Surface Modulation Research Articles

Numerical examination of expanding the effectiveness of thermal photovoltaic framework by changing the level of heat transfer conveyance

In photovoltaic systems, only a tiny portion of solar radiation reaches the module's surface and is converted to electrical energy. The remaining solar radiation is wasted, which raises cell temperature and reduces electrical efficiency. This research focused on examining the effects of different factors on nanofluids. In the simulations performed in this thesis, the inlet temperature of the water fluid changes from 5°C to 30°C. The radiation intensity equals 600W per square meter, and the input speed is 0.07452m per second. The innovation of this article is the use of two nanofluids of aluminum oxide and copper together with a mixture of water to investigate the effect of effective parameters on the electrical, thermal, and overall efficiency of photovoltaic systems, such as the amount of incoming radiation to the surface of the panel, the temperature of the fluid inlet in mountainous areas, the temperature of the absorber. , so that the thermal efficiency of copper and aluminum oxide is investigated and compared. As a result, copper nanofluid can increase the ratio more than aluminum oxide and pure water. There is a direct relationship between the output fluid temperature and the input temperature. With an increase in the input fluid temperature, the output temperature also increases proportionally. Increasing the inlet temperature affects the temperature of the absorber surface, which, in turn, reduces the electrical efficiency of the photovoltaic system. These changes are reduced by adding nanofluids to the photovoltaic system.Although the increase of nanoparticles causes a decrease in the temperature of the absorber plate, and this temperature decrease for copper nanofluid is 10% higher than that of aluminum oxide and pure water until the volume fraction is reached.

Determining the Effect of Photovoltaic Module Surface Temperature on Generation Efficiency

It is imperative to consider the environmental impact of energy production and its cost in deciding how to meet future energy needs. In this regard, it is possible to harness the power of the sun by using photovoltaic (PV) cells. However, when the temperature of a PV cell increases, its generation efficiency is negatively affected. The open-circuit voltage of PV modules is the most sensitive parameter to temperature changes. As the temperature rises, this parameter decreases, and the short-circuit current increases. The circuit's resistance also rises as the electrons’ speed is reduced. Temperature also affects the lifespan of PV cells, increasing the rate of thermal decay in their materials. On the other hand, when solar radiation is absorbed at lower temperatures, the system’s efficiency, power capacity, and useful life increase. PV module surface temperatures can be reduced in a variety of ways, e.g., the surface can be cooled using water. This work studied hybrid PV-thermal modules under the climate conditions of the Hatay province (Turkey) in order to assess the effect of water cooling on their generation efficiency. The results allow stating that up to 52.6% more electricity can be generated by cooling the module's surface. Additionally, it was found that, in order for PV modules to perform efficiently in Hatay's climate, they must operate at a maximum surface temperature of 55 °C.

Experimental and numerical analyses of water droplet condensation on photovoltaic surfaces under clean and dusty conditions

Several studies have investigated the condensation effect on dust agglomerate located on PV surfaces. The phenomena of dust condensation remain minimally addressed by researchers and not understanding well in the field of PV systems. Using rigorous experimentation, this research study explored the accumulation of dust on photovoltaic units. Furthermore, we thoroughly examined the effect of condensation on the glass surface of the unit. The formation of condensed droplets and their consequences were examined through meticulous experiments and mechanical analyses. The experiment was made possible by an ingeniously designed experimental platform, which enabled monitoring the influences of condensation on dust aggregation. The condensation process was carefully observed and analysed using microscopic techniques, while its direct impact on the dust accumulated on the PV module's surface was also examined. The experimental and numerical investigations of droplets condensation, condensing water droplets speed, condensation film thickness, and mud formation layer on the glass cover of PV module were highlighted. The droplets condensation on a glass plane (similar surface to covering glass for PV module) was recorded at different air conditions. The values of air velocity were chosen 0, 2.4, 4.1, 6.3 m/s, to provide a constant air temperature and humidity of the inflow air, the channel was supplied with heating control system. Furthermore, two dust seeding quantities 150 and 300 g were tested to provide a range for different cases for thickness of dust layers with different air velocities. According to the study, condensate time directly correlates with drop equivalent diameter, demonstrating that drop diameter increases proportionally to condensation time. It is indicated that the droplet formation and condensation period accelerated with increasing dust seeding quantity. It is noteworthy that the period of droplet formation and condensation accelerates with the increase in the amount of dust seeding. The results showed that by increasing the air speed from 2.4 m/s to 6.3 m/s, the weight of accumulated dust was decreased from 0.166 g to 0.151 g. Also, the average mud layer thickness was reduced from 27.6 μm to 25.1 μm.

