Spectral Irradiance Distribution Research Articles

Evaluation of the energy conversion performance of different photovoltaic materials with measured solar spectral irradiance

Solar spectral irradiance distributions have a great impact on the photoelectric conversion performance of photovoltaic materials. By average photon energy, this paper assessed the practical conversion performance of ten types of photovoltaic materials based on the spectral measurements of Beijing and Changsha, China. Photon energy utilization efficiency was proposed to assess the practical conversion performance of photovoltaic materials at the same aperture area. Monocrystalline silicon had the best energy utilization efficiency when the spectrum is the red-rich or close to the reference spectrum. However, gallium arsenide would outperform it if the average photon energy exceeded 1.95 eV. Mismatch factor was used at the same rated output power of photovoltaic materials. It is found that the mismatch factor of perovskite with a 1.22 eV bandgap energy ranks the first place when the spectrum is the red-rich or close to the reference spectrum. However, the perovskite with a 1.83 eV bandgap energy has the optimal conversion performance at the average photon energy over 1.83 eV. Moreover, an ideal photovoltaic material with advanced properties was proposed for optimal performance with the regional spectra, which might provide useful instruction for photovoltaic industries to produce the most suitable photovoltaic material considering the annual regional spectrum.

Assessment of the global applicability of three leading indices that characterize the spectral distribution of solar irradiance impacting various photovoltaic technologies

At each instant, the actual solar irradiance has a specific spectral distribution that most generally differs substantially from the standardized reference conditions under which photovoltaic (PV) cells are rated. To help reduce the dimensionality of the calculations needed to quantify the spectral effects on PV cells, various spectral indices have been introduced in the literature to simply characterize the incident spectral distribution with a single number. In previous studies, diverging conclusions have been reached about whether or not a single number can effectively represent a specific spectral distribution. This disagreement needs to be resolved before the usage of spectral indices can be considered best practice. To that effect, this study proposes a novel modeling approach. Here, three spectral indices (Average Photon Energy, APE; Blue Fraction, BF; and Useful Fraction, UF) are critically evaluated and compared using the SMARTS radiative transfer model and a large database of atmospheric inputs that are representative of the vast diversity of possible conditions worldwide, thus avoiding the rarity and limitations of costly experimental measurements. A total of 28,260 pairs of direct normal and global horizontal spectra are obtained, from which the three indices are calculated over six different wavebands that characterize different PV technologies. The key variables that have a significant impact on the indices are found to be: air mass, aerosol optical depth, Ångström exponent, and precipitable water. Using a variety of tests to evaluate the behavior of the three indices relatively to the reference direct and global spectra, results show that UF is prone to anomalous variations under a variety of circumstances. APE and BF behave similarly and reliably, but APE is found more responsive to even small changes in atmospheric conditions, and is thus preferable. A critical finding is that none of the indices can be considered bijective because compensations between red-shifting and blue-shifting atmospheric processes often result in different spectral distributions having the same index value.

A Fiber-Optic Array Spectrometer With Parallel Multichannel Optical Lock-in Detection and its Application to in Situ Lighting Measurements

This paper describes a new optical spectroscopy instrument achieving lock-in detection in all its spectral output channels in a parallel and simultaneous fashion. It is based on two identical compact array spectrometers working in phase quadrature thanks to optical modulators synchronized with an external reference signal. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In the application example, the optical lock-in spectrometer was used to perform spectral irradiance measurements with commercial LED lamps exhibiting temporal light modulation at different frequencies. A remote sensing optical device was designed to measure from a distance the temporal luminous waveform of a specific LED lamp and send it to the reference input of the optical lock-in spectrometer. When the lamps were operating together on top of a large continuous luminous background, the optical lock-in spectrometer successfully retrieved the respective spectral irradiance distributions and color parameters of each lamp, allowing their characterization to be performed independently of the other light sources illuminating the sensor during the measurements.

