Search

• The concept of the SC in buildings coupling PCRs for atmosphere CH 4 removal was quantitively verified. • The effects of CH 4 degradation and indoor ventilation by the system were analyzed. • The photocatalytic efficiency, purification rate, and fresh air rate were analyzed. • The new system could degrade 57.27 μg/s of atmospheric CH 4 under optimal conditions. The techniques for the removal of methane from the atmosphere are highly challenging due to its stable chemical properties, dispersed sources, and low concentrations. This paper proposes a practical small-scale solar chimney (SC) in buildings with photocatalytic reactors (PCRs) for atmospheric methane removal. Two comprehensive numerical models on photocatalytic reaction and indoor ventilation are developed. The numerical simulation considers the performance of methane removal and indoor air ventilation of the proposed system, as well as its specific crucial parameters such as the type of PCRs, solar radiation, and flow channel width. The obtained results show that the SC with honeycomb photocatalytic reactor (HPCR) is more able to remove atmospheric methane than SC with plate photocatalytic reactor (PPCR) under the premise of meeting the ventilation standards. In addition, there is a maximum methane purification rate of 57.27 μg/s under the condition that the air gap width is 0.3 m, the length of the HPCR is 1.5 m, and the porosity is 0.85. It is then proved that the SC in buildings with PCRs can allow small-scale, zero-energy consumption, continuable, and decentralized low-concentration atmospheric methane removal while improving the indoor ventilation. [ABSTRACT FROM AUTHOR]

The SiO 2 -VO 2 -PDMS-driven by mechano-thermochromism intelligent optical management system is proposed to overcome the problem of conventional thermochromic windows with a single ability to modulate the solar spectrum. The design can achieve continuous tuning of the solar spectral transmittance by the deformation of polydimethylsiloxane (PDMS), which can meet the need for thermal comfort in different seasons. [Display omitted] • Combining elastic stretching with thermochromic windows based on Vanadium dioxide (VO 2) can dynamically modulate the solar spectral transmittance to improve thermal comfort. • The SiO 2 -VO 2 double-layer thermochromic window shows a high solar modulation ability (ΔT sol) of 18.4% and average luminous transmittance (Tlum,avg) of 49.1%. • By the deformation of polydimethylsiloxane (PDMS), the optical performance of the stretchable thermochromic window are greatly improved. • The proposed method advances the design of dual-mode smart windows. The thermochromic windows based on vanadium dioxide (VO 2) can intelligently modulate the transmittance of indoor solar radiation, which is significant for reducing building energy consumption. However, conventional thermochromic windows only have the ability of single spectral modulation, continuously switching the solar spectral transmittance in response to varying ambient temperature on a window is challenging. In this work, a SiO 2 -VO 2 -PDMS-driven by mechano-thermochromism intelligent optical management system was proposed for automatic switching and continuous adjustment of the solar spectral transmittance. Compared with the single-layer VO 2 film, the SiO 2 -VO 2 double-layer thermochromic window provides a gradual refractive index change from the top with n air = 1 to the middle with around 1.5, and then to the bottom with a higher refractive index, which suppresses reflections over a wider wavelength range. The results show that the SiO 2 -VO 2 double-layer coating with a refractive index buffer layer exhibits improved optical performance with a solar modulation ability (Δ T sol) of 18.4% and an average luminous transmittance (T lum,avg) of 49.1%. Furthermore, the design can achieve increases in the stretch-related solar modulation ability (Δ T sol,stretch) and the stretch-related luminous transmittance (T lum,stretch) from 18.4% to 43.8% and 49.1% to 60.5%, respectively, which is realized by the deformation of polydimethylsiloxane (PDMS). Combining elastic stretching with thermochromic windows can dynamically modulate the solar spectral transmittance to improve thermal comfort. This work provides a promising approach to improve the industrial application of VO 2 thermochromic windows, contributing to the advancement of research in green buildings, window design, and automotive energy efficiency. [ABSTRACT FROM AUTHOR]

An accurate knowledge of the direct solar irradiance at normal incidence (DNI) is required to size solar energy systems, specially those using solar concentration technologies. In the absence of measurements, DNI can be estimated over an arbitrary site with a dedicated satellite model or by using satellite-derived global horizontal irradiance (GHI) and a phenomenological diffuse-direct separation model. This second procedure is error-prone, specially under partial cloudiness conditions and low solar elevation angles. A novel and simple semi-empirical satellite-based model to estimate DNI in moderate albedo regions using a physical clear sky model and a cloudiness index obtained from visible satellite imagery is proposed and assessed. An ergodic assumption in which the images are spatially averaged to better represent the hourly time basis is used. Over the target region (Southeastern South America, SESA), the new DNI satellite model outperforms the alternative strategy at the hourly level, with an average uncertainty of 20% (versus 25%) when compared with three measurement station's data sets located in center Argentina, southern Brazil and Uruguay. • A simple model to estimate hourly solar direct normal irradiation (DNI) is presented. • Its based on a precise clear sky model and a cloud index obtained from satellite imagery. • Spatial averaging of images over each site improves representation of hourly DNI. • Outperforms strategy of estimating DNI from direct-diffuse separation models and GHI. [ABSTRACT FROM AUTHOR]

• Green photoinitiating systems operating efficiently under solar radiation. • Fast vinyl polymerization in aqueous solutions, regardless of the present atmosphere. • Kinetic analyzes prove that electron donors compete with oxygen for excited dyes. A series of environmentally friendly photoinitiating systems operating under mild conditions of visible light (Vis-PIs) were tested for vinyl polymerization using sunlight as a free of charge radiation source. These Vis-PIs based on water soluble xanthene dyes showed good performances after deaerating with an inert gas, obtaining colorless polymers with gravimetric yields up to 80–90% after short irradiation times (2–15 min). Aqueous solutions of the materials were highly viscous and viscosimetric measurements yielded molecular weights up to 106. Surprisingly, the evaluated Vis-PIs also worked successfully under ambient air atmosphere, obtaining similar polymer yields in the same irradiation times. Photolysis experiments and transient spectroscopy were used to shed light on the mechanism of the process, allowing both triplets and radicals formation of the dyes to be identified even in the presence of air. The kinetics of photopolymerization was studied following the monomer conversion at several irradiation times by FTIR. The results were interpreted based on kinetic data collected as competitive quenching mechanisms between the co-initiator and oxygen for the excited dyes. The present report represents a breakthrough in the search for fast, efficient and inexpensive Vis-PIs with low ecological impact, which can be very useful in outdoor coating applications among others. [ABSTRACT FROM AUTHOR]

The Calcium-looping process is a promising option for thermochemical energy storage in concentrating solar power plants. A crucial element of this process is the solar calcination reactor, where the endothermic reaction of CaCO 3 calcination occurs with formation of CaO and CO 2. The solar energy that is chemically stored in the reaction products can be retrieved by the exothermic reaction of CaO carbonation when needed. In this article, a new computational model is developed for the solar calcination reactor in this Calcium-looping process. The calcination reaction takes place in the riser of a continuous circulating fluidized bed that corresponds to an absorber tube exposed to concentrated solar radiation, which allows the reaction chamber to be indirectly heated. A core-annulus heat transfer model and a modified version of the Kunii–Levenspiel fluid dynamics model are used. In contrast to previous models found in the literature, the change in the mass flow rate of the species and in the density of the phases due to the reaction is considered. Simulation studies are performed with a fixed and imposed concentrated solar irradiance on the reactor wall, which varies in both the axial and angular directions. Wall conduction in the angular direction is also considered. The results show that nearly complete calcination can be achieved with a reactor of 4 m of height. A sensitivity analysis with respect to the model parameters and inlet conditions shows that the calcination conversion is mostly affected by the solids mass flow rate and the bed temperature at the inlet. • Solar calcination of CaCO 3 is crucial in Ca-looping for thermochemical energy storage. • A model of a circulating fluidized bed reactor for solar calcination is proposed. • Simulations are performed with an imposed solar irradiance on the reactor wall. • Nearly complete calcination can be achieved with a reactor of 4 m of height. • Sensitivity analyses show large effect of inlet solids mass flow rate and temperature. [ABSTRACT FROM AUTHOR]

• Design and test a new semicircular concentrator with an acceptance angle of 90°. • Use rising film and enhanced condensation techniques to improve still's efficiency. • When mean daily solar radiation is 606.0 W/m2, the water yield efficiency is 81.6%. • A mass and heat transfer process model is built to predict its performance. This paper presents a concentrating light multistage rising film solar distiller with a central cooling structure (RFSD). The RFSD mainly consists of the semicircular concentrator, a rising film device and a central cooling structure. The structure design of the semicircular concentrator is introduced in this paper. The relationship between the light receptivity of the semicircular concentrator and the solar incident angle was obtained by optical simulation. The mathematical model of RFSD was established, and the process of heat and mass transfer in RFSD was analyzed theoretically. Based on theoretical analysis, an experimental device was built. Furthermore, the device's water yield performance and energy utilization efficiency were tested under actual weather conditions. The experimental results show that when the average daily solar irradiance is 606.0 W / m 2 , the freshwater yielded by the device can reach 4450 g / m 2 , and the average daily efficiency is 81.6%. The comparison between the theoretical and experimental results shows that the theoretical model in this paper can well predict the device's operating parameters. The deviation of the theoretical operating temperature from the experimental value is within 2.3 °C, and the deviation of the daily water yield efficiency is on a scale of 14.1% to 24.8%. [ABSTRACT FROM AUTHOR]

