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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

The Impact of Stochastic Perturbations in Physics Variables for Predicting Surface Solar Irradiance

We present a probabilistic framework tailored for solar energy applications referred to as the Weather Research and Forecasting-Solar ensemble prediction system (WRF-Solar EPS). WRF-Solar EPS has been developed by introducing stochastic perturbations into the most relevant physical variables for solar irradiance predictions. In this study, we comprehensively discuss the impact of the stochastic perturbations of WRF-Solar EPS on solar irradiance forecasting compared to a deterministic WRF-Solar prediction (WRF-Solar DET), a stochastic ensemble using the stochastic kinetic energy backscatter scheme (SKEBS), and a WRF-Solar multi-physics ensemble (WRF-Solar PHYS). The performances of the four forecasts are evaluated using irradiance retrievals from the National Solar Radiation Database (NSRDB) over the contiguous United States. We focus on the predictability of the day-ahead solar irradiance forecasts during the year of 2018. The results show that the ensemble forecasts improve the quality of the forecasts, compared to the deterministic prediction system, by accounting for the uncertainty derived by the ensemble members. However, the three ensemble systems are under-dispersive, producing unreliable and overconfident forecasts due to a lack of calibration. In particular, WRF-Solar EPS produces less optically thick clouds than the other forecasts, which explains the larger positive bias in WRF-Solar EPS (31.7 W/m 2 ) than in the other models (22.7–23.6 W/m 2 ). This study confirms that the WRF-Solar EPS reduced the forecast error by 7.5% in terms of the mean absolute error (MAE) compared to WRF-Solar DET, and provides in-depth comparisons of forecast abilities with the conventional scientific probabilistic approaches (i.e., SKEBS and a multi-physics ensemble). Guidelines for improving the performance of WRF-Solar EPS in the future are provided.

14 SOLAR ENERGY↗
NASA NTRS1972

Space observations of the variability of solar irradiance in the near and far ultraviolet

Satellite observations of the ultraviolet solar irradiance in selected wavelength bands between 1200 and 3000 a were made continuously by photometers consisting of broad-band sensors operated on Numbus 3 and 4 which were launched in April 1969 and 1970. In addition, spectrophotometer measurements of the solar irradiance were made with a dispersive instrument at 12 selected wavelengths from 2550 to 3400 a with a 10 a bandpass on Nimbus 4. Variations of the solar irradiance associated with the solar rotational period were observed since the launch of Nimbus 3. These variations are apparently associated with two source regions separated by about 180 deg in solar longitude. The change in irradiance with solar rotation was found to increase with decreasing wavelengths. Different types of the observed variations in uv solar irradiance can be classified in accordance with characteristics times, e.g. in the order of increasing periods as follows: (1)flare associated enhancements (2) 27-day variations due to solar rotation; (3) a possible biennial effect; and (4) long term variations associated with the 11-year solar cycle.

Heath, D. F.↗
NASA NTRS1992

On the variation of the Nimbus 7 total solar irradiance

For the interval December 1978 to April 1991, the value of the mean total solar irradiance, as measured by the Nimbus-7 Earth Radiation Budget Experiment channel 10C, was 1,372.02 Wm(exp -2), having a standard deviation of 0.65 Wm(exp -2), a coefficient of variation (mean divided by the standard deviation) of 0.047 percent, and a normal deviate z (a measure of the randomness of the data) of -8.019 (inferring a highly significant non-random variation in the solar irradiance measurements, presumably related to the action of the solar cycle). Comparison of the 12-month moving average (also called the 13-month running mean) of solar irradiance to those of the usual descriptors of the solar cycle (i.e., sunspot number, 10.7-cm solar radio flux, and total corrected sunspot area) suggests possibly significant temporal differences. For example, solar irradiance is found to have been greatest on or before mid 1979 (leading solar maximum for cycle 21), lowest in early 1987 (lagging solar minimum for cycle 22), and was rising again through late 1990 (thus, lagging solar maximum for cycle 22), having last reported values below those that were seen in 1979 (even though cycles 21 and 22 were of comparable strength). Presuming a genuine correlation between solar irradiance and the solar cycle (in particular, sunspot number) one infers that the correlation is weak (having a coefficient of correlation r less than 0.84) and that major excursions (both as 'excesses' and 'deficits') have occurred (about every 2 to 3 years, perhaps suggesting a pulsating Sun).

