE–SEM), roughness (profilometry) transmittance (UV–Vis spectroscopy) and dye adsorption capability. Finally, the observed properties were correlated to the performance and the electrochemical behavior (EIS) of a complete DSC. The extensive study allowed to understand the real role played by the water in the ink formulation and, as a consequence, the identification of the optimal amount to be introduced in the system. Water was showed to increase the dispersion and time stability of the particle suspensions, leading to an optimized flow behavior of the inks. The ceramic films so obtained exhibited improved morphologies and enhanced optical properties and dye uptake. However, the optimal concentration for DSC application was found to be not the one that allows the best dispersability of the ceramic particles but the one that best compromised the homogeneity of the film with the highest dye uptake. This key result could not be obtained analyzing just the film morphology but necessitate a thorough analyses of all the different properties (morphological, electrochemical and photovoltaic) related to the final application. The best-performing device recorded an increase in efficiency of the 12% compared to the un-modified system. [ABSTRACT FROM AUTHOR]

This research investigates the contribution of dust to the long-term performance degradation of various photovoltaic (PV) modules that have been operating for almost eighteen years without any cleaning procedures at the Renewable Energy Outdoor Testing Area (ROTA), Murdoch University, Perth, Australia. A solar module analyser was used to assess the PVs’ electrical performance, while a combination of spectrophotometer, scanning electron microscope, electron dispersive spectroscope and X-ray diffraction were used to exam the properties of the dust on the panels. The study found that the degradation of the PV modules’ power output, ranged from 19% to 33%. The degradation is mostly due to non-dust related factors such as corrosion, delamination, and discoloration, which account about 71–84%, although the contribution of dust is still significant at 16–29%. Anova analysis shows that the dust has a fairly uniform impact on the performance degradation of all PV technologies at ROTA. This is in line with the results of spectral transmittance curves for different dust density samples that essentially flat over the wavelength range of the PV modules. An investigation of the properties of dust revealed that dust particles deposited on PV modules’ surface at ROTA were dominated by fine particles built of large amounts of quartz (SiO 2 ), followed by calcium oxide (CaO) and some minors of feldspars minerals (KAlSi 3 O 8 ), which are the main factors in transmittance losses that affect PV module performance. [ABSTRACT FROM AUTHOR]

In the performance analysis of a trough compound parabolic concentrator (CPC), the concept of south projection angle is often used for the nonmeridional sunlight to compare with the acceptance angle of CPC to determine if solar radiation could be collected. The solar altitude and azimuth are the only two factors used to calculate the south projection angle. However, for the solid CPC made of dielectric material, due to the refraction on the air–dielectric interface, the optical path of refracted light within a dielectric CPC would also depend on the refractive index of dielectric material and the tilt angle of CPC. The conventional south projection angle would not be suitable for performance analysis of a solid dielectric CPC. This paper therefore introduces a concept of inner south projection angle which is based on the refracted light and derives a formula using vector analysis. The formula relates the inner south project angle with the solar altitude and azimuth, the refractive index, and the CPC tilt angle as well. Photopia software is meanwhile employed to predict the optical performance of dielectric CPC. The simulation results confirm that use of the inner south projection angle can determine if solar radiation could be collected or transmitted through a dielectric CPC rather than conventional south projection angle. Discussions are given about the correlation between the inner south projection angle and the optical efficiency and transmittance of a trough dielectric CPC. This provides a convenient way to evaluate the performance of a dielectric CPC over a period such as a whole year. [ABSTRACT FROM AUTHOR]

Downward surface shortwave radiation (DSSR) is important in various disciplines and is influenced by the atmosphere and mountainous topography. In this paper, an integrated approach that incorporates a mountainous spectral radiation scheme and an atmospheric broadband transmittance model based on a fine-resolution digital elevation model (DEM) and MODIS atmospheric products is proposed to estimate DSSR. This approach accurately considers important terrain and atmospheric factors and avoids any dependence on ground-based observations except for validation purposes. The results demonstrate that the radiation components exhibit very high spatial heterogeneity and are largely affected by different terrain orientations (especially topographic obstructions), slope, the cosine of the solar illumination angle, and atmospheric environments. Ground-based measurements for 56 clear-sky days from two observation stations are used for validation in the Dayekou watershed of the Heihe River Basin. The experiments show that this algorithm performs well; both the mean bias error percentage (MBE%; −6.2%) and the root-mean-square difference percentage (RMSD%; 7.5%) are less than 10%. [ABSTRACT FROM AUTHOR]

