Incidence Angle Modifier Research Articles

Improving the experimental estimation of the incident angle modifier of evacuated tube solar collectors with heat pipes

This article focuses on the thermal performance testing of evacuated tube solar collectors with heat pipes (ETC-HP) using the ISO 9806:2017 standard test methods: Steady-state testing (SST) and Quasi-dynamic testing (QDT). The main objective of this work is to improve the experimental estimation of the incident angle modifier (IAM) for these types of solar collectors in both test methods. For the QDT method, a novel model for the IAM is presented and validated against SST results. This IAM model, recently developed for flat plate collectors under the SST framework, has demonstrated superior performance compared to other available models. This study marks its first application to ETC-HP technology, showcasing its adaptability across different technologies and test methods. While this work primarily focuses on ETC-HP collectors, the results are applicable to evacuated tubes in general. Thus, the generality of this model and its consistency with the SST method make it suitable for implementation in test standards as a general-purpose model. Regarding the SST method, and aiming to enhance consistency between testing methods, an improved parameter conversion from SST to QDT is also proposed, reducing IAM differences between test methods by 1 to 19 percentage points, with greater improvement at higher incidence angles.

Parametric comparison of a CPVT performance evaluation under standard testing procedures - ISO 9806:2017 and IEC 62108:2016 - for an automated and manual 2-axis tracking solar system stand

Currently, a noticeable lack of literature with respect to a wide-ranging comparison of the precision exhibited by automated and manual two-axis tracking solar systems, particularly within the context of adhering to the standard testing protocols delineated by ISO and IEC. To address this research gap, a symmetrical concentrating Photovoltaic-Thermal solar collector underwent a detailed evaluation encompassing two standard testing procedures such as ISO 9806:2017 and IEC 62108:2016. This comprehensive assessment covered thermal and electrical performance parameters, unfolding across two distinct geographical locations: Athens (Greece) and Gävle (Sweden). Within this experimental framework, an automated two-axis tracking solar system stand was employed at the Greek testing site, while in Sweden it was characterized by the employment of a manual two-axis tracking solar system. The collective peak power performance presented marginal divergence within a narrow range of ± 1% across both testing sites. This culminated in an overall peak power output of 1550 Wpeak, which included an electrical peak capacity of 218 Wpeak and a thermal peak power of approximately 1332 Wpeak. Notably, the most pronounced deviation has been materialized in the transversal and longitudinal Incidence Angle Modifier coefficients, with disparities remaining limited to a threshold of < 5%. These findings underscore the commendable precision hallmarking. In summary, the outcomes presented in this study not only contribute to the extant body of knowledge by bridging the existing gap in literature, but also emphasize the precision inherent to manual two-axis tracking solar systems when compared with automated equivalents.

Model-Based Assessment of the Incident Angle Modifier on the Annual Angular Losses and Gain of PV Modules in Tracking Systems

Model-Based Assessment of the Incident Angle Modifier on the Annual Angular Losses and Gain of PV Modules in Tracking Systems

A novel approach for incidence angle modifier calculation of arbitrarily oriented linear Fresnel collectors: Theory, simulations and case studies

The easiest possibility to assess the combined opto-energy efficiency of Linear Fresnel Collectors (LFC) is to refer to the Incidence Angle Modifier (IAM) concept: for this kind of solar collector, IAM calculation is often performed according to the so-called factorization method. Unfortunately, the factored IAM fails in providing reliable results of the real LFC yield. In this investigation, hourly 3D ray tracing simulations have been carried out on two case-study plants located in Morocco and Italy: reference ray tracing calculated IAMs have been used to develop simple correlations for inferring the instantaneous IAM of arbitrarily aligned LFCs. Instantaneous IAM formulas resulted to be able to provide yield predictions with a Root Mean Square Error equal to 5.57 % of the yearly average IAM, much lower than the factorization method (19.42 %). Subsequently, a reduced 3-day dataset of ray tracing values has been considered to calibrate the regression constants, resulting in still high accuracy for orientations not exceeding 30°. Finally, the analysis of available power at the receiver allowed to further assess the robustness of the proposed approach regardless of the plant orientation angles.