• A test rig of the DX-SAHP system using R134a as refrigerant has been built. • The effect of environmental parameters on evaporation temperature is analyzed. • An evaporation temperature prediction model is constructed by MLR method. • The weights of solar radiation, ambient temperature and wind speed are obtained. • The prediction model contributes to optimum design and operation of DX-SAHP. As known, evaporation temperature is critical for the thermal performance of a direct-expansion solar-assisted heat pump (DX-SAHP), which is subjected to environmental parameters. It is significant to explore the effect of environmental parameters on evaporation temperature and system performance for the optimal design of DX-SAHP systems. An experimental study on the affecting factors of evaporation temperature in DX-SAHP is firstly implemented, and an evaporation temperature prediction model is constructed by multiple linear regression method and validated, which uses solar radiation, ambient temperature and wind speed as independent variables. Based on this, the effect of environmental parameters on evaporation temperature is compared and analyzed. Results show that evaporation temperature is most affected by solar radiation, followed by ambient temperature and wind speed. The weights of solar radiation, ambient temperature and wind speed are 47.6 %, 43.1 % and 9.3 %, respectively. Furthermore, evaporation temperature will have a 1.80, 0.58 and 0.94 °C increase for a 100 W·m−2 increase in solar radiation, a 1 °C increase in ambient temperature and a 1 m·s−1 increase in wind speed, respectively. The prediction model obtains satisfactory accuracy under different conditions and would be helpful for optimal design and thermal performance improvement of DX-SAHP systems. [ABSTRACT FROM AUTHOR]

• 1D particle receiver model has been developed to be integrated into system models. • 1D model shows good agreement (R2 between 0.949 and 0.996) with more complex CFD model. • Particle receivers need higher heat fluxes to operate compared with molten salts. • Particle receivers with low particle absorptivity and large particle diameter cannot operate at low heat fluxes. This study presents a one-dimensional (1D) model for free-falling particle receivers able to be integrated into system models thanks to its simplicity and agreement with high fidelity simulations. The receiver thermal efficiencies calculated with the 1D model are benchmarked against the efficiencies obtained with a more complex CFD model, showing a great fit with a coefficient of determination R2 = 0.996 when there is no wind and R2 = 0.949 when there is wind. The 1D model is used to present some of the most relevant results specific to free-falling particle receivers. Under no wind conditions, the receiver efficiencies obtained with different aperture areas are very similar, although there is a slight decrease in efficiency when the aperture area grows. These trends change with wind depending on the wind speed and direction. The receiver efficiency also increases with the absorptivity. Low-absorptivity particles not only result in lower efficiencies, but also prevent operation of the receiver when the incident solar radiation is small. A similar trend is observed for large particle diameters where the thermal efficiency approaches zero when the incident solar radiation is small. While the presented 1D model is specific to free-falling particle receivers, the main parts of the model could be extrapolated to other designs. [ABSTRACT FROM AUTHOR]

• We assess intra-day/-hour solar radiation derived with SARAH-2 and HelioMont. • Satellite estimates compared with 136 pyranometers at altitudes from 200 to 3570 m. • Daytime intra-hour MAD amounts to 91.7 W/m2 (SARAH-2) and 82.5 W/m2 (HelioMont) • SARAH-2 drastically underestimates the SSR at high altitudes in winter. • The biases depend on season and altitude, with snow cover as a potential challenge. Regional to European scale intra-day forecasts of solar resources and photovoltaic (PV) power generation are of key relevance for operators of solar plants and power grids, as well as power traders, who seek to optimize revenues and maintain grid stability by matching power supply and demand. Our study addresses a key prerequisite for such forecasts: the accuracy of intra-hour and intra-day surface solar radiation (SSR) estimates of the HelioMont Meteosat product, a state of the art satellite product particularly suited for the Alpine region. A second satellite product, SARAH-2, as well as longer time scales, are also examined for comparison. The satellite SSR estimates are analyzed based on 136 ground stations across altitudes from 200 m to 3570 m in Switzerland in 2018. In peak daytime periods, the instantaneous satellite SSR deviates from the ground-measured SSR by a mean absolute deviation (MAD) of 110.4 and 99.6 W/m2 for SARAH-2 and HelioMont, respectively. For the daytime SSR, the instantaneous, hourly, and daily-mean MADs amount to 91.7, 81.1, 50.8, and 82.5, 66.7, 42.9 W/m2 for SARAH-2 and HelioMont, respectively. SARAH-2 drastically underestimates instantaneous SSR in winter at altitudes above 1000 m, possibly due to snow cover. HelioMont performs better in this respect, but the remaining substantial, spatially and temporally heterogeneous biases we identify pose a challenge with regard to the use of HelioMont for accurate intra-day PV estimates and forecasts. [ABSTRACT FROM AUTHOR]

In pursuit of a better indoor thermal environment, radiant heating systems have been widely employed in residential buildings. The effect of the sun patch on floor heating systems is increasingly attracting attention. However, the experimental study on the effect of a moving sun patch is often limited by weather conditions. This study proposes a method to simulate the moving sun patch by heating films in experiments and uses a thermal manikin to evaluate the indoor thermal comfort. The experiments were performed in Troyes, France, which belongs to a temperate oceanic climate. The obtained results show that a moving sun patch decreases the indoor thermal comfort from 1.5 to 1.1 away from comfortable in the case with 11.6% of window-to-wall ratio (WWR). Besides, concerning the overheating problems caused by the sun patch, two potential solutions are proposed. The indoor humidification solution could reduce air overheating duration by 74% in the case with 5.8% of WWR, and by 27% in the case with 11.6% of WWR, respectively. The solution with full return water could reduce the floor surface overheating duration by 40% and by 29%, respectively. In the future, the two solutions can be combined to alleviate the indoor overheating problems induced by the solar radiation. [ABSTRACT FROM AUTHOR]

• Absorber coating degradation depending on the heating and cooling rate. • Optical properties degradation when the coating is removed. • Mismatch effect and substrate oxidation promote degradation. • To use mix rule to estimate the surface absorptance. Concentrating solar power (CSP) is emerging as an increasingly important component of renewable energy. CSP systems are being widely adopted in the establishment of large-scale thermal power plants, with an increase in the number of successfully operating demonstration systems. Special coatings are generally used in various types of receivers for solar collector systems. Selective coatings are used for receivers intended to be operated at low or medium temperatures. Similar selective coatings are not currently available for application under high temperatures. In such cases, high-temperature absorbing coatings are generally used to improve the thermal efficiency of the receiver and protect their tubes from oxidation. It is worthwhile to observe the behaviour of such coatings when exposed to high fluxes for extended periods, in order to develop more efficient technologies. Currently, the essential properties for characterizing the paint are absorptivity, emissivity, and structural integrity of the coating (adhesion and cohesion). Good understanding of the behaviour of this paint under representative operating conditions would help to improve the design of the plant, maintain its performance and maintain the thermal efficiency of the receiver. The principal objective of this study was to provide extensive knowledge of the durability and variation of the optical properties of Pyromark when it is consolidated with improved methods. No degradation or loss of optical performance was observed at temperatures under 700 °C. The substrate affected the crystalline structure of an initial coating at high temperatures owing to the diffusion of metal ions. Concentrated solar radiation was the main factor that affected the integrity of the coating. At concentrations higher than 550× suns, a significant area of the irradiated samples was found to be uncoated. These results can be used to design more accurate latest generation receivers to improve the performance of this technology. [ABSTRACT FROM AUTHOR]

• An accelerated aging methodology under temperature and radiation effects was developed. • Thermogravimetric analysis allowed the determination of activation energy. • After 2.6 years of service life, monolithic hydrophilic aerogel transmission properties are not changed. • Aging implies a yellowish hue continuing to give bluish tendency to objects seen through it. • Monolithic aerogel ensures a high color rendering performance over the years. Innovative transparent solutions such as monolithic aerogel in the building envelope have a considerable impact on both the indoor environmental quality and thermo-acoustic performance. However, the long-term effect of this new material is not yet known in the scientific literature. In this context, the present study investigates the influence of accelerated aging on the optical and color rendering properties of monolithic aerogel. In the aging process, the combined effect of temperature and solar radiation was considered. An acceleration factor for temperature equal to 13.6 was obtained following the Arrhenius Law, after evaluating the activation energy value by means of thermogravimetric analysis. The acceleration factor for radiation was evaluated as the ratio between artificial radiation of the chosen lamps used in the laboratory aging device and the natural radiation of the solar spectrum, by adding the direct and diffuse components related to the site. Accelerated aging equivalent to 2.6 years did not lead to significant changes in the optical transmission properties of the monolithic aerogel; however, the material tends to yellow and a bluish hue is obtained for the color patches seen through the aged material. Furthermore, an increase in the color shift is measured for all colors (from the 5.62–43.40 range to the 6.42–45.30 range), with the higher variations between before and after aging registered for a sample of bluish green color. [ABSTRACT FROM AUTHOR]

