Outdoor Operating Conditions Research Articles

Categorizing Indian states based on operating condition of photovoltaic system

Electricity generation of a photovoltaic (PV) module is primarily affected by local weather conditions, which vary significantly across vast geographic areas. This work introduces an approach to categorize Indian states based on outdoor operating conditions of PV modules that influence performance and reliability. Module temperature and irradiance are the two most important parameters which affect PV performance. Relative humidity (RH), module temperature, and global horizontal irradiance (GHI) are the three most important parameters that affect PV reliability. In this work, the PV module's most frequent operating condition (MFOC) of temperature and irradiance corresponding to maximum energy production has been analyzed for dominant PV technology (multi-crystalline silicon). Data from various sites across India were analyzed and subsequently grouped by state as PV installation decisions are generally based on state-level factors, such as state business policies, incentives, availability of local human resources, state power policies, etc. The MFOC method used in this work was supported by experimental results. Based on estimated states' MFOC, PV module output power has been obtained and compared with its rated power. Further in this work, major stressors affecting PV modules namely average RH, module temperature, and total annual GHI have been analyzed for different Indian states. Based on these specific stressors, states with similar stressor patterns have been grouped by the k-means clustering method. Results of MFOC estimation show potential for additional standardization methods to estimate PV system performance accurately. Statistical analysis of stressors highlights the importance of selecting PV technology modules carefully.

Spectral Effects on the Energy Harvesting Efficiency of Two‐ and Four‐Terminal Tandem Photovoltaics

In this work, the effect of a varying spectral irradiance and top cell bandgap on the energy harvesting efficiency of two‐terminal (2T) and four‐terminal (4T) perovskite//silicon tandem solar cells under outdoor operating conditions is investigated. For the comparison, an optoelectronic model employing a 1 year outdoor data set for a 4T mechanical stacked gallium arsenide (GaAs) on crystalline silicon (Si) tandem device is first validated. Then, the verified model is used to simulate perovskite//silicon tandem devices with a varying perovskite top cell bandgap for a location in Golden, Colorado, USA. A spectral binning method to efficiently reduce and improve the visualization of the 1 min‐resolved environmental data while maintaining the simulation accuracy is introduced. The findings reveal that, for a device that is current matched under standard testing conditions, the annual spectral deviation reduces the energy harvesting efficiency by only 2%rel. When additional realistic losses for the 4T are taken into account, 2T devices are shown to have an energy‐harvesting efficiency that is at parity or higher. Deviations in the top cell bandgap are more than 0.1 eV from current matching result in a reduced energy harvesting efficiency of more than 5%rel for the 2T tandem device.

Moisture-Resilient Perovskite Solar Cells for Enhanced Stability.

With the rapid rise in device performance of perovskite solar cells (PSCs), overcoming instabilities under outdoor operating conditions has become the most crucial obstacle toward their commercialization. Among stressors such as light, heat, voltage bias, and moisture, the latter is arguably the most critical, as it can decompose metal-halide perovskite (MHP) photoactive absorbers instantly through its hygroscopic components (organic cations and metal halides). In addition, most charge transport layers (CTLs) commonly employed in PSCs also degrade in the presence of water. Furthermore, photovoltaic module fabrication encompasses several steps, such as laser processing, subcell interconnection, and encapsulation, during which the device layers are exposed to the ambient atmosphere. Therefore, as a first step toward long-term stable perovskite photovoltaics, it is vital to engineer device materials toward maximizing moisture resilience, which can be accomplished by passivating the bulk of the MHP film, introducing passivation interlayers at the top contact, exploiting hydrophobic CTLs, and encapsulating finished devices with hydrophobic barrier layers, without jeopardizing device performance. Here, existing strategies for enhancing the performance stability of PSCs are reviewed and pathways toward moisture-resilient commercial perovskite devices are formulated.

