Solar Power Density Research Articles

Assessment and Modeling of Workplace Exposure to Solar Ultraviolet Radiation in Makurdi, Nigeria

Solar radiation though beneficial to life but the harmful effects of over exposure especially in Nigeria has been neglected and its measurement/prediction has received negligible attention in the literature. This study measured and modeled workplace exposure to solar ultraviolet radiation (SUVR) in Makurdi, Benue State, Nigeria. Digital broadband meter was used to measure solar power density in three site while polymer Polysolphone dosimeters were fitted on a human manikin and placed in the sun between 10:00 am- 4:00pm (6 hours) to quantify the amount of Solar UVR absorbed by three occupational workers (Traders, Fishermen and Staff/Students). Five dosimeters were deployed in each of the three sites for calibration to measure UV absorbance in J/m2 while seven in each site were used for body parts. UV/VIS-spectrophotometer was handily used to measure both post and pre-absorbance and the UV exposures were calculated. The UV index was also calculated. Result shows that, head top had the highest exposure values 7.19kJ/m2, 6.51kJ/m2 and 7.00kJ/m2, while the least values was under cloth cover 2.47kJ/m2, 2.08kJ/m2 and 2.20kJ/m2 for traders, fishermen and staff/students respectively. Similarly, the calculated cumulative exposures were 3289.36kJ/m2, 497.82kJ/m2 and 1515.60kJ/m2 at the market square, river bank and the campus respectively. These values were higher than international ICNIRP average value 30J/m2. UV index at market square was 9 (media graphic colour purple), while at river bank and BSU campus was 8 (media graphic colour reddish). High mean irradiant values with high UV index indicates high risk of harm from unprotected sun exposure. Therefore, use of sun protective clothing is recommended and reduce time in the sun especially between 1:00pm and 2:00pm to prevent over exposure that will lead to serious harmful effects especially at the market place.

An Assessment of Solar Micro-Grid System in the Islands of Bangladesh for Sustainable Energy Access

The isolated islands in the northern Bay of Bengal face difficulties accessing electricity from the central grid and use fossil fuel-based generators, which causes health risks, environmental damage, and high expenses. So, this study aims to replace these fossil fuel-based power sources with Solar Photovoltaic (SPV) microgrids to provide continuous power to remote islands and contribute to reducing emissions. A specific location on the island of Manpura is selected for the SPV plant installation, considering land availability and vulnerability to erosion. Solar power density and other technical parameters such as Direct Normal Irradiation, Global Horizontal Irradiation, Diffuse Horizontal Irradiation, Global Tilted Irradiation, the optimum tilt angle of Photovoltaic (PV) modules, air temperature, and terrain elevation are analyzed using some prominent online analytical tools named “Global Solar Atlas (GSA)”, “Photovoltaic Geographical Information System (PVGIS)” etc. Based on these datasets, a 10kW ground-mounted PV system using monocrystalline silicon solar panels is designed for off-grid operation. The developed system can generate 14.808 MWh of energy per year. This design’s environmental and social impacts are critically analyzed considering the Sustainable Development Goals (SDGs). Compared with conventional energy sources, the results show that the 10kW microgrid SPV system can reduce CO2 emissions by 284 tons. Financial analysis shows the recovery period of the investment based on electricity production at around 8.8 years, making solar PV microgrids a viable option for remote areas like Manpura Island.

MXene/aramid nanofiber films enables highly efficient photothermal conversion for solar-driven water evaporation

Efficient utilization of solar energy is a resultful strategy to solve the problem of shortage of traditional fossil energy. Solar-driven water evaporation is considered as an effective, low-cost, renewable, and environment-friendly technology for clean water production. Herein, a novel MXene/ANF composite film was fabricated by facile vacuum filtration method. Benefiting from the excellent photothermal conversion property of MXene and the flexibility and stability of ANF, the MXene/ANF composite film exhibits high-efficient photothermal conversion and water evaporation ability. The as-prepared MXene/ANF composite film can reach as high as 98.0 °C at the laser power density of 1 kW/m2 and 54.0 °C under the solar power density of 1 kW/m2. Meanwhile, the water evaporation of MXene/ANF composite film can reach 1.432 kg/m2 under the solar power density of 1 kW/m2. Therefore, the MXene/ANF composite films possess a good prospect to be applied as a solar-driven water evaporation device to solve the problem of shortage of traditional fossil energy and inadequate freshwater supply.

