Showing papers in "Solar Energy in 2019"

Modeling of solar energy systems using artificial neural network: A comprehensive review

Abstract: The development of different solar energy (SE) systems becomes one of the most important solutions to the problem of the rapid increase in energy demand. This may be achieved by optimizing the performance of solar-based devices under some operating conditions. Intelligent system-based techniques are used to optimize the performance of such systems. In present review, an attempt has been made to scrutinize the applications of artificial neural network (ANN) as an intelligent system-based method for optimizing and the prediction of different SE devices’ performance, like solar collectors, solar assisted heat pumps, solar air and water heaters, photovoltaic/thermal (PV/T) systems, solar stills, solar cookers, and solar dryers. The commonly used artificial neural network types and architectures in literature, such as multilayer perceptron neural network, a neural network using wavelet transform, Elman neural network, and radial basis function, are also briefly discussed. Different statistical criteria that used to assess the performance of artificial neural network in modeling SE systems have been introduced. Previous studies have reported that artificial neural network is a useful technique to predict and optimize the performance of different solar energy devices. Important conclusions and suggestions for future research are also presented.

Optimal sizing of an autonomous photovoltaic/wind/battery/diesel generator microgrid using grasshopper optimization algorithm

Abstract: This article focuses on the application of a latest nature-inspired metaheuristic optimization algorithm named Grasshopper Optimization Algorithm (GOA) in the area of microgrid system sizing design problem. The proposed algorithm is applied to an autonomous microgrid system in order to determine the optimal system configuration that will supply energy demand reliably based on the deficiency of power supply probability (DPSP) and cost of energy (COE). Firstly, a robust rule-based energy management scheme (EMS) is proposed to coordinate the power flow among the various system components that formed the microgrid. Then, the GOA is integrated with the EMS to perform the optimal sizing for the hybrid autonomous microgrid for five units of residential in an off-grid location in Yobe State, Nigeria. The proposed microgrid comprises of photovoltaic modules, wind turbine, battery storage system and a diesel generator. The effectiveness of the proposed GOA in solving the optimization problem is examined and its performance is compared with particle swarm optimization (PSO) and cuckoo search (CS) optimization algorithm. In addition, a sensitivity analysis is performed on the COE to highlight the impact of varying sensitive system inputs. The proposed optimization is programmed using MATLAB simulation package. The simulation results confirm that GOA is able to optimally size the system as compared to its counterparts, CS and PSO. In which, a decrement of 14% and 19.3% is achieved in the system capital cost, respectively.

Applications of hybrid nanofluids in solar energy, practical limitations and challenges: A critical review

Abstract: Solar energy is the ultimate perceived solution of incessantly proliferating energy crisis. Diverse range of solar energy conversion systems has been employed to convert solar energy into desired useful form. Performance of solar energy systems is subject to the type of the working fluid that they use for solar energy conversion and transportation. Application of hybrid nanofluids in solar energy systems as working fluid has turned out to be very gainful in terms of performance, owing to distinct thermal transportation characteristics of hybrid nanofluids. Current article has briefly reviewed the studies discoursing the performance of hybrid nanofluid based solar energy systems. Moreover, the performance of solar energy systems based on mono nanofluids has also been overviewed. Considering the importance, fabrication methods and characteristics of hybrid nanofluids as well as their implications on performance parameters of solar systems have been discussed. Reviewed studies have reported remarkable enhancement in power output and efficiency of these systems. However, there are several issues associated with hybrid nanofluids that have abstained the commercialization of binary nanofluid based systems. These issues include instability, increased friction factor, rheological issues, and increased pumping power. Subsequently, economic and ecologic gains of using binary nanofluids in solar energy systems are presented.

Electron and hole transport layers optimization by numerical simulation of a perovskite solar cell

Abstract: In this paper an n-i-p perovskite solar cell was studied using SCAPS simulator. The primary solar cell’s structure is FTO/ITO/Perovskite/PEDOT:PSS/Au which has achieved a power conversion efficiency of η ∼ 13.94%. In order to enhance its performance, several materials were suggested as electron and hole transport layers (ETL and HTL). Among the proposed ETL materials it was found that Zinc oxide (ZnO) and titanium dioxide (TiO2) are the most adequate materials. For the HTL materials, among the proposed materials Copper (I) thiocyanate (CuSCN) forms the appropriate one. Also, the solar cell performance was improved by optimizing the absorber thickness which was found to be 1 µm. With these considerations the power conversion efficiency reached 25.02%. In addition, the detrimental effect of defects at the perovskite/TiO2 interface on the solar cell performance is also presented.