Wilson, Robert M.↗
NASA NTRS1992

A technique for global monitoring of net solar irradiance at the ocean surface. I - Model

An accurate long-term (84-month) climatology of net surface solar irradiance over the global oceans from Nimbus-7 earth radiation budget (ERB) wide-field-of-view planetary-albedo data is generated via an algorithm based on radiative transfer theory. Net surface solar irradiance is computed as the difference between the top-of-atmosphere incident solar irradiance (known) and the sum of the solar irradiance reflected back to space by the earth-atmosphere system (observed) and the solar irradiance absorbed by atmospheric constituents (modeled). It is shown that the effects of clouds and clear-atmosphere constituents can be decoupled on a monthly time scale, which makes it possible to directly apply the algorithm with monthly averages of ERB planetary-albedo data. Compared theoretically with the algorithm of Gautier et al. (1980), the present algorithm yields higher solar irradiance values in clear and thin cloud conditions and lower values in thick cloud conditions.

Frouin, Robert↗
DOE OSTI2022

Solar Irradiance Ramp Forecasting Based on All-Sky Imagers

Solar forecasting constitutes a critical tool for operating, producing and storing generated power from solar farms. In the framework of the International Energy Agency’s Photovoltaic Power Systems Program Task 16, the solar irradiance nowcast algorithms, based on five all-sky imagers (ASIs), are used to investigate the feasibility of ASIs to foresee ramp events. ASIs 1–2 and ASIs 3–5 can capture the true ramp events by 26.0–51.0% and 49.0–92.0% of the cases, respectively. ASIs 1–2 provided the lowest (<10.0%) falsely documented ramp events while ASIs 3–5 recorded false ramp events up to 85.0%. On the other hand, ASIs 3–5 revealed the lowest falsely documented no ramp events (8.0–51.0%). ASIs 1–2 are developed to provide spatial solar irradiance forecasts and have been delimited only to a small area for the purposes of this benchmark, which penalizes these approaches. These findings show that ASI-based nowcasts could be considered as a valuable tool for predicting solar irradiance ramp events for a variety of solar energy technologies. The combination of physical and deep learning-based methods is identified as a potential approach to further improve the ramp event forecasts.

14 SOLAR ENERGY↗
NASA NTRS1981

Radiometer for accurate (+ or - 1%) measurement of solar irradiance equal to 10,000 solar constants

The 10,000 solar constant radiometer was developed for the accurate (+ or - 1%) measurement of the irradiance produced in the image formed by a parabolic reflector or by a multiple mirror solar installation. This radiometer is water cooled, weighs about 1 kg, and is 5 cm (2 in.) in diameter by 10 cm (4 in.) long. A sting is provided for mounting the radiometer in the solar installation capable of measuring irradiances as high as 20,000 solar constants, the instrument is self calibrating. Its accuracy depends on the accurate determination of the cavity aperture, and absorptivity of the cavity, and accurate electrical measurements. The spectral response is flat over the entire spectrum from far UV to far IR. The radiometer responds to a measurement within 99.7% of the final value within 8 s. During a measurement of the 10,000 solar constant irradiance, the temperature rise of the water is about 20 C. The radiometer has perfect cosine response up to 60 deg off the radiometer axis.

Kendall, J. M., Sr.↗
DOE OSTI2024

Measured Long-Term Solar Irradiance for Climate Studies

Solar radiation is primarily measured using high-quality radiometers (e.g., pyranometers and pyrheliometers). These instruments need to be calibrated regularly (every two years at a minimum). They are also susceptible to various sources of uncertainties. Therefore, rigorous data quality assessment is required to obtain high-confidence data from these radiometers. This is especially true when the data is used to understand climatic trends and/or extreme weather events. In this study, we attempted to create a continuous and reliable dataset by correcting the underlying data which we believe contains bias due to reference pyranometers swap procedures. These biases can be significant which can be up to two percentage points thereby influencing the interpretation of climate changes and/or extreme events. This study elaborates on the biases and methods to correct those biases.