Fabrication and thermal performance of a solar-driven heat pipe filled with reduced graphene oxide nanofluids

Nowadays, the solar-thermal technology, converting solar energy into useful thermal energy, was regarded as a direct and facile method to harvest solar irradiation for alleviating the energy crisis and environmental issues. In this work, we reported a transparent solar-driven heat pipe filled with rGO nanofluids, which combined volumetric solar-thermal harvesting and heat pipe technology to realize efficient solar capture while fast transporting of the collected thermal energy to the application ends simultaneously. The rGO nanofluids not only were used as solar volumetric absorbers to absorb solar radiation directly, but also completed the whole thermal cycle as the working fluid. We investigated the impact of filling ratio, inclination angle, working fluids, and solar power density on the thermal property of the heat pipe experimentally. It was found that 20% was the optimal filling ratio for the heat pipe with a lowest thermal resistance of 0.25 K/W at the solar power density of 17.5 W/cm2. Under the vertical operation mode, the heat transfer performance of the solar-driven heat pipe was better than that under the horizontal operation mode. Finally, this developed solar-driven heat pipe had been successfully applied for solar water heating systems, showing excellent heat transfer performance.

Polyurethane sponge assisted recoverable photocatalyst for outdoor weak sunlight-driven efficient water purification

Photocatalysis is an effective technology to address wastewater issue. However, the difficult recoverability of sample powders and poor degradation performance of catalysts under weak sunlight irradiation restrict the commercialization applications. In this work, the Bi2WO6/g-C3N4 heterojunction is synthesized by hydrothermal and calcination techniques, and a three-dimensional polyurethane sponge is introduced to assist the catalyst powder. On the one hand, weather variations produce less affection for Bi2WO6 sample, which exhibits the efficient photocatalytic activity driven by weak sunlight. The construction of Bi2WO6/g-C3N4 heterojunction speeds up separation and transfer of photogenerated carriers, further improving the catalytic performances of pristine Bi2WO6. Under cloudy (solar power density 21.93–52.97 mW/cm2) and overcast (solar power density 3.66–18.99 mW/cm2) weathers, tetracycline degradation efficiencies of Bi2WO6/g-C3N4 reach 64.66% and 55.19% after 150 min of sunlight irradiation, respectively. On the other hand, catalyst powder is tightly loaded onto the surface of polyurethane sponge via polyurethane waterproof coating, which is convenient for material recovery and reuse. After 4 cycles, tetracycline degradation efficiencies of Bi2WO6/g-C3N4 present no significant decrease, saving reaction cost and causing no secondary pollution to water environment. This work provides a promising candidate for large-scale commercialization applications of wastewater treatment.

Cryptomelane Modified Biomass Wastes for Solar Interfacial Evaporation and Stabilization of Cadmium

In this work, after carbonization of two biomass wastes, rice husk and coconut husk, they were modified by hydrothermally synthesized cryptomelane manganese and prepared into a solar interfacial evaporation system to explore their evaporation performance and stabilization performance of cadmium. The results demonstrate that the cryptomelane-modified biochar can obtain an evaporation rate of 1.247 kg m−2 h−1 and a photothermal conversion efficiency of 89.36% under one sun (1 kW m−2). In an outdoor experiment with an average solar power density of only 465.22W m−2, the evaporation capacity reached 4.7 kg m−2 and the evaporation rate reached 0.78 kg m−2 h−1 within 6 h. The cadmium adsorption capacity of biomass waste modified by manganese potassium ore increased by 50.94%, which could be well used for long-term stabilization and recycling of Cd. It could be verified that the cryptomelane-modified biochar material is a low-cost, scalable, and efficient material for interfacial evaporation and reduce wastewater pollution. The evaporation system designed in this work is a feasible way to obtain clean water and solve wastewater problems in the future.