Transparent insulation materials (TIMs) can combine the advantages of opaque insulation with solar collection when applied to building facades. Mathematical models developed to calculate the optical performance of a transparent insulated (TI) system are presented. The TI-system modelled consisted of a 6 mm outer glass pane, a 22 mm wide polymethylmethacrylate (PMMA) capillary cell section and an 8 mm inner glass pane. When solar beam radiation passed through the TI-system, the solar transmittance, absorptance and reflectance that occurred in the system were calculated. Optical interactions at each layer in the TI-system were numerically modelled for five incidence angles. A direct to diffuse transmittance was calculated for solar radiation passing through the PMMA capillary cells with an incidence angle, θ i , in excess of 0°. The calculated transmittance for the PMMA capillary cells at 0° incidence angle was 0.8264 with overall solar transmittance of up to 0.66 calculated for the whole TI-system, a value which is consistent with that found in previous research. This paper presents a method for calculating the optical properties for multiple PMMA capillary cells, encapsulated between two glass panes for different solar incidence angles, with input of relevant data from other sources. This method can also be adapted for other types of glazing systems. [ABSTRACT FROM AUTHOR]

This paper presents the results of study on the effect of dust fouling on the transmittance of PV module glass cover. The study included the effect of dust fouling on overall plane glass transmittance, spectral transmittance of anti-reflective coated glass and characterization of the physical and chemical properties of dust particles. Also, micro-adhesion forces of dust particles on flat glass substrates are included. The results indicated a 20% reduction in glass transmittance and a 5g/m² of dust accumulation on the glass cover of PV modules tilted at 26° (Lat of Dhahran) and exposed for 45days. The anti-reflective coated glass exhibited less reduction in transmittance compared to non-coated plane glass. The adhesion forces of particles on flat surfaces increased with increase in particle size due to increase in contact area between the particles and the surface. At high humidity level there is an increase in the vertical adhesion due to the generated capillary forces between dust particles and glass surface. [ABSTRACT FROM AUTHOR]

Highlights: [•] We analyze the performance of new selective glass for flat plate collectors. [•] We carry out theoretical calculations and measurements on prototypes. [•] Selective glass improves the performance of uncovered collectors. [•] Selective glass improves the performance of low selective single-glazed collectors. [•] Selective glass improves the performance of selective double-glazed collectors. [Copyright &y& Elsevier]

Abstract: A fast scheme for estimation of the instantaneous direct solar irradiance (DSI) at the Earth’s surface is developed based on detailed radiative transfer calculations for the full range of atmospheric conditions. The parameterisation is divided into the components for clear sky and overcast conditions. For the clear sky condition, the effects of absorption due to water vapour, carbon dioxide and ozone on the DSI are explicitly treated. The effects of Rayleigh scattering, aerosols are also treated on a physical basis. Based on the clear sky results, the transmittances due to effects of clouds are determined for both liquid and ice clouds. The results are parameterised in terms of cloud visible optical depth. The input variables required for determination of DSI include precipitable water, column ozone amount, CO2 mixing ratio, aerosol optical depth, cloud visible optical depth, surface pressure and solar zenith angle. These variables are all available in numerical weather prediction (NWP) forecast models or can be obtained from satellite observations. Therefore, the scheme can be used to determine the DSI using NWP model products or satellite data. The scheme has been tested using the observations obtained at three stations of the US Department of Energy Atmospheric Radiation Measurements (ARM) program. The relative mean bias differences under clear-sky and all-sky conditions are better than 3.2% and 5.1%, respectively. The correlation coefficients between modelled results and observations are all greater than 0.99. The sampling errors of DSI due to the use of 3-hourly or 1-hourly low frequency in radiation calculations in NWP models are evaluated using the fast scheme and ARM observational data. It is found that these errors can be greater than 800Wm−2 for many cases where sky condition changes from clear to overcast. Application of the current scheme can reduce these errors to less than 100Wm−2. [Copyright &y& Elsevier]

Highlights: [•] A novel antireflective film with good durability was prepared using spraying method. [•] Base catalyzed sol was modified by polysiloxane and TiO2 sol by sol–gel process. [•] Degradation of transmittance of AR film after damp-heat test was only 0.23%. [•] Single layer antireflective films with transmittance of 95.02% at 565nm were made. [Copyright &y& Elsevier]

