Accurate determination of direct normal irradiance (DNI) is essential for evaluating and monitoring of concentrating solar power (CSP) and solar process heat (SPH) plants. Currently, a bi-axially tracked Pyrheliometer (PHM) is the most accurate measuring device, but requires high maintenance effort and is cost-intensive. As an alternative, the cost-effective pyranometer SPN1 was investigated by comparing highly resolved minute mean DNI measurements of two SPN1 devices to a reference PHM at the Institute for Solar Technology SPF in Rapperswil (Switzerland). To reduce systematic errors, a linear and a quadratic correction function have been applied to four years of measurements. They reduced the root mean square error RMSE from 48.8 W/m2 (11.5% of mean PHM DNI = 426 W/m2) to 37.9 W/m2 (8.9%) and 29.6 W/m2 (6.9%), respectively. It is also shown that even recalibrations based on only one month of data already reduced the RMSE to maximum 33.4 W/m2 (7.8%), if conducted between April and September. Considering the impact of solar elevation and DNI range on the SPN1 accuracy by bifurcating the correction functions only resulted in a negligibly small improvement of the RMSE. Finally, the influence of SPN1’s DNI measurement accuracy on the performance analysis of a real SPH plant in Switzerland was evaluated. After recalibration and correction of DNI values, the evaluation of monitoring data yielded annual efficiencies that were 15% and 12% higher in 2014 and 2015, respectively. It is recommended to recalibrate SPN1 devices over a minimum of one month against a PHM according to the methods presented in this paper.

In practical applications, there are many optical errors in the parabolic trough concentrators (PTC), such as mirror slope errors and tracking errors. Image detection is a no contact technique that has a potential to diagnose the optical errors at large plants in use. In this study, a CCD (Charge Coupled Device) camera was used to directly observe the absorber, and the images of the flux peaks were successful obtained. The CCD image showed two bright peaks on the outer wall of the tubular absorber. By comparing the CCD image with the simulation results, the concave deformation of the parabolic mirror was diagnosed, and the slope error of the parabolic mirror was figured out. The images also revealed that sun tracking errors can cause a synchronous shift in the flux. The flux image method does not influence the normal operation of PTC and is an on-line method, which facilitates the field application.

As an entirely passive cooling strategy, radiative cooling (RC) is an appealing approach to draw heat from the terrestrial surface to outer space. RC can be easily and effectively realized during the nighttime with the absence of sunlight, which coincidently mismatches the operation time of solar collectors. Therefore, it is of possibility and significance to unite the RC device and solar collector to extend the working period and function. In the present work, a novel combined photo-thermal and radiative cooling (PT-RC) module was proposed, experimentally and numerically investigated. By applying separated heating and cooling components, the PT-RC module demonstrated a daytime stagnation temperature of 159.8 °C and a nighttime one of 0.6 °C through a consecutive 24 h experimental duration. By contrast, a conventional photo-thermal (PT) module as a reference showed the highest panel temperature of 153.5 °C during the daytime and the lowest panel temperature of 7.9 °C in the nighttime. Further modeling was conducted to evaluate the thermal performance of the proposed PT-RC module compared with stand-alone PT module and spectrally coupled PT-RC module under different working conditions. This dual-function collector may contribute a potential solution for sustainable energy technology in Zero Energy Building applications.

Soiling is a challenge for both concentrating solar and photovoltaic technologies. Measurement procedures and efficiency sensitivities to soiling for the same surface particle density differ due to the different optical characteristics of both technologies. For this reason, soiling investigations performed at a site for one technology are not necessarily applicable to the other technology. Soiling measurements have been performed mostly under fixed or rarely occurring angles of incidence. In this study parallel measurements of soiling loss and particle mass density found on the main optical surfaces of concentrating solar power (CSP) and photovoltaic (PV) technologies are presented. The measurements are taken on samples of CSP second surface mirror and PV solar glass with consideration of the main optical characteristics of both technologies. Optical soiling losses are found to be higher by a factor of 8–14 in CSP for the same particle surface densities compared to PV. A Mie-based model is presented and validated, that converts the particle mass density and a set of other inputs into the optical soiling loss for either technology for normal angle of incidence and varying angles of incidence. This method facilitates the transfer of soiling loss data from one technology to another. The method can significantly increase the knowledge on soiling for both technologies as more measurement data is made accessible. Additionally, the soiling losses for different angles of incidence can be used to estimate more realistic annual loss parameters for the technologies in question and give recommendations for optimized incidence angles to be used in soiling measurements for both technologies.

Photovoltaic (PV) modules are sensitive to the spectral distribution of solar irradiance. Although numerical weather prediction (NWP) models compute irradiance in several spectral bands, only broadband quantities are provided in the standard outputs used for PV forecasts. This study investigates how this lack of information impacts PV power estimation. A physical PV model is first designed that accounts for the spectral distribution of irradiance and the spectral response of the panels. This model is evaluated using measurements performed at Site Instrumental de Recherche par Télédétection Atmosphérique (SIRTA), Palaiseau, France. The mean relative difference between simulated and measured PV power for a monocrystalline silicon module of 250 W nominal power is −0.9%, and the mean bias is −2.0 W. This model is then used to investigate the impact of solar zenith angle and clouds on the performance of PV modules. PV performance can increase in cloudy conditions by 5% through spectral filtering of near-infrared irradiance, and by 18% when only the useful irradiance is considered to compute performance. This spectral effects is not captured by the PV model when only broadband irradiances are used. In such case errors up to 15% are obtained in simulated PV power compared to using a state-of-the-art NWP model providing irradiance in 14 spectral bands. More generally, broadband global horizontal irradiance appears insufficient for accurate PV power modelling, highlighting the added value of spectrally-and-angularly-refined irradiances. This stresses that PV models should use more detailed irradiance inputs, which could be easily achieved by exploiting internal variables of NWP models.