Statistical analysis of solar thermal collectors in the Solar Keymark Database

Experimental, analytical, or numerical investigations are ordinarily conducted to reveal optimisation potential for solar thermal collectors. At the same time, the ‘Solar Keymark Database’ contains more than 2,000 test reports from certified laboratories featuring properties including thermal efficiency, dimensions, or optical properties. This dataset offers untapped potential for statistical analyses as an alternative optimisation approach. Hence, this paper aims to provide a) the first statistical findings of solar thermal collector properties listed in the Solar Keymark Database and b) insights into statistical relations between these properties. The key correlations observed from the analysis of flat-plate collectors were between efficiency and both gross height (R=0.30) and gross area (R=0.27). We concluded that preferable collector designs may be featured with larger area to height ratios. The analyses of evacuated tube collectors revealed a strong correlation between efficiency and transversal incidence angle modifier (R=-0.65) as a result from different tube spacing. It was noticeable that the quasi-dynamic test method reported significantly higher efficiencies (7.14 percentage points) for evacuated tube collectors, which should be carefully considered for future test procedures. Overall, the statistical analysis was in accordance with conventional bottom-up analyses and revealed insightful dependencies for the present collector data.

Developing optical and thermal models with experimental validation of parabolic trough collector for moroccan industrial heat applications

This work presents the development of advanced optical and thermal models for parabolic trough collector systems (PTCs) through an extensive experimental study utilizing a PTMx-24 collector from Soltigua company, installed at Green Energy Park (GEP) research facility. The optical model leverages Tonatiuh software, employing the Monte Carlo Ray Tracing (MCRT) method. Moreover, a MATLAB script was adjusted to account for Incidence Angle Modifier (IAM) fluctuations in the optical analysis, while incorporating receiver thermal parameters for the thermal analysis. This study assesses the potential of PTCs in the territory of Solar Heat for Industrial Processes (SHIP) over various seasons within a semi-arid climate, offering invaluable insights for sustainable energy utilization. The validation of the models was conducted across four distinct days characterized by diverse meteorological conditions. The optical model demonstrates a remarkable correlation of 97.04 % between the MATLAB script and experimental results. Additionally, results from Tonatiuh software exhibited an important accuracy of 95.92 %. The thermal model showcased outstanding precision, revealing a correlation of 98.5 % compared to experimental results, signifying its adaptability to collectors of varying geometries and parameters. These findings highlight the predictive potential of these models, aiding in the decision-making process to determine the system's performance on specific days with specific meteorological conditions.

Optical efficiency and incidence angle modifier characterization of a Linear Fresnel Reflector collector: Validation of a certified on-site test combining experimental measurements and simulation results

The Linear Fresnel collector (LFR) is an emerging technology for concentrating solar power (CSP) and solar heating for industrial process (SHIP). A new standard has been published in 2022 in order to facilitate the certification of those products in CSP plants worldwide. However, up to now very few of this type of large-size collector have been officially tested by an accredited laboratory or certified by an accredited certification body. This paper summarizes the testing procedure and validation of a methodology used on a LFR by CENER an accredited laboratory for testing according to the standard ISO 9806 [20] for the certification of product by the American certification body [42]. The testing methodology used in this case study was based on the one defined for conventional solar collectors in quasi-dynamic test (QDT) state from the new international standard IEC 62862-5-2 [17] for CSP large-size LFR referring to the international standard ISO 9806 [20] and using optical simulation. The results of the optical and incidence angle modifier of this large-size LFR validates the testing methodology proposed based on the new standard IEC 62862-5-2 [17].

The Influence of the Installation Condition and Performance of Bifacial Solar Modules on Energy Yield

Compared with typical mono-facial photovoltaic (PV) solar modules, bifacial solar modules can make full use of reflected or scattered light from the ground and the surroundings to yield more electrical energy. The electrical energy on the rear side depends on multiple factors, such as the IV parameters of modules, packaging materials, and installation circumstances. In this work, the power generation output is simulated and researched using the PV-SYST software program, based on the different electrical parameters of bifacial solar modules and the installation conditions of the given PV systems. The influencing factors that affect the electrical energy are further analyzed using power-loss diagrams. The results show that improving the surface albedo can raise additional energy by 8.3%, thus behaving significantly better than the mono-facial module. Furthermore, improving the siting height and incidence angle modifier (IAM) of the modules can increase the additional energy by 3.1%. In contrast, adjusting the output current or voltage of the modules adds some energy, while the modules are of the same nominal power value. It was observed that the energy level of a photovoltaic system mainly depends on the installation circumstances, but the electrical parameters of the modules themselves contribute little.