Energy Yield Modeling for Optimization and Analysis of Perovskite‐Silicon Tandem Solar Cells Under Realistic Outdoor Conditions

AbstractA comprehensive algorithm for calculating the energy yield (EY) is used as the most important figure‐of‐merit in determining the capabilities of PV devices in realistic operation. The model is based on advanced optical modeling and extensive opto‐thermo‐electrical characterization. It takes the realistic environmental and device installation data fully into account, as well as the complete set of device specifications including all relevant temperature‐induced variations. A detailed analysis and optimization of two‐terminal perovskite‐silicon tandem devices are done in terms of long‐term electrical energy production at different geographical locations from distinct Köppen–Geiger–Photovoltaic climate zones (KGPV). It is shown that the optimal perovskite bandgap (EG,PK) in a tandem device operating under realistic conditions is in all cases higher than the one optimized under STC, yet does not differ significantly from location to location, which is beneficial from the manufacturing point of view. The optimal EG,PK is influenced primarily by the spectral distribution of incident irradiance, and not so much by the operating temperature conditions. Moreover, a clear linear dependency between the optimal EG,PK and the weighted average photon energy of the incident irradiance is demonstrated, which presents an important rule for rapid tandem design.

Spectral Factor of Colored Solar Cells: A Case Study on the Main Urban Areas in Romania

PV modules for Building-Integrated Photovoltaic (BIPV) applications are made of different colors aimed at raising the visual aesthetic of the building. But a colored coating applied to the surface of a basic PV module is inherently associated to a decrease in conversion efficiency. From a different perspective, the efficiency of a PV module is evaluated under the industry standard test conditions (STC). Due to spectral mismatch, the efficiency of a PV module operating in outdoor conditions may substantially differ from the standard value evaluated at STC. In this study, the influence of spectral solar irradiance distribution on the colored PV module efficiency is evaluated in terms of spectral factor (SF). SF quantifies the relative power gain or loss caused by the spectral difference from STC. The theory is illustrated with a case study on the main four urban areas in Romania. The actual solar radiation spectrum is estimated with the simple Leckner spectral solar irradiance model, based on atmospheric parameters retrieved from the Aerosol Robotic Network (AERONET). The results emphasize that the aesthetic of BIPV comes at a high energy cost: depending on the color, a coating applied on the surface of a crystalline silicon PV module may reduce its conversion efficiency even by half.

Simulations of Luminescent Solar Concentrator Bifacial Photovoltaic Mosaic Devices Containing Four Different Organic Luminophores

In this article, various design configurations of luminescent solar concentrator photovoltaic (LSC-PV) devices have been simulated using Monte Carlo raytracing. These LSC PV devices are composed of mono-crystalline silicon solar cells and cubical poly (methyl methacrylate) lightguides, each containing one of the following dyes: Lumogen F Red 305, Lumogen F Orange 240, Perylene Green, or Perylene-diimide di-tert-butylphenyl, which results in different device colors. In these devices, mono-crystalline silicon bifacial PV cell are placed in between the vertical edge(s) of neighboring cubical lightguides whereas monofacial PV cells are positioned at the bottom of a lightguide. Each device is made out of five cubical 10 &#x00D7; 10 &#x00D7; 10 mm³ lightguides, meaning that the PV cells measure 10 &#x00D7; 10 mm². The main research goal of this article is to evaluate the optical and electrical performance of five of such configured LSC-PV devices. Hence, the spectral distribution of irradiance received by the edges and bottom of the devices has been simulated as well as the optical efficiency of these surfaces and the power conversion efficiency of each device. The theoretical results for power conversion efficiency are in the range of 13.3&#x0025; to 18&#x0025; under irradiance of 1000 W&#x002F;m² and depend on the dyes applied. Hence, this article demonstrates the potential for energy generation by these colorful LSC-PV technologies, which we have called Mosaic devices.

The Calculated Circadian Effects of Light Exposure from Commuting

Light entrains human circadian rhythms, but increased time spent indoors and decreased daylight exposure may disrupt human circadian regulation and cause health problems. Much research is focused on improving indoor lighting conditions to minimize the adverse circadian impact of electric lights, and few studies investigate the circadian impact of daylight during the incidental time that people spend outdoors. For instance, when people commute from home to work, they are exposed to daylight. The purpose of this study is to investigate daylight’s impact on commuters’ circadian rhythms. Measurements of the illuminance and the spectral irradiance distribution (SID) of daylight were taken for three modes of commuting: driving, riding on trains, and walking; and under different weather conditions, on different days, and at different locations throughout the summer and autumn in the Sydney metropolitan region in Australia. With the SID data, three metrics were calculated to estimate the circadian impacts: α-opic irradiance, circadian stimulus (CS), and equivalent melanopic lux (EML). The results suggest that driving or walking on sunny or cloudy days and riding trains on sunny days are beneficial for the commuters’ circadian synchronization.

