Papers by Chris A Gueymard
The Solar Resource Calibration, Measurement, and Dissemination project supports the U.S. Departme... more The Solar Resource Calibration, Measurement, and Dissemination project supports the U.S. Department of Energy's Solar Energy Technologies Office (SETO) initiative to make solar energy cost-competitive with other forms of electricity by improving the tools and methods to measure and model solar radiation and therefore reduce uncertainty in predicting solar output and improve the bankability of solar projects. This project has three tasks that conduct research on advancing solar resource measurements and modeling:
SPIE Proceedings, 2004
; and is made available as an electronic preprint with permission of SPIE. One print or electroni... more ; and is made available as an electronic preprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Proceedings of EuroSun 2018, 2018
Precipitable water (PW) is an influential variable in regards to clear-sky radiation modelling an... more Precipitable water (PW) is an influential variable in regards to clear-sky radiation modelling and solar resource assessment. Thus, the accuracy of solar energy estimates depends on the accuracy of PW measurements. Gridded satellite information is commonly used for solar modelling because of its benefit of a broad geographical coverage, thus a global validation of commonly utilised PW products is imperative. Here, all Level-3 Moderate Resolution Imaging Spectroradiometer (MODIS) daily PW products from the Aqua and Terra satellites (at 1°× 1° spatial resolution) from 01/2000 to 02/2018 are compared and validated against all of NASA's ground-sensing Aerosol Robotic NETwork (AERONET) V3 Level-2 PW daily averages from sites that have at least one year of observations during 2000-2018 (452 sites representing 675,158 observations). Furthermore, sub-categorisation by Köppen-Geiger climate regions enables climate specific validation to ascertain any distinct climatic influence. The results demonstrate significant climatological influences that impact the derived PW products. It is found that the Terra PW is more accurate than the Aqua PW, and that blending these two products yields a higher accuracy of daily PW estimates. The MODIS PW product also suffers from overestimation at larger magnitudes (>3 cm). The absolute errors do not reduce linearly with the PW magnitude, so that relative errors are far worse in areas of low PW, such as the polar climate. The equatorial climate, with the highest PW records, behaves best. Finally, a simple sensitivity test using the REST2 clear-sky radiation model shows that the global PW RMSE (0.511 cm) of the combined MODIS data would result in a 1.5-2.5% under-or overestimate on direct normal irradiance (DNI) depending on latitude relative to using the AERONET mean PW of 1.8971 cm. It is thus concluded that the daily MODIS PW product is not ideal for clear-sky radiation modelling, at least whenever accurate DNI predictions are necessary on a global scale.
Conference Record of the Twenty-Ninth IEEE Photovoltaic Specialists Conference, 2002.
The American Society for Testing and Materials (ASTM), the International Electrotechnical Commiss... more The American Society for Testing and Materials (ASTM), the International Electrotechnical Commission (IEC), and the International Standards Organization (ISO) standard solar terrestrial spectra (ASTM G-159, IEC-904-3, ISO 9845-1) provide standard spectra for photovoltaic performance applications. Modern terrestrial spectral radiation models and knowledge of atmospheric physics are applied to develop suggested revisions to update the reference spectra. We use a moderately complex radiative transfer model (SMARTS2) to produce the revised spectra. SMARTS2 has been validated against the complex MODTRAN radiative transfer code and spectral measurements. The model is proposed as an adjunct standard to reproduce the reference spectra. The proposed spectra represent typical clear sky spectral conditions associated with sites representing reasonable photovoltaic energy production and weathering and durability climates. The proposed spectra are under consideration by ASTM.
Proceedings of the ISES Solar World Congress 2021
Ground-based radiation measurements are required for all large solar projects and for evaluating ... more Ground-based radiation measurements are required for all large solar projects and for evaluating the accuracy of solar radiation models and datasets. Ground data almost always contain low-quality periods caused by instrumental issues, logging errors, or maintenance deficiencies. Therefore, quality control (QC) is needed to detect and eventually flag or exclude such suspicious or erroneous data before any subsequent analysis. The few existing automatic QC methods are not perfect, thus expert visual inspection of the data is still required. In this work, we present a harmonized QC procedure, which is a combination of various available methods, including some that include an expert visual inspection. In the framework of IEA PVPS Task 16, these tests are applied to 161 world stations that are equipped with various radiometer models, and are candidates for an ongoing benchmark of irradiance datasets derived from satellite or weather models. Because the implementation of these methods by experts, and their subsequent decisions, might lead to different QC results, the independently obtained results from nine evaluators are compared for two test sites. The QC results are found similar and more stringent than purely automated tests, even though some deviations exist due to differences in manual flagging.
