Terrestrial Solar Irradiance Research Articles

A Wide Spectral Range Sky Radiance Model

AbstractPre‐computed models of sky radiance are a tool to rapidly determine incident solar irradiance in applications as diverse as movie VFX, lighting simulation for architecture, experimental biology, and flight simulators. Several such models exist, but most provide data only for the visible range and, in some cases, for the near‐UV. But for accurate simulations of photovoltaic plant yield and the thermal properties of buildings, a pre‐computed reference sky model which covers the entire spectral range of terrestrial solar irradiance is needed: and this range is considerably larger than what extant models provide. We deliver this, and for a ground‐based observer provide the three components of sky dome radiance, atmospheric transmittance, and polarisation. We also discuss the additional aspects that need to be taken into consideration when including the near‐infrared in such a model. Additionally, we provide a simple standalone C++ implementation as well as an implementation with a GUI.

Power Generation Analysis of Terrestrial Ultraviolet-Assisted Solid Oxide Electrolyzer Cell

This paper presents a novel system design that considerably improves the entrapment of terrestrial ultraviolet (UV) irradiance in a customized honeycomb structure to produce hydrogen at a standard rate of 7.57 slpm for places with a UV index > 11. Thermolysis of high salinity water is done by employing a solid oxide electrolyzer cell (SOEC), which comprises three customized, novel active optical subsystems to filter, track, and concentrate terrestrial UV solar irradiance by Fresnel lenses. The output of systems is fed to a desalinator, a photovoltaic system to produce electrical energy, and a steam generator with modified surface morphology to generate the required superheated steam for the SOEC. A simulation in COMSOL Multiphysics ver. 5.6 has shown that a customized honeycomb structure, when incorporated on the copper–nickel surface of a steam generator, improves its absorptance coefficient up to 93.43% (48.98%—flat case). This results in generating the required superheated steam of 650 °C with a designed active optical system comprising nine Fresnel lenses (7 m2) that offer the concentration of 36 suns on the honeycomb structure of the steam generator as input. The required 1.27 kW of electrical power is obtained by concentrating the photovoltaic system using In0.33Ga0.67N/Si/InN solar cells. This production of hydrogen is sustainable and cost effective, as the estimated cost over 5 years by the proposed system is 0.51 USD/kg, compared to the commercially available system, which costs 3.18 USD/kg.

Natural and Simulated Solar Radiation.

The extra-terrestrial solar spectrum corresponds approximately to a black body of temperature about 5,800 K, with the ultraviolet region accounting for almost 8% of the total solar energy. Terrestrial solar spectral irradiance peaks at around 500 nm in the blue-green region, whereas the diffuse component peaks in the UVAI-blue region of the spectrum, with the infrared component comprising almost entirely direct radiation. Several factors impact on the magnitude and spectral profile of terrestrial solar spectral irradiance, and these include solar elevation, reflection from land and sea, air pollution, altitude above sea level and cloud cover. Measurements of erythemal UV from a number of ground-based networks around the world indicate an approximate 4-fold difference in ambient annual exposure between Australia and countries in northern Europe. In the absence of measured data, models to compute solar UV irradiance are a useful tool for studying the impact of variables on the UV climate. Simulated sources of sunlight based on a xenon arc lamp can be configured to give a close match to the spectral output of natural sunlight at wavelengths less than about 350 nm, and these are invaluable in the laboratory determination of sunscreen performance, notably the Sun Protection Factor (SPF). However, the divergence -between natural and simulated solar spectra at longer wavelengths may explain why SPFs measured in natural sunlight are less than those determined in the laboratory.

Energy-tunable photon-enhanced thermal tunneling electrons for intrinsic adaptive full spectrum solar energy conversion

Considering that the actual terrestrial solar irradiance is dynamically changing with the atmosphere, the overall efficiencies of most current solar cells are much lower than the reported static values that are based on a standard solar spectrum. The realizations of solar cells, which can maintain high efficiency under variable solar irradiance, are necessary for further improvement of solar energy conversion. In this work, a metal-insulator-semiconductor (MIS) structure based photon-enhanced thermionic energy converter (PETEC) has been proposed for intrinsic adaptive full spectrum solar energy conversion. The basic idea is to form the thermionic electron with desired energy by the photon-enhanced thermal tunneling process. Investigations on its fundamental performance indicate that the MIS-PETEC can have an overall output energy improvement of at least 0.8%, 2.5%, and 3% in typical sunny, rainy, and cloudy days compared to the normal PETEC. Additionally, the total output energy over a year can be improved by at least 3%. These results offer an alternate technique for intrinsic adaptive full spectrum solar energy conversion, which is helpful for the development of next generation high performance solar cells.