Toward a Connected System—Understanding the Contribution of Light from Different Sources on Occupants’ Circadian Rhythms

Light that enters humans’ eyes and impacts circadian rhythms may come from various sources, including the sun, electric lighting systems, and self-luminous displays. Occupants’ activities strongly impact the light entering their eyes, which is difficult to predict and not yet well understood. This study investigated the circadian contributions of light from different sources in real building environments to better understand the variables that influence the circadian health of occupants. Spectral irradiance distributions at a position equivalent to the front of an eye of a seated occupant in various interior office spaces were collected. Daylight and electric light were measured separately, and light emitted from displays was measured when a variety of different computer tasks was performed. Circadian stimulus (CS) and α-opic irradiance, defined by CIE DIS026/E:2018, were further calculated, and the circadian effects of light from different sources were compared. The results show that daylight has the greatest circadian effect, while electric light in spaces that were predominantly designed with conventional downward lighting has a very limited impact. The circadian effect of light from screens was considerably high. The outcomes suggest that, to optimise the circadian effects of light, connected lighting systems are needed to control light from different sources.

Fast and accurate short-circuit current versus irradiance determination of a spectrally nonlinear solar cell using a spectral shaping setup

This work presents a fast and accurate solar cell characterization method for determining the short-circuit current I STC under standard test conditions. Additionally, the short-circuit current versus irradiance relation is derived, including accurately and precisely measured nonlinearities. Similar to the Differential Spectral Responsivity (DSR) method, our White Light Response (WLR) method uses a differential measurement technique with lock-in amplifiers. The first derivative of the short-circuit current versus irradiance relation (AM1.5-weighted differential responsivity) is measured at many irradiance levels without additional spectral mismatch corrections and considers the AM1.5 reference solar spectral irradiance distribution. The WLR method is significantly faster than the DSR method in determining the short-circuit current and nonlinearities. The highly spectrally nonlinear rear side of a bifacial PERC solar cell was investigated. The strong influence of the number of measured AM1.5-weighted differential responsivities and interpolation procedures on the short-circuit current I STC is demonstrated. Finally, the accuracy of the results is discussed by means of a measurement comparison with the fully spectrally resolved DSR methods at PTB and CalLab PV Cells at ISE. • Fast nonlinearity determination in the current versus irradiance curve • AM1.5 reference solar spectrum at a low irradiance is reproduced • Measurement comparison with the Differential Spectral Responsivity (DSR) method • A spectrally nonlinear rear side of a bifacial PERC solar cell is investigated • Interpolation procedure, number of measured differential responsivities is crucial

Gallium content-dependent efficiency limits of CIGS solar cells at AM1.5G solar irradiance

The gallium content-dependent theoretical limit of the efficiencies of Cu ( In , Ga ) Se2 solar cells were studied using a MATLAB model developed based on the Shockley–Queisser detailed balance. The developed model included the temperature dependence of the bandgap according to the gallium content. The original Shockley–Queisser detailed-balance and the developed model at the ASTM G173-03 AM1.5G solar irradiance were used to calculate the gallium content and solar cell temperature-dependent theoretical efficiency limits of a Cu ( In1 − xGax ) Se2-based solar cell. Due to the spectral distribution of the solar irradiance, there were two “peaks” of efficiency: one at values of x around 0.2 prevails at lower temperatures and the other at values of x around 0.6 higher at temperatures above 0°C. Consequently, there is a “pit” with a minimum at x of around 0.5. Values of x corresponding to these values are higher for the temperature-dependent bandgap model. The calculated relative difference between the ultimate efficiency limit and the theoretical efficiency at x = 0.3 at 310 K is <1 % .

