Solar Energy Research Research Articles

A high-resolution three-year dataset supporting rooftop photovoltaics (PV) generation analytics

This paper presents an open-source dataset intended to enhance the analysis and optimization of photovoltaic (PV) power generation in urban environments, serving as a valuable resource for various applications in solar energy research and development. The dataset comprises measured PV power generation data and corresponding on-site weather data gathered from 60 grid-connected rooftop PV stations in Hong Kong over a three-year period (2021-2023). The PV power generation data was collected at 5-minute intervals at the inverter-level. The meteorological data was collected at 1-minute intervals from an on-site weather station. The metadata was represented using the Brick schema, which simplifies data comprehension and the development of smart analytics applications. This paper provides a detailed description on the site specifications, data collection method, data records, and data validation. This dataset can be used in various applications - PV generation benchmarking, PV degradation analysis, PV fault detection, solar radiation and PV power generation forecasting, and the simulation and design of PV systems.

The Advancement of Silicon as A Photovoltaic Material: Historical Accomplishments, Present Efficiency and Future Development

In today's society where energy and environmental issues are increasingly gaining attention, research, development, and utilization of renewable and clean energy continuously attract the interest of academia, environmental protection, and business alike. Its application has already entered people's lives and is gradually expanding its market share. As a result, there is a growing demand for more efficiently designed, environmentally friendly and less costly new energy devices. Among various energy resources such as tidal, wind or geothermal, solar energy stands out as the most widely used clean and renewable resource. Given that solar energy is virtually limitless for humans, the function of solar cells in converting solar energy to electricity demonstrates significant social, environmental, and economic benefits. For the development of solar energy and new research, photovoltaic materials are crucial. Non-toxic and with excellent photovoltaic properties, silicon is the second most abundant element in the Earth's crust and the most abundant in water. Since crystalline silicon solar cells produced for the first time in 1954, silicon has held the most important material position in photovoltaic cell manufacturing and maintained market dominance. The importance of silicon solar cell research, its development and current status are briefly outlined in this paper. It reviews the advantages and disadvantages of existing silicon-based photovoltaic materials and potential future developments. As a photovoltaic material, silicon holds significant advantages compared to others, suggesting a broad scope for both research and commercial prospects in the long term.

Electronic and optical properties of Sb2Se3 and Sb2S3: theoretical investigations

Abstract In recent developments in solar energy research, Sb2Se3 and Sb2S3 emerge as environment friendly photovoltaic absorber materials, distinguished by their narrow bandgap and high absorption coefficient. Theoretical investigations to determine the electronic structure, effective density of states, dielectric function, and absorption coefficient of Sb2Se3 and Sb2S3 crystals have been performed using first-principle methods. The results reveal band gap values of about 0.822 and 1.757 eV (PBE method), 1.114 and 1.778 eV (HSE06 method) for Sb2Se3 and Sb2S3, respectively. The valence band and conduction band edges are primarily formed by Se 4p, S 3p, and Sb 5p hybridized orbitals. The effective density of states (DOS) exhibit magnitudes on the order of 1019 cm−3. Notably, anisotropic characteristics are observed in the real and imaginary parts of the dielectric function. Furthermore, the absorption coefficient surpasses 105 cm−1 at 1 and 1.2 eV for both Sb2Se3 and Sb2S3. The result indicates that these highly efficient absorber materials are suitable in collecting solar energy.

From Catalyst Ink to PEM Fuel Cell Stack: First Full-Size Screen Printed Catalyst Layers Tested within a Generic Stack