• The performance of clear-sky DNI and GHI predictions generated with libRadtran, SMARTS and REST2 is assessed. • A comparison between ground-based AERONET and reanalysis data (CAMS and MERRA-2) is performed. • All radiation models are alternatively operated using input data from the three different data sources. • The best overall combinations to estimate DNI are libRadtran/MERRA-2 and SMARTS/AERONET. • The best overall combinations to estimate GHI are REST2/AERONET and REST2/MERRA-2. In this work, the performance of clear-sky direct normal irradiance (DNI) and global horizontal irradiance (GHI) predictions generated with three state-of-the-art solar radiation models with different degrees of complexity is assessed by comparison with high-quality measured irradiance data at Évora, Portugal. The libRadtran, SMARTS, and REST2 radiation models are alternatively operated using input data from three different data sources: co-located AERONET ground-based measurements, and CAMS and MERRA-2 gridded reanalysis data. For these nine combinations (three models and three data sources), the results are assessed using five statistical indicators, namely mean bias error (MBE), root mean square error (RMSE), fractional bias (FB), fractional gross error (FGE), and coefficient of determination (R 2). Overall, it is found that AERONET is the data source that provides the best DNI estimates. In general, libRadtran and SMARTS produced closer estimates to the ground-based DNI observations. For GHI, however, no firm conclusion can be drawn regarding the best data source. MERRA-2 produces better estimates in combination with libRadtran and SMARTS according to all statistical indicators except R 2 , whereas AERONET is to be preferred according to FB, FGE, and R 2 when using REST2. Curiously, the latter generates better GHI estimates despite being the simplest model. Overall, it is concluded that the best combinations of model/data source to estimate DNI are either libRadtran/MERRA-2 (according to MBE and FB) and SMARTS/AERONET (according to RMSE, FGE, and R 2). In the case of GHI, the best combinations are REST2/AERONET (according to FB, FGE, and R 2) and REST2/MERRA-2 (according to MBE and RMSE). [ABSTRACT FROM AUTHOR]

• Satellite-based methods forecast solar irradiance up to 180 min ahead. • A combination of the optical flow method and a deep learning model was proposed. • The proposed model was compared with conventionally well-known forecast models. • This novel approach enhanced the accuracy and temporal horizons. Short-term global horizontal irradiance (GHI) forecast methodologies are routinely employed to mitigate the instability of photovoltaic power and, more importantly, to secure early participation in the energy auction market. The intra-day forecast model substantially consists of the combination of a cloud motion vector (CMV) derivation and a GHI extraction model. This study utilized optical flow (OF) method to calculate CMV from two subsequent satellite images and predict cloud displacement up to 180 min ahead. Meanwhile, the conventional GHI extraction models (Hammer and the fast all-sky radiation model for solar applications (FARMS) models) were employed to extract future GHI. Moreover, to the best of our knowledge, only a few studies have been dedicated to combining OF method with deep learning model. Hence, this study proposed a novel combination based on OF method and long short-term memory model (LSTM) to enhance temporal horizon and accuracy. After all combinations of OF method and GHI models were simulated and assessed under all-sky conditions, the OF method that combined with LSTM outperformed the OF method combined with conventional models across all time horizons. For root mean square error (RMSE) and forecast skill (FS), the accuracy of OF and LSTM models for all time horizon ranges from 59.64 W/m2 to 120.63 W/m2 and 16.40 % to 54.42 %, respectively. The study findings are expected to encourage the inclusion of satellite data in GHI forecast as well as the optimization of energy management systems that integrate with a photovoltaic system. [ABSTRACT FROM AUTHOR]

• Examination of water droplets optical effect based on measurements of maximum power data of the self-cleaning coated solar cell, which was covered with these water drops. • Presentation of the results at several drop shapes, different locations and different coverage ratios, different angles of incidence rays and dependence on refractive indexes. • Study of the simulation results using the C++ model developed in the Ray Tracer framework. • Examination of results obtained from the simulations data in case of reflected rays. Due to the challenges of environmental protection and the exhaution of traditional energy carriers, electricity produced by solar cells is increasingly coming to the fore. The efficiency of solar cells is significantly influenced by many factors, including the purity of the solar cell. The application of self-cleaning coatings is a novel solution for cleaning. In addition, in case of using water to remove dirt and to cool the solar cell, a drop of water falling on nanotechnology thin layers also affects the radiation reaching the surface of the solar cell. The present study focuses on the latter effect. When a water drop appears, on the one hand, the illumination of the solar cell surface becomes uneven, and on the other hand, the water drop redirects some of the otherwise reflected rays back to the surface of the solar cell, so it has an anti reflective effect, we are investigating these two phenomena. The quantitative findings and conclusions were formulated on the basis of the data generated using the C++ model created in the RayTracer framework program. In addition to the equations describing light refraction and light reflection, the model uses also the Fresnel equations for determine the intensity of the light beam for drops of different shapes, different locations, and different coverage ratios. It also examines the dependence on the spectral components of sunlight and the differences resulting from different angles of incidence. The results obtained with the help of the model are also supported by measurement data on the performance conditions of a solar cell covered with water droplets. In addition, by examining the intensity relationships of solar radiation reaching the surface of water covered solar cells, the results can also be used to examine the optical and energetic effects of water droplets on plant leaves or human skin. [ABSTRACT FROM AUTHOR]

The increased power demand needs the installation of more power-generating units. Apart from conventional power generating stations based on fossil fuel combustion, recently solar power generating stations have attracted a large stake due to various advantages. However, the increased power generation also needs to be focused on various factors like stability, and reliability of the grid system leading to putting more emphasis on active power control techniques. This article reviews different active power control methods including conventional and flexible horizons. The focus of this article is to analyze the reliability factor while extracting power from solar plants. Maximum power point tracking (MPPT) is a well-known strategy for the maximum utilization of solar energy. However, as the dependency on solar energy rises the conventional control strategy needs to be modified for active grid participation of the PV systems. This can be performed by incorporating Flexible Power Point Tracking (FPPT) control strategies instead of MPPT. In this article, a comparison of the two techniques has been performed to choose the best method based on the requirement. Further, the impact of both systems on the grid system has been briefed in this article. Also, benchmarking has been proposed from the analysis to switch over between the modes depending on the power availability. [ABSTRACT FROM AUTHOR]

Heat pumps are widely used in many fields due to their high efficiency and energy saving potential. However, the application of single-stage vapor-compression heat pump dryer is limited due to low drying temperature and the decreasing reliability for high temperature drying. In order to apply heat pump to high temperature drying, a heat pump drying system using a solar assisted flash tank vapor injection cycle (HPDS-SFVIC) is presented. This system allows the solar collector to absorb solar energy at a lower temperature and achieves significant improvement of heating capacity and drying temperature. The effects of component configuration and various operating conditions on the drying system with open, bypass, and closed air circulation loop are evaluated, respectively. The results show that under a typical operating condition, the proposed cycle achieves great performance improvement of 21.8% and 75.8% in both the heating coefficient of performance (COP h) and heating capacity, compared with the conventional cycle. Utilization of solar energy is advantageous to provide higher air temperature for drying. With increased solar radiation intensity and collector area, heating capacity and drying temperature can be improved, while COP h remains constant as 5.0–5.2. When the drying system provides dry air at 65 °C stably, it saves 27.8%–41.7% of power consumption, and COP h is improved by 41.2%–62.1% on average. [ABSTRACT FROM AUTHOR]

• Self-powered thermoradiative absorber-emitter is used for solar thermoelectrics. • An optimal ratio of absorber/emitter surface area of 1 is favored. • A conversion efficiency of 27.86% is achieved at a concentration ratio of 50. • The efficiency of the solar TR-TE system is 6.51 times that of solo thermoelectrics. Solar thermoelectric power, is promising for use in small-scale CSP system due to its flexible architecture and silent operation. However, the conversion performance of standalone solar thermoelectrics is still far from ideal at lower concentration ratio. This paper tends to introduce a self-powered thermoradiative absorber-emitter at the top to enhance the overall solar thermoelectric power generation. Thermodynamic model based on energy balance has been established, and the implications of critical factors on the conversion performance of the thermoradiative-thermoelectric (TR-TE) combined system have been thoroughly examined. The findings show that an optimal ratio of absorber/emitter surface area of 1 is favored due to a tradeoff between thermal radiation loss from the absorber to the ambient and thermoradiative emission dissipation, as well as the thermoradiatives with a low bandgap and a high output voltage. The overall conversion efficiency of the solar TR-TE combined system approaches to 27.86 % at a cold junction temperature of 300 K and a concentration ratio of 50. Accordingly, the maximum efficiency of the combined system is 6.51 times that of independent solar thermoelectrics and is ∼13.67 % higher than independent solar thermoradiatives. In the TR-TE combined system, thermal radiation from the absorber to the environment accounts for 3.83 % of the solar radiation input as compared to 2.47 % in the independent solar TE generator. While the heat dissipated at the cold junction of a solar TR-TE system is 43.66 %, considerably less than that of 84.6 % for independent solar thermoelectrics. [ABSTRACT FROM AUTHOR]