Many phase change materials (PCMs) experience a change in transparency when undergoing a phase transition. These thermo-optically responsive materials can be used to generate passive temperature control systems for building enclosures. The integration of optical and thermal switches into smart temperature-controlling elements requires rationally designed PCMs featuring tunable optical and thermal properties. Two polymers, poly (Octadecyl methacrylate) (PSMA) and poly(2-(2-(octadecyloxy) ethoxy) ethyl methacrylate) (PE2SMA) were synthesized and evaluated for their potential use in passive thermal energy storage systems. UV–Visible Spectroscopy, Near Infra-Red Spectroscopy, and Differential Scanning Calorimetry were used to evaluate the effect that changes in the polymer chemical structure had on the optical and thermal properties of the resulting materials. Insertion of a 6-atom flexible spacer (diethylene glycol) between the pendant crystalline motif and the polymer backbone of PSMA resulted in increases of latent heat storage capacity from 62 J/g to 94 J/g and thermal conductivity from 0.218 W/mK to 0.318 W/mK. Notably, insertion of a flexible spacer also resulted in a melting transition temperature increase from 37.7 °C for PSMA to 48 °C for PE2SMA. The visible transmittance of the polymers increased from 0% to 90% upon transition from crystalline to amorphous state. This study presents a synthetic strategy to control thermal and optical properties of polymeric PCMs materials. The material properties and structure-property relationships derived from this study will enable the refinement of the models used to predict the performance of passive temperature-regulating systems. More accurate models will guide the development of the thermo-responsive polymeric materials required for better perfoming temperature-regulating building enclosures.

Conventional solar air heaters are associated with low thermal and thermohydraulic efficiencies due to the formation of laminar sub-layer created in the region where the flowing air comes in contact with the absorber plate. Hence there is a need to break this laminar sub-layer to improve the convective heat transfer capability of the collector. In this study, a solar air heater with perforated circular absorber plate is adopted with cross-flow configuration. The thermal performance is investigated for 5, 8 and 10 mm perforation vent diameters as well as 24, 36 and 54 number of vents. The configuration with perforated absorber plate provides a better convective heat transfer and thereby leads to better thermal and thermohydraulic efficiencies. This is compared with the base model in the absence of perforated absorber plate for a wide operating range of Reynolds numbers from 3000 to 21000. It is found from the study that when there is an increase in the number of perforations, there is a significant increase in thermohydraulic efficiency, even though there is a marginal drop in thermal efficiency. Also, with an increase in diameter of the perforated vents there is a remarkable improvement in the thermohydraulic efficiency though there is a marginal drop in the thermal efficiency. The best operating range of Reynolds number for the perforated solar collector is found to be between 9,000 to 15,000 having 54 vent perforations corresponding to 8 mm diameter and offers an efficiency of 75.55%.

Copper mining is the largest industry and energy consumer in Chile, utilizing heat from imported fossil fuels of which Chile is not a producer. The goals for decarbonization present opportunities to analyze how the Chilean industry can become sustainable with significant shares of renewable energy including solar heat. The present study analyzes the integration of solar heating to the copper refining process in order to gain insights on the technical, economical, and emissions performance of solar heating systems for the largest copper mining operations in Chile. The solar technologies considered in the analysis are flat plate, evacuated tube, and parabolic trough collectors. The results are validated by comparing with publicly available data from existing solar heating plants in copper mining facilities showing that solar plants are able to supply partially the thermal energy demand, although at different costs in terms of capital and operation and maintenance requirements. The economic analysis indicates that with current fossil fuel prices, solar heating technologies are a valid alternative for cost and emissions reduction in copper mining. Flat plate collectors show the lowest cost for solar heat when compared to evacuated tube and parabolic trough systems considering identical sets of technical and financial parameters. The parametric and sensitivity analysis indicate that the conditions under which solar heating is competitive with traditional fossil-fired heaters. which might still be required as backup systems in order to provide heat in a 24/7 regime, and in all the cases analyzed, a substantial reduction in CO2 emissions can be achieved.

The improper post milking handling and storage results in a complete wastage due to the microorganisms and bacterial multiplication present in raw milk. The torque load minimalizing in the chilling unit using a solar photovoltaic (PV) is indeed a challenging task for the smooth functioning of the milk chilling system especially for the conventional (reciprocating) type of compressors. The variable refrigerant flow (VRF) technology not only solves the toque load problem but also reduces the size of peak power requirement of PV array. The present study enables the design of an improved solar chilling system consists of a chilling tank (200 L capacity) coupled with one tonne of refrigeration unit powered by PV panels (2 kWp) and employing VRF technology to make system more energy efficient by reducing the torque load. Experiments were conducted using different batch sizes (50, 100, 150 and 200 L) to decrease the raw milk temperature from 30 °C to 4 °C. During optimization phase the comparative power required to run various types of compressors (reciprocating, rotary with capacitor and rotary with VRF) were found to be 1.8 kW, 1.2 kW and 0.8 kW, respectively whereas the torque loads were noted to be 3.3 kW, 1.6 kW and zero kW for respective compressor type. The experimental and modeled predicted power consumption and chilling time under different batch sizes revealed excellent correlation coefficient (R2 = 0.99, P < 0.0001). Around one tonne of refrigeration unit is sufficient to chill 200 L of milk up to 4 °C within less than two hours.

Present research paper brings forth the results of simulation-based studies carried out on all-perovskite tandem (both top and bottom subcells made up of perovskites) multijunction devices. The all-perovskite tandem structure presented in this work employs a wide bandgap perovskite, i.e., Cs2AgBi0.75Sb0.25Br6 (1.8 eV) and a narrow bandgap perovskite, i.e., FACsPb0.5Sn0.5I3 (1.2 eV) as top and bottom cell respectively. An additional merit of the reported work is projection of lead (Pb)-free perovskite, Cs2AgBi0.75Sb0.25Br6 and low Pb content-based perovskite, FACsPb0.5Sn0.5I3 based tandem solar cell. The viability of proposed tandem design is performed in two steps firstly, 1.8 eV perovskite-based top cell is simulated and calibrated to fit the state-of-the-art conversion efficiency of 10.1%, and then, 1.2 eV perovskite-based bottom cell is simulated to have a calibrated efficiency of 14.2%. After calibrating the standalone (top and bottom) subcells, both the devices are evaluated for tandem configuration. The current matching conditions between the top and bottom cell is obtained at different thicknesses of the absorber layer in both top and bottom subcell. The optimized thickness for perovskite, 380 nm for top cell and 400 nm for bottom cell are obtained for tandem configuration. Top and bottom cells (fed with the filtered spectrum) reflect the conversion efficiency of 10.01% and 7.36%, respectively. Overall, tandem design showed a conversion efficiency of 17.3% owing to an enhancement in open-circuit voltage (VOC), which is 1.83 V.