data integrity↗
NASA NTRS1983

The nature of the short period fluctuations in solar irradiance received by the earth

An analysis of the periodicities found in the Nimbus-7 satellite measurements of solar irradiance (Solar Constant) indicates variations on three scales. Two of these variations are shown to be related to variations in solar activity as given by various indicators of solar photosphere disturbances. The high frequency periodicity is due to the solar rotation period. The second periodicity is based on the integral effect of the high frequency oscillation over an 11 year solar cycle. The third variation (secular trend) is discussed in regard to the high precision cavity data and the recent record of high altitude solar constant measurements.

Smith, E. A.↗
NASA NTRS2004

Long-Term Total Solar Irradiance (TSI) Variability Trends: 1984-2004

The incoming total solar irradiance (TSI), typically referred to as the solar constant, is being studied to identify long-term TSI changes, which may trigger global climate changes. The TSI is normalized to the mean earth-sun distance. Studies of spacecraft TSI data sets confirmed the existence of 0.1 %, long-term TSI variability component with a period of 10 years. The component varied directly with solar magnetic activity associated with recent 10-year sunspot cycles. The 0.1 % TSI variability component is clearly present in the spacecraft data sets from the 1984-2004, Earth Radiation Budget Experiment (ERBE) active cavity radiometer (ACR) solar monitor; 1978-1993, Nimbus-7 HF; 1980-1989, Solar Maximum Mission [SMM] ACRIM; 1991-2004, Upper Atmosphere Research Satellite (UARS) ACRIM; 1996-2003, Solar and Heliospheric Observatory (SOHO)/VIRGO, Space Science (ATLAS), 2000-2004, ACRIMSAT; and 2003-2004 SOlar Radiation and Climate Experiment (SORCE) active cavity radiometer (ACR) missions. From October 1984, through March 2004, the ERBS/ERBE solar monitor was used to produce the longest continuous data set of total solar irradiance (TSI) variability measurements. The solar monitor is located on Shuttle Atmospheric Laboratory for Applications and the NASA Earth Radiation Budget Satellite (ERBS). Maximum TSI values occurred during the 1989-1991, and 1998-2002, time frames; while minimum [quiet sun] TSI levels occurred during 1986 and 1996. Recent ERBS measurements indicate that the TSI is decreasing to forecasted, minimum levels by 2006. Using the discontinuous non-operational Nimbus-7, SMM ACRIM, and UARS ACRIM mission TSI data sets, Wilson and Mordvinor (2003) suggested the existence of an additional long-term TSI variability component, 0.05 %, with a period longer than a decade. Analyses of the ERBS/ERBE data set do not support the Wilson and Mordvinor analyses approach because it used the Nimbus-7 data set which exhibited a significant ACR response shift of 0.7 Wm-2

Lee, Robert Benjamin, III↗
NASA NTRS1999

The Contribution of the Solcon Instrument to the Long Term Total Solar Irradiance Observation

On century time scales, the variation in the total solar irradiance received by the earth is believed to be a major climate change driver. Therefore accurate and time stable measurements of the total solar irradiance are necessary. We present the latest contribution of the SOLar CONstant (SOLCON) instrument to these measurements, namely its measurements during the International Extreme Ultraviolet Hitchhiker (IEH) 3 space shuttle flight, and its results: the verification of the ageing of the Earth Radiation Budget Satellite (ERBS), and the measurement of the Space Absolute Radiometric Reference (SARR) adjustment coefficients for the Variability of solar IRradiance and Gravity Oscillations (VIRGO) radiometers.

Dewitte, S.↗
NASA NTRS1991

Spatial and temporal variability of global surface solar irradiance

Consideration is given to a fast scheme for computing surface solar irradiance using data from the International Satellite Cloud Climatology Project (ISCCP). Daily mean solar irradiances from the fast scheme reproduce the detailed global results from full radiative transfer model calculations to within 6 and 10 W/sq m over the ocean and land, respectively. Comparison of calculated monthly mean results using 5 m of ISCCP data (July 1983-July 1984) with climatology from the 1970s at six temperature-latitude ocean weather stations shows agreement within published estimates of interannual variability of monthly means at the individual stations. A further test against a 17-day time series at a continental site, where ground and satellite data were spatially and temporally coincident, showed an accuracy of better than 9 W/sq m on a daily basis and less than 4 percent bias in the 17-day mean. Frequently used bulk formulas for solar irradiance are also evaluated in each of these tests.