Performance enhancement of photovoltaic modules with passive cooling multidirectional tapered fin heat sinks (MTFHS)

The electrical output of photovoltaic (PV) modules degrades with continued exposure to extreme temperatures caused by solar radiation. The uniqueness of this research lies in the utilization of multidirectional fins with varying heights, which effectively accelerate heat transfer in PV cooling systems by inducing a transition in the boundary layer within the confined zone of the fins. The research aims to investigate the effect of using Multidirectional Tapered Fin Heat Sinks (MTFHS) to improve the efficiency of PV modules by utilizing aluminum alloy material as heatsinks. The proposed multidirectional design aims to facilitate enhanced heat transfer by promoting airflow in the central area of the PV module. The experimental procedures in our study differ from previous research as we utilized the latest generation of PV modules (405 Wp, PERC Half-cut cells) to fill the discrepancy between laboratory-based investigations and practical applications. Two PV modules were tested for an outdoor parametric analysis under outdoor operating conditions, with solar irradiance recorded from 200 to 1000 W/m2 and ambient temperatures ranging from 26° to 38 °C. Findings indicated that the proposed MTFHS could lower PV module temperatures by 12 ⁰C. Reduced temperature boosts PV module efficiency by 1.53%. Cooling advancements proved vital in contributing to sustainability in PV system installations.

A novel metaheuristic MPPT technique based on enhanced autonomous group Particle Swarm Optimization Algorithm to track the GMPP under partial shading conditions - Experimental validation

In order to maximize the benefit of solar panels, it is crucial to enhance the operating efficiency of PV systems. Usually, the PV arrays are exposed to harsh outdoor operating conditions that affect their operating efficiency. Extraction of global maximum power point (GMPP) among the other local MPPs (LMPPs) from the distorted characteristics of the PV array is considered the main challenge of PV system controllers under partial shading conditions (PSCs). Classical MPP tracking (MPPT) techniques have incompetent performance in tracing the GMPP under the PSCs of PV arrays. Therefore, many metaheuristics-based MPPT techniques are developed by researchers to defeat the problems related to the PSCs and cope with GMPP and other LMPPs. Among all metaheuristic algorithms, Particle Swarm Optimization (PSO) and its modified versions are the most common optimization methods owing to their easy implementation, simplicity, and low computational burden. On the other hand, the standard PSO (SPSO) algorithm suffers from low convergence speed, and difficulty in tuning its parameters, and it may be trapped in LMPP under fast changes in solar radiation and/or PSCs. In order to tackle these issues, a novel metaheuristic MPPT technique based on an Enhanced Autonomous Group PSO (EAGPSO) algorithm is proposed. A comparative study between EAGPSO and other versions of PSO techniques is performed to emphasize the efficacy of the EAGPSO technique. The simulation results demonstrate that the proposed EAGPSO algorithm is superior to the counterpart versions of the PSO algorithms in terms of fast-tracking time, high obtained power, and high energy efficiency. Experimental validation of the EAGPSO technique has been conducted using an array of 3*3 series–parallel PV panels under PSC. The EAGPSO algorithm results have been compared with SPSO and AGPSO techniques. The experimental results show that, among the investigated MPPT techniques, the proposed EAGPSO technique has the highest MPPT efficiency of 98.6% and the lowest power oscillations of about 2.03% of the tracked power with a tracking time of 2.6 s.

Environmental aging effects on high-performance biocomposites reinforced by sisal fibers

Among the innovative materials, an important role is played by the so-called biocomposites, generally made by an eco-friendly matrix reinforced with natural fibers. Unfortunately, due to the degradability of the green matrixes as well as to hydrophilicity of the natural fibers, the resistance of such innovative materials to the environmental agents is, in general, relativity low, and it can significantly limit their use in outdoor conditions. To contribute to the knowledge of the effects of the leading environmental agents on the mechanical properties of high-performance biocomposites made of a green epoxy matrix reinforced by agave fibers, a systematic experimental testing campaign has been carried out by considering three types of biocomposite laminates (unidirectional, cross-ply and quasi-isotropic with a Vf = 70%). In detail, the different effects of aging on matrix and reinforcement have been highlighted by also considering samples consisting of simple epoxy matrix alone. The usual outdoor operating conditions associated with frequent exposure to sunlight (temperature and UV cycles) and humidity have been reproduced by subjecting the biocomposites to an accelerated aging process. Successive tensile and delamination tests have shown that aging leads to significant mechanical properties reductions, ranging from about 40% (tensile) to about 70% (delamination). A systematic analysis of the experimental results has allowed to develop reliable models that can be used to predict the degradation affecting the mechanical properties when these biocomposites are subjected to the actual aging related to the outdoor service conditions.

