Impact of local broadband turbidity estimation on forecasting of clear sky direct normal irradiance

Inman, Rich H.; Edson, James G.; Coimbra, Carlos F.M.

doi:10.1016/j.solener.2015.04.032

Cited by 44 publications

(18 citation statements)

References 32 publications

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“…TL has been reported for numerous places (Hussain et al, 2000;Formenti et al, 2002;Diabaté et al, 2003;Polo et al, 2009a;Eltbaakh et al, 2012;Bertin and Frangi, 2013;Inman et al, 2015;Khalil and Shaffie, 2016). Using hourly data from nine Spanish regions, Polo et al (2009b) proposed and evaluated a methodology to estimate daily Linke's turbidity in clear sky conditions based on measures of global horizontal irradiance at noon.…”

Section: Introductionmentioning

confidence: 99%

Temporal variability of atmospheric turbidity and DNI attenuation in the sugarcane region, Botucatu/São Paulo/Brazil

Santos

Escobedo

2016

Atmospheric Research

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In this study, attenuation of direct normal solar irradiance (DNI) in Botucatu / São Paulo, an area under the influence of local and adjacent agricultural burning, is expressed using the Linke's turbidity factor (TL) in the period from 1996 to 2008. Two methodologies represented as TL Dj and TL Li were used. Temporal variability (hourly average for the season and monthly average) is presented. Turbidity was correlated with wind speed and air temperature. Frequency distribution and cumulative frequency are analyzed to determine turbidity predominance levels in the local atmosphere. Optical depth information of aerosols at 550 nm (AOD 550nm) and water vapor were obtained by the Terra satellite using the MODIS sensor. The highest degree of DNI transmission is observed in the morning. Close to solar noon, transmission is smaller (greatest TL value). Diurnal TL variability is more evident in the hot period than in the cold period. May and June were the months of lowest DNI attenuation (highest atmospheric transparency). The highest DNI attenuation occurs in spring (TL Dj = 4.22 ± 0.05 and TL Li = 4.65 ± 0.06) and summer (TL Dj = 4.27 ± 0.14 and TL Li = 4.69 ± 0.15). Wind speed and air temperature were positively correlated with TL. In N 28% of hours of clear sky, turbidity exceeded the value of 4.0. The region of Botucatu seems to be influenced by water vapor and aerosols from different origins. This study concludes that these factors significantly reduce DNI incidence on the surface, with higher atmospheric transparency in the cold period and lower atmospheric transparency in the warm period.

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Section: Introductionmentioning

confidence: 99%

Temporal variability of atmospheric turbidity and DNI attenuation in the sugarcane region, Botucatu/São Paulo/Brazil

Santos

Escobedo

2016

Atmospheric Research

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“…Alternatively, one can also use a "cloudiness index" where the reference forecast is referred to as "smart persistence" by Inman et al (2015). This reference model includes the effects of air mass, aerosols, turbidity, i.e., every major atmospheric effect except that of clouds.…”

Section: Acknowledgmentmentioning

confidence: 99%

“…This is because it is virtually impossible for a forecast to improve over smart persistence under cloudless skies, since the smart persistence reference model includes all effects of diurnal variability (solar zenith angle) and columnar optical depths of water vapor and aerosols. These types of smart persistence reference forecasts are typically updated sub-hourly (Inman et al, 2015;Reno and Hansen, 2016).…”