Bishop, James K. B.↗
NASA NTRS1986

The Mg 280-nm doublet as a monitor of changes in solar ultraviolet irradiance

Solar irradiance data gathered with the Nimbus 7 spacecraft from 1978-1985 are compared with atmospheric MG 289-nm doublet emission line data to evaluate the possibility of using the rotational line data to calculate the total solar UV input. The satellite instrumentation is described, including the calibration equipment and procedures. The spacecraft records solar irradiance once per day and the remainder of the time records irradiance scattered by the atmosphere. The measured irradiances are converted to equivalent brightness temperatures, which can be interpolated for specific layers of the atmosphere. Sample daily data are provided to illustrate the correlation between variations in the Mg-II core radiation and the soalr UV irradiance. Techniques are defined for correcting for periodic variations in instrument performance to quantify long-term solar UV radiance variations. Using the atmospheric Mg-II doublet radiation for measuring soalr UV irradiance is concluded of value for characterizing the effects of solar radiation on the atmosphere.

Heath, D. F.↗
NASA NTRS2015

Total and Spectral Solar Irradiance Sensor (TSIS) Project Overview

The main objective of the Total and Spectral solar Irradiance Sensor (TSIS) is to acquire measurements to determine the direct and indirect effects of solar radiation on climate. TSIS total solar irradiance measurements will extend a 37-year long uninterrupted measurement record of incoming solar radiation, the dominant energy source driving the Earths climate and the most precise indicator of changes in the Suns energy output. TSIS solar spectral irradiance measurements will determine the regions of the Earths multi-layered atmosphere that are affected by solar variability, from which the solar forcing mechanisms causing changes in climate can be quantified. TSIS includes two instruments: the Total Irradiance Monitor (TIM) and the Spectral Irradiance Monitor (SIM), integrated into a single payload. The TSIS TIM and SIM instruments are upgraded versions of the two instruments that are flying on the Solar Radiation and Climate Experiment (SORCE) mission launched in January 2003. TSIS was originally planned for the nadir-pointing National Polar-orbiting Operational Environmental Satellite System (NPOESS) spacecraft. The TSIS instrument passed a Critical Design Review (CDR) for NPOESS in December 2009. In 2010, TSIS was re-planned for the Joint Polar Satellite System (JPSS) Polar Free Flyer (PFF). The TSIS TIM, SIM, and associated electronics were built, tested, and successfully completed pre-ship review as of December 2013.In early 2014, NOAA and NASA agreed to fly TSIS on the International Space Station (ISS). In the FY16 Presidents Budget, NASA assumes responsibility for the TSIS mission on ISS. The TSIS project includes requirements, interface, design, build and test of the TSIS payload, including an updated pointing system, for accommodation on the ISS. It takes advantage of the prior development of the TSIS sensors and electronics. The International Space Station (ISS) program contributions include launch services and robotic installation of the TSIS payload onto an ISS Express Logistics Carrier, mission operations, and communications. Total and Spectral solar irradiance data products will be produced, calibrated, and made publically available through the Goddard Earth Science Data and Information Services Center (GES DISC).The NASA GSFC TSIS project at GSFC is responsible for project management, system engineering, safety and mission assurance, and engineering oversight for the TSIS payload. The TSIS project has contracted with the University of Colorado Laboratory for Atmospheric and Space Physics (LASP) for the design, development and testing of TSIS, support for ISS integration, science operations of the TSIS instrument, data processing, data evaluation and delivery to the GES DISC. TSIS will be delivered to Kennedy Space Center for integration in 2017, with launch and installation onto ISS planned for late 2017-early 2018. After a 90-day check-out period, NASA plans five years of TSIS operations.