Ink Design Enabling Slot‐Die Coated Perovskite Solar Cells with >22% Power Conversion Efficiency, Micro‐Modules, and 1 Year of Outdoor Performance Evaluation

AbstractThe next technological step in the exploration of metal‐halide perovskite solar cells is the demonstration of larger‐area device prototypes under outdoor operating conditions. The authors here demonstrate that when slot‐die coating the halide perovskite layers on large areas, ribbing effects may occur but can be prevented by adjusting the precursor ink's rheological properties. For formamidinium lead triiodide (FAPbI3) precursor inks based on 2‐methoxyethanol, the ink viscosity is adjusted by adding acetonitrile (ACN) as a co‐solvent leading to smooth FAPbI3 thin‐films with high quality and layer homogeneity. For an optimized content of 46 vol% of the ACN co‐solvent, a certified steady‐state performance of 22.3% is achieved in p‐i‐n FAPbI3‐perovskite solar cells. Scaling devices to larger areas by making laser series‐interconnected mini‐modules of 12.7 cm2, a power conversion efficiency of 17.1% is demonstrated. A full year of outdoor stability testing with continuous maximum power point tracking on encapsulated devices is performed and it is demonstrated that these devices maintain close to 100% of their initial performance during winter and spring followed by a significant performance decline during warmer summer months. This work highlights the importance of the real‐condition evaluation of larger area device prototypes to validate the technological potential of halide perovskite photovoltaics.

Prototype of a novel hybrid concentrator photovoltaic/thermal and solar thermoelectric generator system for outdoor study

In this study, a novel prototype of a hybrid concentrator photovoltaic/thermal and solar thermoelectric generator system has been designed and constructed for combined heat and power production. In the developed hybrid system, both the solar cells and thermoelectric modules that share a common heat transfer medium are exposed to concentrated irradiance via a compound parabolic concentrator and a parabolic trough concentrator, respectively. To assess the performance of the hybrid system, a prototype of the hybrid system was built and tested under outdoor operating conditions, and the findings were compared with those of a transient numerical simulation conducted using ANSYS Fluent. The average PV temperature obtained during the test period at a flow rate of 3.8 L/min is 318.19 K which is ∼5.6% lesser compared with a conventional hybrid CPVT-TEG system. The outdoor trials show maximum electrical efficiency of 4.86% and thermal efficiency of 40% when the solar irradiance is greater than or equal to 1000 W/m2. The overall efficiency of the developed prototype is 3 times higher compared to a standalone PV system. The hybrid system helps to reduce carbon emission by 0.5 kg/h, with an associated environmental cost of 0.025 €/h.

A modeling study on developing the condensing-frosting performance maps for a variable speed air source heat pump

For a variable speed (VS) space heating air source heat pump (ASHP) unit, to comprehensive study its frosting suppression and heating performances, a condensing-frosting performance map has been proposed. An experimental study using an experimental VS ASHP unit to obtain condensing-frosting performance maps was previously reported. However, obtaining such performance maps experimentally was time consuming and costly, and it was therefore considered highly necessary to develop a mathematical model to obtain performance maps through modeling study. In this paper, therefore, a mathematical model for the experimental VS ASHP unit was firstly developed by referring to previously published mathematical models for VS air conditioners. The developed model was experimentally validated using reported experimental data. The average relative errors between the measured and predicted total output heating capacity and COP were at 3.7% and 3.6%, respectively, and the average error between the measured and predicted outdoor coil surface temperature was at 0.2 °C. A follow-up modeling study was then carried out using the validated model to obtain condensing-frosting performance maps for the experimental VS ASHP unit having different outdoor coil surface areas and at different outdoor operating conditions. The modeling study results suggested that by increasing outdoor coil surface area of the experimental VS ASHP unit from 50% to 150%, its surface temperature on average was increased by more than 1.37 °C, which was inducive to a better frost suppression performance, and the total output heating capacity by more than 11.07%, but at a higher initial manufacturing cost. The modeling study results also indicated that the developed model can be a useful tool in studying the characteristics of VS ASHPs during both frosting and frost-free operations, which was important for guiding the design and control of ASHPs for their efficient and reliable operations.