Colored Daytime Radiative Cooling Textiles Supported by Semiconductor Quantum Dots

Radiative cooling, a zero-energy, eco-friendly cooling technology, has attracted tremendous attention recently for its potential of fighting global warming and climate changes. Radiative cooling fabrics with diffused solar reflections typically have reduced light pollution and can be mass-produced with currently available techniques. However, the monotonous white color has hindered its further applications and no colored radiative cooling textiles are available yet. In this work, we electrospun PMMA textiles containing CsPbBrxI3-x quantum dots as the colorant to achieve colored radiative cooling textiles. A theoretical model to predict the 3D color volume and cooling threshold was proposed for this system. As indicated by the model, a sufficiently high quantum yield (>0.9) will guarantee a wide color gamut and strong cooling ability. In the real experiments, all of the fabricated textiles show excellent color agreement with the theory. The green fabric containing CsPbBr3 quantum dots achieved a subambient temperature of ∼4.0 °C under direct sunlight with an average solar power density of 850 W/m2. The reddish fabric containing CsPbBrI2 quantum dots also managed to cool 1.5 °C compared to the ambient temperature. The fabric containing CsPbI3 quantum dots failed to achieve subambient cooling with a slightly increased temperature. Nevertheless, all of the fabricated colored fabrics outperformed the regular woven polyester fabric when placed on a human hand. We believed that the proposed colored textiles may widen the range of applications for radiative cooling fabrics and have the potential to become the next-generation colored fabrics with stronger cooling ability.

Photo-thermal design and analysis of a novel CPC coupled solar air evacuated tube collector

The conventional evacuated tube solar air collector can’t reach a higher temperature due to poor heat transfer between absorber and air. To maintain a low heat loss at medium temperature and enhance heat transfer, a novel evacuated tube solar air collector coupled with a compound parabolic concentrator is proposed. The matching shape is designed and optimized for the concentrator reflecting surface using non-imaging optics, and by ray tracing, the optical performance is obtained. The corresponding photothermal conversion and heat transfer models are established, and numerical simulation is conducted for thermal performance analysis. The results show that the thermal performance is mainly affected by the air flow rate, the inlet temperature, and the heat source energy density. Compared with the existing single-pass evacuated tube collector, the novel collector has advantages in heat output temperature, thermal efficiency, adaptability to flow rate changes, and potential for series temperature rise under most conditions. When concentrated solar power density is 800–1600 W/m2, the maximum outlet temperature of a novel collecting evacuated tube can reach to a limiting value of 181.17 ℃, representing its thermal insulation performance, while that of the contrast one is 153.25℃. Under normal inlet temperature of 25℃, the maximum output temperature of a single tube of the novel collector is 146.05℃ at a flow rate of 1.02 m3/h, and the maximum thermal efficiency of 59.21% can be achieved at a flow rate of 3.58 m3/h.

Thermal effect on curved photovoltaic panels: Model validation and application in the Tabuk region.

This paper aimed to investigate the temperature effect on photovoltaic (PV) cell parameters. The PV cell parameters such as series and parallel resistances, diode ideality factor, and diode saturation current, are not considered in the reported stepwise modeling. The present work aims to improve available models used in the modeling and simulation of PV modules to support the researcher and power project developer. All the required temperature-dependent parameters are determined to model the simulated PV module with high accuracy using Simulink/MATLAB software. To validate the method, a 36-cell-50W solar panel with different radii of curvature is set up to assess solar power outputs under varying irradiance and temperature conditions. For the present application, the Tabuk region (Saudi Arabia) is chosen based on its location and climatic conditions. The method provided conformity to the measured power outputs for varying Global Horizontal Irradiance (GHI) and temperature conditions. The maximum power output of the PV module increases from 14.4 W to 25.8 W when the received solar power density varies from 307 W/m2 to 526 W/m2 depending on the level of curvature starting from a semi-cylindrical shape to a vaulted shape to a flat shape. The curved PV module shows slightly higher power variation with temperature as compared to the flat one. Above 25°C, the power output is about 20% less at a maximum temperature of 65°C. When the temperature drops below 25°C, the power outputs increase about 6% and 11.5% for corresponding temperatures of 15°C and 5°C, respectively.