Solar thermal utilization is an important part of renewable energy applications, and its development and application have received extensive attention. Based on the development status of medium and low temperature solar thermal utilization systems, this paper first introduces the application and performance research on subsystems of the solar system including heat collection, heat storage and heat utilization units. It then introduces the theoretical and experimental development of matching relationships and dynamic performance of the medium and low temperature thermal utilization systems. Lastly, a case study analysis of a solar thermal system performance was carried out under different thermal boundary conditions. The influence of the boundary conditions of the heat storage system and the actual weather conditions on its performance is explored. The results showed that the boundary conditions of constant temperature and the boundary conditions of constant heat flow density have their own advantages. The heat source conditions provided by heat transfer medium are similar to the constant heat flux boundary condition. The work of this paper provided a theoretical basis for the subsequent application and performance study of solar medium and low temperature thermal utilization systems.

PV/T (photovoltaic/thermal) technology is a combination of PV module (photovoltaic utilization) and collector (photothermal utilization), which can improve the comprehensive utilization efficiency of solar energy and has a broad application prospect. In this paper, PV/T module is coupled with heat pump evaporator to form a direct-expansion solar PV/T heat pump which is suitable for heat application in high latitude area. To achieve stable residential heating, a solar PV/T heat pump system coupled with build-in PCM (phase change material) heat storage is therefore proposed and simulated. Meanwhile, the mathematical model of solar PV/T heat pump coupled with build-in PCM heat storage system is established and verified. The simulation results show that the temperature of underfloor heating which using build-in PCM heat storage can reach 22–31 °C after 39 h when the circulating water is 40 °C. Moreover, the heating COP (Coefficient of Performance) increases with the increase of solar radiation, ambient temperature and area of PV/T collector, and decrease of wind speed, respectively. A 20 m2 PV/T panel module can output 21.4% of the electricity to power grid when the solar radiation intensity is 600 W/m2 and meet the heat demand of a 100 m2 room while maintain the operation of the system. Meanwhile, the heating COP can reach 5.79 which is 70% higher than the conventional air conditioning system and the electrical, thermal, overall efficiencies are 17.77%, 55.76% and 75.49%, respectively.

In recent years, researchers are fascinated to counter problem of PV-efficiency decline arising from high operating temperatures, especially in hot climates. This article conducts a comprehensive review of research activities performed in last 5 years, on cooling techniques with phase-change materials (PCMs), nanofluids and their combined use, leading to efficiency enhancement. By passive cooling approach with PCMs, it is found that maximum enhancement up to 20% in PV-efficiency can be achieved. Effectiveness of PCM for PV is more prominent in summer than in winter. Incorporations of fins inside PCM container at PV rear, results in much improved heat conduction within PCM. Now-a-days, researchers have grown interest in composite PCMs for PV cooling due to their enhanced thermal conductivity. Moreover, better heat regulation as well as PV-surface temperature uniformity can be achieved with two PCMs at a time having different melting points. Studies suggest that combination of passive & active cooling techniques helps in further lowering of PV-cell temperature, leading to enhancement in PV-efficiency with additional thermal power generation. PV-efficiency of water-based hybrid PV/T systems can be improved by 32% by integration with PCM. Although nanofluid-based PV/T systems have been proved to enhance PV-efficiency by more than 60%, but combined use of PCM & nanofluid is more effective approach for PV cooling than individual use of PCM or nanofluid. If combination is made between nanofluid & nano-PCM, electrical power & efficiency can further be enhanced. Nanofluids can also be considered a good spectral filter alternative as they require small thickness and are able to be tuned by varying nanoparticles conc. Finally, environmental impacts & economic viability of mentioned cooling techniques, were discussed. Studies show that PV/PCM systems become expensive & less feasible when operated in single junction due to long payback period up to 20 years. Economic feasibility can be increased by combining passive & active cooling techniques which can increase system compactness and lower its cost.

In this study, electrical, thermal and exergy efficiencies of PVT using fins in different materials and configurations were experimentally investigated, and optimization analysis of control parameters affecting thermal and exergy efficiencies was performed. Experiments were carried out according to frequent and sparse configurations of fins made from copper, aluminum and brass materials in both monocrystal and polycrystal panels, and compared to non-fins (empty) status. Efficiency values for both frequent and sparse fin configurations have increased significantly compared to non-fins condition. Also, the ideal number of fins for each fins material according to both electrical and thermal efficiencies were investigated. The Taguchi method was used to determine the best combination of control parameters affecting thermal and exergy efficiencies. Additıonally, analysis of variance (ANOVA) was carried out to determine contribution rates of control parameters affecting both efficiencies. It has been found that for all experiments, the most effective factor on both efficiencies was fins material, and then air velocity and panel temperature, respectively.

Solar Parabolic Trough Collectors (PTC) are alternative clean solution for the thermal power plants to generate electricity and thermal energy. It can be configured to support small, medium and high temperature applications. In PTC, solar radiation is concentrated to a pipe coated selectively and enclosed in a glass tube with vacuum maintained in the annulus, through which a heat transfer fluid is circulated. Heat transfer analysis of PTC is important to determine the operating characteristics as well as for optimization of the parameters under different operating conditions. In this paper a heat transfer model is developed for receiver tube with the focus on a complete radiation heat transfer model for the annulus. For the analysis the receiver tube is divided into severe elements where the governing energy equations are discretized using Finite Volume Method. Gerhart factor is used for modelling the radiation heat transfer. View factors are computed using contour integration technique and analytical solutions. Heat transfer results are then validated with the test results obtained from Sandia National Laboratory. The results obtained show close agreement with the test results. Also the result is compared with other four published models. Based on the RMSE analysis, it is proven that our model is the best among all the four models compared.