Highlights: [•] 69,000 pairs of sunshine–radiation readings were examined from 670 sites. [•] Relationship between atmospheric transmittance and sunshine fraction is non-linear. [•] Reason for non-linearity is clouds get optically thicker with decreasing sunshine fraction. [•] A generalization of the Angstrom–Prescott equation most efficiently fits data. [•] Fundamental connection between diffuse fraction and sunshine–radiation relationship. [Copyright &y& Elsevier]

Abstract: This paper reports the use of a combination of numerical calculations and experimental work to establish the optimum photovoltaic transmittance (T pv) and durability of the quarter wave, the quarter-half wave, and the non-quarter wave double-layer TiO2–SiO2 and ZrO2–SiO2 antireflective coatings (ARCs) on solar glass towards practical photovoltaic applications. Numerical calculations based on 4×4 propagation matrix method indicated that the non-quarter wave double-layer ARCs exhibited higher T pv values than those of the quarter wave and the quarter-half wave ARCs. Such calculated values are in good agreement with the experimental T pv values. For examples, the T pv values for the non-quarter wave double-layer TiO2–SiO2 and ZrO2–SiO2 ARCs prepared by sol–gel reached 94.4±0.1% and 94.3±0.1%, respectively. In terms of the coating durability, the non-quarter wave double-layer coatings with a dense and thicker TiO2 or ZrO2 barrier layer on solar glass exhibited less than 1% reduction in T pv after 96h highly-accelerated temperature and humidity stress test (HAST), as compared with the standard single-layer porous SiO2 used in industry which tested in the same HAST conditions to be greater than (15.4%) after 48h. Single crystalline Si modules encapsulated by the non-quarter wave TiO2–SiO2 or ZrO2–SiO2 AR-coated glass are more durable, with only less than 10% degradation in efficiency after 48h HAST, as compared with Si modules encapsulated by single-layer porous SiO2 AR-coated glass which have signification loss in efficiency (circa. 21.8%). [Copyright &y& Elsevier]

Abstract: This work develops air-conditioning-type building materials suitable for different climate regions. Results show that using traditional building materials alone is unsuitable for any climate region, and that building materials of various thermal properties are needed to satisfy the requirements specific to each location. Low solar absorptance and high emittance materials are appropriate for hot climates, whereas high solar absorptance and low emittance materials are suitable for cold climates. Materials with variable solar absorptance and emittance properties are applicable to regions characterized by cold winters and hot summers. In addition, cement that is reversibly thermochromic at normal temperature and materials with variable transmittance properties can warm buildings in winter and prevent overheating in summer, thereby satisfying the need to create a thermally comfortable building environment. [Copyright &y& Elsevier]

Abstract: In order to obtain high sunlight transmittance for silicon thin film solar cells, the textured surface such as pyramid shapes is commonly considered along the boundary between the silicon layer and the transparent conductive oxide (TCO) layer. Layered structure design having the improved transmittance into the light absorbing layer for specific frequencies is derived using the so called topology optimization design method combined with the time dependent finite element analysis. A triangle patterned textured surface is considered as the initial shape for two-dimensional wave analysis and the periodic boundary condition is applied to both sides of the unit-structure model. The design objective is set to maximize the energy flux at the specified wave absorbing area during some time period so that the objective function is evaluated as the time integration of a Poynting vector formulation. A multiple layered pattern representing a silicon layer and a TCO layer in turn is obtained for the optimal shape of the light absorbing boundary. As thicknesses of each layer are associated with the incident beam wavelength, various wavelengths of incident light condition are considered and each of the optimal design cases according to the wavelength are compared. [Copyright &y& Elsevier]

Abstract: In this research, the effect of surface roughness of flexible polymeric top cover layer on the efficiency of a dye-sensitized solar cell (DSSC) was investigated. In order to assess the durability of polyethylene terephthalate (PET) and polyethylene terephthalate naphthalate (PEN) the wear properties of these materials were first investigated. It was found that PEN was about 2.3 times more wear resistive than PET. PEN was used for further investigation regarding the effect of surface roughness on the light transmittance and electrical efficiency of DSSC. The surface roughness of PEN was varied by sand blasting to simulate an erosion process. It was found that PEN with a maximum average surface roughness of 1.6μm resulted in 10% decrease in light transmittance and consequently degraded the cell efficiency of DSSC by 13%. The decrease in electrical efficiency due to increasing surface roughness was found to be proportional to the light transmittance. [Copyright &y& Elsevier]