Nowadays, using clean and renewable energy is one of the necessities of life. Investment and use of renewable energy have been steadily increasing since 2004. During the crisis and non-crisis periods, such as the great cryptocurrency crash in 2018, Bitcoin fluctuation, and the COVID-19 pandemic in 2020, fluctuations in the stock market such as the clean and renewable energy had very few than in the oil market. Among all renewable energy sources, solar energy is of great importance. Solar energy is an essential energy source for creating eco-friendly and sustainable systems. In order to satisfy rising energy demands, solar energy systems have garnered considerable interest as a significant renewable energy source. Concentrated solar power (CSP) and photovoltaic systems (PVS) are the two most common types of solar energy systems deployed for this purpose. Current solar photovoltaic (PV) technology has its limitations. To overcome the limitations of the PV, the concentrated photovoltaic system (CPVS) has the intention to replace large PV panels with affordable optics that concentrate solar radiation onto smaller PV panels. The scope of this assessment has been expanded to include specific issues pertaining to CPVS with mirrors and to highlight new developments in Low Concentrator Photovoltaic System (LCPVS) techniques. This review aims to exhibit and debate the current state of solar concentrating systems in the world, as well as to recommend future actions that will improve the solar energy contribution to the global energy supply. From the authors' perspective, considering an LCPVS using mirrors as a reflector and water for cooling can be a great choice to increase the overall efficiency and has been suggested to reduce the cost of installing solar panels compared with other types of the CPVS. Moreover, the choice of CPVS type is decided by the requirements and objectives. Although the application of LCPVS improves the total efficiency of the solar panel, its influence on generating electrical power is larger than its effect on rising heat. [ABSTRACT FROM AUTHOR]

• Solar thermal collectors can be controlled based on time-of-use (TOU) electricity rates. • This TOU-based control strategy can increase annual cost savings by 30% • The TOU control strategy works better for systems with smaller solar fractions. • Only a simple time-based controller is required to implement this control strategy. • The target cost for a 1-year payback period is approximately $1000. Homes and commercial buildings account for roughly 40% of U.S. energy consumption. A significant portion of this energy consumption, and therefore utility cost, comes from domestic hot-water use. Solar collectors such as flat plate collectors, evacuated tubes, and combined photovoltaic/thermal panels, are renewable options that collect thermal energy and could help reduce utility costs. Hot water is generated by pumping a working fluid through the solar collector, where the fluid captures thermal energy via absorbed solar radiation incident on the collector surface. The collection of heat coincides with the availability of solar radiation, but the best time to use this thermal energy depends on the utility rate at a given time, which often changes throughout the day. In this work, we implement and simulate a control strategy using Transient System Simulation Tool (TRNSYS) that reduces utility costs by controlling when the system stores and uses thermal energy based on solar availability and time-of-use electricity rates. Our modeled results show that the control strategy can reduce utility costs associated with using hot water between 3% and 30%. We also show how the on-peak utility rates, the size and type of the solar collectors, and the location's climate impact the results. [ABSTRACT FROM AUTHOR]

[Display omitted] • Performance, complexity and cost determines the preferability of SAHP. • Each SAHP has a range of ambient conditions in which it excels in performance. • The increase in performance with the complex structure brings along the cost problem. • It is possible to use PV/T with low cost add-ons in IDX-SAHPS. • Finned collectors can increase heat gain from air in DX-SAHPS. Solar assisted heat pump (SAHP) systems have been a popular research topic in last decades because of their proven improved performance by integrating solar energy to system. Filling the literature gap in SAHP systems comparison in terms of performance and structure, contributes to the determination of the appropriate type. For this purpose, in order to compare the systems, 77 recent studies are reviewed. Systems are classified according to their configurations to provide an infrastructure for comparison. Considering the collector structure, the effect of solar radiation and ambient temperature on SAHP systems performance are examined, and the ambient condition ranges preferable for each system are identified. The complexity of systems is expressed with the type and number of components used, and the costs of the systems are compared taking into account the payback period. Reviewed studies reveal that, direct expansion systems should be preferred because of their utilization of solar and air simultaneously as heat source, below solar irradiation of 400 W/m2. Indirect expansion systems are more complex than direct expansion systems and this limits their preferability. However, replacing the solar-side evaporator with a solar air preheater, thereby integrating the existing solar system and air source heat pump system, can simplify the indirect expansion systems. The temperature rise problem that prevents the use of photovoltaic thermal panels in indirect systems can be eliminated with low-cost external cooling devices. [ABSTRACT FROM AUTHOR]

• Accuracy of the 1-km MAIAC AOD and 2-km elevation-based MERRA-2 AOD currently used for NREL's NSRDB were evaluated. • The performance of MAIAC AOD is better than MERRA-2 AOD with smaller RMSE and MBE and higher R. • Simulated DNI using NREL's PSM with MAIAC AOD has higher accuracy than using MERRA-2 AOD. Solar irradiance, especially for direct normal irradiance (DNI), is sensitive to the atmospheric aerosols, which can strongly extinguish DNI over areas with elevated aerosol loadings. The National Solar Radiation Database (NSRDB), developed by the National Renewable Energy Laboratory (NREL), uses AOD from MERRA-2 reanalysis and is further downscaled from 0.5° to 2-km based on elevation. However, the elevation-based downscaling may not accurately represent AOD, especially over the areas with large AOD gradients. This study examined whether the 1-km MODIS MAIAC satellite-retrieved AOD product can better represent the AOD distribution and be used to improve solar irradiance assessment. We focused on areas with relatively high AOD over North America (California, and New York City, US, and Mexico City in Mexico, in particular). The evaluation of MAIAC AOD and MERRA-2 AOD against ground-truth AERONET AOD shows that MAIAC AOD exhibits smaller RMSE by about 0.05 and higher correlation coefficient by 0.1–0.6 than MERRA-2 AOD. In addition, MERRA-2 AOD shows larger negative bias. The simulated DNI using MAIAC AOD (DNIMAIAC) and using MERRA-2 AOD (DNINSRDB) were evaluated with DNI observations. The results show the performance of DNIMAIAC is better than that of DNINSRDB with smaller RMSE by 0.5 - 1.5%, smaller positive mean bias by 0.8 - 3.1 % and comparable correlation for the 3 sites analyzed. Overall, 1-km MAIAC AOD shows higher accuracy than 2-km elevation-based MERRA-2 AOD, leading to better performance of the simulated DNI using MAIAC AOD. Therefore, 1-km MAIAC AOD can be used to improve the accuracy of solar resource assessment. [ABSTRACT FROM AUTHOR]

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

• The mesh calibration achieved the required precision with minimal sample size. • The transmissivity of mesh screens was measured with <1 % error with 5–7 samples. • Layer arrangement in mesh screens affected their transmissivity by up to 0.3%. • The dependence between layers influenced mesh screen transmissivity by up to 1%. • Interlayer dependence and arrangement must be considered to achieve <2 % error. Mesh screens can be installed over a photovoltaic (PV) module to provide varying degrees of outdoor solar irradiance for I-V curve measurements. In such tests, it is often not possible to cover the PV module and the irradiance sensor with the mesh screen at the same time, requiring the transmissivity of the mesh to be accurately measured beforehand. This paper describes a measurement method and evaluates the uncertainty in determining the transmissivity of mesh screens used to attenuate solar radiation on PV modules. The method involves modeling the short-circuit current of the PV module as a function of irradiance and temperature indoors and measuring the transmissivity of mesh screens outdoors. Two mesh screens with nominal transmissivities of 50 % and 70% were assembled and used in single-layer and double-layer configurations, resulting in four different mesh filters. The transmissivity of each configuration was measured under four different conditions obtained by combining two angles of incidence for solar radiation – normal and 30° - and using two PV modules, one with monocrystalline and the other with polycrystalline silicon cells. The proposed measurement method succeeded in measuring the transmissivity and determining the optimal sample size for all mesh screen configurations, taking 5 to 7 measurements to obtain an uncertainty of less than 1%. The work highlights the importance of measuring the transmissivity of mesh screens and provides valuable results for future research using this method to study the performance of PV modules at low irradiance levels. [ABSTRACT FROM AUTHOR]

• Within the scope of the study, a global expression that gives the photovoltaic panel cell temperature, which is one of the most important parameters in the theoretical analysis of photovoltaic systems, is shared. • In the current studies in the literature, there are empirical expressions that give the photovoltaic panel cell temperature, but the results obtained from these expressions do not overlap with each other. In order to obtain the instantaneous efficiencies of photovoltaic panels and, accordingly, the production values theoretically, there is a need for a global expression that gives the photovoltaic panel cell temperature. • Within the scope of the study, expressions that give ambient temperature, solar radiation and wind speed depending on the day and time were created by using the long-term meteorological data of Kütahya province. These statements are valid only for the province of Kütahya and can be applied to the desired region with the method described in the study. • With the expressions shared in this study, the feasibility status of photovoltaic systems can be examined. The expressions created were compared with the real data and very consistent results were obtained. Energy efficiency is one of the most important issues of today. The limited reserves of fossil fuels make the use of renewable energy sources more attractive. Photovoltaic panels are one of the ways to utilize solar energy, which is one of the renewable energy sources. The instantaneous efficiency of photovoltaic panels is related to the cell temperature of the panels. In the current studies in the literature, there are empirical expressions that give the photovoltaic panel cell temperature, but the results obtained from these expressions do not overlap with each other. In order to obtain the instantaneous efficiencies of photovoltaic panels and, accordingly, the production values theoretically, there is a need for a global expression that gives the photovoltaic panel cell temperature. In this study, a global expression was developed that gives the photovoltaic panel cell temperature depending on the ambient temperature, solar radiation and wind speed. In addition, using the meteorological data of Kütahya for many years, expressions giving ambient temperature, solar radiation and wind speed were created. [ABSTRACT FROM AUTHOR]