Daylight and glare metrics are useful to quantify visual performance, minimize visual discomfort, and promote energy savings. This study evaluates the performance and robustness of some dynamic and static daylight and glare metrics by field studies in twenty architectural studios, daylit by different strategies (i.e., skylight, clerestory, side-lit windows). Experimental datasets (measurements and questionnaire surveys) were collected from three universities during different months. The daylight and glare metrics were also calculated by simulation and compared to occupants’ responses and onsite measurement. Based on the results, the metrics are rated based on their consistency with occupants’ perception. Moreover, the acceptable thresholds of metrics, recommended by standards and experts, are investigated. Results show that occupants’ perceptions are correlated to Point-in-Time-Illuminance (EP), Spatial Daylight Autonomy (sDA), and Useful Daylight Illuminance (UDI) respectively, while no significant correlation has been observed between grid-based glare metrics and users’ responses. According to the results, among annual metrics, UDI300-3000/50% ≥ 75% and Annual Sunlight Exposure (ASE1000, 250h ≤ 10%) have better performance in predicting daylight availability and visual discomfort. Consequently, two simple indices (EDSDaylight and ESDGlare) are presented to predict daylight satisfaction and visual discomfort based on architectural parameters to be used in the early design stage.

Conventional jaggery making process utilizes the bagasse for boiling of sugar cane juice which releases pollutants into the atmosphere and high particulate matter from these emissions causes air pollution. In this article, solar powered jaggery industry with freeze pre-concentration is proposed with conventional and modified heating pans. The system performance, environmental impacts and economic feasibility were assessed by carrying out 4E (Energy-Exergy-Environment-Economic) analyses using the developed mathematical model. These systems were designed to produce 300 kg of jaggery per day when operated for 7.5 h in 3 batches with average solar direct normal irradation of 662 W/m2 and 343 °C. These systems are integrated with auxiliary heating for uninterrupted production in the absence of sunlight. These systems can mitigate nearly 2015.95 to 3062.15 tons of CO2 emission during its 25 years of lifespan under 300 clear days of operation each year. Jaggery produced by this technique is rich in its colour and completely safe for human consumption as no artificial clarificants are used. Amount invested in these systems can be recovered in a span of 12.03 to 13.45 years for jaggery selling price of USD.0.514/kg or INR.36/kg.

A new strategy for preparation of Cu2ZnSn(SxSe1−x)4 (CZTSSe) thin film solar cells by a two-step sulfurization of Cu-Zn-Sn-Se precursors is introduced. The growth evolution of the CZTSSe films has been characterized compositionally and structurally and the growth mechanism has been revealed. A single-phase CZTSSe film without any secondary phase was observed with a solar cell efficiency of 8.55%. A sulfur rich CZTSSe layer was obtained at grain boundaries which is proposed to be beneficial by forming a hole barrier at grain boundary to reduce the recombination. This solar cell is further characterized using photoluminescence (PL) and capacitance-voltage (C-V) and drive-level capacitance profiling (DLCP) technology.

In this paper, we demonstrate a simple and effective method to control the visibility of embedded silicon solar cells in building-integrated photovoltaic (BIPV) windows by surface structure modification and metal-oxide back coating. The surface structure modification by etching the front glass in BIPV modules and the use of a thin niobium pentoxide (Nb2O5) film as a back coating enable the silicon solar cells to be hidden from view without a serious loss in the power efficiency. By employing the etched front glass and Nb2O5 back coating, silicon solar cells embedded in the BIPV module exhibited power conversion efficiency of 15.23% and fill factor of 65.05%. We also investigate the origin of the improved photovoltaic performance of the solar cells in the BIPV modules. The surface modification of the front cover glass of the BIPV windows enhances the light absorption in the solar cells, which results in the improved photovoltaic performance degraded by a metal-oxide back coating. We believe that the proposed surface modification which induces light trapping and anti-reflection into the cover glass of the BIPV modules with a metal-oxide back coating film is a promising and practical solution for the successful integration of BIPV windows with high efficiency and invisibility.

A 3D simulation of optical photogenreation, electrical characteristics, and thermal/heat distribution across the structure of a perovskite solar cell with a reduced graphene oxide (RGO) contact is presented. COMSOL Multiphysics package has been used to solve the coupled optical-electrical-thermal modules for this hybrid cell where the RGO added as the bottom electrode instead of a conventional metallic contact to enhance the heat dissipation towards a higher device stability. The Wave Optic module, Semiconductor module, and Heat Transfer in Solid module were coupled and solved for the proper input parameter values taken from relevant literature. The optical photogeneration, current-voltage characteristics, electric-field and the thermal maps of the cell are presented. The RGO contact doesn’t significantly impact on the optical and electrical output of the cell, but it accelerates the heat dissipation. The heat is mainly generated across the cell from the light absorption, Shockley-Read-Hall non-radiative recombination, and Joule heating. Compared to the cell with the Au electrode, the RGO contacted cell is showing a minimized heat accumulation and gradient at the bottom junction of the RGO/Spiro interface which promises a thermal stability of the cell. The nan-radiative and joule heat distribution also show a moderated density for the RGO contacted cell which are assigned to the high heat conductivity of the RGO layer compared to traditional metallic electrodes. Our simulations results are of the rarely presented thermal simulations for such devices and prove the superiority of graphene over plane metallic contacts for heat dissipation and thermodynamic aspect of a solar cell.

In this work was systematically studied the Al3+ doped ZnO nanoparticles effect on the performance of CdS quantum dot sensitized Titania solar cells. Varying the spin coating speed, ZnO nanoparticles with different Al3+ conentrations (00, 0.1. 0.2, 0.4 M %) were deposited over TiO2/CdS. The introduction of undoped ZnO nanoparticles results in a small increase of the Voc (from 524 to 547 mV), impedance analysis indicate that this increase is due to a recombination process reduction. On the other side, low Al3+ doped ZnO increase at the same time the short circuit current (from 7.15 to 8.46 mA/cm2) and the open circuit voltage (from 524 to 576 mV) resulting a 39% of relative enhancement of photoconversion efficiency (from 1.9 to 2.65%). Light absorption and External Quantum Efficiency (QE) measurements indicate that small concentrations of Al3+ promote the formation of new energy levels where extractible charge carriers are photogenerated resulting in an increase in the Jsc meanwhile, impedance analysis show that Al3+ as a dopant in ZnO reduce the recombination process and at the same time increase the transport process, resulting in the observed increase of Voc and contributing to the increase of Jsc.