Autogenic electrolysis of water powered by solar and mechanical energy

A dual-bandgap photoelectrochemical (PEC) cell with two semiconductors stacked in tandem is a widely adopted concept to capture a large fraction of the solar spectrum for water splitting. While two photons are theoretically needed to produce one H2 molecule using single-bandgap PEC cells, four photons are generally required for one H2 molecule in the dual-bandgap cells because of an unavoidable charge recombination at the solid-solid interface. Here, triboelectric effects are exploited in the form of triboelectric nanogenerator (TENG) to allow for the generation of one H2 molecule at the expenses of two photons in a dual-bandgap device using an array of core/shell p-type silicon/anatase-TiO2 nanowires as photoelectrode. The TENG, that converts mechanical energy to electricity, efficiently suppresses the charge recombination at the interface and significantly increases the energy of the photo-generated carriers required for the simultaneous water reduction and oxidation. The synergy of photoexcitation and triboelectrics results in a rate of hydrogen production in a neutral Na2SO4 electrolyte around 150 times higher than that of the counterpart, i.e., the device in the absence of TENG. Furthermore, the TENG-induced enhancement in the PEC water splitting remains substantial even when the solar power density is reduced to 20 mW/cm2.

Simulation of Photovoltaic Thermoelectric Battery Characteristics

Solar radiation is an environmentally friendly and affordable energy source with high release of energy. The use of a photovoltaic thermoelectric battery makes it possible to increase the efficiency of converting solar and thermal radiation into electrical energy, both on serene and cloudy days. An original battery structure with photovoltaic and thermoelectric converters is proposed. The 3D model of the proposed photovoltaic thermoelectric battery was realized in the COMSOL Multiphysics software environment with the use of a heat transfer module. The simulation was performed for the geographical coordinates of Minsk and taking into account the diurnal and seasonal variations of both the ambient temperature and the power density of the concentrated AM1.5 solar spectrum, the maximum value of which being varied from 1 to 500 kW/m2. The dependences of the maximum temperature values of the photovoltaic thermoelectric battery and the thermoelectric converters as well as temperature gradient patterns in the thermoelectric converters have been calculated. The dependences of the maximum temperature gradient values inside the thermoelectric converters on the solar power density are obtained. The graphs of the temperature gradients inside the thermoelectric converters of the photovoltaic thermoelectric battery by concentrated solar radiation versus the time of day in the middle of July and January are provided. It is shown that the output voltage increases up to the maximum values of 635 and 780 mV, respectively, in January and in July were achieved due to the temperature stabilization of the back side of the external electrodes of the proposed device

Low-cost and reusable carbon black based solar evaporator for effective water desalination

Solar distillation is considered a low-cost, environmental-friendly approach for freshwater production. However, water output and photothermal efficiency of conventional solar evaporators are low. This study developed highly efficient bilayer photothermal functional films (noted as CBMCE) by depositing carbon black nanoparticles (CBNPs) dispersion on mixed cellulose ester (MCE) support via simple vacuum filtration. To further increase water production, multilayer enhanced evaporators (MEER) were fabricated by coupling optimal CBMCE with polystyrene foam and air-laid paper. The effects of operating conditions on solar evaporation were systematically investigated, including loading rate of CBNPs on MCE, solar power densities, water depths, relative humidity, and different water types (deionized water, synthetic seawater, municipal wastewater, and 13.5 wt% NaCl solution). Experimental results indicated that the average water evaporation rate (AER) increased with increasing incident solar density and decreased with increasing water depths, aqueous solution salinity, and relative humidity. For 13.5 wt% NaCl solution, MEER achieved maximum AER of 5.6 kg·m−2·h−1, enhanced evaporation rate and evaporation efficiency by ~124.0% and ~123.5%, respectively. Economic analysis showed desalination of 13.5 wt% NaCl solution using MEER had a life cycle cost of ~$1.89/m3 fresh water produced. This study demonstrates that MEER are highly efficient, low-cost, and reusable functional materials for solar desalination.

