A User's Manual for DELSOL3 - prod.sandia.gov - Sandia National ...
A User's Manual for DELSOL3 - prod.sandia.gov - Sandia National ...
A User's Manual for DELSOL3 - prod.sandia.gov - Sandia National ...
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determined by DHOPT (Namelist BASIC). The larger DHOPT is, the farther the<br />
heliostat separations are allowed to vary from the initial values in searching <strong>for</strong><br />
an optimum. However, the larger DHOPT becomes, the larger are the potential<br />
errors in interpolation and differentiation.<br />
To prepare <strong>for</strong> field buildup, the code does four preliminary calculations <strong>for</strong><br />
every zone. First, it finds the “best” aspect ratio at each density. If the land<br />
and wiring costs are negligible, the best aspect ratio at a given density would<br />
be the aspect ratio that gives the minimum shading and blocking. Second, the<br />
code finds the density that gives the maximum average per<strong>for</strong>mance/cost ratio<br />
(PCR) <strong>for</strong> that zone. When the zone is first added to the field, it will be at this<br />
density. Third, DELSOL finds the marginal value of increasing the density be-<br />
yond the density that optimizes the average PCR. The marginal value is defined<br />
as the change in the busbar energy cost <strong>for</strong> adding or subtracting one heliostat<br />
from that zone. The marginal values decrease with density beyond the density<br />
that optimizes the average PCR. These marginal values determine how the den-<br />
sity in the zone is increased during field buildup after the zone has been added to<br />
the field. Finally, when the first three calculations are completed <strong>for</strong> every zone,<br />
DELSOL ranks the zones accordingly from maximum to minimum average PCR.<br />
This ranking determines the order in which zones will be added to the field.<br />
Field buildup proceeds as follows:<br />
1) The zone with the best average PCR is used as the initial field zone; then,<br />
1<br />
2) The unused zone with the best average PCR is added to the field and<br />
the density of all zones already in the field is increased. The number of<br />
heliostats to be added to each zone already in the field is determined by<br />
requiring that the marginal value of adding one more heliostat to any<br />
zone is the same. (If the marginal values were unequal an optimum field<br />
would not exist since the energy cost could be lowered by moving a heliostat<br />
from a lower to a higher marginal value zone.);<br />
3) Step (2) is repeated until: (a) all design powers are achieved; (b) a flux<br />
limit constraint is exceeded; or (c) all the zones have been added to the<br />
field.<br />
I V. B-9. Effectiveness of Heliostat Density Opt irnizat ion-DELSOL optimizes<br />
heliostat densities to <strong>prod</strong>uce a given amount of annual energy, E, at a minimum<br />
energy cost. However, in many cases the optimization results in a field layout<br />
having a lower annual efficiency/design efficiency ratio, thus <strong>prod</strong>ucing less an-<br />
nual energy at a constant design point power. That is, although the annual ef-<br />
ficiency after optimization will be higher (requiring fewer heliostats <strong>for</strong> a given<br />
amount of annual energy), the design point efficiency might be increasing even<br />
more rapidly. Since the heliostats are only added until the design point power<br />
is reached, fewer heliostats would be in the field than if the annual energy were<br />
kept constant, so the annual energy might not be as large as be<strong>for</strong>e. Thus, capital<br />
cost of heliostats and annual energy both might decrease. Then, if field cost is a<br />
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