<7, is the standard deviation of the sunlight flux distribution due to spherical aberration error; CT2 is the standard deviation of the sunlight flux distribution due to all other collector errors except for spherical aberration, i.e. those due to <52. The flux distribution is calculated as follows: the paraboloid is divided up into equal plaquettes. The radii of curvature of each segment are taken to be the averages of the radial and circumferential radii of curvature of the paraboloid, respectively. Each plaquette is then arranged so that the center of its reflected solar image coincides with the aperture at the center of the receiver. The focal plane consists of the beams reflected on the top side, center, and bottom side of each plaquette. The flux distribution within the focal plane is calculated by a two-dimensional ray-tracing program. 2. Parametric Study The relations between the sun image size and the other optical parameters were investigated in the above manner. Figures 8-12 show the effects of changing the optical parameters (focal ratio//Ds, number of divisions n, number of different radii allowed i, error J2, and offset h/D^ on the sun image size cr/ = a^/R) for both offset and symmetric configurations. From these figures, it can be seen that the sun image size (7f decreases when the configuration is symmetric, f/Ds is 0.5-1.0, n and i are increased, and ^2 is decreased. h/Ds has little effect on (7f. 3. Focal Ratio Figure 13 shows the relation between focal ratio and solar flux distribution. From this, we set the optimal focal ratio to be 0.6, considering minimization of system length and keeping the solar image small.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==