Automatic classification of defective photovoltaic module cells in electroluminescence images

Abstract: Electroluminescence (EL) imaging is a useful modality for the inspection of photovoltaic (PV) modules. EL images provide high spatial resolution, which makes it possible to detect even finest defects on the surface of PV modules. However, the analysis of EL images is typically a manual process that is expensive, time-consuming, and requires expert knowledge of many different types of defects. In this work, we investigate two approaches for automatic detection of such defects in a single image of a PV cell. The approaches differ in their hardware requirements, which are dictated by their respective application scenarios. The more hardware-efficient approach is based on hand-crafted features that are classified in a Support Vector Machine (SVM). To obtain a strong performance, we investigate and compare various processing variants. The more hardware-demanding approach uses an end-to-end deep Convolutional Neural Network (CNN) that runs on a Graphics Processing Unit (GPU). Both approaches are trained on 1968 cells extracted from high resolution EL intensity images of mono- and polycrystalline PV modules. The CNN is more accurate, and reaches an average accuracy of 88.42%. The SVM achieves a slightly lower average accuracy of 82.44%, but can run on arbitrary hardware. Both automated approaches make continuous, highly accurate monitoring of PV cells feasible.

A review of photovoltaic systems: Design, operation and maintenance

Abstract: Nowadays renewable energies are becoming more important in the generation of electricity. Fossil resources do not present a sustainable option for the future since they are non-renewable sources of energy that contribute to environmental pollution. Within the sources of renewable generation, photovoltaic energy is the most used, and this is due to a large number of solar resources existing throughout the planet. At present, the greatest advances in photovoltaic systems (regardless of the efficiency of different technologies) are focused on improved designs of photovoltaic systems, as well as optimal operation and maintenance. This work intends to make a review of the photovoltaic systems, where the design, operation and maintenance are the key points of these systems. Within the design, the critical components of the system and their own design are revised. Regarding the operation, it is reviewed the general operation and the operation of hybrid systems, as well as the power quality. Finally, in relation to the maintenance of PV systems, it has been studied their performance, thermography and electroluminescence, dirt, risks and failure modes.

Modeling and experimental validation of a PVT system using nanofluid coolant and nano-PCM

Abstract: The photovoltaic/thermal (PVT) system is developed to combine the two separate systems to reduce the located area and cost, improve the efficiency and save lots of materials. However, different PVT designs and configurations had been proposed with air, water, nanofluid, phase change materials (PCM) and mix of these cooling methods. In this paper, a mathematical model was proposed for the new nanofluid/nano-PCM PVT system. Experiments had been conducted to validate the mathematical model results. The comparison confirmed the ability of the proposed mathematical model to satisfactory simulate and match the experimental results. The experimental and mathematical model results show that electrical and thermal efficiencies are 13.7%, 13.2% and 72%, 71.3% respectively. However, it is found that the maximum temperature registered in glass, PV cell, wax, and nanofluid are 41.2, 39.92, 38.8 and 36.5, respectively. The proposed mathematical model accuracy compared and validated with experiment results and shows a good consistent and agreement.

Thin film technology for solar steam generation: A new dawn

Abstract: The sun is considered as the most promising abundant renewable energy source that can be exploited to solve many of human beings’ challenges such as energy and water scarcity. Solar energy can be utilized in steam and vapor generation processes which has a great importance in many engineering applications such as water desalination, domestic water heating, and power generation. However, dilute solar flux (∼1000 W/m2) cannot supply the absorber with enough power required to overcome water latent heat of vaporization to evaporate water. Optical concentrators such as parabolic trough collector, parabolic dish reflector, and circular Fresnel lens can be used to concentrate the solar radiation to achieve the required power however they suffer from complexity and high cost. Moreover, the efficiency of the conventional solar desalination devices such as solar stills decreases dramatically with increasing bulk water quantity, due to the heat loss to bulk water. Therefore, the need to solar steam generation (SG) devices, that localize heating on a thin layer of water rather than the water bulk, arises. Thin film technology has shown promising progress in SG in which solar energy is utilized to wastewater desalination. The past five years have seen a significant surge in the development of thin film based SG devices. In this review, recently developed thin film-based SG devices are scrutinized with respect to their physical mechanisms, fabrication methods, structure, advantages, and disadvantages. Different types of thin-film materials, including: metal-based nanoparticles, metal oxides, carbon-based materials, polymers, etc.; as well as different substrates materials, including: wood, paper, cotton fabric, carbon fabric, polystyrene foam, and gauze, have been discussed. Moreover, different preparation and synthetization methods of the steam generation devices have been discussed. Suggestions for future research directions are also presented.