• The regional applicability of triangular solar air collector is analyzed. • The thermal efficiency of the optimal collector is increased by 5.6%. • A novel optical model for non-concentrating solar collector is proposed. • Two kinds of optical efficiency are defined and compared. • The economy and carbon emissions of the whole life cycle are calculated. Improving the applicability of solar air collectors in different climatic regions is important for its popularization. In this study, a novel triangular solar air collector (TSAC) was proposed. The insulation material (TSAC_1), transparent cover plate (TSAC_2) or double transparent cover plate (TSAC_3) could be fitted on the side of TSAC to adapt to different climates. The optical model and heat transfer model of the TSACs were established and verified. Two optical efficiencies were defined and the optical properties of three TSACs were compared. The effect of environment temperature, global solar radiation, solar azimuth angle and insulation material absorption on the thermal performance of TSACs were analyzed. Based on meteorological parameters of eight cities in different climate and solar energy distribution regions, the applicability of TSACs was compared, and their life-cycle economics and CO 2 emission reduction capacity were assessed. Results indicate that the TSAC_2 has the highest optical efficiency, and 15.2 % higher than that of TSAC_1. Three TSACs are suitable for different climatic regions, the average thermal efficiency of the optimal TSAC applied to the eight cities is 47.3 % during the heating period, which is 5.6 % higher than that of the single TSAC_1. TSACs have good economics in all climate regions, and the average net CO 2 emission reduction of whole life cycle is 3230.3 kg. [ABSTRACT FROM AUTHOR]

• A improved stepped solar still (ISS) is developed and experimentally investigated. • The stepped solar still performance is inhanced using a built-in external condenser. • The daily productivity of the improved stepped solar still is 30% to 150% higher than the standard stepped solar still. • Effect of brine water flow rate and thickness of glass cover on the performance of the newstepped solar still is investigated. • The ISS can produce 3960 mL/m2/day with the efficiency of about 36 %. In this study, an improved stepped solar still with a built-in passive condenser is proposed and experimentally investigated. In the new design, the solar still body is divided by a central inclined stepped absorber assembly carrying a group of basins into two parallel chambers; The upper chamber is an evaporation chamber, and the bottom chamber is called the condensation chamber and is located on the under of the absorber assembly. Solar radiation heated the saline water and evaporated it. A fraction of the resulting vapor is condensed on the inner glass cover surface while the rest is naturally circulated to the condenser chamber to be condensed there. Air is naturally circulated between the chambers through two slits at the bottom and the top of the absorber assembly. The improved stepped solar still (ISS) was designed and fabricated, and its performance was experimentally evaluated under Kerman climatic conditions in June and October. For comparison, a standard stepped solar still (SSS) with the same size and properties is also constructed and tested. Results show that for the same condition, the daily yield of the improved stepped solar still is 30% to 150% higher than the standard stepped solar still. Also, the daily efficiency of the ISS reached as high as 36%. The influence of brine water flow rate and glass cover thickness on the performance of the stepped solar still is also investigated. Finally, the cost of distillate water for the improved stepped solar still and standard stepped solar still is estimated. [ABSTRACT FROM AUTHOR]

Interpolation is a fundamental process in solar resource assessment that glues consecutive components of the modeling chain. Most interpolation techniques assume that the interpolating function must go through the interpolation points. However, this assumption does not fit with averaged datasets or variables that must be conserved across interpolation. Here I present a mean-preserving splines method for interpolating one-dimensional data that conserves the interpolated field and is appropriate for averaged datasets. It uses second-order polynomial splines to minimize the fluctuations of the interpolated field, restricts the interpolation results to user-provided limits to prevent unphysical values, deals with periodic boundary conditions in the interpolated field, and can work with non-uniform averaging grids. The validity and performance of the method are illustrated against regular second- and third-order splines using relevant case examples in the solar resource assessment realm. • Regular splines interpolation is not appropriate for all kind of data. • Averaged data requires mean-preserving interpolation approaches. • Mean-preserving splines for uniform/non-uniform grids that prevent unphysical values. • Mean-preserving splines outperform regular splines for averaged data. [ABSTRACT FROM AUTHOR]

[Display omitted] • Boulders and fines of organic mixtures are evaluated in solar stills. • These organic mixtures are black walnut hull, coffee, madder, and black tea. • The experiments on solar stills are divided into four different scenarios. • The black walnut hull organic mixture produces the maximum amount of freshwater. • The highest daily efficiency of black walnut hull organic mixture is 44.2%. In this research, for the first time, the effect of primary particles (boulders) and secondary particles (fines) in organic mixtures of coffee, black walnut hull, madder, and tea (which are cheap, abundant, and biodegradable) on the improvement of solar stills' daily efficiency is evaluated as an alternative to metal-based nanofluids. A laboratory still simulator is utilised under laboratory conditions to measure the organic mixture's behaviour accurately. Furthermore, the effect of the concentration of organic mixtures and the particle size of organic materials are investigated, as well as the effect of boulders and fines, independently. In addition, two identical solar still systems are used under environmental conditions. The results show that these mixtures increase solar radiation absorption and water production. In most experiments, the maximum amount of produced freshwater belongs to the organic mixtures of the black walnut hull. The highest daily efficiencies of the solar still containing saline water and organic mixtures of black walnut hull and coffee are 44.2% and 40.3%, respectively. Finally, an economic analysis of organic mixtures of black walnut hull and coffee shows that freshwater costs are 0.0107$/L and 0.0112$/L, respectively. Therefore, these organic mixtures seem feasible for solar irradiance absorption and freshwater production. [ABSTRACT FROM AUTHOR]

• A solar single/double-effect compound absorption refrigeration system was proposed. • The dynamic model of proposed system was established by the state space method. • Proposed system was not suitable for frequent switching on cloudy. • Proposed system had advantages over the traditional absorption refrigeration system. • PBP , NPV and IRR were 11.84 years, 375.8 USD and 5.39 %, respectively. A single/double-effect compound absorption refrigeration system driven by solar compound parabolic collectors is proposed, which can realize mode switching according to the temperature of the heat source. The mechanism model of the system is established, and the sixth-order state space model of the single-effect mode and the ninth-order state space model of the double-effect mode are obtained through further simplification. The validity of the model is verified. The results showed that compared with the single-effect system and the double-effect system, the cooling capacity and cooling time of the system on sunny days are increased by 20.35 % and 5.34 h respectively; On cloudy days, frequent switching of the system is not conducive to operating; In addition, on overcast days, the system always runs in single-effect mode, and the total daily cooling capacity is small. When the t s (the temperature to switch to single-effect mode) and t s,d (the temperature to switch to double-effect mode) are 85 °C and 135 °C, the daily total refrigerating capacity of the system is 102.85 kWh. Compared with t s is 95 °C and t s,d is 155 °C, the refrigerating capacity is increased by 10.12 %. Finally, the economic analysis of proposed system shows that, compared with the compression refrigeration system, the payback period of the system was11.84 years when COP CRS (coefficient of performance of compression refrigeration system) was 4 and c e was 0.18 USD/kWh. The NPV (net present value) and the IRR (internal recovery rate) of the system were 375.8 USD and 5.39 %, respectively. The system is expected to be used in areas with sufficient solar radiation. [ABSTRACT FROM AUTHOR]

• Thermo-mechanical analysis of porous volumetric solar receiver. • Higher values of porosity, pore size and inlet velocities improve mechanical stability. • Uniform solar heat flux distribution ensures mechanical safety. • Near wall region at the inlet is most prone to failure. The damage caused by high working and non-uniform temperature distributions is one of the major obstacles to the development of receivers exposed to concentrated solar radiation. The thermal and mechanical performance of a typical porous Silicon Carbide volumetric receiver with foam structure is investigated in the present study with a coupled thermo-mechanical model. The developed model includes coupling of fluid flow, thermal and mechanical models to determine flow field, temperature and stress distributions. The main objective is to investigate the effects of various geometric, structural and design parameters on the absorber's thermal and mechanical performance and to identify the failure-prone regions when the absorber works under steady-state conditions. The effects of porosity, pore size, inlet velocity, absorber's geometrical dimensions, and incident solar flux distribution on the receiver's performance are investigated in detail. It is observed that higher porosities, pore sizes and inlet velocities result in lesser thermal stresses in the porous absorber. The uniformity of the incident radiation flux also reduces thermal stresses and improves the absorber's performance. The near-wall region at the inlet is found to be most prone to mechanical failure. The results of the study provide important conclusions to help in the selection of the proper set of parameters that ensure the efficient, safe and reliable working of the receiver. [ABSTRACT FROM AUTHOR]

