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

Note that when IDENS=l or 2 the azimuthal spacing and, therefore,
the density depend on the tower height, THT.
The AR and AAz spacings from the above equations are tested to insure that
the mechanical limits on adjacent heliostats are not exceeded; i.e., that adjacent
heliostats will not hit each other in any combination of orientations. If the me-
chanical limits are violated, the azimuthal spacing is adjusted to accommodate
the full exclusion circle of the heliostat.
Sections 1V.B-2 and 1V.B-3 discuss in depth the process and result of opti-
mizing heliostat densities using one of the above sets of relationships as a starting
point. By specifying the variable IHOPT=l (namelist OPT) and also specifying
the variables DHOPT (namelist BASIC), heliostat density optimization for a con-
stant annual energy can be requested. Essentially, the values of AR and AAz are
varied within limits to determine if a better field density can be obtained, based
on cost. Since this is an optimization for a constant annual energy, which varies
from system to system and which is not directly related to the user-specified de-
sign point power, a system with an optimized heliostat density may have a higher
levelized energy cost for a fixed design point power than a comparable system
without optimized densities. This is discussed further in Section 1V.B-3.
11. C-I. Slip Planes-The individual placement of heliostats in a radial layout
pattern given only the zone average AR and AAz leads to a complication as one
moves radially inward from the center of the zone. Heliostats on successive rows
become more compressed until they incur an unacceptable increase in shading
and blocking (or reach mechanical limits for the zones close to the tower). The
problem can be alleviated by removing a fixed fraction (1-l/FSLIP) of the he-
liostats in the unacceptably compressed row and by restarting the layout pattern
based on the new number of heliostats in the row. Figure 11-10 illustrates this in-
terruption in the layout pattern for the default slip (FSLIP=1.33); the circular
row at which the adjustment is made is called the “slip plane” in analogy with
discontinuities in crystal structures. The number of rows between slip planes in-
creases as the radius increases and as the tower height increases. (See Reference
12 for additional discussion on slip planes.)
DELSOL calculates a zone by zone correction to account for the helio-
stat number change at a slip plane. The user specifies the slip ratio, FSLIP in
namelist FIELD, to be the number of heliostats present on the slip plane row be-
fore any are removed divided by the number remaining after removal. The default
value for FSLIP (4/3) is a satisfactory one for most intermediate to small sys-
tems. By choosing a value of FSLIP=l, the user effectively eliminates the slip
plane correction in the code.
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