Hybridizing cuckoo search algorithm with biogeography-based optimization for estimating photovoltaic model parameters

Abstract: Accurate estimation of model parameters plays a very important role in modeling solar photovoltaic (PV) systems. In the past decade, meta-heuristic algorithms (MHAs) have been used as promising methods for solving this problem. However, due to the non-linearity and multi-modality existed in the problem, many HMAs may present unsatisfactory performance due to their premature or slow convergence. Therefore, how to develop algorithms efficiently balancing the exploration and exploitation, and identify the PV model parameters accurately and reliably is still a big challenge. In this paper, to improve parameter estimation of solar photovoltaic models, we propose a hybrid meta-heuristic algorithm, called biogeography-based heterogeneous cuckoo search (BHCS) algorithm. Specifically, BHCS hybridizes cuckoo search (CS) and biogeography-based optimization (BBO) by employing two search strategies, namely heterogeneous cuckoo search and biogeography-based discovery. The cooperation of the two strategies helps BHCS achieve an efficient balance between exploration and exploitation. Furthermore, the proposed algorithm is applied to solve four parameters estimation problems of different photovoltaic models, including single diode model, double diode model and two PV panel modules. Experimental results demonstrate that BHCS has very competitive performance in terms of accuracy and reliability compared with CS, BBO and several other meta-heuristic algorithms.

Performance analysis of MAPbI3 based perovskite solar cells employing diverse charge selective contacts: Simulation study

Abstract: The rapid development in the field of organo-metal halide perovskite solar cells (PSCs) has led to the report of power conversion efficiency of >25%. However, their large-scale deployment and possible commercialization endeavor are currently limited due to the presence of high-temperature processed electron transport material (ETM) such as TiO2 and the expensive hole transport material (HTM) in the state-of-the-art devices. By employing Solar Cell Capacitance Simulator (SCAPS)-1D, we attempted to propose low cost charge selective materials as ETM and HTM, which can deliver high photovoltaic performance. For this, the evaluation of TiO2, ZnO and SnO2 as ETMs was validated. Besides this, the role of thickness of ETMs was also investigated in a PSCs using CH3NH3PbI3 as light harvester and Spiro-OMeTAD as HTM. Our simulation results suggests that 90 nm of SnO2 layer outperforms as ETM for device fabrication. Furthermore, in our pursuit to avoid the usage of Spiro-OMeTAD, different organic and inorganic HTMs (P3HT, CuSbS2, Cu2O, CuSCN) have been investigated, and specifically the HTM thickness was optimized for high performance. We have found that by using the configuration of FTO/SnO2 (90 nm)/MAPbI3/CuSCN (100 nm)/Au a PCE of 26.74% with a Voc of 1180 mV can be acheived. The role of metal cathode work function was also studied to replace the expensive gold (Au) electrode.

An improved P&O algorithm integrated with artificial bee colony for photovoltaic systems under partial shading conditions

Abstract: For an efficient Photovoltaic (PV) system, tracking of true maximum power point (MPP) is essential. Therefore the maximum power point tracking (MPPT) controller is mandatory for harvesting maximum power from the solar panel. Perturb and Observe (P&O) MPPT is the simplest and most widely used low-cost MPPT method for tracking MPP. The major drawback of P&O is steady state oscillations around MPP and tracking of local MPP (LMPP) instead of global MPP (GMPP) under partial shading conditions (PSC). Thus, this paper proposes a modified P&O MPPT that can be used under PSC effectively, by integrating Artificial Bee Colony (ABC) algorithm in the first stage and P&O algorithm in the second stage. In the proposed method GMPP is first tracked by calling ABC algorithm followed by the P&O algorithm for LMPP. Thus the local search ability of P&O and global search ability of ABC are effectively combined to produce optimum duty cycle for the boost converter in a fast and efficient way. In this paper, the proposed ABC-PO algorithm is implemented in MATLAB/Simulink model and it is compared with different MPPT algorithms such as P&O, Incremental conductance (INC) and ABC. The simulation results clearly depicted that the proposed ABC-PO algorithm gives more than 99.5% efficiency under PSC.