Proceedings of EuroSun 2018, 2018
International Journal of Climatology, 2017
Ground-based meteorological observations are used here as proxy data, as well as aerosol reanalys... more Ground-based meteorological observations are used here as proxy data, as well as aerosol reanalysis estimates for training, to reconstruct aerosol optical depth (AOD) time series over Romania during a multidecadal period (1961-2015). The approach uses sunshine duration fraction (SDF) data computed for cloudless summer days (identified from 6-hourly cloud observations) and AOD data from the Modern-Era Retrospective analysis for Research and Applications, version 2 (MERRA-2) reanalysis. MERRA-2 AOD data were validated first by comparing them to high-quality AErosol RObotic NETwork (AERONET) ground observations at eight stations located in Central and Eastern Europe. The comparison of MERRA-2 AOD data with AERONET ground observations showed that the reanalysis estimates are reasonably accurate, but tend to underestimate AOD in the region of interest. Spaceborne AOD observations from Moderate Resolution Imaging Spectroradiometer (MODIS) were also considered, but were found too biased and not complete enough for this task. A significant linear relationship between MERRA-2's AOD and SDF data at the 57 of the 86 available stations was found, allowing the use of both a linear and bivariate regression models to back-calculate the historical AOD time series from SDF observations. This reconstruction is restricted to clear summer days here because of the limited temporal resolution of the available cloud observations. The long-term trends of the computed AOD time series correctly delineate the expected dimming and brightening periods that have been widely reported over Europe. The proposed method is suitable over areas where very long and concomitant time series of daily sunshine and hourly cloud observations are available, but also has limitations that are discussed.
2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC), 2015
35Th Cospar Scientific Assembly, 2004
Solar Energy, 2016
At any site, the bankability of a projected solar power plant largely depends on the accuracy and... more At any site, the bankability of a projected solar power plant largely depends on the accuracy and general quality of the solar radiation data generated during the solar resource assessment phase. The term ''site adaptation" has recently started to be used in the framework of solar energy projects to refer to the improvement that can be achieved in satellite-derived solar irradiance and model data when shortterm local ground measurements are used to correct systematic errors and bias in the original dataset. This contribution presents a preliminary survey of different possible techniques that can improve long-term satellite-derived and model-derived solar radiation data through the use of short-term on-site ground measurements. The possible approaches that are reported here may be applied in different
Bankable data for solar energy projects needs to ensure as much as possible the accuracy and gene... more Bankable data for solar energy projects needs to ensure as much as possible the accuracy and general quality of solar radiation data to be used in the solar resource assessment studies for any site of interest in a project development. The term "site adaptation" is being used in the framework of solar energy projects to refer to the improvement that can be achieved in satellite-derived (or more generally model-derived) solar irradiance when short-term local ground measurements are used to correct systematic errors and bias of the original dataset. This document presents a review of different techniques for correcting long-term satellite-derived solar radiation data by using short-term ground measurements. The collaborative work has been done within the framework of Task 46 "Solar Resource Assessment and Forecasting" of the International Energy Agency's Solar Heating and Cooling Programme. Different approaches whose use depends on the origin and characteristics of the uncertainties of the modelled data are presented. Recommendations to the use of ground measurements and the results of several approaches to improve satellite-derived data are shown through this report highlighting the importance of using site adaptation and the different degree of improvement that can be achieved depending on the climatological characteristics of the site.
Solar Energy, 1994
... MJ mZ) Year Month 1 2 3 4 5 6 7 8 9 10 11 12 1 2 ... Differences n computed annual irradiatio... more ... MJ mZ) Year Month 1 2 3 4 5 6 7 8 9 10 11 12 1 2 ... Differences n computed annual irradiation oninclined surfaces using isotropic and anisotropic and anisotropic sky-diffuse models, Solar Energy ...Evaluation of hourly tilted surface radiation models, Solar Energy45, 9-17 (1990 ). ...
A new capability for ingesting gridded aerosols data into the Weather Research and Forecasting (W... more A new capability for ingesting gridded aerosols data into the Weather Research and Forecasting (WRF) mesoscale model is being developed. The aim is to improve the shortwave downward solar radiation as-sessment and forecasting by equipping the model with a mechanism to ingest both high temporal and high spa-tial resolution aerosol data. This results in a reduction of the bias caused by any misrepresentation of the aerosol optical properties and their spatio-temporal variability. The main impact of this improvement is on the direct and diffuse components of solar radiation. We present here a preliminary study over the Continental United States using the Goddard Space Flight Center shortwave scheme, MODIS Level 3 aerosol optical depth data, and three ground stations of NOAA's SURFRAD radiation network. Results under cloudless conditions showed a relative improvement in the mean bias error of about 80% in the direct normal irradiance and up to about 70% in the diffuse irradiance, wi...
Proceedings of the EuroSun 2014 Conference, 2015
Solar Energy, 1998
Global and diffuse radiation and surface meteorological measurements at Edmonton, Montreal, Port ... more Global and diffuse radiation and surface meteorological measurements at Edmonton, Montreal, Port Hardy, Toronto and Winnipeg for the years 1977-1984 are analyzed to yield estimates of atmospheric precipitable water and turbidity. Three methods of estimating the precipitable water and two methods of estimating the turbidity are used and compared. Laboratory measurements of pyranometer response as a function of zenith angle are used to correct the global radiation measurements. Circumsolar radiation is removed from the direct radiation obtained from the difference of measured global and diffuse radiation. The magnitude of this circumsolar correction is discussed in the light of recent measurements and calculations of the circumsolar ratio. Turbidity time series are presented, showing a clearly defined El Chichon eruption signature in 1983-1984. A comparison with earlier results is included.
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Papers by Chris A Gueymard