Numerical investigation of increasing the efficiency of thermal photovoltaic system by changing the level of heat transfer distribution

In photovoltaic systems, only a small fraction of solar radiation effectively reaches the module's surface and is converted into electrical energy. The unused solar radiation results in elevated cell temperature and reduced electrical efficiency. In the photovoltaic-thermal system, the circulation of fluids such as water or air around the panels allows for the utilization of otherwise wasted thermal energy, leading to increased electrical efficiency and overall system efficiency. The objective of this article is to examine the thermal efficiency of copper and aluminum oxides in photovoltaic systems when combined with nanofluid. The aim is to identify any changes in efficiency that may arise from this combination. This article presents a novel approach by employing a combination of aluminum oxide and copper nanofluids, along with a water mixture, to investigate the influence of key factors on the electrical, thermal, and overall efficiency of photovoltaic systems. These factors encompass incoming radiation levels on the panel surface, fluid inlet temperature in mountainous regions, and absorber temperature. The study aims to analyze and compare the thermal efficiency of copper and aluminum oxide in this particular context. In the present study, the finite volume method is used to solve the equations. According to the research findings, raising the initial temperature of the incoming fluid results in a proportional increase in the outlet temperature. However, it is important to note that the thermal efficiency remains constant regardless of changes in the initial fluid temperature. Furthermore, copper oxide exhibits superior thermal efficiency compared to aluminum oxide, and the use of nanofluids enhances the thermal efficiency of photovoltaic systems.

Photovoltaics literature survey (No. 181)

Photovoltaics literature survey (No. 181)

A generalized approach for the determination of optimum tilt angle for solar photovoltaic modules with selected locations in Ethiopia as illustration examples

The amount of total solar energy that strikes the photovoltaic module's surface directly affects how much power is generated. On the other hand, solar energy is influenced by the solar module's location, tilt angle, and orientation. The models presented in this study can be used to determine the seasonal and annual optimal tilt angles of photovoltaic modules at any location in Ethiopia as a function of the location's latitude and elevation without the need for solar radiation data. Both isotropic and anisotropic diffuse solar radiation models were used to determine the monthly, seasonal, and annual optimal tilt angles. The monthly average daily global horizontal solar radiation for a total of 44 study sites, 32 for training and 12 for testing, were retrieved from the National Aeronautical and Space Administration database. The optimal tilt angle and regression models were determined by developing and applying algorithms in the programming languages MATLAB and R. The proposed model estimates the optimal tilt angle with the fewest statistical validation errors. By using the proposed monthly optimal tilt angles, solar radiation gains of 6.76% - 8.48% (for isotropic models) and 10.16% - 26.97% (anisotropic models) were obtained for Bahir Dar city. The solar radiation gains for the cities of Adigrat, Butajira, and Gode were found to be 7.18–9.02% (isotropic) and 10.90%–28.06% (anisotropic), 5.43%–7.05% (isotropic) and 8.48%–25.99% (anisotropic), and 4.33%–5.79% (isotropic) and 6.96%–23.03% (anisotropic), respectively. The results of this study were further confirmed by comparing them to previously published papers and online PVGIS and NREL's PVWatt software tools.

Wideband RCS Reduction by Single-Layer Phase Gradient Modulated Surface.