Dynamic global maximum power point tracking of the PV systems under variant partial shading using hybrid GWO-FLC

Abstract: Maximum power point tracker (MPPT) techniques have been used to extract the maximum power available form photovoltaic (PV) energy systems. Conventional MPPT techniques like perturb and observe (PO one global maximum power point (GMPP) and many local maximum power points (LMPPs). Most of conventional MPPT techniques may stick to one of the LMPPs, which reduce the MPPT efficiency of PV systems. Soft computing techniques like particle swarm optimization (PSO), gray wolf optimization (GWO), and Cuckoo search optimization (CSO) etc. can catch the GMPP of PV system under the same PSC. These latter techniques suffer from two problems, the first problem is the high oscillations around the GMPP, the second problem is that, they cannot follow the new GMPP once it changed its position due to the searching agents will be busy around old GMPP caught. The solution of these two problems are the motivation of this research. GWO has been used to catch the GMPP and the problem of oscillations around the GMPP has been solved by hybridizing this technique with fuzzy logic controller (FLC) for soft tune the output generated power at the GMPP. The FLC characterizes by accurate GMPP catching with almost zero oscillations. The second problem is solved in this paper by reinitializing the GWO with two new initialization techniques. The results obtained from GWO-FLC with two different re-initialization techniques have been compared to the results of PSO without reinitializing its particles. The results obtained from this work prove the superior performance of the new proposed technique in terms of dynamic GMPP catching and MPPT power efficiency in case of time variant PSCs.

Feasibility design and techno-economic analysis of hybrid renewable energy system for rural electrification

Abstract: This paper validates the optimal design and techno-economic feasibility of hybrid renewable energy system (HRES) for rural area electrifying applications Plan to a design of improved performance electrification system through village owned renewable resources, such as solar irradiations, wind speed and bio mass etc The selected HRE system has to meet out electrical needs in optimum performance manner Hear conducted a case study on remote village Korkadu is located in Union Territory of Pondicherry, India The expected village demand of 17932 Kwh/day and peak of 1956 Kw was met with proposed HRE structure, which is consists of solar PV array, wind turbine, Bio mass power generator and Battery backup system in effectively Load growth of the village was predicted through artificial neural network (ANN-BP) feed-back propagation and Levenberg-Marguardt (LM) data training optimum technique Encounter the optimum performance of different HRE configuration was evaluated over by HOMER software System’s economic dispatch was analysed through various dispatch strategy and come across the proposing companied dispatch strategy has more economical and performance benefits as total NPC of system as INR 121 million, one unit energy generation cost as INR 1371 and annual battery throughput as 36648 KWh/yr This study also expresses the comparison analysis between proposed HRES structure performance with basic utility grid extension The consequence of the proposed work shows the HRES in remote location can be a cost effective solution for sustainable development of rural regions

Toward development of high-performance perovskite solar cells based on CH3NH3GeI3 using computational approach

Abstract: We reported numerical simulations of device performances made of methylammonium germanium halide (CH3NH3GeI3)-based perovskite solar cells. The main goal here is to seek for an efficient method to improve the device efficiency of alternative lead-free perovskite based on germanium solar cells by using various organic and inorganic hole transport materials. For that aspiration, the effect of several parameters on the solar cell performance were investigated such as thicknesses of perovskite, HTM, defect density, hole mobility, and metal electrode work function on the charge collection. The device simulation revealed that the optimum thickness of CH3NH3GeI3 absorber is found around 600 nm. Furthermore, Ge-based perovskite solar cells with Cu2O and D-PBTTT-14 as HTM exhibited a remarkable overall power conversion efficiency reaching 21%. The defect density reduction is a critical factor to improve the solar cell performance and should be controlled under the order of ∼1015 cm3. Further simulations were performed to study the effect of operating temperature on the performance. Our simulation results advocate for a viable route to design hole-transporting materials for highly efficient and stable perovskite solar cells with low cost.

Numerical study of Cs2TiX6 (X = Br−, I−, F− and Cl−) based perovskite solar cell using SCAPS-1D device simulation

Abstract: The present work represents the study of numerical simulation of Cesium Titanium (IV) Halide thin film based lead-free Perovskite Solar Cells (PSCs) using Solar Cell Capacitance Simulator (SCAPS). For this study, an alternative inorganic material cell architecture CuSCN/Cs2TiX6/CdS/Si has been proposed, where X is halide like Br, I, F and Cl. The effects of variation in absorbing layer thickness and device working temperature on the solar cell performance were simulated through SCAPS simulator. This simple cell architecture has helped us to study and optimize the device parameters. The 1D optimization for the proposed lead-free Perovskite based solar cell resulted in optimized active layers thickness, device temperature and quantum efficiency for Cs2TiBr6, Cs2TiI6, Cs2TiF6 and Cs2TiCl6 active materials. The study resulted in optimized thickness of 1.0 µm, 1.5 µm, 1.5 µm and 1.5 µm for Cs2TiBr6, Cs2TiI6, Cs2TiF6 and Cs2TiCl6 active materials, respectively. The optimized device temperature was found to be at 80 °C for Cs2TiBr6, 60 °C for Cs2TiI6, 75 °C for Cs2TiF6 and 75 °C for Cs2TiCl6.