Outdoor performance evaluation of a novel photovoltaic heat sinks to enhance power conversion efficiency and temperature uniformity

The non-uniformity of photovoltaic (PV) temperature can further deteriorate its power conversion efficiency and technical lifetime over long field exposures. This study proposed novel fins for a PV module temperature reduction and enhancing temperature uniformity. The proposed multi-level fin heat sinks (MLFHS) consist of a novel geometry of extruded aluminum material attached to the rear side of the PV module. The developed outdoor experimental setup consists of two identical 120 Wp monocrystalline PV modules; one served as a reference module for comparison against the module with the proposed novel heat sink geometry. The temperature distributions across PV modules and the electrical parameters were then recorded and analysed. A substantial drop in the module temperature of 8.45 °C was observed at solar irradiance and ambient temperature of 941 W/m2 and 36.17 °C, respectively. As a result, the heat sink improved the overall power output up to 9.56% under outdoor operating conditions. Furthermore, the prominent effect of temperature uniformity was perceived for solar irradiance greater than 600 W/m2 and improved by 14.8%. These findings are foundational for passive cooling methodologies to guide further research and development of an efficient PV cooling methodology.

An Experimental Investigation of Parabolic Trough Collector Using Industrial-Grade Multiwall Carbon Nanotube (MWCNT) - H2O Based Nanofluid

Solar thermal systems for heating have a high level of reliability. The usage of parabolic trough collectors (PTC) for domestic applications is still quite limited; furthermore, commercial utilization of nanofluids in these applications is rare. The influence of MWCNT nanofluid as a heat transfer fluid on the efficiency of a locally developed parabolic trough collector was examined experimentally. The effect of surfactant on nanofluid stability was also investigated, and it was revealed that nanoparticles could be evenly suspended in base fluid for at least 10 days and less than one month using Triton X-100. Experiments were also conducted to determine the optimal quantity of Triton X-100 surfactant; it is possible to make nanoparticles stable for 28 days in base fluid with the ratio of Triton X-100 to MWCNT as 0.5:1. At 2.0, 3.0, and 4.0 L/min flow rates, MWCNT/H2O is used at three-particle concentrations of 0.1 %, 0.2 %, and 0.3 % by weight. The experiment is carried out under outdoor operating conditions. With 3 L/min at 0.2 wt. %, MWCNT nanofluid achieves a maximum thermal efficiency that is 22 % greater than the water. The findings provide important information about the commercialization of a locally developed PTC.

Experimental investigation of condensation in energy recovery ventilators

Membrane-based Energy Recovery Ventilators (ERV) have become an important part of modern ventilation systems for commercial and residential buildings due to their high sensible and latent effectiveness. Using ERVs in winter conditions, however, can result in condensation and frost formation. Whereas frost formation requires extremely low temperatures, condensation can occur even in mild winter weather conditions. In this study, a widely used ERV is experimentally tested under various indoor and outdoor operating conditions. Short time tests are used to determine the onset of condensation while long time tests are used to investigate the effect of channel blockage due to condensation on pressure drop and effectiveness of the ERV. The presence of condensation is inferred from visual observation of water in the exchanger, investigation of the sensible and latent effectiveness, and measurements of pressure drop over the exchanger. It is shown that condensation increases the sensible effectiveness of the supply side and decreases the sensible effectiveness of the exhaust side. Additionally, the latent effectiveness of both air streams increases when condensation occurs, although the increase in exhaust side latent effectiveness is more significant. Increasing the relative humidity and temperature of the indoor air increases the possibility of condensation and its rate, while increasing flowrate only increases the rate of condensation and does not affect its onset. Finally, the accumulation of water in the channels significantly increases the pressure drop in the exhaust side while it does not significantly impact the effectiveness.

Effects of Evaporator and Condenser Temperatures on the Performance of a Chiller System With a Variable Speed Compressor

The operation and performance of heat-pump systems are affected by indoor and outdoor operating conditions. Power consumption and system efficiency are related to evaporator and condenser working pressures. Intelligent controllers such as a proportional integral (PI) controller improve the performance of variable speed refrigeration systems (VSRs) with electronic expansion valve (EEV). Evaporator and condenser pressures affect the system power consumption and efficiency. In this study, the influence of evaporator and condenser temperatures on the performance of a variable speed refrigeration system with an EEV was experimentally investigated at constant cooling load. The experimental system comprises of a rotary compressor, shell-and-coil condenser, EEV, and shell-and-coil evaporator for one-ton cooling capacity with refrigerant R410. Compressor speed and EEV opening are controlled by a PI controller with two control loops and the refrigerant superheat (DS) is maintained at 7°C. The results show that at constant cooling capacity, the refrigerant flow rate rises with the increase in the compressor speed. The coefficient of performance (COP) is improved with low compressor speed. The System COP is increased by 3.3% with increasing evaporator inlet water temperature for 2°C due to the reduction in the compressor speed and compression ratio. High condenser inlet water temperature promotes the refrigerant subcooling.