This paper deals with the design and fabrication of an unpretentious (single-layer, without any lump element) broadband (97%, 11.3–32.3 GHz) radar cross-section reduction (RCSR) modulated surface (MS). The proposed structure uses sinusoidal modulation gap sizes between square patches within square unit cells to form a phase gradient that plays an effective role in improving the RCSR bandwidth. An MS with dimensions of 250 × 250 mm2, consisting of 40 × 40 unit cells with a period of 6 mm printed on a RO4003C (lossy) substrate of 0.06λLF (λLF being the wavelength at the lower frequency) thickness, has been prototyped. The MS has square patch (SP) unit cells with seven different gap sizes. A genetic algorithm (GA)-based fine-tuning has been implemented to further increase the performances of the structure. Measurements on it have been conducted considering both mono- and bi-static arrangements and for oblique incidences for both TM and TE polarization tests. A good agreement between simulation and measurement results proves the validity of the design criteria.

A 1.66Gb/s and 5.8pJ/b Transcutaneous IR-UWB Telemetry System with Hybrid Impulse Modulation for Intracortical Brain-Computer Interfaces.

Intra-cortical extracellular neural sensing is being rapidly and widely applied in several clinical research and brain-computer interfaces (BCIs), as the number of sensing channels continues to double every 6 years. By distributing multiple high-density extracellular micro-electrode arrays (MEAs) in vivo across the brain, each with 1000's of sensing channels, neuroscientists have begun to map the correlation of neuronal activity across different brain regions, with single-neuron precision [1]. Since each neural sensing channel typically samples at 20 to 50kS/s with a > 10b ADC, multiple MEAs demand a data transfer rate up to Gb/s [2]. However, these BCIs are severely hindered in many clinical uses due to the lack of a high-data-rate and miniature-wireless-telemetry solution that can be implanted below the scalp, i.e., transcutaneously (Fig. 24.2.1). The area of the wireless telemetry module should be miniaturized to ~3cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> due to neurosurgical implantation constraints. A transmission range up to 10cm is highly desirable, in order to improve the reliability of the wireless link against e.g., antenna misalignment, etc. Finally, the power consumption of the wireless telemetry should be limited to ~10mW to minimize thermal flux from the module's surface area, avoiding excessive tissue heating. Most of the conventional transcutaneous wireless telemetry systems adopt inductive coupling, but the data-rate is limited to a few Mb/s. A near-infrared (NIR) optical transcutaneous TX using a vertical-cavity-surface-emitting laser (VCSEL) [2] demonstrated a data-rate up to 300Mb/s but suffers from a limited transmission range (4mm) and requires a sub-mm precise alignment between the implant TX and a wearable RX. Impulse-radio UWB (IR-UWB) is promising for the targeted requirements [3]–[5].

Low-Cost, Low-Profile Wide-Band Radar Cross Section Reduction Using Dual-Concentric Phase Gradient Modulated Surface

Design criteria of low-cost, dual-concentric metasurface possessing wideband phase gradient (PG) are introduced. The radar cross-section reduction (RCSR) is explained by anomalous reflection that characterizes the superficial planar. The geometry consists of two single band RCSR modulated surfaces (MSs) that are triggered in each other. Each MS is built-up of square patch (SP) unit cells configured as a modulation structure to realize PG that causes anomalous reflection and monostatic RCSR behavior. Applying sinusoidal modulation to the sequence of the SP unit cells leads to the formation of PG along the surface and hence the intensity of the reflected wave is reduced for the broadside direction (θr=0∘). The proposed structure fabricated on a 0.8 mm thin FR-4 substrate extends over 249 × 249 mm2. It achieves a wide RCSR bandwidth from 20.9 GHz to 45.7 GHz (i.e., relative bandwidth of 75%) as designed in Dassault Systèmes (CST) Microwave Studio as a full-wave simulator and confirmed by the measurement results.