Outdoor Electrical Performance of Photovoltaic Mini‐Modules with Enhanced Broadband Omnidirectional Antireflective Nanostructured Glass

Front glass structured with random subwavelength structures provides photovoltaic (PV) modules with a spectrally broadband omnidirectional antireflective property, enhancing also the incident angle modifier factor and boosting energy production in the field. However, long‐term outdoor monitoring allowing a monthly quantification of the electrical improvement of PV devices laminated with nanostructured glasses has been missing so far. Herein, two mini‐modules, one laminated with flat glass and the other laminated with nanostructured glass, are installed in a single‐axis solar tracker, and the solar irradiance and the short‐circuit current (Isc) are monitored for over 4 months, from September to December. This monitoring provides the quantification of the impact of a broad range of sunlight's angle of incidence (AOI) on the electrical enhancement of the device. The relative Isc improvement between two samples averaged for each month is calculated, ranging from 3.0% in September up to 4.0% in December. Besides, the influence of the solar AOI on the Isc improvement is investigated for sunny days, analyzing separately the Isc performance in the morning/afternoon hours, which corresponds to a normal incidence, and at noon, when the AOI is higher, obtaining more than 5.0% with AOI higher than 60°.

Simulation of Colored BIPV Modules Using Angular-Dependent Spectral Responsivity

An accurate energy yield estimation for building-integrated photovoltaic (PV) applications with colored glass under field conditions is a key factor for architects, building planners, and potential investors. The power output of these installations depends not only on the angle of incidence but also on the incident solar spectrum. The aim of this work is to simulate the short-circuit current of PV single-cell laminates with colored solar glass under field conditions. Therefore, we use angular-dependent spectral responsivity measurement data from a physical setup. Test samples with gold-, blue-, blue-green-, and gray-colored solar glass and a reference with standard solar glass, oriented on a tilted surface, are simulated. The results for one month of field validation indicate a good agreement with a relative root mean square error between 1.9% and 2.5% for the test samples. A model comparison reveals larger errors for the blue, blue-green, and gold test samples when the spectral responsivity at normal incidence and the incident angle modifier for broadband direct irradiation are used instead. It is concluded that short-circuit current simulation using indoor characterization from spectrally resolved measurement setups provides improved accuracy that is particularly suitable for bankable energy yield estimates of colored building-integrated PV modules.

Thermal and Optical Analyses of a Hybrid Solar Photovoltaic/Thermal (PV/T) Collector with Asymmetric Reflector: Numerical Modeling and Validation with Experimental Results

This study presents a combined thermal and optical, three-dimensional analysis of an asymmetric compound parabolic collector (ACPC) with an integrated hybrid photovoltaic/thermal (PV/T) receiver with the aim of establishing a sustainable approach in two ways: firstly, by determining the optimal tilt angle for operations, and secondly, by introducing an innovative simulation method which reduces computational cost while calculating thermal performance. Initially the Incident Angle Modifier (IAM) was calculated for a wide range of incident angles, and the ray-tracing results were verified using three different simulation tools (Tonatiuh, COMSOL, and SolidWorks) with mean deviations being lower than 4%. The optimal tilt angle of the collector was determined for seven months of the year by conducting a detailed ray-tracing analysis for the mean day of each month considering whole day operation. In the thermal analysis part, the authors introduced novel numerical modeling for numerical simulations. This modeling method, designed with sustainability in mind, enables lighter computational domains for the air gap while achieving accurate numerical results. The approach was established using two distinct simulation tools: COMSOL and SolidWorks. From the optical analysis, it was found that in all months examined there is a four-hour time range around solar noon in which the optimum tilt angle remains constant at a value of 30°. The numerical models constructed for the thermal analysis were verified with each other (6.15% mean deviation) and validated through experimental results taken from the literature regarding the examined collector (&lt;6% mean deviation). In addition, the two simulation tools exhibited a deviation of around 6% between each other. Finally, the thermal performance of the collector was investigated for the mean day of September at solar noon by adopting the optimal tilt angle for that month according to the optical analysis, considering inlet temperatures from 20 °C up to 80 °C.