Evaporative cooling of the dehumidified air in a desiccant cooling system with the aid of solar energy is an attractive energy saving option to cool the process air for air conditioning purposes. This paper is concerned with the dynamic simulation and performance analysis of three configuration schemes of a solar-based ventilation mode desiccant cooling system energized by a photovoltaic-thermal (PV/T) solar collector for the weather conditions of Lahore (31.52°N, 74.36°E). In configuration-1 (C-1), the auxiliary heater is installed in the air conditioning loop to heat the return air up to the desired regeneration temperature. In configuration-2 (C-2), the auxiliary heater is installed in the solar heating loop to raise the temperature of the liquid water to a certain elevated temperature. The configuration-3 (C-3) is similar to C-2 except there are no evaporative coolers and all the cooling is achieved via conventional vapor compression chiller. The primary energy savings, solar fraction, and the thermal efficiency of the solar collector are the energetic performance parameters which are used to compare the performance of three configuration schemes and to analyze the influence of various parameters such as regeneration temperature, solar collector size and tilt, flow rates, and storage volume. The simulation results demonstrated that the C-1 scheme performs best in terms of solar fraction and primary energy savings while C-3 schematic resulted in the least values of primary energy savings.

In this study, solar energy is utilized for providing fresh water by purification of tab water using rotating belt utilizing the addition of hygroscopic solutions containing kaolin or calcium chloride. The function of the hygroscopic solution is to increase the surface area and thus the percentage of evaporation on the rotating belt. It was shown that the use of hygroscopic material enhances the production of fresh water to a significant level. Additionally, the use of kaolin has been shown to be superior to the use of calcium chloride. The use of kaolin in the proposed solar desalination device has increased solar desalination from 10.8 kg/m2·day of using pure tap water to 32.1 kg/m2·day. A mathematical model was established to the use of hygroscopic material in this solar desalination using rotating belt. It was found that the maximum system efficiency was 61% after utilizing kaolinite; approximately seven times more comparing to the efficiency without using kaolinite (8.7%).

In this study, a novel nanodiamoands (NDs)/zinc (Zn) nanocomposite have been investigated as counter electrode (CE) in flexible dye sensitized solar cell (DSSC) device as potential replacement for platinum (Pt). Simple drop casting method has been employed to fabricate CE on indium tin oxide (ITO) coated Polyethylene terephthalate (PET) substrate. Various concentrations of Zn in optimized NDs layer have been investigated. Scanning electron microscopy (SEM) and X-Ray diffraction (XRD) methods have been utilized to study surface morphology and structural composition. Uv–vis has been employed to study light absorption characteristics. Fourier Transform Infrared (FTIR) has been used to identify redox active functionalities. Electron Impedance Spectroscopy (EIS) and Cyclic Voltametery (CV) have been employed to study electron transfer and catalytic activity and finally I-V testing has been conducted using sun simulator. The optimized layer of NDs displayed 78.52% equivalent performance compared to Pt based CE at optimum layer thickness. The introduction of Zn nanoparticles further improved the catalytic activity comparable or even exceeds the performance of Pt based reference CE. A 6.23% increase in performance has been observed at 8% Zn concentration compared to Pt based reference device. Further increment in concentration leads to reduction in performance due to charge trapping sites and agglomeration of nanoparticles.

The compound parabolic concentrator photovoltaic (CPC-PV) cell module is composed of two symmetrical mirrors and a crystalline silicon solar cell. In this study, two new CPC-PV cells based on known CPC-PV cell are established by changing the location and number of bus-bar in crystalline silicon solar cell. The effect of different location and number of bus-bar on the electrical performance of CPC-PV cells was investigated. The numerical simulation of three CPC-PV cells is performed using a two-dimensional finite element model. The electrical performance of three CPC-PV cells are compared, and surface voltage distribution, current density and internal current flow of the crystalline silicon solar cell for each CPC-PV cell are analyzed. The results show that compared with the known CPC-PV cell with bus-bar placed on the right side of the crystalline silicon solar cell, the electrical efficiency of the CPC-PV cell when the bus-bar is placed in middle region of the crystalline silicon solar cell is relatively improved by 14.76%. Finally, it is concluded that the bus-bar optimization based on the non-uniform illumination intensity distribution formed by the concentrator will help to improve the electrical performance of the CPC-PV cell.

Dye sensitized solar cells (DSSCs) are the third generation photovoltaics that convert solar radiation into electricity. DSSCs have been widely studied due to their low cost and ease of fabrication. In this study, TiO2 photoanodes have been sensitized with organic dyes RhB and D149 and their performance was compared with conventional N719 sensitized photoanode. Further, the consequences of addition of chenodeoxycholic acid (CDA) on the performance of DSSCs sensitized with RhB, D149 and N719 dyes were analyzed. The photoanodes were characterized using FESEM, EDXs and XRD techniques. To reduce the cost of DSSCs, Graphite from HB pencil along with PEDOT:PSS (Gr-PEDOT) was used as catalytic material instead of expensive platinum in counter electrode. The electrocatalytic activity of prepared counter electrode was investigated by cyclic voltammetry. The performance of DSSCs was investigated by I-V characteristic measurement and Electrochemical Impedance Spectroscopy. The photo conversion efficiency of RhB, D149 and N719 sensitized DSSCs were found to be 1.42%, 6.67% and 6.34% respectively. At optimized condition, the addition of CDA in dye solution remarkably increased the performance of RhB, D149 and N719 sensitized DSSCs by 23.24%, 15.74% and 10.41% respectively. The electrochemical impedance spectroscopy has been analyzed in terms of Nyquist plot and an equivalent circuit has been modelled to find out series resistance, resistance due to redox reaction at counter electrode and charge transfer resistance at TiO2/dye/electrolyte interface.

All solution-processed semi-transparent perovskite solar cells (PSCs) with high efficiency were fabricated with Ag nanowire (AgNW) top electrode directly coated on the organic electron transport layer (ETL). A unique AgNW/ETL interface morphology was attained by the fabrication of the AgNW-C60 composite electrode through a sequential spin-coating method. The C60 filler spin-coated on the AgNW network engendered a high contact area and favourable energy level alignment at the interface between the ETL and AgNW. As a result, devices based on AgNW-C60 electrode far outperformed devices with pristine AgNW electrodes. By adjusting the thickness of the AgNW film, the AgNW-C60 devices attained a PCE of 11.02%. The incorporation of C60 into the AgNW electrode also led to remarkable stability improvement. The low-temperature solution-processed and semi-transparent AgNW-C60 top electrode is also applicable to other PSC structures with various interfacial layers, thus showing a promising path towards fully-printable, flexible and translucent photovoltaic devices.