Observation-based solar and wind power capacity factors and power densities

Power density is the rate of energy generation per unit of land surface area occupied by an energy system. The power density of low-carbon energy sources will play an important role in mediating the environmental consequences of energy system decarbonization as the world transitions away from high power-density fossil fuels. All else equal, lower power densities mean larger land and environmental footprints. The power density of solar and wind power remain surprisingly uncertain: estimates of realizable generation rates per unit area for wind and solar power span 0.3–47 We m−2 and 10–120 We m−2 respectively. We refine this range using US data from 1990–2016. We estimate wind power density from primary data, and solar power density from primary plant-level data and prior datasets on capacity density. The mean power density of 411 onshore wind power plants in 2016 was 0.50 We m−2. Wind plants with the largest areas have the lowest power densities. Wind power capacity factors are increasing, but that increase is associated with a decrease in capacity densities, so power densities are stable or declining. If wind power expands away from the best locations and the areas of wind power plants keep increasing, it seems likely that wind’s power density will decrease as total wind generation increases. The mean 2016 power density of 1150 solar power plants was 5.4 We m−2. Solar capacity factors and (likely) power densities are increasing with time driven, in part, by improved panel efficiencies. Wind power has a 10-fold lower power density than solar, but wind power installations directly occupy much less of the land within their boundaries. The environmental and social consequences of these divergent land occupancy patterns need further study.

Highly-dispersed nickel nanoparticles decorated titanium dioxide nanotube array for enhanced solar light absorption

Honeycomb titanium dioxide nanotube array (TiO2-NTA) decorated by highly-dispersed nickel nanoparticles (Ni-NPs) has been grown under control on Ti foil by anodization and subsequent electrodeposition. The pore diameter and length of TiO2-NTA, and the size and quantity of Ni-NPs can be controlled via modulating the variables of the electrochemical processes. It has been found that the pretreatment of TiO2-NTA in the Cu(NO3)2 solution and further annealing at 450 °C in air could greatly improve the dispersion of the electrodeposited Ni-NPs. Absorption of the light in the solar spectrum from 300 to 2500 nm by the Ni-NPs@TiO2-NTA is as high as 96.83%, thanks to the co-effect of the light-trapping of TiO2-NTA and the plasmonic resonance of Ni-NPs. In the water heating experiment performed under an illuminating solar power density of ∼1 kW m−2 (AM 1.5), the ultimate temperature over 66 °C and an overall efficiency of 78.9% within 30 min were obtained, promising for applications in photothermal conversion and solar energy harvest.

Thermal and chemical analysis of methane dry reforming in a volumetric reactor under highly concentrated solar radiation

The heat transfer and thermochemical reaction are numerically investigated for the solar driven methane dry reforming process, coupling with the solar radiation transport from concentrator to the interior of volumetric reactor. Using a Monte Carlo ray tracing method, the solar radiation concentration with a multi-dish system and absorption by the foam structure in the reforming reactor are simulated. The solar power density distribution in reforming reactor and the optical efficiency of system are determined and compared at different foam structural parameters. Then, an integrated model of transport phenomena is developed to analyze the thermal and chemical performances under different operating conditions. The results indicate that solar radiation absorption and distribution in the reactor are greatly affected by the foam structural parameters, while the optical efficiency has no significant variation. Assumption of the concentrated solar radiation as collimated leads to a temperature deviation of approximately 10%. Besides, the methane conversion increases with increasing porosity and cell size, and decreases markedly with increasing inlet velocity and CH4/CO2 ratio.

Design of polymer multilayer heterostructure broadband reflector for the near-infrared using genetic algorithm

A broadband reflector for the near-infrared (NIR) was designed using a multilayer heterostructure consisting of several quarter-wave stacks (QWSs), which were composed of polymethyl methacrylate (PMMA) and polyethylene terephthalate (PET) films. Taking the solar power density as the target and using the Bragg wavelength of each QWS as the variable, the genetic algorithm was applied to look for the optimal multilayer heterostructure for broadband NIR reflection. As high as 99.46% total energy reflectivity in the short-wavelength NIR region (780 to 1100 nm) and 89.56% total energy transmissivity in the visible light region (380 to 780 nm) were realized by a multilayer heterostructure consisting of six quarter-wave PMMA/PET stacks, which can be easily fabricated based on the micronano multilayer coextrusion technology. The designed structure possesses good stability, and its total energy reflectivity is not sensitive to the incident angle of light. The proposed broadband NIR reflector can be applied to buildings as energy-saving films.