• Absorption subcooling CO 2 refrigeration system driven by solar energy & waste heat. • Optimize thermodynamic performance and assess carbon emission of systems. • Effect of maldistribution of solar radiation and ambient temperature is discussed. • Annual performance factor and life cycle carbon emissions are evaluated in cities. • Hybrid absorption subcooling shows better performance in hot and solar rich areas. A novel hybrid solar energy and waste heat driving absorption subcooled carbon dioxide (CO 2 /R744) booster refrigeration system (SE + WH) is proposed to improve the energy efficiency of the traditional CO 2 refrigeration system used in supermarkets. The thermodynamic and energy conversion model of the system is established. Then, the optimization method of the two-dimensional golden section search algorithm is introduced to optimize the system energy efficiency taking the variation of ambient temperature and solar radiation intensity into account. Moreover, considering the maldistribution of solar energy and the influence of meteorological conditions in China, eight typical cities are selected to assess the annual performance factor and life cycle carbon emissions to achieve energy saving and carbon emission potentials. The performance of hybrid solar energy and waste heat driving absorption subcooled CO 2 booster refrigeration system is the best with the COP enhanced by 3.05–42.30 % at the solar radiation intensity of 1200 W/m2 and the temperature of 0–35 °C in contrast to the baseline system. In addition, the discharge pressure of the new proposed hybrid system can be reduced by 7.86 % when the ambient temperature is 34 °C. The annual performance factor of the new proposed hybrid system in Haikou can be increased by 14.47 %, and the life cycle carbon emissions are effectively reduced by 39.54 %. The payback period is also reduced by 4.01 % and 3.37 % for Beijing and Shanghai. Consequently, the novel configuration of the hybrid absorption subcooling subsystem is recommended, particular in hot or warm climate areas with rich solar energy. [ABSTRACT FROM AUTHOR]

• Hybrid solar desalination system. • Active mode operation and passive mode operation. • Solar desalination systems efficiency and economic analysis. • Trend in distillate cost, and yield by hybrid solar desalination systems. • Innovation type, feedwater, weather variabilities, operation mode impact on distillate quantity. In this paper, a hybrid solar desalination system was fabricated and incorporated with a water heater powered by a photovoltaic (PV) system. It was experimentally evaluated at Universiti Teknologi Petronas, Malaysia. Daytime operating conditions without the use of a PV system were considered for the conventional operation, while the use of PV alone or combined with direct solar radiation was considered as the modified system. This study was carried out to determine the freshwater yield, weather variabilities impact on yield, economic analysis, and system efficiency of hybrid solar desalination systems. An encyclopaedic review of five years of different researchers from different countries was critically analysed and compared with this study to see their trends and relationship. Within the study period, solar still distillate cost ranges from 0.0051 to 0.8857$/L, and 0.006 to 0.789$/L for the modified and conventional systems respectively. Similarly, the distillate cost for this study is 0.0374$/L and 0.0892$/L for the conventional and modified systems respectively. Also, the distillate yield ranges from 0.93 to 24.3 L/m2.day with an average of 12.1 L/m2.day, for the modified system, and 0.55 to 6.63 L/m2.day with an average of 3.35 L/m2.day for the conventional systems. The hourly system efficiency is 30.07 %, and 8.29 % for the modified and conventional systems respectively. Solar still is economically reasonable with good efficiency as obtained from the result. The findings also suggested that researchers should target a distillate yield of at least 6 L/m2.day and a distillate cost of 0.2$/L or lower for innovation, for a good and economical system. [ABSTRACT FROM AUTHOR]

• The RC model of the STPV-IGU is established. • The hypothesis that solar radiation absorption occurring at the glass boundary node plane is more reasonable. • The thermal resistance of the glass has the least effect on the model. • The simplest model can be simplified to 3R2C. • The expression of the heat dissipation time constant of the STPV-IGU is given. Photovoltaic (PV) glazing not only reduces energy consumption for air conditioning, but also uses PV output for building use. However, the relatively complex PV glass structure makes it more difficult to predict PV power generation and characterize their thermal performance for building load prediction. In this work, the resistance-capacity (RC) model of the semi-transparent photovoltaic insulating glass unit (STPV-IGU) is established. Three hypotheses of solar radiation absorption are proposed. According to the experimental data, it is proved that the hypothesis based on uniform absorption and solar radiation absorption occurring at the glass boundary node plane is more reasonable, and the simulation results agree well with the experimental data. Secondly, the model is simplified, and the simulation results show that the thermal resistance of the glass has the least effect on the model. And the simplest model can be simplified to 3R2C. Finally, the expression of the heat dissipation time constant of the glass system is derived from the simplified model, and the heat dissipation time constant of the STPV-IGU system is calculated to be 40.84 min under normal temperature conditions. [ABSTRACT FROM AUTHOR]

• A modified solar assisted ejection-compression heat pump cycle is proposed. • Performances of proposed cycle are theoretically studied. • The modified cycle outperforms the basic ejection-compression cycle. • The modified cycle has performance improvement potential for drying application. In this paper, a modified solar assisted ejection-compression heat pump cycle (SEHPC) is proposed for drying application. Based on the basic ejection-compression heat pump cycle (BEHPC), an auxiliary flash tank and an internal heat exchanger are introduced to improve its heating performances. The introduction of flash tank can improve the heat absorption in evaporator and increase the volumetric heating capacity in condenser, which eventually reduce the throttling losses and enhance the performance of the SEHPC. The performances of the modified cycle with refrigerant R1234yf are analyzed and compared to those of basic cycle by developing the thermodynamic models based on the energy, exergy and economic analysis. Moreover, the main parameters, including evaporation temperature, condensation temperature, generation temperature, ejector back pressure, and the solar radiation intensity, are selected as variables for research. The theoretical results indicate that compared to BEHPC, the mechanical coefficient of heating performance COP w , the thermal coefficient of heating performance COP t , the volumetric heating capacity q hv and the exergy efficiency η ex of SEHPC are increased by 5.2%, 8.4%, 17.1%, and 8.0%, respectively, under a specified working condition. Furthermore, the SEHPC outperforms BEHPC under all given working conditions, especially at high condensation temperature and high generation temperature. The economic analysis results show that the cost per unit of exergy production by SEHPC is 6% lower than that of BEHPC. Additionally, the maximum exergy destruction occurred in the solar collector, which means great optimization potential in solar collector. This study demonstrates that SEHPC has practical performance improvement potential for heat pump drying application. [ABSTRACT FROM AUTHOR]

The utilization of external agents is crucial in enhancing the production of active solar water stills. This analysis highlights the importance of incorporating external solar thermal collectors, photovoltaic panels, and concentrated solar power technologies to optimize the functionality and performance of solar water stills. External solar thermal collectors efficiently capture supplementary energy from the surroundings, while integrated photovoltaic panels revolutionize solar distillation by integrating energy generation with water evaporation processes. The incorporation of concentrated solar electricity further enhances system efficiency. Additionally, we explore the potential of active solar water stills with Heat Pumps, offering a promising avenue for significant advancements in solar distillation technology. Moreover, we introduce the innovative concept of using surplus water as a cooling agent for photovoltaic panels, enhancing both water purification and energy generation effectiveness. Throughout this comprehensive analysis, we consider a range of variables including maximum solar radiation, daily yield, thermal efficiency, condensation productivity, recovery period, and production cost. By incorporating these variables, we provide readers with a thorough understanding of the dynamic development and future prospects of active solar water stills, emphasizing the influence of external factors on system performance and efficiency. [ABSTRACT FROM AUTHOR]

• Double-layer cloud detection method for visible cloud image is proposed. • Double-layered clouds usually have different brightness, serving as the basis for detecting their shape. • The cloud base height serves as the basis for double-layered cloud judgment. • This method achieves an accuracy of 98.3% and 80.5% under non-overlapping and overlapping double-layer cloud conditions, respectively. Double-layer cloud is a special cloud condition, and clouds in two layers have different effects on solar radiation reaching ground. Getting the shape of double-layer clouds is helpful to study the change of solar irradiance. The proposed double-layer clouds detection method is based on the cloud base height (CBH) and brightness of double-layer clouds. The CBH is calculated based on binocular parallax, which requires two images filmed synchronously by two cameras, and the brightness is offered by the brightness channel in HSV color space. The accuracy of this method is 98.5% for single-layer clouds and 89.4% for double-layer clouds. The reasons for misidentifications are (1) the brightness contrast decreases when the high-layer clouds are thick, (2) the distant low clouds have different brightness in top and bottom. [ABSTRACT FROM AUTHOR]

• Experimentally study the gasification reaction of a typical Chinese coal. • Establish an analytical model of dish solar concentrator system. • Establish an energy model of solar gasification reaction system. • Analyze the effects of solar concentrator and reaction on energy characteristics. • Analyze the irreversible losses of the system based on thermodynamic second law. Coal gasification driven by concentrated solar energy can effectively realize solar energy storage and resource utilization of coal, which is in line with the carbon neutrality requirement. Solar-driven coal gasification involves many energy transfer and conversion processes such as solar energy concentration and collection, coal chemical reactions and heat transfer. To explore the basic energy conversion principles, this work first experimentally studied the gasification reaction kinetics and product characteristics of a typical Chinese coal, and established an analytical model of dish solar concentrator system. Besides, an energy analysis model of the solar gasification system was further established based on thermal balance. The influence of solar concentration and reaction conditions on system energy characteristics was investigated, and the system irreversible loss was analyzed based on thermodynamic second law. The results show that the system efficiency increases slightly when the solar concentration ratio exceeds 500. As a key factor affecting system performance, temperature can directly affect gasification efficiency. The energy efficiency and exergy efficiency of the system are 72.86% and 68.82%, respectively at 1000°C. The irreversible loss (17.87%) in the coal gasification module is greater than that in the concentrated solar process. In practical engineering, it is necessary to optimize the reactor design and reaction parameters to improve the coal conversion ratio and reduce exergy waste. Optimizing solar receiver and reducing the emissivity are also important to reduce the irreversible loss of solar radiation exergy. This work provides reference for the system design of concentrated solar-driven coal gasification. [ABSTRACT FROM AUTHOR]