The PEM fuel cell industry is currently facing the challenge of upscaling its production, trying to reduce costs, allowing the fuel cell an easier entry in the mobility sector. Therefore, research on developing production processes, increasing throughput rates and quality control along the value chain is of special interest. Often, new materials, which show enhanced performance or durability are developed on very small scale. However, their key properties need to be investigated from a perspective of scalability, starting from catalyst ink to stack-level.Fraunhofer ISE and Center for Solar Energy and Hydrogen Research (ZSW) had the unique opportunity to investigate the production parameters along the whole value chain of a PEM fuel cell: starting with the catalyst ink at Fraunhofer ISE and ending with a generic stack at ZSW [1]. This generic stack is the approach to have a standardized open access stack design for the industry and research community with the size (active area 283cm²) and power output corresponding to the current automotive market, developed by ZSW and EKPO [2].In this study, the catalyst ink volume and catalyst layer area have been upscaled in a sheet-to-sheet process to meet the requirements of the generic stack automotive size membrane electrode assemblies (MEAs) with focus on heavy duty vehicles, hence aiming for platinum loadings of 0.4 mg/cm² (cathode) and 0.1 mg/cm² (anode). With on small scale proven ink recipes, specifically developed for screen printing cathode and anode electrodes [3], more than 50 catalyst layers have been produced with an upscaled area of 378cm² by a semi-automatic industrial screen printer. Flatbed screen-printing is a well-developed high throughput printing technology, known from printed electronics and solar cell metallization industries. Its benefit lies in the printability of high layer thicknesses with less solvent mass (high viscous pastes) and its degree of freedom to manufacture any structure, enabling platinum reduction in the electrodes by catalyst layer design.The catalyst coated membranes (CCMs) have been manufactured by a decal transfer on state of the art membranes with a roll-calendar. Special focus lies on this challenging transfer process for larger active areas. Two different membrane types, two different decal foils and different transfer process parameters like velocity and temperature have been investigated for all. The optical and gravimetrical transfer yields are the most important quality parameters during transfer because they strongly affect the costs of CCM production, especially when platinum material is not transferred, sticking to the decal foil. The optimal transfer parameters have been chosen to further produce MEAs towards stack-level. Afterwards, the CCMs were cut to fit the generic stack format and sent to ZSW in Ulm, Germany.At ZSW, the sub gaskets and gas diffusion layers (GDLs) from SIGRACET® SGL 22BB have been applied to form the 7-layer MEA. 15 CCMs have been stacked with bipolar plates and sealed to form a short stack. In addition, 15 commercially available CCMs were added as reference to the same stack. The whole manufacturing process chain is seen in Figure 1. After conditioning, the polarization curves have been measured at two different gas pressure settings. All other operating conditions were kept the same.As can be seen in Figure 2, the screen printed CCMs from Fraunhofer ISE (red) show very similar performance in comparison to the commercial reference (black) within the stack. In addition, the voltage deviation between the CCMs is slightly smaller for the ISE-CCMs, indicating a very good reproducibility in production. This study showed for the first time that screen printed catalyst layers can be upscaled to industrial active areas, overcoming challenges in printing, drying and transfer, while reaching similar performance as commercial references in a short stack. In future experiments many more iterations along the production chain will follow, to further improve the stack performance and investigate the effect of production pathways, process parameters and new materials.[1] “HyFab-BW - HyFab-Baden-Württemberg”, https://www.ise.fraunhofer.de/en/research-projects/hyfab-bw.html; Fraunhofer ISE, accessed April 2024[2] “Manufacturer-independent fuel cell stack: an innovative development platform for industry and science”, https://www.zsw-bw.de/en/research/fuel-cells/topics/stack-technology.html; ZSW; accessed April 2024[3] L. Ney, J. Hog, R. Singh, N. Göttlicher, P. Schneider, S. Tepner, M. Klingele, R. Keding, F. Clement, U. Groos, J Coat Technol Res 20 (2023) 73–86. https://doi.org/10.1007/s11998-022-00710-1. Figure 1

Development of an optical method to align a high-flux solar furnace.

High-flux solar furnaces are valuable tools for applied research and development in solar energy. However, misalignment of concentrator facets can produce optical losses and lower the concentration ratio of these systems. This study proposes a practical method to align a faceted solar furnace. The optical method uses a computer projector that illuminates the facets with a well-defined light pattern to quantitatively and qualitatively determine any misalignment associated with the mirrors. Through the Monte Carlo ray-tracing technique, the complete solar furnace, projector, and observation plane are optically modeled for the development of the methodology. A theoretical sensitivity analysis of the technique is reported, along with the experimental validation of the determined mirror misalignments, which results in a detection accuracy of 0.32mrad.