Photosynthesis and Bio-Optical Properties of Fluorescent Mesophotic Corals

Mesophotic coral ecosystems (MCEs) are light-dependent coral-associated communities found at 30–150 m depth. Corals inhabiting these deeper reefs are often acclimatized to a limited and blue-shifted light environment, enabling them to maintain the relationship with their photosynthetic algal symbionts (family Symbiodiniaceae) despite the seemingly suboptimal light conditions. Among others, fluorescent proteins produced by the coral host may play a role in the modulation of the quality and spectral distribution of irradiance within the coral tissue through wavelength transformation. Here we examined the bio-optical properties and photosynthetic performances of different fluorescence morphs of two mesophotic coral species Goniopora minor and Alveopora ocellata, in order to test the photosynthesis enhancement hypothesis proposed for coral fluorescence. The green morph of G. minor and the low fluorescence morph of A. ocellata exhibit, in their natural habitats, higher abundance. The morphs also presented different spectral reflectance and light attenuation within the tissue. Nevertheless, chlorophyll a fluorescence-based, and O2 evolution measurements, revealed only minor differences between the photosynthetic abilities of three fluorescence morphs of the coral G. minor and two fluorescence morphs of A. ocellata. The fluorescence morphs did not differ in their algal densities or chlorophyll concentrations and all corals harbored Symbiodiniaceae from the genus Cladocopium. Thus, despite the change in the internal light quantity and quality that corals and their symbionts experience, we found no evidence for the facilitation or enhancement of photosynthesis by wavelength transformation.

Programmable spectral shaping demonstrated at the solar spectral irradiance distribution.

Highly accurate short-circuit current measurements of photovoltaic devices require spectrally adjustable radiation sources. This paper presents an optical setup, which is able to generate and adjust the spectral irradiance in the wavelength range from 355 nm to 1200 nm with an optical resolution of 7 nm to 15 nm. A grating light valve (GLV) is used as a spectral shaping tool. We prove the highly resolved spectral shaping capability by matching the spectral irradiance of the generated radiation to the AM1.5g reference solar spectral irradiance distribution, slightly smoothed to consider the limited bandwidth of the spectrometer. Remaining deviations are mostly lower than the spectral measurement noise of 0.5 % to 3 %.

Quantitative effects of PM concentrations on spectral distribution of global normal irradiance

Daylight refers to a free and valuable resource exhibiting photometric and radiometric features, and the physical parameters commonly used to represent its features are irradiance and illuminance. They are both obtained by the spectral power distribution (SPD) of global irradiance, demonstrating that values noticeably affect indoor thermal and luminous environments. Nevertheless, outdoor particulate matter (PM) significantly affects SPD conditions, and two relative spectral notions, i.e., percentage of spectral irradiance (PSIr) and percentage of spectral illuminance (PSIl), were proposed to study the effects of PM10 concentrations in radiometry and photometry with a field measurement, Beijing. As a result, the strong impact of PM10 on PSIr/ PSIl can be noticed in the range (380 to 540 nm) (P-value < 0.01) by correlation analysis, and a wavelength of 510 nm was taken to build models between PM10 and PSIr/ PSIl based on regression analysis. With this wavelength, PSIr varies from 0.29 to 0.25%, and PSIl ranges from 0.48 to 0.42% with the increase of PM10 concentrations from 0.01 to 0.098 mg/m3. With the verification of the model, several bands were further analyzed to comprehensively verify the monotonic correlations, and the band ranging 480 ~ 520 nm were reasonably proved that PSIr/PSIl and PM10 can be well indicated by each other. As influenced by the complexity of spectral transmittance through the glazing, the mutual characterization between solar spectrum and particulate matters can contribute to the building energy-efficient design and develop indoor thermal and luminous environment research in the future.

Measurement Uncertainties in I–V Calibration of Multi-junction Solar Cells for Different Solar Simulators and Reference Devices