• Solar radiation and DLI distribution of PVGR surfaces were measured in Singapore. • A high correlation was found between solar radiation and DLI above vegetation. • View factors among PVGR surfaces and sky were determined by ray tracing method. • A numerical model of solar radiation transfer was developed and validated for PVGR. • The effect of PVGR design parameters on DLI of vegetated surfaces was determined. Photovoltaic roof and green roof are both sustainable building technologies. However, these two types of roofs may compete with each other in terms of space utilization. A novel solution that integrates photovoltaic panel with green roof (PVGR) has gained increasing attention in recent years, which can effectively transforms this competition into synergism. Solar radiation play a crucial role in the functioning of both types of roof, but there is limited research on the distribution characteristics of solar adiation for PVGR. Additionally, there are few studies on photosynthetically active radiation (PAR) or daily light integral (DLI) under the shading of PV arrays, which hinders the rational selection of plant species. To address this gap, a field experiment was conducted in Singapore. The results revealed that on a clear day, the maximum incident solar radiation and PAR on vegetation surface between PV arrays was up to 1136 W/m2 and 1876.6 μmol/m2/s, respectively, whereas they were significantly lower at only 279 W/m2and 360.3 μmol/m2/s below PV panels, respectively. Regression analysis demonstrated a highly linear relationship between DLI and solar radiation with an average ratio of 1.799. A numerical model for solar radiation transfer in PVGR was developed based on sky view factor calculated through ray tracing method. The model demonstrated good performance after comparison with observed values, and the effect of PVGR design parameters on view factors and average annual DLI of vegetated surfaces was clarified. The findings drawn herein contribute to optimizing PVGR design in terms of thermal performance and selection of plant species. [ABSTRACT FROM AUTHOR]

• The paper discusses challenges in integrating solar power in Norway, limited to 36% of feasible capacity. • Seasonal variations in solar energy production emphasize the need for year-round energy management. • A critical threshold of 36% feasible solar power integration highlights the importance of balancing production and consumption. • Effective energy management is crucial for aligning solar production with consumption patterns. This research study delves into the solar energy potential and capacity in Norway, aiming to assess the viability of solar power integration in the country's urban landscape. Through a comprehensive analysis, historical data, and PVsyst simulations, the study reveals that solar photovoltaic (PV) systems offer significant promise in contributing to Norway's renewable energy goals. The study uncovers a seasonal variation in solar energy production, with peak generation during the summer months due to extended daylight hours and more intense sunlight. However, winter months experience lower solar energy production due to limited daylight hours and weaker solar radiation. To fully exploit solar energy potential, effective energy management strategies such as energy storage, smart grid technologies, and demand response mechanisms are crucial. Moreover, the research highlights the relationship between energy consumption and solar energy production, emphasizing the importance of efficient energy management and capacity planning. Bridging the gap between supply and demand requires optimized solar energy utilization aligned with consumption patterns. A key finding of this study is the identification of a pivotal threshold: up to 36% of the feasible solar power, equivalent to 31 GWp, can be integrated into the grid to match daily production and consumption. However, exceeding this threshold leads to challenges in peak production times, necessitating exports or additional strategies to accommodate the excess energy. In conclusion, this study underscores the promising prospects of solar energy integration in Norway. By leveraging solar power's potential, implementing effective energy management measures, and addressing challenges, Norway can work towards a more sustainable and resilient energy future, reducing reliance on fossil fuels and making significant strides in combating climate change. [ABSTRACT FROM AUTHOR]

• A comparative study of three cases for tabular solar still was carried out. • Enhanced tabular solar still with air injection, nanocoating and nanofluid was studied. • An energy, exergy, and economic analyses for the system were conducted. • The advanced tabular solar still distillate production cost per liter was 0.032$. • The advanced tabular solar still productivity has a 79.88 % increase over classic still. Nowadays, due to freshwater scarcity intensifying, researchers are actively seeking to improve solar desalination, a technology with immense potential, but there are still limitations in production capacity. This study investigated the integration of various additives in tubular solar still (TSS) at three configurations. In Case I, a V-corrugated basin and an air parabolic trough collector (PTC) equipped with evacuated tubes were integrated. Then, with the same attachments, CuO nanocoating was applied to the basin surface in Case II, aiming to enhance heat absorption. Finally, in Case III, CuO nanofluid was used in the presence of all previous enhancers. The system was studied during summer days with weather parameters having average ranges (minimum – peak) of 32.5–37.5 °C (ambient temperature), 318.5–1000 W/m2 (solar radiation), and 1.1–2.3 m/s (wind speed). The results were very acceptable and competitive. All modified configurations of the advanced TSS (ATSS) significantly increased distillate production compared to the classic TSS (CTSS), with a range of 49.84–79.88 %. Case III stood out as the most successful configuration, achieving outstanding gains in both energy and exergy efficiencies. Compared to the CTSS, Case III boasted an impressive 83.69 % improvement in energy efficiency and a staggering 242.45 % increase in exergy efficiency. This refers to a system that not only produces more desalinated water but also does so with significantly less wasted energy, making it a more environmentally sustainable solution. Case III also offered a good economic advantage with a 13.51 % cost reduction compared to CTSS. [ABSTRACT FROM AUTHOR]

• The efficiency of a solar system is highly dependent on the incident solar radiation that reaches the active surfaces. • Optical characteristics of the protective layer of solar panels are crucial for efficient solar energy harvesting. • Dust accumulation (soiling) is one of the most important external factors affecting PV performance and efficiency. • The removal of dust by mechanical cleaning process becomes complicated under strong dust adhesion. • Every cleaning approach has beneficiary features and drawbacks unique to cleaning soiled solar PV panels. This review offers a comprehensive, in-depth analysis of the dust soiling research, including critical observations on dust soiling effects and dust removal techniques for solar energy harvesting applications. The efficiency of a solar energy harvesting system is highly dependent on the incident solar radiation that reaches the active surfaces. Optical characteristics of the protective layer of solar panels, including high transmittance and low absorption, are crucial for efficient solar energy harvesting. Environmental dust reduces the optical transmittance of such surfaces, consequently lowering the device's performance. Therefore, the removal of dust particles becomes critical for efficient energy production. Dust-removal technologies mainly involve natural processes, electrostatic, mechanical, and self-cleaning surface Nano-films. Some of the adopted cleaning techniques require expensive external power, such as pumping/compression, due to the high repelling forces needed to remove such particles. This review evaluates and compares the existing dust removal strategies while focusing on the environmental, technical, and economic perspectives. The findings presented in this study remain crucial toward enlightening the PV scientific world regarding the soiling impact on solar energy harvesting and dust mitigation strategies to maintain high-performance solar PV operations. [ABSTRACT FROM AUTHOR]

• An integrated energy and humidity model was assessed for a tomato glass greenhouse. • Dynamic energy and water demands were obtained by using the 15-minute time step data for solar radiation and temperature. • The TOMGRO model was applied to calculate the tomato growth rate and production and evaluate the evapotranspiration models. • Effects of structure, orientation, humidity and temperature fluctuations on energy and water consumption was investigated. • Energy consumption rises by around 6.12 % for every 2 °C increase in daytime and nighttime temperatures. The design, operation and maintenance of solar greenhouses in optimum condition can improve the water and energy consumption and agricultural production. This study has been integrated the energy, humidity and growth models to determine the cooling, heating and water requirements for producing tomato in the even span, uneven span and arc roof type greenhouse structures with north–south and east–west orientations. In the proposed integrated framework, firstly, the incident and transmitted diffuse, direct and ground solar radiations for any side of solar greenhouse, along with different evapotranspiration models and TOMGRO model for tomato growth and production have been assessed comprehensively. Then, by using the set point day and night temperatures and relative humidity the phenomena of the energy and water transfer such as convection, longwave radiation, infiltration, and cover condensation as well as TOMGRO state variables have been calculated. By considering the temperature, humidity, structure and orientation as decision variables, the east–west uneven span structure with day/night temperatures of 20/16 °C and relative humidity of 80 % is recommended as the best case in Pakdasht city of Iran. This solar greenhouse requires 0.92 MW/m2 and 3.83 MW/m2 heating and cooling energy, respectively, to produce 46.68 kg/m2 mature tomatoes during the whole cultivation period. This research has provided a tool to select the most appropriate structure and orientation of a solar greenhouse in any location based on the trade-off between energy and water consumption and tomato production. [ABSTRACT FROM AUTHOR]