Design of broadband near-infrared reflector using polymer multilayer heterostructure with low-refractive-index contrast

In the paper, to achieve total reflection in the short-wavelength near-infrared (NIR) region (780–1100 nm), a broadband NIR reflector using polymer multilayer heterostructure composed of several quarter-wave stacks was proposed. The reflector used two kinds of polymer materials: PMMA and PET with low-refractive-index contrast. Taking the solar power density as the target and the Bragg wavelength of each quarter-wave stack as the variable, a searching method based on arithmetic progression was applied to find the optimal results for broadband NIR reflection. The simulation results show that the broadband NIR reflector can obtain higher total reflectivity with the increase of the number of quarter-wave stacks, and 99.06% total reflectivity in the short-wavelength NIR region can be achieved by the polymer multilayer heterostructure with six quarter-wave stacks. The proposed polymer multilayer heterostructure can be fabricated by the micro–nanomultilayer co-extrusion technology based on torsion lamination, and could be applied in agriculture as NIR-blocking films.

Large-scale cauliflower-shaped hierarchical copper nanostructures for efficient photothermal conversion.

Efficient solar energy harvesting and photothermal conversion have essential importance for many practical applications. Here, we present a laser-induced cauliflower-shaped hierarchical surface nanostructure on a copper surface, which exhibits extremely high omnidirectional absorption efficiency over a broad electromagnetic spectral range from the UV to the near-infrared region. The measured average hemispherical absorptance is as high as 98% within the wavelength range of 200-800 nm, and the angle dependent specular reflectance stays below 0.1% within the 0-60° incident angle. Such a structured copper surface can exhibit an apparent heating up effect under the sunlight illumination. In the experiment of evaporating water, the structured surface yields an overall photothermal conversion efficiency over 60% under an illuminating solar power density of ∼1 kW m(-2). The presented technology provides a cost-effective, reliable, and simple way for realizing broadband omnidirectional light absorptive metal surfaces for efficient solar energy harvesting and utilization, which is highly demanded in various light harvesting, anti-reflection, and photothermal conversion applications. Since the structure is directly formed by femtosecond laser writing, it is quite suitable for mass production and can be easily extended to a large surface area.

Optical Damage Tests on Reflecting Materials for Solar Applications Using Concentrated Sunlight

Concentrated Solar Power (CSP) and Concentrating Photovoltaics (CPV) usually involve secondary optics (lenses or mirrors) in order to improve system energetic performances. These secondary elements should collect the sunlight concentrated by the primary optic. Therefore, the materials suitable for the realization of secondary concentrators must withstand a long-time exposure to solar high power densities without significant decay of their optical performances. An accurate optical characterization of these materials should include an investigation on their degree of resistance to high-power light, by means of exposing them to concentrated sunlight for several hours in monitored conditions.This paper presents the optical study on three samples of two different materials, which are possible candidate for the construction of secondary reflectors for a solar furnace. The goals of this study were to test the samples endurance at the working power density, verifying if an achievable damage threshold exists and eventually correlating it with some measurable parameters like exposure time or temperature. In synthesis the tests were of two types: field tests with sun exposure and laboratory optical characterization.The field test consisted in exposing the samples (named A, B and C) to sunlight by using a dual-axis solar tracker and a suitable Fresnel lens. Samples A and B were sections of the same glass mirror. Sample C was a multilayer mirror based on an aluminum substrate. The measured parameters were: temperature of the back side of the sample; solar power density concentrated on the sample; exposure time.The optical characterization involved measurements of reflectance, regularly performed to check variations in the optical features. Only sample B suffered a structural failure at the end of the exposure period, and this involved only the glass cover; none of the samples showed appreciable decays in reflectance during the whole exposure period.

Output Characteristics of Solar-Power-Driven Thermionic Energy Converter

A solar-power-driven thermionic energy converter abbreviated as Solar TEC is operated by illumination of solar light condensed by a large-scale Fresnel lens 105 cm in length and 70 cm in width. It was found that an output current takes large peaks at the lower emitter temperature because the emitter work function closely related to the thermionic electron emission decreases at a constant cesium pressure with decreasing emitter temperature. The maximum short circuit current was 0.73 A at 62 s after the onset of the illumination throughout the experiment for 500 s, where the solar power density on the ground was approximately 800 W/m2. The barrier index also took a minimum value of 2.3 eV at the same time. To increase the output characteristics of the Solar TEC, the emitter and cesium temperatures should be increased along the curve of β=1, where β denotes the space charge neutrality. It was found that the emitter with a light trap is effective in improving the energy conversion efficiency of the Solar TEC, since it realizes high absorptivity and low emissivity at once, which causes the emitter to have high thermal efficiency for solar power illumination.