Evaluation of Convective Heat Transfer and Natural Circulation in an Evacuated Tube Solar Collector

The evacuated tube solar collector ETC is studied intensively and extensively by experimental andtheoretical works, in order to investigate its performance and enhancement of heat transfer, for Baghdad climatefrom April 2011 till the end of March 2012. Experimental work is carried out on a well instrumented collectorconsists of 16 evacuated tubes of aspect ratio 38.6 and thermally insulated tank of volume 112L. The relationbetween convective heat transfer and natural circulation inside the tube is estimated, collector efficiency, effect oftube tilt angles, incidence angle modifier, The solar heating system is investigated under different loads pattern (i.eclosed and open flow) to evaluate the heat loss coefficient from tank and tubes, test the collector with variousaspect ratios (32.9 and 27.2). The enhancement in collector performance is studied by using two reflectors (FlatPlate and Curved Plate) and nanofluid (Water-AL2O3).Theoretical work is run by software (Fluent 6.3), to computethe velocity and temperature profiles within the tube, for different tube diameters, effect of tube junction angle andstagnant region in the bottom of the evacuated tube. The experimental results shows that the heat loss coefficientfor tube is W/m2.K and for tank is W/m2.K, the maximum collector temperature is 79°C in winter and99°C in summer, while that belong to nanofluid collector is 99°C in winter. The best tilted angle (optimum) ofevacuated tube is 41° annually. The collector efficiency increased when using nanofluid of (1, 0.6, 0.3)% volumefraction as(28.4, 6.8, 0.6)% respectively. The efficiency decreases as (33, 62)% when decreasing tube aspect ratiofrom 38.6% to 32.9% and 27.2% respectively. An increase of (16.9 and 7.08)% in collector efficiency is obtainedwhen using curved and flat plate reflectors respectively. From simulation the best junction angle of the tank is22.5°. The stagnant region is influenced with changing heat flux, tilted angle and aspect ratio.

Design, optimization and economic viability of an industrial low temperature hot water production system in Algeria: A case study

Solar energy has a great potential in many areas of industrial activity in Algeria. This is because most of Algeria has high levels of sustainable solar insulation. Unfortunately, few industries use solar energy for hot water generation, but some industrial processes require hot water at temperatures that can be easily obtained from solar thermal panels. This paper presents a case study to investigate the technical and financial feasibility of a solar-powered industrial agro-processing system in Algiers. Based on the solar collectors connection type for which the economic feasibility study was carried out, an appropriate design of the system was determined. The latter was actually done by analyzing the levelized cost of energy savings. The design of the thermo-solar process is carried out based on F-chart method with a new approach by integrating the incidence angle modifier and of using real and experimental data requirements to determine realistic achievable performance of the solar process. The results showed that, in comparison to the currently used electrical system, the electrical energy savings achieved by the solar-powered system make it an economically viable option with a solar coverage rate of 80%. The investment depreciation balance shows that the use of such a thermal solar energy system will be more competitive than fossil fuels system if the price of electricity in the country increases from 0.048 to 0.075 €/kWh.

Why Does the PV Solar Power Plant Operate Ineffectively?