With increased penetration of solar energy sources, solar power forecasting has become more crucial and challenging. This paper proposes a copula-based Bayesian approach to improve probabilistic solar power forecasting by capturing the joint distribution between solar power and ambient temperature. A prior forecast distribution is first obtained using different underlying point forecasting models. Parametric and empirical copulas of solar power and temperature are then developed to update the prior distribution to the posterior forecast distribution. A public solar power database is used to demonstrate effectiveness of the proposed method. Numerical results show that the copula-based Bayesian method outperforms the forecasting method that directly uses temperature as a feature. The Bayesian method is also compared with persistent models and show improved performance. This article includes supplementary material (data and code) for reproducibility.

This paper presents the hardware implementation of a digital solar array simulator (DSAS) to evaluate and validate the operation of maximum power point tracking (MPPT) algorithms and photovoltaic (PV) inverters used in solar power conditioning systems (SPCSs). The required criteria for designing and setting up a genuine SAS are high-accuracy static behavior, fast transient response, and high flexibility for the emulation of the different PV modules. A four-phase interleaved buck converter is chosen as the proposed power stage of the SAS because of its advantages of power management, filtering reduction requirements, and output ripple minimization. The proposed SAS control system has been digitally implemented by a digital signal processor (DSP)-based controller, in which third-order integral-lead compensator and resistive feedback method have been chosen to reproduce precise and stable operating points. Experimental results confirm the proper and satisfactory steady-state operation and dynamic response of the proposed DSAS.

A laboratory-scale solar reactor prototype dedicated to calcination processes of non-metallic mineral particles is tested and characterized. The prototype consists of an indirect heating shallow cross-flow fluidized-bed reactor-receiver. It is composed of 4 compartments in series in which the particles are thermally treated with solar power in order to drive the endothermic calcination reaction. The particles are fluidized in the reactor with preheated air and are heated up to 800 °C through the front wall of the reactor receiving the concentrated solar flux (about 200 kW/m2). The tests are carried out at the 1-MW Odeillo’s solar furnace (France). The thermal decomposition of a continuous stream of 9.4 kg/h of dolomite (CaMg(CO3)2) is investigated in this paper. The half decomposition of dolomite (CaMg(CO3)2 → CaCO3 + MgO + CO2) is performed with a degree of conversion of 100%. The complete decomposition of dolomite (CaMg(CO3)2 → CaO + MgO + 2CO2) is not reached because, with respect to the CO2 partial pressure in the reactor, the temperature of particles is not high enough to decompose the calcium carbonate. The calculated thermochemical efficiency (i.e. the energy absorbed by the endothermic calcination reaction compared to the solar energy provided to the system) is 6.6%. This low efficiency is neither surprising nor critical since the reactor design was not optimised with respect to energy efficiency but designed to the control of particle flow and front wall solar flux distribution. A numerical model considering the 4 compartments of the reactor as 4 ideal continuous stirred tank reactors in series is developed. The model accounts for the mass and the energy balances, as well as the reaction kinetics of the half decomposition of dolomite. The model gives consistent results compared to the experimental data. These results are a proof of concept of continuous calcination reaction using concentrated solar energy in a cross-flow fluidized-bed reactor.

This paper experimentally investigates the performance of conventional single slope solar still and the impact of integrating a flat plate collector (FPC) as well as parabolic trough collector (PTC) supported with a packaged glass ball layer (PLGB), which acts as a thermal storage medium to the systems. The incident solar energy from the PTC-FPC is collected by two separate loops of finned pipes acting as heat exchangers in still basin. Experiments were conducted during winter and summer seasons with saline water depth of 50 mm. Results revealed that solar still integrated with PTC, FPC and PLGB has a higher freshwater production rate of 6.036 kg/m2/day during summer and 2.775 kg/m2 in winter. Moreover, FPC-PTC-PLGB solar still found to have increased productivity by 172% in winter and 203% in summer, compared to conventional solar still. The efficiency in winter for the solar still with FPC-PTC-PLGB is found to be 16.24% compared to 21.83% in summer, which is higher than the efficiency of conventional solar still at 8.1% (winter) and 12.15% (summer). An economic analysis was carried out for all different parameters investigated to confirm the feasibility of integration of FPC-PTC-PLGB. The price of one liter water produced from conventional solar still (CSS) was $0.067 whereas for the developed solar still (DSS) it was $0.22.

Compared with direct steam generation (DSG), direct vapor generation (DVG) system based on organic working fluid has better application potential in low and medium temperature distributed system. However, there is a lack of understanding of the two-phase flow instability that commonly occurs in DVG systems and can cause fatal damage to the system. In this paper, Ledinegg instability is considered as a common flow instability, and its occurrence characteristics and avoidance strategies are presented. First, a theoretical model was established to study Ledinegg instability of organic working fluid. Then, the effects of heat flux q, inlet subcooling Tc, length-to-diameter ratio L/D and fluid properties are analyzed. Particularly, a characteristic parameter RL representing the possibility of Ledinegg instability is proposed for the first time in performance evaluation of Ledinegg instability. The results show that as L/D decreases from 200 to 100, RL reduces from 0.88 to 0.25. As q increases from 10 kW/m2 to 30 kW/m2, RL increases from 0.54 to 1.03. When Tc is less than 3 °C, RL approaches 0 and Ledinegg instability disappears. With the increase of surface tension σ and the latent heat of vaporization r, the decreases of vapor-liquid density ratio ρsv/ρsl and the decreases of vapor-liquid viscosity ratio μsv/μsl, RL increases. The physical equation describing RL of Ledinegg instability is helpful to guide DVG system to reduce or avoid Ledinegg instability in design and operation.