Reconfiguration strategies for reducing partial shading effects in photovoltaic arrays: State of the art

Abstract: Power delivered by a Photovoltaic (PV) cell reduces significantly due to non-uniform irradiance. Consequently, in the case of PV module or array, the generated output power get reduces and further deteriorates the overall system performance. The reduction of output power is not directly proportional to the shading area but depends on the shading pattern and type of array configuration chosen. Many solutions have been reported in the literature to reduce partial shadings. However, the reported solutions may fail to enhance maximum power to the possible extent. Therefore, to compensate these power losses a promising technique is required which relies on reconfiguration strategies, namely reconfigure the PV modules within the PV array in order to increase maximum power at a higher level. These strategies are classified into dynamic and static reconfiguration techniques. This paper presents the state of the art of reconfiguration strategies for PV array’s to increase maximum power under partial shading and mismatch conditions. In addition to this, the challenging issues for hardware implementation of both dynamic and static reconfiguration techniques are discussed in this paper. Based on the review study, it can be concluded that the dynamic reconfiguration techniques are relatively expensive, but this can effectively compensate the partial shading and mismatch effects in PV array as compared to static technique.

Experimental performance evaluation of single basin dual slope solar still with circular and square cross-sectional hollow fins

Abstract: The paper encompasses the experimental performance evaluation of double slope single basin solar still with circular and square cross-sectional hollow fins. Mild steel circular hollow fins (25 mm diameter, 20 mm height and 2 mm thick) and mild steel square hollow fins (25 mm side length, 20 mm height and 2 mm thick) were welded upon two different mild steel absorber plates, having a dimension of 300 mm × 600 mm × 2 mm. The performance of the double slope single basin solar still was carried out at the location 20.61°N, 72.91°E. The productivity was evaluated for the variation of water depth (10 mm, 20 mm and 30 mm) in basin for the square fin and circular fin solar stills. The results depict that 10 mm water depth is more productive basin water depth for the both solar stills among the different variants. The maximum distilled water output of 1.4917 kg/m2-day was obtained from the circular finned solar still for the 10 mm basin water depth, whereas the square finned solar still was achieved the maximum distilled water output of 0.9672 kg/m2-day.

Numerical and outdoor real time experimental investigation of performance of PCM based PVT system

Abstract: Photovoltaic power generation is a suitable option to counter depleting and environmentally hazardous fossil fuels. However, increased cell temperature of the photovoltaic module reduces the electrical performance. Therefore, for enhancing the electrical performance as well as to obtain the useful thermal, a combined photovoltaic thermal system is suitable technology. Furthermore, the addition of phase change materials into photovoltaic thermal systems adds more dual benefits in terms of cooling of PV cell as well as heat storage. Hence, there are still issues to transfer heat from the system efficiently, which cause lower performance of PVT and PVT-PCM systems. In this paper, the aluminium material of thermal collector is used by introducing a novel design to enhance heat transfer performance, which is assembled in PVT and PVT-PCM systems. Experimental validation is carried out for the 3D FEM-based numerical analysis with COMSOL Multiphysics® at 200 W/m2 to 1000 W/m2 varying irradiation levels while keeping mass flow rate fixed at 0.5LPM and inlet water temperature at 32 °C. The experiment is carried out at outdoor free weather conditions with passive cooling of the module by an overhead water tank scheme. A good agreement in numerical and experimental results is achieved through experimental validation. Cell temperature reduction of 12.6 °C and 10.3 °C is achieved from the PV module in case of the PVT-PCM system. The highest value of the electrical efficiency achieved is 13.72 13.56% for PV and 13.85 and 13.74% for PVT numerically and experimentally respectively. Similarly, for PVT-PCM, electrical efficiency is achieved as 13.98 and 13.87% numerically and experimentally respectively. In the case of the PVT system, electrical performance is improved as 6.2 and 4.8% and for PVT-PCM, it is improved as 7.2 and 7.6% for numerically and experimentally respectively.

