PARAMETERS OF DIRECT SOLAR ENERGY FLUX IN CLEAR SKY TAKEN INTO ACCOUNT OF ATMOSPHERE TRANSPARENCY

• Datum: 2019
• Hauptverfasser: Halchak, V., Boyarchuk, V., Syrotiuk, V., Syrotyuk, S.
• Format: Artikel
• Sprache: Ukrainisch
• Veröffentlicht: Institute of Renewable Energy National Academy of Sciences of Ukraine 2019
• Schlagworte: solar energy; clear-sky model; zenith angle; atmospheric optical thickness; turbidity factor; direct flux; intensity; irradiation.
• Online Zugang: https://ve.org.ua/index.php/journal/article/view/198
• Назва журналу: Vidnovluvana energetika

It is often impossible to make assessment of efficiency of solar power plants with tracking devices, placed in different climatic zones. The reason is that insolation regimes can hardly or never be reproduced artificially. Therefore, calculations mostly apply month average figures ​​of an hourly change of intensity of a direct solar energy flux under conditions of clear sky, which are mentioned in actinometric guides. However, they also describe local features of insolation, such as local deviations from the symmetry with respect to midday. Therefore, energy estimation is proposed to be carried out with the use of hourly values ​​of intensity of a direct solar energy flux, calculated according to the clear regulated parameters of atmospheric transmittance. Simulation of the corresponding dependencies was carried out according to the correlation, recommended by the European Solar Radiation Atlas (ESRA) for the variant of a clear-sky model, i.e. the indicator of the Rayleign component of the optic thickness of ideal atmosphere δR(m) and seasonal character of the values ​​of the Linke-Kasten turbidity factor TLК. The obtained model graphs, which are symmetric with respect to midday, are compared to the data of the registration at the meteorological stations, located in Boryspil and Kovel, close to the latitude of 50°. Significant variations are caused by local daily and seasonal characteristics of the actual atmospheric conditions. However, integral indexes of insolation, particularly the registered daily amounts of direct solar energy flux, are close to the model, with consideration of seasonal changes in the turbidity factor: 4 - in summer, 3,5 - at spring equinox and 3,0 - at winter solstice. The solar flux is measured by the expression with the seasonal corresonding coefficients. The extression is convenient for assessing of the current power and daily productivity of solar power plants with tracking devices in any region. However, local insolation features are estimated by the effect of small deviations from the idealized flux. Ref. 17, tabl. 3, fig. 5.