Building Thermal Insulation Performance and economic benefits

Three different insulating scenarios were investigated using Energy-plus software, to study the effect of using expanded polystyrene boards on building energy consumption at the Libyan Center for Solar Energy Research and Studies. The three insulation scenarios with different polystyrene insulation thicknesses and densities were investigated. Polystyrene total cost, Payback period, total and net money saving using insulation, as well as the percentage gain were calculated for each case in the three investigated scenarios for 50 years. The most money saving scenarios after 50 years is by insulating the building roof and external walls with an average insulation thickness of 7 cm, reaching about 78000 L.D and a tariff of 0.9261 L.D /kWh. While the least money saving is the roof scenario with an insulation thickness of 2.5 cm, reaching more than 29000 L.D and the same tariff. The highest percentage gain values are 76 %, 103 % and1090 % at the roof scenario, 2.5 cm insulation thickness and energy tariffs of 0.15 L.D /kWh, 0.1732 L.D/kWh and 0.9261 L.D/kWh, respectively. While the lowest percentage gain values are about 17.5 %, 35.7 % and 725 % at the wall scenario 10 cm insulation thickness and energy tariffs of 0.15 L.D/kWh, 0.1732 L.D/kWh and 0.9261 L.D/kWh, respectively. the payback period of total insulation cost is significantly dependent on insulation thickness and energy tariff. These results show that low energy tariff (current energy tariff) values economically are not cost effective regarding the payback period. Consequently, prices do not motivate residents to save energy with the use of thermal insulation unless actual energy prices are considered.

Scientometric Trends and Impact of Solar Energy and Waste-to-Energy Research (2008-2022): Insights into Growth, Citation Patterns, and Collaboration

Research on solar energy and waste-to-energy technologies has expanded due to the growing emphasis on sustainable energy sources, and scientometric studies have provided valuable insights for future directions in these areas. The study examines the scientometric trends and impact of research in solar energy and waste-to-energy from 2008 to 2022, focusing on key indicators such as citation rates, growth rates, publication efficiency, and collaboration patterns. The study analyzed 17,469 research papers on solar energy and 8,149 on waste-to-energy published from 2008 to 2022 using scientometric methods. Key indicators, such as average citations per paper, annual growth rate, exponential growth rate, activity index, publication efficiency index, relative growth rate, doubling time, and degree of collaboration, were calculated. The highest average citation per paper was 64.30 for solar energy and 86.09 for waste-to-energy. The peak annual growth rate (AGR) was 50.00 in 2006 for solar energy and 38.64 in 2020 for waste-to-energy. Exponential growth rates reached 1.50 in 2013 for solar energy (585 publications) and 1.39 in 2020 for waste-to-energy (1,062 publications). The activity index was highest in 2022, with 144.05 for solar energy and 143.72 for waste-to-energy. The average publication efficiency index for both fields was 1.49, and the study highlighted significant contributions by multiple authors across both topics. Other indicators, including relative growth rate (RGR), doubling time (Dt) for publications and citations, and degree of collaboration, underscored substantial research momentum and collaboration in these fields. The data show a strong growth trend and significant impact on research in waste-to-energy and solar energy, along with a noticeable increase in collaborative research initiatives. These patterns indicate an ongoing interest in and solid understanding of renewable energy technologies, which are essential for achieving future sustainability and energy objectives.

Sensitized Singlet Fission in Pentacene-Subphthalocyanine Conjugates

The goal of harnessing the theoretical potential of singlet fission (SF), a process in which one singlet excited state is split into two triplet excited states, has become a central challenge in solar energy research. Covalently-linked dimers provide crucial models for understanding the role of chromophore arrangement and coupling in SF. Sensitizers can be integrated into these systems to expand the absorption bandwidth through which singlet fission can be accessed. Here, we define the role of the sensitizer-chromophore geometry in sensitized singlet fission model systems. To this end, several conjugates have been synthesized consisting of a pentacene dimer (SF motif) connected via a rigid alkynyl bridge to subphthalocyanines (the sensitizer motif). Steady-state and time-resolved photophysical measurements are used to confirm that both conjugates operate as per design, displaying near unity energy transfer efficiencies and high triplet quantum yields from SF.