Electrical and Meteorological Data Acquisition System of a Commercial and Domestic Microgrid for Monitoring PV Parameters

This paper centers on the design and installation of a robust photovoltaic (PV)-based microgrid data acquisition system (DAS) that can monitor different PV systems simultaneously. The PV-based microgrid consists of three solar systems: off-grid, hybrid and grid-assisted systems, each with 3.8 kWp located at SolarWatt park, Fort Hare Institute of Technology (FHIT), South Africa. The designed DAS is achieved by assembling and connecting a set of sensors to measure and log electrical and meteorological parameters from each of the three power plants. Meteorological parameters use a CR1000 datalogger while the electrical output parameters use a DT80 data logger. Calibration was done by voltage signal conditioning which helps to reduce errors initiated by analogue signals. The designed DAS mainly assist in assessing the potential of solar energy of the microgrid power plant considering the energy needed in the remote community. Besides, the simultaneous monitoring of the three systems ensures that the outdoor operating conditions are the same while comparing the logged data. A variable day and a week, data were used to verify the reliability of the system. The back of the array temperature was observed to be 42.7 °C when solar irradiance was 1246 W/m2. The ambient temperature and relative humidity were obtained at 21.3 °C and 63.3%, respectively. The PV current in all three systems increases with the solar irradiance and is highest around midday. The results obtained show that the designed DAS is of great interest in PV system developments.

Ternary Organic Semiconductor Blend for High Photovoltaic Performance Under Both Indoor and Outdoor Operating Conditions

Ternary blend in Organic Photovoltaics (OPVs) have been known as a way to increase performance in both low light intensity and AM 1.5G conditions. We have conducted a comparative study on 2 Donors:1 Acceptor (2D:1A) blends and 1 Donor:2 Acceptors (1D:2A) blends; 1D:2A blends have the higher performance and thermal stability than 2D:1A blends. In particular, non-fullerene acceptor (NFA) used for the 1D:2A blends have a good effect on packing property and crystallinity. The 1D:2A with optimized morphology reduced charge recombination on various irradiation conditions while the efficiency of 2D:1A devices depends on the fluorescence resonance energy transfer mechanism. The synergistic effect of 1D:2A blend with NFAs secures better efficiency and sustainable photoelectric properties under both indoor and outdoor operation conditions. Our analysis of the experiments reveals that NFA optimizes the arrangement of molecules to build more efficient ternary bulk heterojunctions in 1D:2A blends. Finally, the optimized ternary OPVs show effectively high power conversion efficiency of over 25% in both 200 lux and 1000 lux light–emitting diode conditions and present new opportunities in various practical applications.

Upscaling the fabrication routine of bioreplicated rose petal light harvesting layers for photovoltaic modules

The hierarchical micro-/nanotextures adorning the petal surfaces of certain flower species exhibit outstanding sunlight harvesting properties, which can be exploited for photovoltaic (PV) applications via a direct replication approach into polymeric cover layers. This route has been so far hampered by the restricted size of the original bio-template and by the limited number of replication cycles when a polymeric mold is used. Here, we therefore introduce an upscaling strategy allowing the fabrication of mechanically stable, temperature resistant and large area nickel mold inserts which can be employed for hot embossing lithography, and ultimately for the mass production of bioreplicated films that improve light management in PV modules. As a proof-of-concept, we laminate the thus produced textured foils, here corresponding to rose petal replicas, onto glass encapsulated copper indium gallium diselenide (CIGS) solar modules with a surface of 100 cm2. We demonstrate an increase of the power output of 5.4% with respect to a device with an uncoated glass cover layer (measured in outdoor operating conditions). This improvement is notably attributed to the excellent light in-coupling properties of the replicated texture at high oblique incidence angles.