In this paper, a novel Diamond-Like Carbon (DLC)-based structure is proposed as an alternative material for transparent electrode applications. In this context, DLC/Ag/DLC multilayer structure was successfully fabricated by combining pulsed laser deposition (PLD) and RF magnetron sputtering techniques. DLC films were deposited at room temperature via PLD on a quartz substrate and their optical constants were extracted using ellipsometry technique. A new hybrid approach based on FDTD method supported by particle swarm optimization (PSO) technique was introduced to find out the best geometry and appropriate intermediate ultrathin metal film of the DLC/Metal/DLC multilayer structure, promoting wider opportunities to overcome the transparency-conductivity trade-off. The optimized design is then prepared by successively depositing DLC films and sputtering ultra-thin Ag layer. Characterizations showcased that the elaborated DLC/Ag/DLC tri-layered structure offers a high Haacke FoM of 55.2 × 10−3 Ω−1, emphasizing the ability of the presented systematic investigation for providing promising pathways to reach enhanced light management and reduced resistive losses. Therefore, the elaborated DLC/Ag/DLC multilayer structure opens up new perspectives towards realizing high-performance transparent electrodes based on free-critical raw materials (CRM), which are strongly desirable for optoelectronics and low cost thin film photovoltaic applications.

The I–V curve tracer is an instrument that captures the I–V characteristics of photovoltaic (PV) generators corresponding to variable environmental conditions. The device is widely used to evaluate power generation performance and detect the fault conditions of PV power generators. Various I–V tracer techniques have been developed and proposed to trace the IV characteristics and ensure high accuracy and fast speeds. A comprehensive classification and analysis was undertaken to identify the advantages and disadvantages of different technologies. This study proposes and uses five performance indices to evaluate the performance of I–V tracers. The quantitative fidelity of commercial I–V tracers were also reviewed and evaluated. This paper serves as a valuable reference tool that should be used to guide the direction of future research and lead future improvements in the field.

Spinel Nickel cobaltite oxide (NiCo2O4) have received great interest due to its usage in several industrial applications. The motivation of the present study is to explore the usefulness of spinel Nickel cobaltite oxide as inorganic charge transporting layer for standard perovskite solar cells (PSCs). This is the first demonstration of successful use of NiCo2O4 nanoparticles as hole transporting layer (HTL) in standard PSCs with the triple cation perovskite material. The synthesis of nanoparticles was done using a facile chemical precipitation method without the use of surfactant. The synthesized nanoparticles were characterized by the various techniques like X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), Field emission scanning electron microscopy (FE-SEM), and UV–vis spectroscopy (UV–vis). The co-ordination of Ni in Co3O4 matrix, as well as M+nO bond lengths, were confirmed by the XAS studies. The standard mesoporous PSCs were fabricated by spin-coating a thin layer of NiCo2O4 (120 nm), and fabricated PSCs show an esteemed power conversion efficiency (PCE) of >14% (under standard illumination conditions) and long-term stability (under ambient condition RH = 30–40%) as compared to the spiro-based PSCs. To improve the device performance further we also fabricated the PSCs using the interfacial hole transporting layer, presenting a PCE of >16% with almost negligible hysteresis that is comparable to the normal standard PSCs based on spiro-OMeTAD as HTL. The performance of PSCs was further analysed by Electrochemical Impedance Spectroscopy (EIS), Photoluminescence (PL), Time-resolved Photoluminescence (TrPL) studies. The results showed the reduced recombination resistance in the PSCs using NiCo2O4 as well as interfacial layer. These outcomes indicate the effectiveness of NiCo2O4 interlayer for stable and highly efficient perovskite solar cells.

Gel polymer electrolytes (GPEs) with polyacrylonitrile (PAN)-based polymer, ethylene carbonate (EC) and propylene carbonate (PC) plasticizers, and different amounts of tetrabutylammonium iodide (TBAI) salt and iodine (I2) have been prepared and used in dye-sensitized solar cells (DSSCs). The maximum room temperature conductivity of 5.14 mS cm−1 is obtained for electrolyte with a composition of 8 wt% PAN-30 wt% EC-30 wt% PC-30 wt% TBAI-2 wt% I2 (S3 electrolyte) which influenced by the highest charge carrier density of 7.93 × 1020 cm−3 estimated from fitting the impedance Nyquist plot. The DSSC fabricated with S3 electrolyte revealed the highest power conversion efficiency of 3.45% with open-circuit voltage (Voc) of 582 mV and short-circuit current density (Jsc) of 12.9 mA cm−2. The incident photon-to-current conversion efficiency of the DSSC with highest efficiency is 54.01%. The electrical impedance spectroscopy of the same cell shows the lowest series resistance indicating the superiority of electrolyte charge transport characteristics in DSSC. In addition, electron transfer time constant τtr and electron recombination time τrec, charge collection efficiency ηcc, electron diffusion coefficient D and diffusion length LD of DSSC fabricated with GPEs prepared have been estimated by intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy techniques. The DSSC with highest efficiency shows lowest τtr of 34.46 ms and highest τrec of 90.41 ms due to the huge amount of TBA+ ions that covered the surface area of mesoporous TiO2. The ηcc of 0.62, D of 4.00 × 10−5 cm2 s−1 and LD of 19.02 μm further support the photovoltaic efficiency of DSSC.

Power conversion efficiency of perovskite solar cells (PSC) has improved around 500% in less than five years, with the current highest recorded efficiency of a standalone PSC of 25.2%. One of the significant components of PSCs that contribute to this improvement is the transport layer, necessary in the separation and injection of charge carriers. Over the years, organic hole transport layers (HTLs) such as 2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) have been investigated, developed, and utilized successfully, but facile and low-cost synthesis, good stability, yet efficient HTL remain to be major challenges. Therefore, alternative HTLs based on inorganic materials are being studied. This short review presents progress in the studies of an alternative HTL material for PSCs, Cu2ZnSnS4 (CZTS), known for the ease of synthesis and band tuning, composition based on abundant and non-toxic elements, good electrical properties, and superior stability. Focus is on the effects of integration of CZTS as HTL in PSC, and opportunities for further improvement.