India’s solar energy research: performance and social network analysis

India’s solar energy research: performance and social network analysis

Comprehensive numerical modeling of intermittent flow cooling with enhanced photovoltaic efficiency in PVT/NPCM systems

The photoelectric conversion efficiency of photovoltaic thermal (PVT) systems is a key concern in solar energy research. The widespread use of continuous nanofluid cooling in PVT/NPCM (Nano-Enhanced Phase Change Material) systems leads to heightened energy consumption. In order to improve efficiency of the PVT/NPCM systems, a two-dimensional transient heat transfer numerical model is established to analyze the PVT/NPCM system with intermittent flow cooling. Corresponding govern equations with boundary conditions are proposed, and numerically solved by using the finite element method. Simulation results are compared with experimental data, showing a deviation of less than 7 %. The findings indicate that the intermittent cooling reduces the flow energy consumption required to drive 2220 L of nanofluid compared to continuous cooling over a 7-h period. Furthermore, under intermittent cooling conditions, the average electrical efficiency stands at approximately 19.7 %. Notably, the electrical efficiency of PVT/NPCM systems employing intermittent flow cooling closely aligns with those employing continuous flow cooling, exhibiting a maximum deviation of merely 0.0348 %. Additionally, intermittent flow cooling emerges as a favorable choice under solar radiation intensities surpasses 1000W/m2, enabling a significant reduction in overall energy consumption while maintaining commendable cooling performance.

Novel design and performance evaluation of an indirectly forced convection desiccant integrated solar dryer for drying tomatoes in Pakistan

The process of drying agricultural products for food preservation is a difficult task that requires a significant amount of energy. The increasing cost and depletion of fossil fuels have led to the development of a food dryer that utilizes renewable energy sources. This research paper proposes the design and performance evaluation of an indirectly forced convection desiccant integrated solar dryer (IFCDISD) at the Solar Energy Research Lab at USPCAS-E, NUST Pakistan. Tomatoes were chosen as the test product due to their importance and widespread consumption. The drying process involves slicing the tomatoes and placing them on the IFCDISD rack, where a desiccant called calcium chloride (CaCl2) is integrated into the dryer. The experiments were conducted during both sunshine (SS) hours and Off-sunshine (OSS) hours. The IFCDISD operates using sunlight during SS hours and utilizes the absorbed heat of CaCl2 in OSS hours via a forced DC brushless fan powered by battery charged thro solar panel. The tomatoes were weighed before and after each drying mode, and the moisture removal was calculated. The results show that the dryer efficiency was 50.14 % on day 1, 66 % on day 2, and an overall efficiency of 58.07 %. The moisture content removal was 42.858 % on day 1, 22.9979 % on day 2, and an overall moisture content removal of 58.07 %. Moreover, the payback period is 5.1396 and the carbon mitigation was recorded as 2.0335, and the earned carbon credit was recorded as 11559.6.

Generation and application of typical meteorological year data for PV system potential assessment: A case study in China

The potential assessment of photovoltaic(PV) systems is of great significance for installing and laying out PV. Short-term meteorological data cannot reflect the local climate characteristics, so it is not suitable for the potential assessment of PV. A typical meteorological year(TMY) can reflect a region's climatic characteristics, and therefore, it is appropriate for the potential assessment of PV. Although the generation methods of TMY for building energy consumption simulation are mature, there are still limited studies on TMY for PV. Given this, this study employs a method to generate TMY data suitable for the Chinese region, while redefining the influencing factors and their respective weights. A TMY dataset was built for 90 cities based on 38 years of measured data in China and applied to BAPV potential assessment. The study assesses annual generation, CO2 reduction, levelized cost of electricity (LCOE), and net returns(NR). The results reveal the highest annual electricity generation in the Northwest region, with Shiquanhe, Golmud, and Ejina sites reaching 215.65 MWh, 201.2 MWh, and 197.5 MWh, respectively. Conversely, southern and coastal regions, notably Chongqing, exhibit the lowest generation at 75.75 MWh. BAPV in Class I tariff areas, along with some Class II and III areas, can achieve demand-side parity (DSP) in full on-grid mode. Through operational adjustments, DSP can be implemented in 23 currently ineligible areas. This study provides dataset support for calculating PV system power generation and analyzes PV potential across diverse cities. The results contribute to policy formulation and future solar energy research, facilitating precise calculations for efficient green power planning in pursuit of carbon neutrality.

