For the receiver surface temperature above 506 C, this heat loss
rate decreases leading to a higher gain of energy by the system.
This requires a reduction in the heliostat aperture area in order
to be in the limit of the desired output power.
In the last part, the performance of the receiver has been studied.
To this end the effect of the receiver surface temperature and
the incident heat flux on the receiver efficiency has been investigated.
Fig. 7 shows the evolution of the receiver efficiency as a
function of the receiver surface temperature. It can be seen that
the receiver efficiency reaches a maximum value. This maximum
occurs for a receiver surface temperature of 506 C. The maximum
efficiency is then of the order of 0.9. This could be explained by taking
into account the results shown in Fig. 6. Indeed, for temperature
above 506 C, there is a fast rate of increase in the receiver
absorbed energy; this should lead to a higher efficiency. However
for higher temperature, the receiver absorbed energy decreases,
which should result in a lower efficiency.
In Fig. 8, the effect of the incident heat flux on the receiver efficiency
is reported. It can be noticed that there is an increase in the
receiver efficiency with the incident heat flux. However the values
of this efficiency level off at high values of the incident heat flux.
This is probably due, as shown in Fig. 6, to the reduction in the receiver
absorbed energy at high incident heat flux.