Thermal behavior analysis of different solar PV modules via thermographic imaging

The temperature of a photovoltaic (PV) system is a critical factor in the photovoltaic conversion process; hence, the practical performance of a PV system significantly depends on its temperature. Several different methods exist for the determination of PV module temperature. In this study, thermography was employed to investigate the thermal behavior of different solar PV modules under outdoor operating conditions. It was observed that the temperature difference across the area of a PV module could reach as high as 12.5–14.8 °C depending on the type of PV module. Hence, the trends for the lowest and highest temperature were not predictable. Glass-to-glass non-frame PV modules exhibited the highest temperature gradients compared to glass-to-Tedlar non-frame modules. The observed temperature gradients demonstrated that measuring the temperature at a single point on the module was not sufficient to accurately represent the temperature over the entirety of the PV module.

Optimized Design of Silicon Heterojunction Solar Cells for Field Operating Conditions

Solar modules are currently characterized at standard test conditions (STC), defined at 1000W/m2 and 25 {\deg}C. However, solar modules in actual outdoor operating conditions typically operate at lower illumination and higher temperature than STC, which significantly affects their performance ratio (average harvesting efficiency over efficiency in STC). Silicon heterojunction (SHJ) technology displays both good temperature coefficient and good low-illumination performances, leading to outstanding performance ratios. We investigate here SHJ solar cells that use a-SiCx(n) layer as front doped layer with different carbon contents under different climates conditions. Adding carbon increases transparency but also resistive losses at room temperature (compared with carbon-free layers), leading to a significant decrease in efficiency at STC. We demonstrate that despite this difference at STC, the difference in energy harvesting efficiency is much smaller in all investigated climates. Furthermore, we show that a relative gain of 0.4 to 0.8 percent in harvesting efficiency is possible by adding a certain content of carbon in the front (n) layer, compared with carbon-free cells optimized for STC.

Application of intelligent load control to manage building loads to support rapid growth of distributed renewable generation

Electricity utilities are faced with the mounting challenge of providing a stable supply of power to meet the growing demand while also integrating rapid growth in distributed variable renewable generation. Traditional means of balancing short- and long-term supply and demand imbalance will be expensive. Alternative approaches of using flexible loads in buildings are needed to mitigate the imbalance at a lower cost. This paper shows how the intelligent load control (ILC) process can be used to manage loads in buildings by dynamically prioritizing loads for curtailment using both quantitative and qualitative criteria. The ILC process can be deployed on low-cost computing platforms without the need for any additional sensing. ILC was first validated in a simulation environment to provide two grid service use cases: (1) managing monthly peak electricity demand and (2) managing buildings’ electricity consumption during a capacity bidding event. After being successfully tested in a simulation environment, ILC was deployed on real buildings to manage electricity consumption to provide two different use cases under different outdoor operating conditions. Both the simulation tests and the real building experiments were deployed using VOLTTRON™, a distributed sensing and control platform. The results from the tests and experiments showed that ILC was able to manage the controllable loads (heat pumps) in the building to maintain the electricity consumption at the desired level without a significant impact on occupant comfort. Overall, the results demonstrate that the ILC allows coordination of the controllable loads and provides a more intelligent means of load management than the traditional duty-cycling approach.

Seasonal Performance Comparison of Four Electrical Models of Monocrystalline PV Module Operating in a Harsh Environment

To accurately predict the performance of a photovoltaic (PV) system, it is necessary to assess the effectiveness and accuracy of the methods used in modeling PV cells. This paper presents and analyzes the performance of a monocrystalline PV module (SYP80S-M) installed in outdoor operation conditions in Adrar, Algeria. The monthly experimental results are compared with those calculated by four different methods: single(fourand five-parameter) and double-diode (seven-parameter) model. The monthly average performance ratio, efficiency, and output energy were calculated and compared based on year data. Statistical analysis shows good correspondence of all models with the experimental monthly average energy data. However, the results reveal that the double-diode seven-parameter model outperforms the other models with 99.55% forecasting accuracy. In general, the accuracy of the models increases during hot months with the root-mean-square error (RMSE) varying between 2.2 and 4.4 and mean bias error (MBE) lower than 2.1, while RMSE values are higher at 4.5 and those of MBE exceed 0.37 for the cold months.