Section: Acknowledgmentmentioning

confidence: 99%

Verification of deterministic solar forecasts

et al. 2020

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The field of energy forecasting has attracted many researchers from different fields (e.g., meteorology, data sciences, mechanical or electrical engineering) over the last decade. Solar forecasting is a fast-growing subdomain of energy forecasting. Despite several previous attempts, the methods and measures used for verification of deterministic (also known as single-valued or point) solar forecasts are still far from being standardized, making forecast analysis and comparison difficult. To analyze and compare solar forecasts, the well-established Murphy-Winkler framework for distribution-oriented forecast verification is recommended as a standard practice. This framework examines aspects of forecast quality, such as reliability, resolution, association, or discrimination, and analyzes the joint distribution of forecasts and observations, which contains all time-independent information relevant to verification. To verify forecasts, one can use any graphical display or mathematical/statistical measure to provide insights and summarize the aspects of forecast quality. The majority of graphical methods and accuracy measures known to solar forecasters are specific methods under this general framework. Additionally, measuring the overall skillfulness of forecasters is also of general interest. The use of the root mean square error (RMSE) skill score based on the optimal convex combination of climatology and persistence methods is highly recommended. By standardizing the accuracy measure and reference forecasting method, the RMSE skill score allows-with appropriate caveats-comparison of forecasts made using different models, across different locations and time periods.

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“…Another possibility lies in using the andogenous statistical model developed by Reno et al (Reno et al, 2012). In this sense, Inman et al proposed a clear-sky detection algorithm based on this model (Inman et al, 2015). The authors focused on the sensitivity of day-ahead clear-sky DNI forecasts to local fluctuations in atmospheric turbidity.…”

Section: Introductionmentioning

confidence: 99%

A new approach to the real-time assessment of the clear-sky direct normal irradiance

Nou

Chauvin

Thil

et al. 2016

Applied Mathematical Modelling

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Highlights• A new approach to the real-time assessment of the clear-sky DNI is described• An existing clear-sky DNI model is part of the approach • A methodology for the computation of atmospheric turbidity is developed• Clear-sky DNI data are detected using a wavelet-based multi-resolution analysis• An evaluation procedure, allowing changes in DNI to be simulated, is proposedA new approach to the real-time assessment of the clear-sky direct normal irradiance AbstractIn a context of sustainable development, interest for concentrating solar power and concentrating photovoltaic technologies is growing rapidly. One of the most challenging topics is to improve solar resource assessment and forecasting in order to optimize power plant operation. Since clear sky defines the nominal operating conditions of the plants, improving their management requires the use in real-time of clear-sky direct normal irradiance (DNI) models. Typically, accuracy is best achieved by considering water vapor and aerosol concentrations in the atmosphere separately. However, measuring such physical quantities is not easy and requires a weather station close to the considered site. When these data are not available, the attenuating effects can be modelled by atmospheric turbidity factors which can be obtained from DNI under clear-sky conditions. So, the main purpose of the present paper is to propose an efficient approach to assess the clear-sky DNI in real time. This approach combines an existing empirical model, proposed by Ineichen and Perez, with a new methodology for the computation of atmospheric turbidity. It takes advantage of the fact that changes in atmospheric turbidity are relatively small throughout the day in comparison to changes in DNI, even when the sky is free of clouds.In the present study, we considered data from two experimental sites (Golden, in the USA, and Perpignan, in France) and used a wavelet-based multi-resolution analysis as a clear-sky DNI detection tool. In addition, we compared the proposed approach with several combinations of empirical models and ways of computing atmospheric turbidity. The first model is a polynomial of the cosine of the solar zenith angle, whereas the two other models use atmospheric turbidity as an additional input. Regarding its calculation, monthly and daily mean values have been considered. Moreover, we defined a procedure in order to evaluate the accuracy of all the considered approaches. This procedure allows changes in DNI caused by clouds to be simulated using a noisy signal applied to clear-sky periods. In both sites, our approach to the real-time assessment of the clear-sky DNI outperforms the other approaches. In the worst case, the mean absolute error is reduced by 8 W m −2 in comparison to the approaches based on monthly mean values of atmospheric turbidity, and reduced by about 30 W m −2 when taking the polynomial-based model as a reference.

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Impact of local broadband turbidity estimation on forecasting of clear sky direct normal irradiance

Cited by 44 publications

References 32 publications

Temporal variability of atmospheric turbidity and DNI attenuation in the sugarcane region, Botucatu/São Paulo/Brazil

Temporal variability of atmospheric turbidity and DNI attenuation in the sugarcane region, Botucatu/São Paulo/Brazil

Verification of deterministic solar forecasts

A new approach to the real-time assessment of the clear-sky direct normal irradiance

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