Factors affecting the thermal performance of the flat plate solar collector using nanofluids: A review

Abstract: Exploitation of solar energy is one of the most significant solutions for facing the current energy management dangers. Flat plate solar collector (FPSC) is one of the most important applications of solar energy in different domestic applications. The use of nanofluids in FPSCs, due to their superior thermo-physical properties, makes it an effective way to enhance the performance of FPSCs. This paper sequentially reviews the studies carried on metal, metal oxides, semiconductor crystalized oxides, and carbon based nanofluids used as heat transfer fluid (HTF) within FPSCs. Various parameters that affect thermal performance of the FPSC such as type of nanoparticle, nanoparticle concentration, nanoparticle size, and mass flow rate of the nanofluid are extensively analyzed in this review. The studies examine different types of single nanofluids or hybrid nanofluids with the FPSC at the same operating conditions are also discussed. Based on the results reviewed in this work, it is revealed that a significant improvement in energy and exergy efficiencies of the FPSC have been obtained by using carbon based nanofluids compared to metal oxides nanofluids under the same conditions. It is also found that the copper oxide nanofluid is the best amongst the metal oxides nanofluids as it improves the efficiency by 6.3–37.3% compared to conventional fluids when it is used with concentration varied from 0.025 to 2%, and mass flow rate ranges from 1 to 8.8 kg/min. A noteworthy observations, proportionalities, and future trends for each nanostructure type are also discussed with detailed and comparative approach.

Parameter estimation of photovoltaic models with memetic adaptive differential evolution

Abstract: Parameter estimation of photovoltaic (PV) models plays an important role in the simulation, evaluation, and control of PV systems. In the past decade, although many meta-heuristic methods have been devoted to parameter estimation of PV models and achieved satisfactory results, they may suffer from consuming large computational resources to get promising performance. In order to fast and accurately estimate the parameters of PV models, in this paper, a memetic adaptive differential evolution, namely MADE, is developed. The proposed MADE can be featured as: (i) the success-history based adaptive differential evolution is used for the global search; (ii) the Nelder-Mead simplex method is employed for the local search to refine the solution; and (iii) the ranking-based elimination strategy is proposed to maintain the promising solutions in the external archive. To verify the performance of our approach, it is applied to estimate the unknown parameters of different PV models, i.e., the single diode model, the double diode model, and the PV module. Experimental results obtained by MADE are compared with several state-of-the-art methods reported in the literature. Comparison analysis demonstrates that the proposed MADE exhibits remarkable performance on accuracy and reliability. It also consumes less computational resources than other compared methods.

Performance analyses of mixed mode forced convection solar dryer for drying of stevia leaves

Abstract: In the present work, experimental investigations carried out on drying of Stevia leaves in a newly developed solar dryer of mixed mode forced convection type (MFSCD) and open sun drying (OSD) are presented. Experiments have been performed under the average solar radiation of 567 W/m2, ambient temperature of 30 °C and drying air flow rate of 0.049 kg/s. The safe (final) moisture content of stevia leaves 0.053 (d.b) has reached in 330 min and 870 min of drying time in MFSCD and OSD, respectively. The overall dryer efficiency and average exergy efficiency of the MFSCD were found as 33.5% and 59.1%, respectively. Quality analyses were carried out for fresh, open sun-dried and solar dried stevia leave samples. It was found that the anti-oxidant and the flavonoids were rich in solar dried samples compared to that of OSD samples. The color preservation is good in solar dried samples compared to OSD. Sensory analysis (flavor, aroma and taste) carried out on stevia leaves indicated that the solar dried stevia leaves provided better score compared to OSD samples. The estimated payback period of the newly developed dryer was found as 0.65 yr.

Latent thermal energy storage for solar process heat applications at medium-high temperatures – A review

Abstract: Solar thermal energy has the potential to cover the heat demands of industrial processes. However, there may be a time mismatch between energy supplied by the solar field and the process demand. In this case, a thermal energy storage (TES) allows the use of heat at hours without solar irradiation available. Thermal energy storage for solar hot water or heating systems using low temperatures have been optimized since many decades and are in a mature stage. Developments at high temperatures (above 200 °C) for CSP applications have also been deeply studied. However, until this present paper, limited attention has been paid to TES for solar thermal industrial applications at medium-high temperatures (120–400 °C), where there is a potentially huge demand. When talking about TES several aspects have to be discussed: the heat demand that TES is going to be designed to supply, the material where the energy will be stored and the performance of the TES system which includes not only the material but also tanks, piping and connections. In this review, food, brewery and chemical industries were identified as the industries with higher potential in which TES and solar energy could be integrated. Heat integration methodologies have been reviewed to optimize the use of the solar energy in the industrial processes. Regarding the material, latent heat storage or phase change materials (PCM) were selected for this study because they are a very promising type of storage to be integrated in thermal industrial processes, although the state of the art of latent heat thermal energy storage (LHTES) systems is still far from broad commercialization. Until now, no reviews of latent heat storage for industrial applications at medium-high temperatures (120–400 °C) have been published. Therefore, literature related to PCM and latent heat storage (LHS) systems to be used in industrial thermal processes is here reviewed in order to have a general overview of the available technologies for their integration together with solar thermal energy in industrial processes at both experimental and numerical level. More than 100 potential PCMs for heat storage applications in the range of temperatures 120–400 °C have been found. Inorganic eutectic compositions are the group with more potentially available PCM for these applications, with values of heat of fusion between 74 and 535 kJ/kg. Finally, the works related to the performance of the system from the experimental and modelling point of view were presented. The review of experimental TES systems which include PCM in the studied range of temperatures 120–400 °C showed that most of the experimental set-ups were developed for direct steam generation for CSP applications. Regarding numerical modelling, the type of configuration more simulated is the shell and tube configuration.

