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Article Dans Une Revue Applied Mathematical Modelling Année : 2016

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

Résumé

In 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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Dates et versions

hal-01345997 , version 1 (18-07-2016)

Identifiants

Citer

Julien Nou, Rémi Chauvin, Stéphane Thil, Stéphane Grieu. A new approach to the real-time assessment of the clear-sky direct normal irradiance. Applied Mathematical Modelling, 2016, 40 (15-16), pp.7245-7264. ⟨10.1016/j.apm.2016.03.022⟩. ⟨hal-01345997⟩
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