Different types of dual-junction solar cells (perovskite/silicon and GaInP/(Al)GaAs) are used in an investigation of measurement uncertainty for electrical characterization of multi-junction solar cells. A method traceable to international reference standards is presented. The spectral mismatch factor matrix is introduced and used with a Monte-Carlo method including manifold correlated and uncorrelated uncertainties. In this way, a detailed analysis of the solar simulator's spectral irradiance and its influence on uncertainty becomes possible. The use of subcell-adapted and broadband reference solar cells is addressed regarding their impact on uncertainty. This allows for finding optimal conditions for calibration with lowest measurement uncertainty. The short-circuit current of a series connected multi-junction solar cell is affected by luminescence coupling and other effects. With an experimental method it is shown how the uncertainty of the device short-circuit current can be precisely determined. The spectrometric characterization method allows deriving uncertainties of all I–V parameters. In this way a complete evaluation of measurement uncertainty for the calibration of multi-junction solar cells at standard testing conditions is introduced. This article is an extension to our work presented at the 46th IEEE PVSC. Here, we have added a detailed analysis of the influence of different solar simulator spectral irradiance distributions on measurement uncertainty by evaluating a Monte Carlo simulation introducing correlation coefficients. In addition for the first time, it is shown how luminescent coupling influences the calibration of multi-junction solar cells and how the effect needs to be implemented into the uncertainty of measurement for the short-circuit current as well as efficiency.

Spectral Irradiance Distribution in Underwater Light Field Generated by an LED Light Source

Yang, P.; Wu, Z.; Chen, Y.; Guo, Y.; Zhang, P., and Song, H., 2020. Spectral irradiance distribution in underwater light field generated by an LED light source. In: Yang, Y.; Mi, C.; Zhao, L., and Lam, S. (eds.), Global Topics and New Trends in Coastal Research: Port, Coastal and Ocean Engineering. Journal of Coastal Research, Special Issue No. 103, pp. 453–457. Coconut Creek (Florida), ISSN 0749-0208.Artificial underwater illumination has a wide range of applications in coastal zone research, marine engineering, marine resource exploration and development, and marine ecological environment monitoring. In this article, the distribution of spectral irradiance has been discussed for an underwater light field generated by an underwater LED light source. Theoretical representations of the spectral irradiance have been derived according to physical principles and underwater spectral irradiance measurement have been accrued out along the optical axis of the light source and in the vertical plane perpendicular to the optical axis. Experimental results show that the spectral irradiance along the optical axis of the light source decays with respect to the distance, following the law of square attenuation and exponential attenuation. The irradiance in the vertical plane approximately matches the Gaussian distribution.

Rear‐side spectral irradiance at 1 sun and application to bifacial module power rating

AbstractThe air mass 1.5 global (AM1.5G) reference spectral irradiance distribution is defined in the international standard IEC 60904‐3, accounts for the direct, diffuse, and albedo components directing 1000 W/m2 (1 sun) of global irradiance at a photovoltaic (PV) module's front side. Bifacial PV modules, however, receive an additional irradiance contribution from the rear side, which is not accounted for in the reference irradiance. This work strives to shed light on the amount of expected light that arrives on the rear side of a PV module, when the front‐side irradiance and ambient conditions match the conditions used for the calculation of AM1.5G. For this purpose, an optical model was developed to simulate the rear‐side spectral irradiance of PV modules, whose validity was verified by outdoor measurements. The results show that the average rear‐side irradiance at a set of conditions as defined in IEC 60904‐3 lies in the range of 130 to 150 W/m2. The results of this work lay the foundation to define the bifacial Standard Test Conditions (BSTC), which can be used to support the technical specification IEC TS 60904‐1‐2 and international standard IEC 60904‐3 and establish supplementary requirements for the power rating and label verification of bifacial PV modules.

Errors in PV power modelling due to the lack of spectral and angular details of solar irradiance inputs

Photovoltaic (PV) modules are sensitive to the spectral distribution of solar irradiance. Although numerical weather prediction (NWP) models compute irradiance in several spectral bands, only broadband quantities are provided in the standard outputs used for PV forecasts. This study investigates how this lack of information impacts PV power estimation. A physical PV model is first designed that accounts for the spectral distribution of irradiance and the spectral response of the panels. This model is evaluated using measurements performed at Site Instrumental de Recherche par Télédétection Atmosphérique (SIRTA), Palaiseau, France. The mean relative difference between simulated and measured PV power for a monocrystalline silicon module of 250 W nominal power is −0.9%, and the mean bias is −2.0 W. This model is then used to investigate the impact of solar zenith angle and clouds on the performance of PV modules. PV performance can increase in cloudy conditions by 5% through spectral filtering of near-infrared irradiance, and by 18% when only the useful irradiance is considered to compute performance. This spectral effects is not captured by the PV model when only broadband irradiances are used. In such case errors up to 15% are obtained in simulated PV power compared to using a state-of-the-art NWP model providing irradiance in 14 spectral bands. More generally, broadband global horizontal irradiance appears insufficient for accurate PV power modelling, highlighting the added value of spectrally-and-angularly-refined irradiances. This stresses that PV models should use more detailed irradiance inputs, which could be easily achieved by exploiting internal variables of NWP models.