Study of the influence of dust deposits on photovoltaic solar panels: Case of Nouakchott

Degradation performance of photovoltaic (PV) modules by real weather conditions has become increasingly problematic. In the desert climate, dust accumulation is one of the main concerns that may cause a significant deterioration of PV efficiency. In the present work, experimental investigations were carried out to understand the effect of dust on the electrical performance of PV modules under Toujounine, Nouakchott, Mauritania weather conditions. The measurements were performed with an I-V tracer ftv200. The measured parameters were I-V and P-V curves, open-circuit voltage (Voc), short-circuit current (Isc), current and voltage at maximum power (Imp and Vmp) and maximum power (Pmax); as well as the measurement of temperature of panels and Irradiation. The study was carried out according to the following cleaning scenarios: panels cleaned before each measurement (Clean panels 01), panels undergoing systematic cleaning with the central unit (Clean panels 02) and chains undergoing no cleaning (Dusty panels 03). Then, the modeling of reliability as a function of maximum power by Weibull's law, for clean and dusty panels is evaluated. According to the experimental results, disturbances in I-V and P-V curves for dusty panels were noticed. Also, a decrease in the Isc and the Imp for dusty panels compared to clean panels was found. These results are explained by the effect of dust accumulation on the module's surface, which blocks the solar radiation and thus reduces the conversion efficiency of PV modules. Again, dust reduces the output power of photovoltaic modules by 21.57% for dusty panels per clean panels. Finally, a low reliability for dusty panels compared to clean panels was found, due to the loss in the output power under the dust effect. These results clearly show the importance of properly maintaining and servicing the photovoltaic modules to avoid their degradation by dust deposits.

Three Bypass Diodes Architecture at the Limit

In this work, we demonstrate that partial shading of one solar cell in a state-of-the-art monocrystalline photovoltaic module with three bypass diodes results in hot cells with critical peak temperatures of 164 $^\circ$ C. We examine two solar modules in the IEC 61215-2 MQT 09 hot-spot endurance test, one with 367.3 W $_\text{P}$ featuring 72 full-cells and the other with 388.6 W $_\text{P}$ featuring 144 half-cells. For the solar module with 72 solar cells, we measure a maximum temperature of 164 $^\circ$ C, which results in a degradation of the encapsulation material and increases the risk of solar module failure. The high temperature results from the hot cell effect due to the power dissipation in the reverse-biased solar cell caused by partial shading. Our experiments show that the half-cell solar module is advantageous in terms of solar cell shading compared to the full-cell solar module. Although the half-cell solar module has a higher power output than the full-cell solar module, we measure a cooler peak temperature of 150 $^\circ$ C. However, under certain shading conditions, the half-cell solar module can exhibit similar temperatures as the full-cell solar module. Based on our experimental results, we develop an electrical and a thermal model to predict the temperature of novel high-power solar modules with solar cells from larger silicon wafer formats in case of partial cell shading. Our predictions consider the trends of further increasing solar cell and module efficiencies, larger silicon wafer formats, and larger solar modules. We simulate a maximum peak temperature of 176 $^\circ$ C at the solar module's surface, which significantly increases the risk of solar module failure. Our results show that new high-power solar modules employing solar cells that are made from larger silicon wafer formats need a new protection against overheating. Three bypass diodes per solar module are no longer sufficient.

An empirical correlation of ambient temperature impact on PV module considering natural convection

&lt;p&gt;&lt;span&gt;In this paper, the effect of the ambient temperature on the PV modules for different angles of inclinations and different intensities of the solar radiation on the surface of the PV module is considered by using empirical correlations for natural convection. An analytical model based on the energy balance equilibrium between the PV module and the environment conditions has been used. Also an expression for calculating the electric power of silicon PV modules in a function of the ambient temperature, the intensity of the solar radiation, the incident angle of the solar radiation to the surface of the PV module and the efficiency of the PV modules at STC conditions have been used. By comparing the obtained both results, it can be seen that the largest deviation between the power values obtained by the analytical model and expression is about (5 %). The results obtained indicates that in the case of a small number of PV modules corresponding to the required number for an average household, it is more economical to invest additional resources in increasing the PV module's surface area than in case of the PV module with sun tracking system. &lt;/span&gt;&lt;/p&gt;

Development and Performance Evaluation of Solar Photovoltaic Module’s Surface-to-Rear Temperature Controlled Valve for Cooling Application

