A User's Manual for DELSOL3 - prod.sandia.gov - Sandia National ...

11. Problem Geometry
This section describes the field layout geometries and options, the various co-
ordinate systems used in the DELSOL calculations, heliostat layout patterns, he-
liostat geometries and error sources, tower and receiver configurations, aiming
strategies, and flux point positions and the usage of flux points.
1I.A. Coordinate Systems and Andes
The geometry used in the calculations is shown in Figures 11-1 and 11-2. Po-
lar (zenith) angles are measured from vertical. Azimuthal angles are measured
clockwise from the south as shown in Figure 11-2, although field azimuthal angles
(Figure 11-3) will be measured clockwise from the north. There are four basic vec-
tors and coordinate system: 8, from the heliostat center to the center of the sun;
ii, directed along the heliostat normal; i, the reflected vector from the heliostat
center to the aim point on the receiver; and i, the outward surface normal of the
receiver.
The orientation of the heliostats is determined by Snell’s law: the angle of
incidence equals the angle of reflection, i.e.,
fi.s=fi.i
Solving for ii and i gives
ii = (8 + t^>/(ls + tl)
i = 2(ii * i)ii - s
The five Cartesian coordinate systems are listed in Table 11-1. The (;t,jt) plane
of the reflection normal system is given the special name “image plane”.
1I.B. Heliostat Zoning
In design optimization runs, DELSOL does not consider individually each of
the thousands of heliostats required in large systems. Instead, the code calculates
the performance at a set of field points. It is assumed that each field point rep-
resents the average performance in a surrounding zone of heliostats. For runs in
which only the performance is calculated, the field can be described with the zon-
ing approximation, or the coordinates of each individual heliostat can be defined.
Zones are numbered radially outward and are numbered azimuthally starting with
the north zone and proceeding clockwise, as shown in Figure 11-4.
11.B-I. Zoning OptioneThere are two options for zoning: 1) zoning
that completely surrounds the tower and that can be used with any receiver
(INORTH=O); and 2) finer zoning of the area north of the tower which can be
used only with a single north facing cavity or flat plate receiver (INORTH=l).