spectral emission↗
DOE OSTI2025

Spatiotemporal Downscaling Model for Solar Irradiance Forecast Using Nearest-Neighbor Random Forest and Gaussian Process

Accurate solar photovoltaic (PV) capacity estimation requires high-resolution, site-specific solar irradiance data to account for localized variability. However, global datasets, such as the National Solar Radiation Database (NSRDB), provide regional averages that fail to capture the fine-scale fluctuations critical for large-scale grid integration. This limitation is particularly relevant in the context of increasing distributed energy resources (DERs) penetration, such as rooftop PV. Additionally, it is critical to the implementation of the U.S. Federal Energy Regulatory Commission (FERC) Order 2222, which facilitates DER participation in U.S. bulk power markets. To address this challenge, this study evaluates Nearest-Neighbor Random Forest (NNRF) and Nearest-Neighbor Gaussian Process (NNGP) models for spatiotemporal downscaling of global solar irradiance data. By leveraging historical irradiance and meteorological data, these models incorporate spatial, temporal, and feature-based correlations to enhance local irradiance predictions. The NNRF model, a machine-learning approach, prioritizes computational efficiency and predictive accuracy, while the NNGP model offers a level of interpretability and prediction uncertainty by numerically quantifying correlations and dependencies in the data. Model validation was conducted using day-ahead predictions. The results showed that the average Goodness of Fit (GoF) of the NNRF model of 90.61% across all eight sites outperformed the GoF of the NNGP of 85.88%. Additionally, the computational speed of NNRF was 2.5 times faster than the NNGP. Finally, the NNGP displayed polynomial scaling while the NNRF scaled linearly with increasing number of nearest neighbors. Additional validation of the model on five sites in Puerto Rico further confirmed the superiority of the NNRF model over the NNGP model. These findings highlight the robustness and computational efficiency of NNRF for large-scale solar irradiance downscaling, making it a strong candidate for improving PV capacity estimation and real-time electricity market integration for DERs.

Asiedu, Shadrack (ORCID:0009000646004826)↗
NASA NTRS1990

Total solar irradiance variability - 5 years of ERBE data

Data obtained by the ERBS solar monitors measuring total solar irradiance variability are discussed. The ERBS and NOAA-99 monitors derived 1365 W/sq m as the magnitude of the solar irradiance, normalized to 1 astronomical unit. The NOAA-10 monitor yielded 1363 W/m as the magnitude of the irradiance. The long-term precision of the monitors was demonstrated by the detection of the decreasing and increasing trends in the irradiance at levels of the order of 0.03 to 0.05 percent per year. The ERBS and NOAA-9 measurements demonstrated that solar variability exists in a systematic mode which is directly correlated with the solar magnetic activity, indicated by sunspot activity. It is argued that during the decline of sunspot cycle 22, the solar irradiance variability may be entirely different from that which was observed during the decline of cycle 21.

Lee, Robert B., III↗
NASA NTRS1996

Total Solar Irradiance Variability: A Review

Observations of total solar irradiance from space within the last two decaades convinced the skeptics that total irradiance varies over a wide range of periodicities: from minutes to the 11-year solar activity cycle. Analyses based on these space-borne observations have demonstrated that the irradiance variations are directly related to changes at the photosphere and the solar interior.

solar irradiance solar luminosity irradiance model↗
NASA NTRS1987

Physical interpretation of variations in total solar irradiance

Radiometry from the Solar Maximum Mission and Nimbus 7 satellites has demonstrated that the solar constant varies at a peak-to-peak level of up to 0.2 percent on time scales of weeks. The rotation and evolution of dark spots and bright faculae across the sun's disk accounts for most of that variation. Reasonable explanations have been put forward to explain how the spot-blocked heat flow might be stored, and to explain the source of the intense radiation that gives rise to the increased irradiance produced by the bright magnetic faculae. Time-dependent models of the response of the solar convection zone to small perturbations also indicate that slower variations in total solar irradiance of comparable magnitude are likely. More precise observations of the total solar irradiance and radius over long time scales are required to demonstrate the existence of such climatologically relevant changes, and to test models that would enable the interpretation and prediction of these changes.

Foukal, P.↗