This study investigated the effectiveness of the developed solar photovoltaic (PV) module's surface-to-rear temperature-controlled solenoid valves for PV module cooling application. The cooling fluid is regulated by energizing normally closed (NC) solenoid valve with control parameters as modules rear and surface temperatures. ATmega32 microcontroller was utilized as central processing unit with two (2) LM35 as input sensors and solenoid valve as an output device. Each of 2-LM35 temperature sensors were dedicated to measure module's rear and surface temperatures respectively. The measured temperature values were coded as controlled parameters for regulating cooling fluid discharge by energizing a NC solenoid valve. The system was observed to discharge cooling fluid by energizing the solenoid valve under module's surface and rear temperature difference of less than or equal to 1.50C (Ts-Tr≤1.50C). The module's mean surface temperatures of 49.310C and 54.920C were recorded for temperature-controlled PV cooling applications and a standard solar photovoltaic/thermal (PV/T) system. The maximum recorded surface temperatures for temperature-controlled PV cooling and a standard PV/T systems were 54.00C and 57.60C respectively. The mean absorber temperatures of 45.510C and 40.870C were respectively recorded for temperature-controlled PV cooling and standard PV/T. The maximum absorber temperature recorded for temperature-controlled PV cooling and standard PV/T were 48.300C and 41.630C respectively. The solar cells temperature is reduced by 5.38% through solenoid valve temperature controlled solar module cooling application.&#x0D; Keywords: Temperature-controlled, ATmega32, solenoid valve, solar module, cooling application.

Output power loss of crystalline silicon photovoltaic modules due to dust accumulation in Saharan environment

Photovoltaic (PV) module efficiency is much lower when operating in outdoors than under controlled laboratory conditions. Dust accumulation on the surface of PV modules results in lower performance and daily energy losses due to the decrease in glass cover transmittance. These losses in energy output are significant in large PV farms especially in arid and desert areas. In this research, the effect of dust accumulation on the performance of crystalline PV modules was investigated experimentally under outdoor conditions in a Saharan environment at the city of Ouargla, Southeast of Algeria. In addition, the power generation of a 30 MW grid-connected PV power plant installed in the same area before, during and after a sandstorm was evaluated. The results showed that approximately 4.36 g/m2 of dust accumulated on the PV module's surface after 8 weeks of outdoor exposure without cleaning. This caused a drop in PV energy production of 8.41%, 6.10% and 0.51% in maximum power output, short circuit current and open circuit voltage respectively in comparison to a cleaned PV module. Furthermore, deposited dust on the surface of the PV modules at this farm from this sandstorm led to a 32% reduction in generated energy (i.e. 5.18 MWh).

Effect of soiling on wind-induced cooling of photovoltaic modules and consequences for electrical performance

This study investigates the effect of soiling on the cooling capacity of the wind and its consequences for the performance of photovoltaic modules. Cooling and electrical characteristics were measured on a glass-glass module for wind speeds up to 4 ms−1 and soiling levels up to 41 gm−2. Soiling can promote the cooling of photovoltaic modules and affects the influence of wind on module performance. Soiling may result in less external heating of the module's surface because of the higher albedo of a soiled module compared to a clean one. Also, soiling results in a decrease of the amount of heat to be evacuated by the wind whereas the capacity of the wind to evacuate heat is not affected; the surplus in cooling capacity can be used to cool the module to a lower temperature than if the module were clean. Soiling had a negative effect on the short-circuit current and the maximum power whereas no direct effect on the open-circuit voltage was observed, but soiling did stimulate the positive effect wind has on the voltage. The study sheds more light on the physical processes that occur on and near the surface of a soiled photovoltaic module.

Experimental study of the dew formation effect on the performance of photovoltaic modules

