Solar radiation parameters

HYGEOS provides solar radiation parameters necessary for planning financial activities with photovoltaic (PV) and concentrated solar plants (CSP), as:

  • the global horizontal irradiance (GHI),

  • the direct normal irradiance (DNI),

  • the slant path transmittance (Tsp, for tower CSPs, see the ASoRA project).

Any other parameter can be joined, as the circumsolar ratio, GHI for tilted panels, wind speed, air temperature, ...


Accuracy and precision

Special care is given to accuracy and precision by selecting the best input parameters to the radiative transfer codes. We consider the spatial and temporal variability of clouds, aerosols, water vapor, ozone and other absorbing atmospheric gases.

As experts in radiative transfer simulation, we apply state-of-the-art radiative transfer codes, and we even develop our own codes for specific needs (e.g. SMART-G).


Spatio-temporal coverage

Computations are made for any specific site location as well as for regions. Time series can extend over several tens of years at the time resolution of 1 hour. On-demand studies can also be performed to meet the specific user needs. Please contact HYGEOS.


Examples

The Figure 1 shows the impact of desert dust aerosols on DNI on 1 day at Ouarzazate, Morocco [Elias et al., 2017]. Computations are made with the SMART-G radiative transfer code with AERONET providing the input data on aerosols and water vapor. 28 July 2012 could be considered as a reference with smallest attenuation by aerosols and water vapor at Ouarzazate. As desert dust aerosols were observed by AERONET on 22 March 2012, the difference with the 28/07 shows the magnitude of the desert dust impact on DNI.

The Figure 2 shows the variability of the slant path attenuation (= 100% - transmittance) caused not only by aerosols but also by water vapor [Elias et al., 2017]. Aerosols further attenuate solar radiation between the heliostat and the receiver, by ~3 to ~21% in August 2012, according to the aerosol load. The slant path attenuation by aerosols could change by a factor 3 in 1 to 4 days in August 2012.


Figure 1. Comparison of computed (red) and observed DNI (black circles) at Ouarzazate on 2 days in 2012 [Elias et al., 2017].


Figure 2. The slant path attenuation at Ouarzazate in August 2012, caused by aerosols (red) and by both water vapor absorption and Rayleigh scattering (black) [Elias et al., 2017].


Contact at Hygeos: Thierry Elias