Enhancing solar hybrid system efficiency in Libya through PSO & flower pollination optimization

The integration and optimization of Concentrated Solar Power-Photovoltaic (CSP-PV) hybrid systems have become a focal point in the field of solar energy research and development. The fusion of the strengths from both forms of power generation in the CSP-PV hybrid system offers the potential to deliver affordable and manageable solar energy solutions. However, the key parameters of the CSP plant can vary in different situations. Taking these variations into account is crucial for optimizing the overall performance of the CSP-PV hybrid system and ensuring its adaptability to different scenarios. Therefore, there is a need for a method that can optimize all the main parameters of the CSP and the hybrid system at the same time. The maximum acquired energy from the CSP is 7 kWh with meeting the objective of Levelized Cost of Energy (LCOE). In this paper utilized the Flower Pollination Algorithm (FPA). method to globally optimize the CSP-PV Hybrid System. The experimental results prove the effectiveness of this method.

Feature of SiO2 concentration on solar thermal functional characteristics of flat plate solar collector

Solar collectors configured with flat plate innovation pushed to drive the prime role in research in solar renewable energy due to economic, sustainable, and eco-friendly. Besides, the low thermal efficiency and heat loss are the major drawbacks of using flat plate-type solar collectors. The current research adopts the 2% volume fractions of SiO2 nanofluid as the working fluid. Their effects on solar thermal functional characteristics of solar collectors made with the flat plate are experimentally analyzed with the mass-flow rate of 2 Lpm, 2.5 Lpm, 3 Lpm, and 3.5 Lpm, respectively, for air dryer applications. A flat plate solar collector?s investigational thermal performance is compared with water fluid. The significance of a 2% volume fraction of SiO2 nanofluid is operating at 3.5 Lpm recorded higher temperature (71?C), optimum thermal efficiency of 84.1%, and better drying efficiency of 83.4%. The optimum results of the present investigation utilized for air dryer applications.

Creating Cloud Segmentation Data Set Using Sky Images of Afyonkarahisar Region

The use of sky images in solar radiation intensity estimation has been one of the most studied topics in the literature since it improves the estimation results. The first step in processing sky images with image processing methods is to separate the pixels in the images as clouds or sky. This process is known as cloud segmentation in the literature. In this study, the sky is photographed using the sky imaging system installed at Afyon Kocatepe University Solar and Wind Energy Application and Research Center at times with different clouding characteristics and cloudiness rates in Afyonkarahisar Region. The photographs are divided into 25 parts, and small sky patterns are obtained. The pixels in the obtained sky patterns are manually segmented, and a cloud segmentation dataset is created for future studies. Since the resulting dataset contains high-resolution images and prelabeled data, it can be used to obtain more accurate results for the segmentation process and allows learning algorithms to learn faster. The dataset can be used by researchers in studies such as solar energy forecasting, meteorology, and weather forecasting, and the dataset in this paper will be shared with researchers upon request.

Characterization of FeS2 pyrite microcrystals synthesized in different flux media

This study reports pyrite FeS2 microcrystals synthesized in different alkali metal fluxes. Material properties are compared, including the energy band diagrams and PL spectra. A pathway to decrease impurities’ concentration in pyrite has been shown.

Interfacial Modulation through Mixed‐Dimensional Heterostructures for Efficient and Hole Conductor‐Free Perovskite Solar Cells

AbstractPerovskite solar cells have led the new surge of solar energy research. However, their instability is a pressing issue mostly attributed to the perovskite interface with charge‐selective transport layers. In this work, diethylammonium iodide (DEAI) surface treatment is used to mitigate interfacial non‐radiative recombination losses by forming a mixed phase of layered perovskite on the surface. This results in enhanced device performance with the power conversion efficiency of 23.3% and improved operational stability under thermal stress. Moreover, the DEAI treatment facilitates interfacial hole transfer, enabling a carbon‐based hole transport layer‐free perovskite solar cell with a power conversion efficiency of 15.6%.