Abstract The performance of photovoltaic modules is related to climatic conditions. The aim of this study was to investigate the effect of dew formation on the performance parameters of two solar cell types including mono-crystalline silicon (mc-Si) and polycrystalline silicon (pc-Si) in the laboratory scale. The experiments were performed by using an environmental chamber equipped with a solar simulator based on LED light. The dew formation on the panel surface was conducted at three levels of 45, 60 and 75% and ambient temperature of 25 °C. Based on the psychometric chart, the dew points temperature are 12.5, 8.5 and 4.5 °C lower than 25 °C corresponding to the relative humidity levels of 45, 60 and 75%, respectively. The percentages of the covering of dew on the module surface were estimated to be 45.19, 63.50 and 83.62% at relative humidity levels of 45, 60 and 75%, respectively. The performance parameters including the open-circuit voltage, short-circuit current, maximum power, maximum voltage, and maximum current were determined from the I V and P V characteristics curves for the humid air and dew formation conditions. Moreover, the output electrical power and the variations in relative efficiency were calculated. The results showed that the presence of dew on the surface of solar modules enhanced the photovoltaic performance parameters compared to humid air. For the mc-Si solar cell, at the dew formation condition with considering corrected the effect of temperature, the relative efficiency increased about 2.83, 3.13 and 4.06% the corresponding to the humid air conditions, while the values for pc-Si solar cell were 1.45, 3.26 and 4.39%. All photovoltaic performance parameters were decreased linearly by increasing the amount of dew covering on the module's surface.

Experimental investigation of wind effects on a standalone photovoltaic (PV) module

The pressure field on the upper and lower surfaces of a photovoltaic (PV) module comprised of 24 individual PV panels was studied experimentally in a wind tunnel for four different wind directions. The results show that the pressure distribution on the module surface is symmetric about its mid-plane for head-on wind (0° and 180°) and asymmetric at other wind directions. The inter-panel gap (which is essential in large PV modules) is found to influence module's surface pressure field. Pressure magnitudes on the module surface were increased with the module inclination angle, as expected. It is also observed that the mean pressure magnitudes on the PV module under smooth wind exposure are higher than those under open terrain wind exposure.

Quality of surface modules in machine parts

In the modular approach, all the surfaces of machine parts are divided into three classes of surface modules: basing surface modules; working surface modules; and coupling surface modules [1]. Representing machine parts as sets of surface mod� ules permits the design of the manufacturing process by combining machining modules. That entails the creation of a bank of machining modules. Working surface modules are characterized by a great diversity of designs and quality requirements, on account of their wide range of functions. Correspond� ingly, we need the corresponding machining modules. Working surface modules include sets of frictional surfaces (bearings, guides, etc.); contact surfaces of kinematic elements (working surfaces of gear teeth and racks, cam surfaces, etc.); combinations of cutting surfaces (cutters, mills, countersinks, etc.); sets of working surfaces for dies; contact surfaces of rails and wheels; and combinations of surfaces for the storage of powders, liquids, and other media. The composition and geometry of working surface modules, as well as the corresponding quality require� ments, will be determined by the processes in which they are involved. With the same surface composition and geometry, the quality requirements will depend on the intended functions. Therefore, for the same struc� ture of working surface modules, different machining modules may be required.

Plant washing as a pest management technique for control of aphids (Homoptera: Aphididae).

Changes in aphid presence following plant washings were evaluated on hibiscus plants, Hibiscus rosa-sinensis L., that supported natural aphid infestations--primarily melon aphid, Aphis gossypii Clover. Type of plant module (such as stems, tight buds, open flowers, and sepal caps) and percent of module's surface covered by aphids were recorded for each branch tip on every plant. Plant washing was done with tap water, applied for 30 s three times a week for 3 wk. Aphid presence was recorded each week. Aphid presence on plant structures immediately before and after a single 30-s wash treatment was also examined. In the 3-wk study, mean percent coverage of plant parts with aphids was significantly affected by wash treatment, plant module type, and their interactions, as well as by time and the interaction of time with wash treatment. By the third week, unwashed plants had 33.1% of stems and branch tips scoring >5% coverage with aphids, and 17.9% of unwashed stems and branch tips had 20% or more of their surface area covered by aphids. Washing plants prevented aphid coverage from ever exceeding the 5% class on all module types. In the second experiment, buds and stems with high numbers of aphids before washing generally experienced notable declines with a single wash. When the prewash coverage was 10% or greater, reduction in coverage ranged from 50 to 100% of the prewash amount. In 64% of the cases, the reduction in coverage was 75% or more of the prewash amount. Plant washing can provide a viable means of management for small, soft-bodied arthropods such as aphids.