Quality, reliability, and durability are the key features of photovoltaic (PV) solar system design, production, and operation. They are considered when manufacturing every cell and designing the entire system. Achieving these key features ensures that the PV solar system performs satisfactorily and offers years of trouble-free operation, even in adverse conditions. In each cell, the quality of the raw material should meet the quality standards. The fulfillment of the quality management system requires every part that goes into the PV solar system to undergo extensive testing in laboratories and environments to ensure it meets expectations. Hence, every MWh of electricity generated by the PV solar system is counted, the losses should be examined, and the PV system’s returns should be maximized. There are many types of losses in the PV solar system; these losses are identified and quantified based on knowledge and experience. They can be classified into two major blocks: optical and electrical losses. The optical losses include, but are not limited to, partial shading losses, far shading losses, near shading losses, incident angle modifier (IAM) losses, soiling losses, potential induced degradation (PID) losses, temperature losses, light-induced degradation (LID) losses, PV yearly degradation losses, array mismatch losses, and module quality losses. In addition, there are cable losses inside the PV solar power system, inverter losses, transformer losses, and transmission line losses. Thus, this work reviews the losses in the PV solar system in general and the 103 MWp grid-tied Al Quweira PV power plant/Aqaba, mainly using PVsyst software. The annual performance ratio (PR) is 79.5%, and the efficiency (η) under standard test conditions (STC) is 16.49%. The normalized production is 4.64 kWh/kWp/day, the array loss is 1.69 kWh/kWp/day, and the system loss is 0.18 kWh/kWp/day. Understanding factors that impact the PV system production losses is the key to obtaining an accurate production estimation. It enhances the annual energy and yield generated from the power plant. This review benefits investors, energy professionals, manufacturers, installers, and project developers by allowing them to maximize energy generation from PV solar systems and increase the number of solar irradiation incidents on PV modules.

Performance Evaluation of Novel Concentrating Photovoltaic Thermal Solar Collector under Quasi-Dynamic Conditions

Concentrating Photovoltaic Thermal (CPVT) collectors are suitable for integration in limited roof space due to their higher solar conversion efficiency. Solar sunlight can be used more effectively by CPVT collectors in comparison to individual solar thermal collectors or PV modules. In this study, the experimental investigation of a novel CPVT collector called a PC (power collector) has been carried out in real outdoor conditions, and the test set-up has been designed based on ISO 9806:2013. A quasi-dynamic testing method has been used because of the advantages that this method can offer for collectors with a unique construction, such as the proposed collector, over the steady-state testing method. With a quasi-dynamic testing method, it is possible to characterize the collector within a wide range of incidence angles and a complex incidence angle modifier profile. The proposed novel collector has a gross area of 2.57 m2. A maximum power output per collector unit area of 1140 W is found at 0 °C reduced temperature (1000 W/m2 irradiance level), while at a higher reduced temperature (70 °C), it drops down to 510 W for the same irradiance level. The data have been fitted through a multiple linear regression method, and the obtained efficiency curve coefficients are 0.39, 0.192, 1.294, 0.023, 0.2, 0, −5929 and 0 for Kθd, b0, c1, c2, c3, c4, c5 and c6, respectively. The experimental characterization carried out on the collector proved that the output powers calculated by using the obtained parameters of the quasi-dynamic testing method are in good agreement with experimental points.

A Spot-Area Method to Evaluate the Incidence Angle Modifier of Photovoltaic Devices—Part 1: Cells

The angle of incidence of solar irradiation on photovoltaic modules varies throughout the day. At larger angles of incidence, the modules are subject to higher reflection losses, resulting in lower light transmission and energy yield. The impact of the relative angular transmittance on the energy yield is often evaluated with a correction factor, commonly referred to as incidence angle modifier (IAM). In this article, a new method to quantify the IAM of photovoltaic devices is presented, which is different from the methods proposed in IEC 61853-2: It encompasses a spot-area irradiation, a customized angle probe holder, and a current-to-voltage converter. This first part focuses on single-cell minimodules and validates the new method on two different cell architectures—an interdigitated back-contact solar cell and a four-busbar solar cell, with an analysis of the measurement bias due to busbars. A second part will follow on the implementation of the same method to commercial-size silicon modules. The study is intended to contribute to the IEC 61853-2 standard. A detailed uncertainty analysis is presented and the method is validated versus IEC 61853-2. Our proposed method shows great potential as it is less expensive and more adaptable than existing standard methods.

