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

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flux level. DELSOL determines the best combination of receiver size (with its
associated cost, receiver losses, and spillage losses) and heliostat field size (with
its associated cost and field losses). For a given set of component costs, as a re-
ceiver size decreases below its optimum, spillage increases and so field costs in-
crease more than the decrease in receiver cost. If at that receiver size the allow-
able flux limit is not reached, then it is not cost effective to force the system to
have a peak flux at the FLXLIM(1) limit.
The second reason why a peak flux limit may not be obtained during system
optimization is that the receiver size is being varied in discrete steps, rather than
continuously. In this case, the user can come closer to a given flux limit by using
more closely spaced receiver sizes, or the flux limit can be set slightly higher than
actually desired since the flux from the optimum will generally be below the limit.
In any case, the user should request a more accurate detailed flux map during a
final performance calculation to verify that flux limits are being met, if desired,
but not exceeded.
1V.D-2. Iieliostat Field Land Constraint-DELSOL allows the heliostat field
to be constrained within a number of arbitrarily oriented rectangles. The input
defining the land constraint is described in Section I1.B-4. As mentioned in Sec-
tion 1V.C-4, with a land constraint it. is necessary to search for the optimal loca-
tion of the tower with respect to the constraint. Only the heliostat locations are
constrained. The code does not require the tower to be in the land constraint.
However, the user should make sure that land is available for the tower.
There is an additional complication in land constrained designs when the
thermal energy is not used at the base of the tower. In repowering or process
heat applications the thermal energy may have to be transported to a point near
the edge of the land constraint. DELSOL does not consider the cost or losses in
the piping run from the tower position to the use point. The user may want to
fold in these effects manually. For example, consider a rectangular land constraint
whose sides are parallel to the N/S and E/W directions. DELSOL will gener-
ally prefer to locate the tower south of the center of the land constraint. Sup-
pose, however, that the thermal energy is required at the northern boundary of
the field. It may then be cost effective to move the tower further north from the
DELSOL optimum if the savings in the pipe run may more than offset the in-
creased cost of thermal energy at the tower base.
1V.E. “Smart” Optimization Searching Algorithm
DELSOL has to consider NUMTHT x NUMREC x NUMHTW x NUMPOS
combinations of tower height, receiver sizes, and tower positions in searching for
the minimum energy cost system. Figure IV-1 shows a schematic of the opti-
mization search. There are four nested iterations of the discrete system variables:
tower height, first receiver variable, second receiver variable, and tower position.
Since the zone by zone performances do not depend on the tower location, these
performances are calculated outside of the tower position loop. For each set of