Investigation on the optical and energy performances of different kinds of monolithic aerogel glazing systems

Aerogel glazing system is an advanced energy-efficient glazing system designed to reduce the building energy consumption. However, there is no study focused on the energy performances of aerogel glazing systems filled with different aerogels. To analyse the energy performance, the solar extinction coefficient is an indispensable parameter, which is unknown yet. In this research, the solar extinction coefficient is calculated by Mie scattering and Monte Carlo method. The spectral distribution of solar irradiance is taken into account. The influences of porosity and nano-particle’s size are discussed. Then, the solar heat gain coefficients of different aerogel glazing systems versus incidence angle are calculated. Finally, a dynamic heat transfer model is used to simulate the energy performances of different aerogel glazing systems. A case study is carried out for Hong Kong. The results indicated that the porosity of monolithic aerogel has greater influence than the diameter, and the reciprocal effect between the porosity and the diameter is negligible. It is also figured that aerogel with small nano-particle and low porosity will lead to a better energy conservation performance in cooling dominated region.

Description of short circuit current of outdoor photovoltaic modules by multiple regression analysis under various solar irradiance levels

Short-circuit current (ISC) values of test photovoltaic (PV) modules, i.e., multi-crystalline silicon, heterostructure-with-intrinsic-thin-layer, single-crystalline silicon back-contact, CuInSe2 (CIS), and CdTe modules, are descripted using multiple regression analysis based on environmental factors (solar irradiance, average photon energy (APE), and module temperature (Tmod)) under several solar irradiance levels. The APE is an index of the solar spectral irradiance distribution. PV module irradiance sensor (PVMS), single-crystalline silicon PV module, is used to investigate simultaneous solar irradiance (IrrTPVMS). It is disclosed that ISC is primarily determined by IrrTPVMS. Error between the estimated ISC and measured ISC of test PV modules is investigated. Consequently, precise ISC description (low error) is obtained when IrrTPVMS is utilized. The more precise description of the ISC for CIS and CdTe PV modules, having the bandgap (Eg) different from PVMS, is realized when adding APE environment factor even under low IrrTPVMS (≥0 kW/m2), accumulated on both sunny day and cloudy day suggesting the enhancement of investigation opportunity. This is because APE minimizes spectral mismatch error caused by Eg difference between PVMS and test PV module. Moreover, the precision of ISC description is further increased under enhanced IrrTPVMS of ≥0.5 kW/m2 (on sunny day) due to stable solar irradiance.

Comparative Review of Artificial Light Sources for Solar-Thermal Biomass Conversion Research Applications

AbstractIn recent years solar-thermal methods of waste biomass conversion are promptly gaining on attention. For researchers working in areas that suffer from lack of natural solar power, the choice of proper solar simulator for the study is crucial. Solar simulator consist of artificial light source enclosed in proper housing with optical and cooling system, powered by dedicated power supply. Solar simulators are not only granting independence from external conditions, yet provide possibility of research expand due to tuneable output power and emissive spectrum. Over the years, solar simulators were powered by different types of lamps. Throughout the history, the solar simulators were used mainly in photovoltaic and space research, crystal growth industry, and the material testing. For mentioned purposes, the total thermal output power of simulator was playing secondary role in comparison to urgent need of spectral match, irradiance distribution and beam uniformity with terrestrial or extra-terrestrial sunlight. For thermal applications, solar simulators are facing the challenge of providing high output power, described by high radiant heat flux and high heat flux density over the specified target area. In presented paper the comparison of xenon arc, metal halide lams and tungsten halogen for thermal applications has been presented with emphasis on available thermal power, spectral match with natural sunlight and operational issues. The course of decision taken during the selection of artificial light source for construction of laboratory-scale solar pyrolytic reactor is proposed.