Perovskite and perovskite/silicon tandem solar cells hold great promise for commercialization for their high efficiency and low cost. One of the major challenges for semi-transparent perovskite and tandem devices is the availability of suitable transparent electrodes. Here, we report an alternative high-performance cerium-doped indium oxide (ICO) transparent electrode with high mobility, low carrier concentration and high transmittance by Radio frequency (RF) magnetron sputtering at room temperature (RT) for thus applications. A high mobility of 51.6 cm2/Vs, a low resistivity of 5.74 × 10−4 Ω cm as well as a high average transmittance of 83.5% ranging from 400 nm to 1800 nm were obtain at RT. The spectral response of a planar semi-transparent perovskite solar cell (ST-PSC) proportion accelerated in 450–700 nm range and resulted in an absolute 1.1 mA/cm2 (from 17.38 to 18.48 mA/cm2) and 1.47 mA/cm2 (from 13.63 to 15.10 mA/cm2) short-circuit current improvement by replacing commercial ITO electrodes with ICO at different illuminate sides. Finally, the preliminary perovskite/silicon-heterojunction (SHJ) two-terminal tandem solar cell achieves a relative 8.06% improvement in power conversion efficiency (PCE) (from 18.85% to 20.37%) in the use of ICO transparent electrode, illustrating a promising alternative transparent electrode to further improve high-efficiency semi-transparent perovskite and its tandem solar cells.

Anisotropic mechanical strain as low as 0.1% modifies the electronic response of crystalline semiconductor-based devices and in particular affects the performance of solar cells. We measure the dark current-voltage characteristic of silicon heterojunction solar cells under different levels of tensile uniaxial stress and observe a reversible change of the j-V curve with applied strain. Using a two-exponential description of the j-V characteristic to fit our experimental data, we obtain the strain dependence of the diffusion saturation current and find a decrease of about 3% for a tensile strain level of 6.7×10-4. We compare these experiments to a theoretical model that accounts for the effect of strain on the band energy levels, densities of states and mobilities of carriers. The theoretical estimation of the change in saturation current is found to be in reasonable agreement with experimental results.

The passivated emitter and rear cell (PERC), with advantages of reducing rear surface recombination and improving rear surface reflectivity, is extensively applied in monocrystalline and multicrystalline silicon solar cells. In this study, we investigated the rear PERC structure with various contact patterns (type I to VI) and line spacings (800–1000 µm) using 156.75 mm × 156.75 mm p-type Czochralski mono crystalline silicon wafers. The void formation on the rear-side contacts of PERC structures played an important role in affecting conversion efficiencies. A smaller laser ablated opening width may easily lead to the formation of voids under screen printing and co-firing backside aluminum. Further evidence from the electroluminescence (EL) measurements confirmed that the higher laser ablation power would result in a slightly dark region for the solar cell with a rear-side contact opening width greater than 45 µm. The type III backside contact pattern (dash 2:1) with a line spacing of 900 µm surpassed all other contact patterns owing to its excellent aluminum back surface field. As a result, by optimizing both the backside contact pattern and line spacing of PERC solar cells, the best conversion efficiency of 22.25% and 20.9% for the average PERC solar cells were achieved.

As the crucial material of photovoltaic field, the development of polysilicon has attracted intense attention on reducing its cost and improving the polysilicon chemical vapor deposition (CVD) performance. Two-dimensional numerical models have been developed to investigate the local heat and mass transfer performance of polysilicon CVD system by introducing wave-like and trapezoid-like obstacles in the gas flow channels. Effects of different channel configurations on the local velocity, temperature, concentrations of six components, Nusselt number (Nu), Sherwood number (Sh) and seven coordinate angles along the flow direction are presented and detailed analyzed. The disturbing obstacles increase both the local and total Nu, as well as Sh. The seven coordinate angles caused by velocity vector, temperature gradient, and concentration gradient increase near the disturbing structures and decrease out of the disturbing obstacles. However, the disturbing obstacles decrease the total intersection angles leading better heat and mass transfer performance. In brief, compared to conventional straight channel, the proposed channels increase the gas flow velocity and, hence, improved the silicon CVD characteristics.

In this study, nickel oxide (NiOX) thin films were prepared by direct current (DC) reactive magnetron sputtering. The various properties of NiOX thin films including deposition rate, morphology, electrical and optical properties as well as grain structure and chemical composition were systematically investigated. The material properties of NiOX were finely modified under the monitoring of target voltage during sputtering. NiOX thin films were applied as hole transport layers (HTLs) in all-inorganic CsPbI2Br perovskite solar cells (PSCs). The highest efficiency of 12.6% had been achieved for the optimized all-inorganic CsPbI2Br PSCs with the inverted structure of Glass/FTO/NiOX(HTL)/CsPbI2Br/[email protected]60 (electron transport layer, ETL)/Ag. The PSC still yielded over 90% of its initial power output after 10 h operation without encapsulation.

Carbon quantum dots (CQDs) are emerging nanostructures which consist of carbon atoms and are typically below 10 nm in size. The CQDs are almost surface passivated or are functionalized with organics or biomolecules. CQDs have superior properties such as fluorescence emission, water-solubility, cheap and easy synthesis methods, low toxicity, biocompatibility, easy functionalization, and chemical inertness. The CQDs have found versatile applications in different areas such as in vivo and in vitro bioimaging, drug delivery, gene delivery, sensors, solar energy conversion, photoelectrochemical (PEC) cells, photovoltaic solar cells, photocatalysis, and light-emitting diodes (LEDs). CQDs could impart in photocatalytic reactions from two aspects; CQDs can be used alongside semiconductors as electron sink and could suppress electron-hole recombination and also CQDs can generate electron-hole pairs, as well. The CQDs with a wide spectral absorption and high absorption coefficients can enhance the photocatalytic activity. CQDs can also be used as sensitizers in the photoanode of solar cells. Due to the low cost and low toxicity of the CQDs in comparison to semiconductor quantum dots (QDs), they could be considered as potential alternatives in solar energy conversion applications. In this review, the CQDs are introduced and their optical properties are clarified. Recent advances of the CQDs in photocatalysis, PEC, and solar cells are reviewed.

Solar still water production enhancement was measured in experimental single-slope basin-type solar stills (BTSS) by perturbing the water surface of the still. The perturbation is achieved by the injection of air bubbles into the water basin, which produces surface ripples, thus increasing the overall evaporative surface area and stimulating the mass transfer coefficient. Overall, distilled water production is therefore enhanced as the evaporation improves. The position and flowrate of the air bubble injectors do not seem to affect the amount of evaporation increase. Two very low-tilt covered, shallow BTSS were operated simultaneously side by side. Only one of them was subjected to mass transfer enhancement, in order to produce conclusive mass transfer enhancement results. These results can be accommodated in a computer simulation program with the introduction of a simple intensification factor. Experimental work was carried out in the semi-desert, water-starved, highly insolated region of La Paz, BCS, Mexico.