Absorption of light by a particulate monolayer: Effect of ordering, concentration, and size of particles

Absorption of light by a free standing monolayer of monodisperse crystalline silicon (c-Si) spherical particles is investigated using the quasicrystalline approximation (QCA) of the theory of multiple scattering of waves. The simulation results for the partially ordered monolayer and the highly ordered monolayer with imperfect triangular lattice are presented in the ranges of particle diameters from 0.05 µm to 1 µm, monolayer filling factors from 0.1 to 0.7, and wavelengths of incident light from 0.3 µm to 1.12 µm. The spatial pattern of a monolayer affects the absorption coefficient most strongly when the particle sizes are comparable with the wavelength. The spatial-order-induced peaks in the absorption spectra of a highly ordered monolayer are studied. The spectral absorption by such a monolayer can be more than 30 times greater than that of the partially ordered monolayer in the narrow wavelength intervals. The integrated over the terrestrial solar spectral irradiance “Global tilt” ASTM G173-03 absorption coefficient is analyzed. In the wavelength range of 0.3 µm ≤ λ ≤ 1.12 µm the integral absorption can be almost twice as large as that for the partially ordered monolayer. In the wavelength range of small absorption index of c-Si (0.8 µm ≤ λ ≤ 1.12 µm) the integral absorption coefficient of highly ordered monolayer can be more than 10 times greater than for the partially ordered monolayer.

High-flux optical systems for solar thermochemistry

High-flux optical systems (HFOSs) are optical concentrators used to increase the radiative flux of the natural terrestrial solar irradiation. High radiative flux concentration leads to high energy density in solar receivers which allows to obtain high temperatures. In solar thermochemical applications, the high-temperature heat drives endothermic thermochemical reactions. HFOSs have been deployed for research and development of solar thermochemical devices and systems, from solar reacting media to solar reactors. Here, we review the designs and characteristics of HFOSs as well as challenges and opportunities in the area of high-flux optical systems for solar thermochemical applications.

Light absorption by ordered planar structure of crystalline silicon particles: Simulation as applied to enhancement of the solar cell performance

Light absorption by a single spherical crystalline silicon (c-Si) particle and by monolayers of submicron c-Si particles arranged in triangular lattice is examined within the wavelength range from 0.28 to 1.12 μm. Data for spectral and integrated (over the terrestrial solar spectral irradiance “Global tilt” ASTM G173-03) absorption coefficients of monolayer demonstrating the possibility to enhance light absorption by a particulate active layer of crystalline silicon are presented. They are calculated in the quasicrystalline approximation of the theory of multiple scattering of waves. It is shown that in the narrow wavelength intervals (up to 10 nm) the spectral absorption coefficient of monolayer can be more than 100 times larger than the one of the plane-parallel plate of equal volume of material. Some results on the transmittance and reflectance of partially ordered monolayer are presented as well. The potentialities of light absorption enhancement in a single monolayer and three-monolayer system are considered.

Measurement of terrestrial and aerial solar spectral radiations in Antarctica for the vicarious calibration of the Resourcesat-1 AWiFS sensor

Terrestrial and aerial ground truth data collection with indigenously developed radiometers around Maitri, Antarctica was carried for the vicarious calibration of the Resourcesat-1 Advanced Wide Field Sensor (AWiFS). Measured and theoretically computed incoming solar spectral irradiance values match within ±3%. The AWiFS B2 image shows spatial non-uniformity of the test site of 2–4%. The variability of terrestrial solar spectral irradiance is within 3% for a duration of ±1.5 hours at the time of the satellite pass. On the basis of test results, it is concluded that Maitri, Antarctica is a potential test site for carrying out calibration/validation of optical sensors. AWiFS B2 pre-flight and estimated post-flight calibration coefficients are found to be within ±2%.