Nanograss-Assembled NiCo2S4 as an Efficient Platinum-Free Counter Electrode for Dye-Sensitized Solar Cell.

Dye-sensitized solar cells (DSSCs) are often viewed as the potential future of photovoltaic systems and have garnered significant attention in solar energy research. In this groundbreaking research, we introduced a novel solvothermal method to fabricate a unique "grass-like" pattern on fluorine-doped tin oxide glass (FTO), specifically designed for use as a counter electrode in dye-sensitized solar cell (DSSC) assemblies. Through rigorous structural and morphological evaluations, we ascertained the successful deposition of nickel cobalt sulfide (NCS) on the FTO surface, exhibiting the desired grass-like morphology. Electrocatalytic performance assessment of the developed NCS-1 showed results that intriguingly rivaled those of the acclaimed platinum catalyst, especially during the conversion of I3 to I- as observed through cyclic voltammetry. Remarkably, when integrated into a solar cell assembly, both NCS-1 and NCS-2 electrodes exhibited encouraging power conversion efficiencies of 6.60% and 6.29%, respectively. These results become particularly noteworthy when compared to the 7.19% efficiency of a conventional Pt-based electrode under similar testing conditions. Central to the performance of the NCS-1 and NCS-2 electrodes is their unique thin and sharp grass-like morphology. This structure, vividly showcased through scanning electron microscopy, provides a vast surface area and an abundance of catalytic sites, pivotal for the catalytic reactions involving the electrolytes in DSSCs. In summation, given their innovative synthesis approach, affordability, and remarkable electrocatalytic attributes, the newly developed NCS counter electrodes stand out as potent contenders in future dye-sensitized solar cell applications.

NTNU-SINTEF SolarNet: A solar irradiation monitoring network at high latitudes

This study presents a monitoring network for solar irradiation at high latitudes, called NTNU-SINTEF SolarNet. The network collects, with a time resolution ranging from seconds to hours, solar irradiance data, e.g. global horizontal irradiation, diffuse horizontal irradiation, direct normal irradiation, global tilted irradiation, solar energy generation, which are required in solar irradiation modelling in built environments. The network will be used for specific applications, such as (i) anomalies detection, (ii) influences of ground albedo, and (iii) ageing/degradation of solar modules, that are described in this paper. Some characteristics that make the NTNU-SINTEF SolarNet relevant for solar energy research at high latitudes are identified: short distances among the sensors, the ease of data accessibility, the use of the same sensor typologies, and different solar module technologies. The research holds the potential to boost the solar energy digitalization, impacting on several aspects such as predictive and adaptive control strategies for energy management, design of renewable energy system, multi-scale optimization and efficient exploitation of solar energy.

Acceptance of Solar Technology by Enterprises in the Mekong Delta Region, Vietnam

Objective: This study aims to demonstrate the influencing factors of solar technology acceptance by enterprises in the Mekong Delta, Vietnam. Method: The research data were collected using the quota sampling method, with a sample size of 292 active businesses in the Mekong Delta: Can Tho City (80 enterprises), Long An Province (77 enterprises), Tien Giang Province (68 enterprises), and Kien Giang Province (67 enterprises). The collected data will be processed using SPSS and AMOS software. The quantitative analyses employed to test the research hypotheses include a reliability test by Cronbach's alpha, exploratory factor analysis (EFA), confirmatory factor analysis (CFA), and structural equation modeling (SEM). Results: The study has identified five factors that positively influence the intention to use solar technology by businesses, including effort expectancy, performance expectancy, social influence, hedonic motivation, and facilitating conditions. Additionally, the study has shown the significant and decisive impact of intention to use on the behavior of using solar technology. Conclusions: The research findings further validate the suitability of the UTAUT in the field of renewable energy technology. The research results will provide important scientific materials for business managers in the solar energy field and researchers studying the acceptance of solar energy technology.