Flux density modelling in a solar tower power plant with reduced shading effect

This paper dealt with the assessment of the flux density on the receiver surface. The studied case was a heliostat field configuration simulated in a region of southern Tunisia (latitude: 30.25°N, longitude: 9.55°E), the simulation time was chosen to be the two equinoxes and the two solstices. The developed code can be summarized in three steps: the study of the optical losses, the estimation of the flux distribution on the receiver surface and the approximation of the total flux density. The code is then validated according to a ray tracing method. A detailed analysis of heliostats behaviour throughout the day proves that the heliostat field is more efficient on June 21
^st
; its optical efficiency can reach 0.6726% at 1 pm. It decreases in 21
^st
December, its minimum value is 0.4757% at 7 am. While, on September and March, the heliostat field admits a moderate optical efficiency, in the order of 0.6305%. The analysis of the flux distribution map on the receiver surface shows that, in the morning, the peak of the flux is slightly offset from the east to the west side of the target surface, reaching more than 14kW/m
²
during both equinoxes. At midday solar, the flux density distribution is more or less homogeneous over the entire circumference of the receiver. The flux density varies between 10kW/m
²
and 14kW/m
²
during the 21
^st
December and from 11kW/m
²
to 14.5kW/m
²
on September 21
^st
, from 11kW/m
²
to 14.7kW/m
²
on March 21
^st
and 11kW/m
²
to 15kW/m
²
on June 21
^st
. In the afternoon, the flux distribution is less intense on the west side. During the hours of sunshine, the heliostat field guarantees a minimum total power of 100MW whatever the solar coordinates. A comparative study between the results of the model developed in MATLAB and those obtained by the TONATIUH software reveals a good agreement.