Comprehensive review on effect of dust on solar photovoltaic system and mitigation techniques

Abstract: The power sector has been facing the problems of the continuous increase in demand and lack of sufficient generation of electric energy using fossil fuels. The environmental problems (pollution and global warming), the continuously increasing cost of fossil fuels and the shortage of fossil fuels are mainly concerned to harvest energy from sustainable and clean sources. One of the promising sustainable energy sources is solar energy. Electrical energy can be produced from solar radiation by using the photovoltaic system. Though, power generation from PV solar system is not yet viable because of its low efficiency. Apart from low efficiency, other factors, especially environmental factors such as dust, hail, humidity and temperature and installation elements such as tilt angle, installation site, and altitude influence the performance of the PV module. This study reviews the currently available works on the subject of causes of dust deposition on the surface of the PV module, the impact of dust settlement on the electrical, optical and thermal characteristics of PV module. This paper also synthesizes current understanding of the effect of the hailstorm on the PV module and provides a prospectus for future research on this topic. A protecting system for the PV module from the hailstorm is needed to develop. The current review also summarizes the past, present studies of different types of mitigation technique so that it can be helpful in choosing the most suitable method for dust cleaning.

Nanostructured photoanode and counter electrode materials for efficient Dye-Sensitized Solar Cells (DSSCs)

Abstract: The access of dye-sensitized solar cells (DSSCs) in the photovoltaic market is still a challenge owing to low power-conversion-efficiency (PCE) and stability. The foremost aim of this review is to emphasize the technical issues in DSSCs that reduce their efficiency. A DSSC consists of glass substrates, photoanode, photosensitizer, electrolyte and catalytic counter-electrode. Electrode materials play a critical role in the photovoltaic (PV) performance of DSSCs. The PV performance of DSSCs depends on many factors e.g. electron collection at photoanode, light harvesting efficiency of photoanode, a scattering of electrons inside the photoanode, and the fast reduction of an electrolyte at the counter electrode. In this review, physical, electronic, and morphological properties of electrodes materials will be examined for efficient DSSCs. This review paper comprises of four parts. First part highlights the importance, structure and charge transport mechanism of DSSCs. The second section describes the types, electronic and morphological properties of photoanode materials. The third part covers the nature and catalytic properties of materials used for counter-electrodes. Finally, challenges, market and future directions of DSSCs will be described in the last part of this review.

Methodology of Köppen-Geiger-Photovoltaic climate classification and implications to worldwide mapping of PV system performance

Abstract: Photovoltaic (PV) already proves but even more promises to be massively deployed worldwide. To evaluate the performance of PV systems globally and assess risk due to different climate conditions, we propose a methodology for the global Koppen-Geiger-Photovoltaic (KGPV) climate classification that divides the globe into 12 zones with regard to the temperature, precipitation and irradiation, and standardizes the evaluations of the performance in regions with similar climatic conditions. Additionally, we present implications of KGPV to simulated PV performance using monthly data, for current and future operation of PV systems worldwide including climate change scenarios. A set of electrical and thermal performance indicators of crystalline silicon PV modules in different KGPV zones is analyzed and their evolution over time due to climate changes caused by high greenhouse gas emissions discussed. Results show that the KGPV scheme proves to be a convenient methodology to relate the KGPV climate zones with PV performance.

Optimization and assessment of floating and floating-tracking PV systems integrated in on- and off-grid hybrid energy systems

Abstract: Considering the targets of Thailand in terms of renewable energy exploitation and decarbonization of the shrimp farming sector, this work evaluates several scenarios for optimal integration of hybr ...