Experimental Electrical Assessment Evaluation of a Vertical n-PERT Half-Size Bifacial Solar Cell String Receiver on a Parabolic Trough Solar Collector

A two-trough parabolic-shaped concentrating photovoltaic solar collector with a vertical half-size ‘phosphorus-passivated emitter rear totally diffused’ bifacial cell string receiver was designed and built for household applications, with the aim of smooth the electrical ‘duck curve’. The study consisted in testing the concentrating photovoltaic solar collector outdoors, under real weather conditions, for its daily electrical peak power and efficiency, as well as for its electrical transversal and longitudinal Incidence Angle Modifier direction. The outdoor testing measurements were conducted in a parabolic trough with low concentration coupled with a central vertical half-size ‘phosphorus-passivated emitter rear totally diffused’ bifacial cell string receiver. Furthermore, the electrical transversal Incidence Angle Modifier showed to be very delicate due to the position and outline of the receiver, which led to an electrical peak efficiency close to 10% at ±25° (i.e., for an electrical power output of around 49.3 W/m2). To validate the measured parameters, a ray-tracing software has been used, where the measured Incidence Angle Modifiers have a very good agreement with the simulated Incidence Angle Modifiers (e.g., deviation of &lt;4%). Consequently, the concentrating solar collector met the objective of lowering the Photovoltaic cell stress and high radiation intensity, by shifting the electrical peak power at normal (e.g., at 0°) to higher incidence angles (e.g., ±25°); this aids the electrical demand peak shaving, by having the highest electrical power production displaced from the highest intensity solar radiation during the day.

Random subwavelength structures on glass to improve photovoltaic module performance

Glass samples have been processed by a single-step self-masking RIE (Reactive Ion Etching) process to obtain random subwavelength structures (SWSs), which mimic anti-reflective and anti-soiling patterns present in nature. The SWSs fabricated on glass provide an excellent broadband omnidirectional anti-reflective (AR) property (¡1% absolute reflectance) in the spectral region (300–1200) nm due to the graded refractive index that these SWS produce in the air–glass interface, reducing the reflectance. Moreover, these SWSs increase the roughness of the glass surface enhancing its wettability and anti-soiling properties. In order to quantify the performance improvement of photovoltaic devices when using these structured glasses as front cover, commercial PERC (Passivated Emitter and Rear Contact) solar cells have been laminated with these structured glasses using the standard configuration (glass/EVA/Solar Cell/EVA/backsheet) and their electrical parameters such as I–V curve, spectral response, and IAM (Incidence Angle Modifier) factor have characterized.

Germany: Orion – carbon black

Glass samples have been processed by a single-step self-masking RIE (Reactive Ion Etching) process to obtain random subwavelength structures (SWSs), which mimic anti-reflective and anti-soiling patterns present in nature. The SWSs fabricated on glass provide an excellent broadband omnidirectional anti-reflective (AR) property (¡1% absolute reflectance) in the spectral region (300–1200) nm due to the graded refractive index that these SWS produce in the air–glass interface, reducing the reflectance. Moreover, these SWSs increase the roughness of the glass surface enhancing its wettability and anti-soiling properties. In order to quantify the performance improvement of photovoltaic devices when using these structured glasses as front cover, commercial PERC (Passivated Emitter and Rear Contact) solar cells have been laminated with these structured glasses using the standard configuration (glass/EVA/Solar Cell/EVA/backsheet) and their electrical parameters such as I–V curve, spectral response, and IAM (Incidence Angle Modifier) factor have characterized.

Control Strategies Applied to a Heat Transfer Loop of a Linear Fresnel Collector

The modelling of Linear Fresnel Collectors (LFCs) is crucial in order to predict accurate performance for annual yields and to define proper commands to design the suitable controller. The ISO 9806 modelling, applied to thermal collectors, presents some gaps especially with concentration collectors including LFCs notably due to the factorisation of the incidence angle modifiers and the fact that they are considered symmetric around the south meridian. The present work details the use of two alternative modellings methodologies based on recorded experimental data on the solar system installed at the Cyprus Institute, in the outskirts of Nicosia, Cyprus. The first modelling is the RealTrackEff, which is an improved ISO9806 modelling, and the second is constructed using the CARNOT blockset in MATLAB/Simulink. Both models include all the elements of the heat transfer fluid loop, i.e., mineral oil, with a tank and a heat-exchanger. First, the open loop’s studies demonstrated that the root mean square on temperature is 1 °C with the RealTrackEff; 2.9 °C with the CARNOT and 6.3 °C with the ISO9806 in comparison to the experimental data. Then, a PID control is applied on the experimental values in order to estimate the impact on the outlet temperature on the absorber and on power generation. Results showed that the error on the estimation of the heat absorbed reaches 32%.