• Optical responsive asphalt is proposed to control pavement temperature. • Optical responsive asphalt features large fluorescent intensity and solar reflectance. • Optical responsive asphalt yields cooling effectiveness of 6.4 °C and warming effectiveness of 0.7 °C. The application of conventional asphalt contributes to extremely high pavement temperature in hot season as its black color entails large solar absorption. In this study, optical responsive asphalt is proposed to control pavement temperature, which is developed by introducing temperature-sensitive TiO 2 quantum dots (TiO 2 QDs) into traditional asphalt. Temperature-sensitive TiO 2 QDs are prepared by blending thermochromic polymer and TiO 2 quantum dots with varied concentrations. Optical characterizations on temperature-sensitive TiO 2 QDs have demonstrated that peak value of solar absorption in temperature-sensitive TiO 2 QDs at 45 °C is 14.29 %–22.86 % higher than that at 15 °C; the maximum fluorescent intensity of temperature-sensitive TiO 2 QDs at 45 °C is 8.5 % higher than that at 15 °C. The results from optical characterizations on temperature-sensitive TiO 2 QDs modified asphalt show that the incorporation of temperature-sensitive TiO 2 quantum dots endows asphalt low solar reflectance at high temperature and high solar absorption at low temperature. Fluorescent intensity of modified asphalt at 45 °C is increased by 21.6 %, 10.2 % and 5.7 % than that at 15 °C for asphalt containing 5 %, 10 %, and 20 % temperature-sensitive TiO 2 QDs, respectively. Indoor solar radiation simulation tests have revealed that compared with traditional asphalt, temperature-sensitive TiO 2 QDs modified asphalt coating could yield cooling effectiveness of 6.4 °C at high temperature. Meanwhile, outdoor solar radiation test indicates TiO 2 QDs modified asphalt coating could realize warming effectiveness of 0.7 °C at low temperature. The outcomes on temperature-sensitive TiO 2 QDs modified asphalt with temperature-adaptability properties makes an advancement in functional pavement. [ABSTRACT FROM AUTHOR]

• Selective themoradiative and graphene thermionic emission effects promote mutually. • STR-GTI achieves an energy efficiency of 34.34 % at a concentration ratio of 425. • STR-GTI outperform STR & GTI by 102.03 % in exergy efficiency. • Spectral narrowing, graphene thermionic help resilience against solar fluctuations. Thermionic conversion, due to its simple solid-state structure capable of converting heat to electricity directly, is promising for concentrated solar power. However, because of the extremely high cathode temperature, a large portion of the heat is lost to the environment. The paper introduces a novel concept of selective thermoradiative-graphene thermionic conversion (STR-GTI) that involving a combined control of photon and electron emission to modify the radiation dissipation. A detailed thermodynamic model is developed to evaluate the energy transfer irreversibility of STR-GTI solar conversion. The results demonstrate that the selective themoradiative photon emission and graphene thermionic electron emission effects synergistically reduce internal irreversible losses in the STR-GTI system, leading to a maximum energy efficiency of 34.34 % at a concentration ratio of 425, cathode work function of 1.8 eV and thermoradiative bandgap of 0.2 eV. The STR-GTI system outperforms both individual GTI and STR converters in terms of exergy efficiency and entropy production minimization. It exhibits a remarkable 102.03 % increase in exergy efficiency compared to the STR & GTI system at a thermoradiative voltage of −0.14 eV, accompanied by a 28.56 % reduction in exergy loss and a 37.83 % decrease in entropy production. The combination of narrowing the spectral radiation bandwidth and significant electron emission capabilities of graphene contribute to the system's resilience against solar radiation fluctuations. [ABSTRACT FROM AUTHOR]

• Propose a heat concentration collector for desalination system by reflection enhanced. • The optimal inclination angle of the reflector is obtained by calculation. • The daily freshwater production of the system was 17.04 kg. • The optimized reflector increased the freshwater production by 35% • The heat recovery increased the freshwater production by 13.16% A saline-alkali water distillation system by reflection enhanced solar heating is proposed to treat the saline-alkali soil washing water. In this system, the heat concentration collector employs heat collecting plate to receive solar radiation energy, and converges to small-area steam generating tube through efficiently heat transfer. Without expensive optical tracking equipment, the system also employs an external reflector to reflect the solar radiation to the surface of the heat concentration collector. Thereby the energy flow density is further increased, and the useful energy and vaporization intensity is promoted. The latent heat of the steam is reused by heat recovery to enhance the energy utilization efficiency. The optimal inclination angles of reflector in different seasons and system performance were theoretically calculated. In the spring equinox, summer solstice, autumn equinox, and winter solstice, the optimal inclination angles of the reflector were 30°, 45°, 30°, and 15°, respectively. The freshwater production, useful energy, and heat recovery efficiency of the system were investigated by experiments. The daily freshwater production of the system was 17.04 kg, and the maximum production rate was 3.44 kg/h. The reflector increased the useful energy and freshwater production of the system by 33.68% and 35%, respectively. With heat recovery, the initial temperature of the saline-alkali water was increased to 53.8 °C and the freshwater production was increased by 13.16%. [ABSTRACT FROM AUTHOR]

Volumetric solar thermal receivers are composed of semi-transparent media that are irradiated from the top and absorb solar radiation directly. Previous theoretical studies have suggested that these receivers can capture a high percentage of the incoming energy by eliminating temperature differences between the absorber and the heat transfer fluid. However, the complex interaction between radiation-induced natural convection and volumetric heating which governs the receiver thermofluid behavior has never been experimentally investigated. We present a comprehensive experimental study in which these interactions are investigated from a design perspective. A 6.5 kW solar simulator is installed in a beam-down configuration, and molten nitrate salts are used as base fluids to replicate real-life conditions. Key receiver parameters, namely the fluid absorption coefficient, receiver height, surface emissivity, input flux and heating time are varied experimentally to investigate their influence on operating regime transitions and capture efficiency. Receivers dominated by natural convection are shown to achieve capture efficiencies up to 20 times higher than those dominated by conduction. The χ 2 goodness-of-fit test is employed to demonstrate that theoretical predictions regarding the receiver physics are reasonably accurate and existing models can be effectively used for design optimization. Finally, a proof of concept for chloride salts-based high-temperature volumetric receivers is presented. The design insights obtained from the experiments are summarized as design guidelines for future commercial scale-up. • Experimentally investigated molten salts-based volumetrically absorbing receivers. • Investigated the effects of five key parameters on receiver thermofluid response. • Experimentally validated the presence of three distinct operating regimes. • Demonstrated that theoretical predictions regarding receiver physics are reliable. • Presented a proof-of-concept for chloride salts-based high-temperature receivers. [ABSTRACT FROM AUTHOR]

Energy-efficient windows are being used to increase the thermal insulation of a façade. Such insulating windows contain an ultra-thin, multilayered, transparent silver coating that acts as an infrared mirror which significantly reduces thermal losses that occur through radiation from inside the building. These so-called low-emissivity coatings revolutionized the field of building insulation but also decreased solar heat gain coefficient which reduces the potential for energy savings during winter. Insulating windows in cold climates should achieve a selective behavior in the transmittance of EM waves. Ideally, solar energy should be transmitted and mid-infrared radiation reflected, thus reducing the heating needs in buildings. This scientific paper presents a numerical investigation based on finite-difference time-domain (FDTD) focused on the optical transmission characteristics of silver plasmonic square nanohole arrays and explores their potential application in insulating windows. It is found that a nanohole array with a periodicity of 350 nm and a linewidth of 50 nm gives outstanding properties and represents a good candidate to achieve high solar heat gain in low-e coatings. The findings contribute to the understanding of plasmonic effects in nanohole arrays and offer insights into the practical application of such structures in the development of advanced insulating windows with enhanced optical performance. • Simulation of silver plasmonic nanohole arrays for high solar spectrum selectivity. • High selectivity for arrays with a periodicity if 350 nm and linewidth of 50 nm. • Useful for advanced insulation windows with enhanced optical performance. [ABSTRACT FROM AUTHOR]

• Lightness evaluation in specimens treated with TiO 2 in the long term. • TiO 2 effect on light radiation of coating mortars. • Aesthetic perception maintenance of facades treated with TiO 2. • Solar absorption on surfaces treated with TiO 2. • The color difference on surfaces treated by TiO 2. The importance of colours is not limited to the aesthetic but also other parameters like thermal comfort. Painting light colours on the building's external surfaces increases its reflection of solar radiation, reducing the heat gains. In contrast, dark colours can increase solar heat gains by absorbing more radiation. Regarding the TiO 2 answer to the lightness on the facade, different samples of TiO 2 were tested. First, in the laboratory for methylene blue dye degradation and second in a natural environment using different forms of treatment (powder and suspension) on mortars, measured by a spectrophotometer over three years to determine the loss of lightness over time. The methylene blue test showed that the TiO 2 -P25p, TiO 2 -PC-S7s, and TiO 2 -E502s samples had the same effectiveness after exposure to artificial UV radiation, while the TiO 2 -PC105p sample presented the worst performance. Concerning the lightness, after thirty-seven months of the natural exposition, the white painted specimens had the best results than specimens with TiO 2 suspensions and specimens with TiO 2 in powder. Beyond the absorptivity, the white painted specimens could be considered with low absorptivity. In contrast, the specimens treated with TiO 2 suspension and those treated with TiO 2 powder could be medium absorptivity. Regarding the visual aesthetic perception, the study concludes that for the final user, there is no great difference in white painted specimens, while for the other (powder and suspension), the colour difference can be noticed well over three years of exposure. [ABSTRACT FROM AUTHOR]