The effect of dust accumulation and cleaning methods on PV panels’ outcomes based on an experimental study of six locations in Northern Oman

Abstract: The Sultanate of Oman, similar to other GCC countries, is affected by the fluctuation of oil prices, which led the decision-makers in this country to move towards renewable energy and particularly the establishment of photovoltaic (PV) solar power plants. This step requires a thorough study before spending millions of dollars to build such power plants. Since dust is one of the main problems of PV in the GCC countries, this study investigates the influence of certain weather factors such as wind speed, relative humidity on dust accumulation and the effect of the cleaning method applied to each city separately. After a full year of observation and data collection on climatic conditions and the output of the six systems installed and used in this study, it is found that the cities of Liwa and Sohar, followed by Muscat, exhibit the highest percentage of dust and contaminants. The most prominent pollutants are the particulate matters (PM) from the chimneys of the power plants, and smelters in the industrial city of Sohar. Also, the movement of a considerable number of vehicles in Muscat caused a rise in the concentration of PM deposited on PV cells. For the other three cities (Al-Khabourh, Suwaiq, and Shinas), they are far from any industrial zone, and because of reduced traffic, the percentage of accumulation of dust and pollution of PV cells was limited. Nine available methods have been used to clean the PV cells after the dust accumulated for one month. From these methods, it is found that the use of water is sufficient to wash the PV cells in the cities of Al-Khaburah, Shinas, and Al-Suwaiq, but the effect of cleaning is more reduced on Sohar, Liwa, and Muscat. Because of PM and many chemical compounds, the use of a sodium solution was the best option in cleaning the PV cells of these three cities. It was noted that the loss of solar cell productivity decreases during the rainy season, which acts as a natural cleaner for the PV. The study also found that dew in the cities studied before sunrise causes the interaction of some salts of sodium, magnesium, and calcium and builds a layer of cohesive salts, which are difficult to clean.

Review on greenhouse microclimate and application: Design parameters, thermal modeling and simulation, climate controlling technologies

Abstract: This paper provides an updated literature review about greenhouse systems and helps to identify the most preferable characteristics of a greenhouse for diverse climates and operating conditions. Data on appropriate properties of the covering materials and comparisons of several cladding materials were extensively discussed. The selection process of the greenhouse shape and orientation for different climates is presented, and comparisons between several shapes and orientations are made. This paper also examines the existing thermal models and simulation tools used to optimize the thermal operating conditions of the greenhouse. Furthermore, many recent studies are presented where greenhouses are combined with several systems to provide a favorable microclimate for crops, under extreme, tropical and subtropical climates. Finally, other applications such as greenhouse dryers and seawater greenhouse desalination are also discussed.

A review of solar thermal energy storage in beds of particles: Packed and fluidized beds

Abstract: This review summarizes different solar thermal energy storage techniques from a particle technology perspective, including sensible, latent and thermochemical techniques for low- and high-temperature applications that use particles as the storage medium in the thermal energy storage system. The focus is on applications, experimental results, modeling and future trends. This review describes two different particle technologies used to store thermal energy: packed and fluidized beds. The advantages and disadvantages of both technologies are reviewed throughout different studies found in the literature for various thermal energy storage systems. Packed beds have the main advantage of thermal stratification, which increases the efficiency of solar collectors in low-temperature sensible energy storage systems and augments the exergy content in the bed. Moreover, they have been proven to be suitable as dual-media thermocline storage systems for CSP plants. In contrast, the high mixing rates of fluidized beds makes them suitable for the rapid distribution of concentrated solar energy in particle receiver CSP systems. In addition, their high heat and mass transfer rates, compared with those of packed beds, make them the preferred particle technology for thermochemical energy storage applications. This review also notes that it is important to find new materials with an appropriate size and density that can be properly used in a fluidized bed. Additionally, more specific research efforts are necessary to improve the understanding of the behavior of these materials during the fluidization process and over a high number of charging/discharging cycles.

Performance analysis for hybrid PV/T system using low concentration MWCNT (water-based) nanofluid

Abstract: This paper presents experimental work on utilising Nanofluid as a working agent for Photovoltaic Thermal Systems (PV/T). PV/T systems are one kind of hybrid systems in energy utilisation. They convert the incident solar radiation into two energy types; electricity and heat. In this research, experimental outdoor tests were directed to assess the execution of PV/T system that utilises water-based Multi Walls Carbon Nano Tubes “MWCNT” as a heat storage/heat absorption agent. The effect of varying Nanofluid volume concentration ratio was studied within the range (0%:0.3%) while fixing the circulation rate at 1.2 l/min. By analysing the experimental results, it can be noted that adding Nano Particles to the base fluid caused the thermal properties to have a significant increment leading the PV/T system to have a better thermal and electrical efficiency. The best system efficiencies were obtained at 0.075% V of MWCNTs – water based Nanofluid. At this concentration, a temperature reduction of 12 °C for the PV panel was attained at maximum incident radiation leading to an overall system efficiency of 83.26%. Also, an average temperature reduction of 10.3 °C was achieved over the daytime leading to an overall efficiency of 61.23%.