A study of extreme overirradiance events for solar energy applications using NASA’s I3RC Monte Carlo radiative transfer model

Near the Equator, some cloud types can boost the terrestrial solar irradiance to above 1.8kW/m2. Even at high latitude close to 60°N, we have measured bursts up to 1.6kW/m2, almost at sea level. For comparison, the extraterrestrial irradiance peaks at about 1.4kW/m2 in early January. The global upper limit for extreme overirradiance is still unknown. The enhancement is strongest within about 3° from the unobstructed solar disk. We use the NASA’s I3RC Monte Carlo model to simulate the radiative transfer of solar photons in a cloudy atmosphere. The geometry includes an overhead sun and an infinite plane parallel water cloud with a ‘circular’ gap of the same angular diameter as that of the solar disk (≈0.53°). We vary the effective droplet radius, cloud’s thickness, and liquid water mass density. At a non-absorbing λ=0.67μm, we obtain a maximum enhancement factor of about 1.80 times with respect to the clear-sky downwelling flux, at an optimal cloud optical thickness of about 3.1. Although these values are very similar to those obtained by Wen et al. (2001) with the DISORT model, the simulated extent of the strong narrow forward scattering (within 1.5° around the sun) differs significantly from our experimental observation (about 8°). We conclude that a revision of the Mie scattering phase functions programmed in the I3RC code may be necessary, and that the obtained enhancement threshold at sea level is not entirely physical, as perhaps was the result in Wen et al. (2001). Interestingly, there are typographical errors in some equations in the original German paper by Mie (1908) which survived the English translations from 1976 and 1978. The typos were corrected only recently in the Spanish translation from 2007.

Estimating Solar Irradiation Absorbed by Photovoltaic Panels with Low Concentration Located in Craiova, Romania

Solar irradiation is one of the important parameters that should be taken into consideration for the design and utilization of a photovoltaic system. Usually, the input parameters of a photovoltaic system are solar irradiation, the ambient environment temperature and the wind speed, and as a consequence most photovoltaic systems are equipped with sensors for measuring these parameters. This paper presents several mathematical models for solar irradiation assessment. The starting point is represented by the mathematical model of extraterrestrial irradiation, and resulting finally in the model for solar irradiation, absorbed by a low concentration photovoltaic panel. These estimating models of solar irradiation have been particularized for the Craiova, Romania, and have been verified through numerical simulation. Regarding terrestrial solar irradiation, four mathematical models have been adopted, namely Adnot, Haurwitz, Kasten and Empirical (EIM). Of these, the most appropriate for the Craiova location were the models Adnot and Empirical. Consequently, for the calculation of the solar irradiation absorbed by the photovoltaic (PV) panels with low concentration, these models have been taken into consideration. In this study, a comparative analysis was also carried out with respect to the solar irradiation absorbed by the PV panels without concentration and those with collectedness of the solar radiation. This analysis was based on the results of numerical simulation and experimental tests.

Pumpless evaporative cooling of actively heated surfaces

In this paper we study the ability of a passive, evaporative pumping system to dissipate thermal energy from a constant heat flux source. For that, an instrumented experimental setup was built wherein a thin, flat porous membrane was placed on top of a circular copper made heater. Evaporation from the membrane continually drew distilled water from a reservoir through the system. The tests aimed to parametrically determine the effect of the heat flux dissipated by the membrane on the evaporation rate, heater temperature, and the suction pressure created by evaporation. The maximum suction pressure can ultimately be used to estimate the maximum pumping height differential between the evaporative surface and the free water surface of the reservoir. The results obtained indicated that there was a direct relationship between the heater power and the evaporation rate, within the range of parameters investigated. Also, the results showed that for a heat flux up to 2220W/m2, which is more than twice the terrestrial solar irradiation, the heater temperature was roughly 45°C, 28°C below the temperature of an equivalent surface cooled purely by natural convection.

A low cost high flux solar simulator

A low cost, high flux, large area solar simulator has been designed, built and characterized for the purpose of studying optical melting and light absorption behavior of molten salts. Seven 1500 W metal halide outdoor stadium lights are used as the light source to simulate concentrating solar power (CSP) heliostat output. Metal halide bulbs and ballasts are far less costly per-watt than typical xenon arc lamp solar simulator light sources. They provide a satisfactory match to natural sunlight; although ‘unfiltered’ metal halide lights have irradiance peaks between 800 and 1000 nm representing an additional 5% of measured energy output as compared to terrestrial solar irradiance over the same range. With the use of a secondary conical concentrator, output fluxes of approximately 60 kW/m 2 (60 suns) peak and 45 kW/m 2 (45 suns) average are achieved across a 38 cm diameter output aperture. Unique to the design of this simulator, the tilt angle and distance between the output aperture and the ground are adjustable to accommodate test receivers of varying geometry. Use of off-the-shelf structural, lighting and electrical components keeps the fabrication cost below $10,000.

Unintentional fires caused by products that focus sunlight

Unintentional Fires Caused by Products that Focus Sunlight Objectives The ability of myriad and sundry transparent and reflective objects to set fires by focusing sunlight has likely known since before...

Design and development of field radiometers for ground truth data collection at Antarctica

Four types of low-cost, multi-band, ground-truth radiometers have been indigenously developed at Space Applications Centre, Ahmedabad, for data collection at Antarctica. These instruments are easy to operate and portable. They are designed so as to incorporate a set of interference filters with desired spectral characteristics in the spectral region from 400 nm to 3000 nm. It is possible to tune these instruments for various types of remote sensing applications. The instruments have been calibrated in the absolute quantities of spectral radiance (w/cm2-sr-μ) and spectral irradiance (w/cm2-μ). The total radiometric calibration uncertainty including the uncertainty of standard source is of the order of ±3.5% for spectral irradiance and is of the order of ±7.5% for spectral radiance. All the instruments were tested and operated at Antarctica and voluminous radiometric ground truth data has been collected during 26th Indian Scientific Expedition to Antarctica. Measurements were carried out in terms of following parameters: a) spectral reflectance measurement of ice and fresh snow surfaces, b) terrestrial solar spectral irradiance: direct and global components. This paper gives salient features, specifications, theory of operation and description of these instruments. Some of the test results of the measured data collected at Antarctica are also presented.

Strong signature of the active Sun in 100 years of terrestrial insolation data

AbstractTerrestrial solar irradiance data of the Smithsonian Astrophysical Observatory from 1905 to 1954 and of Mauna Loa Observatory from 1958 to 2008 are analyzed. The analysis shows that, with changing solar activity, the atmosphere modifies the solar irradiance on the percentage level, in all likelihood via cosmic ray intensity variations produced by the active sun. The analysis strongly suggests that cosmic rays cause a large part of the atmospheric aerosols. These aerosols show specific absorption and scattering properties due to an inner structure of hydrated ionic centers, most probably of O2‐ and O2+ produced by the cosmic rays.

Solar Irradiation Estimation from Sunshine Duration by Geno-Fuzzy Partial Approach

Terrestrial solar irradiation estimations are obtained mostly from the sunshine duration measurements through almost linear models such as the classical Angstrom formulation. The parameters of such model are estimated through the least squares technique in practical studies. In this article, more efficient model based on the fuzzy system concept is proposed for the architecture of solar irradiation estimation from the sunshine duration measurements. Especially, partial fuzzy modeling accounts for the possible local nonlinearities in the form of piece-wise linearizations. The parameters estimation of such a fuzzy model is achieved through the application of genetic algorithm technique. The fuzzy part of the model provides treatment of vague information about the sunshine duration data whereas the genetic part furnishes an objective and optimum estimation procedure. The application of geno-fuzzy model as proposed in this article is presented for three stations in Turkey and the results are constrasted by the previous classical approaches.

Solar eclipse observation: some simple devices

The terrestrial solar irradiance is evaluated in view of the energy absorbed by the retina and the blue light hazard. The evaluated irradiance is compared with the known safety standard, to determine the safety requirement of solar eclipse observation devices. Simple devices are then proposed. The first is a folded pinhole camera, giving a magnified sun image from a relatively small box. The second is a pinhole projector, used to display the image in a large room, while the third is a compact multimirror periscope enabling one to see the sun sharper than with a pinhole camera.

Terrestrial solar spectra, solar simulation and solar cell short-circuit current calibration: A review

In this paper the main issues in modeling and measuring terrestrial solar spectra and their relation to the short-circuit current of solar cells are addressed. These issues are (1) the measured and modeled terrestrial solar spectra, (2) the optimal light sources and their filtering for simulating the standard terrestrial solar irradiance spectrum and (3) the consequences of a mismatch between the chosen standard terrestrial solar spectrum and the actual irradiance conditions for the rated efficiency of a solar cell. In addition, this review provides the photovoltaics community with a tutorial document and a summary of the current activities and results in this field.

The Sensitivity of Solar Transmittance, Reflectance and Absorptance to Selected Averaging Procedures and Solar Irradiance Distributions

The sensitivity of the solar weighted optical properties of selected materials to different terrestrial solar spectral irradiance distributions and computational techniques has been investigated. The spectral transmittance, reflectance, and absorptance of typical materials employed in solar thermal conversion systems were used for the calculations. The values obtained for several different solar irradiance distributions and calculational methods show only small differences. A single terrestrial solar irradiance distribution is recommended for use as a standard.