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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a final per<strong>for</strong>mance calculation on the optimized system. This difference will be<br />
most noticeable in flux profiles.<br />
The speed of the Hermite method results from the fact that a severely trun-<br />
cated polynomial (6th order) expansion is an accurate approximation to the flux<br />
density. As discussed in Reference 5, the accuracy of the Hermite method in-<br />
creases as the error sources of heliostat per<strong>for</strong>mance and/or their effect on the<br />
flux profile become larger. Specifically, DELSOL becomes more accurate in pre-<br />
dicting the flux and spillage when: (1) the errors increase; (2) the slant range in-<br />
creases; or (3) the size of the heliostat is reduced (either physically or effectively<br />
by focusing or canting).<br />
To calculate the fraction of the flux intercepted by the receiver, Equation<br />
(1II.F-1) must be integrated over the projection of the receiver on the image<br />
plane. The resulting two dimensional integral can be evaluated analytically in one<br />
dimension and numerically, using a 16 point Gaussian quadrature, in the other.<br />
I1I.F-I. More Accurate Images from Canted Heliostats-The normal method<br />
used in DELSOL is to use a single Hermite series to represent the heliostat’s im-<br />
age. When the heliostat to receiver distance is small this can result in a blurring<br />
of the sharp edges of the image. A slower running option which calculates a more<br />
accurate image is available <strong>for</strong> canted heliostats (INDC=l in Namelist HSTAT).<br />
The location of the center of the image from each cant panel is calculated. Then<br />
a separate Hermite series is used to represent the image from each cant panel.<br />
This option can only be used in per<strong>for</strong>mance calculations with a single<br />
aimpoint at the center of the receiver (IAUTOP=l, Namelist REC). Its<br />
effect on an optimized system can be determined by rerunning a per<strong>for</strong>mance cal-<br />
culation on the optimized system with INDC=l.<br />
II1.F-2. When to do Fluz Calculations-Flux calculations should be done ei-<br />
ther to design flux limited systems or to define a detailed flux map of a previously<br />
optimized system. There<strong>for</strong>e, flux calculations should not be done (IFLX=O) dur-<br />
ing an initial per<strong>for</strong>mance calculation. It is recommended that, during system op-<br />
timization, a grid of flux points be defined covering either the entire heat absorb-<br />
ing surface or a known area of concern, and that up to four points from that grid<br />
be checked during optimization to verify that flux limits are not exceeded. During<br />
the final per<strong>for</strong>mance calculation, fluxes should be calculated <strong>for</strong> points over the<br />
entire heat absorbing surface to verify that flux limits have not been exceeded at<br />
any other points than those checked during optimization.<br />
1II.G. Time Independent Losses<br />
The hourly and seasonal variation of: a) atmospheric attenuation from the he-<br />
liostat to the receiver, b) receiver radiation and convection losses, and c) piping<br />
insulation losses are assumed negligible. In addition, mirror and receiver reflec-<br />
tivity, the thermal to electric conversion efficiency, and parasitic loads are repre-<br />
sented by constant time averaged values.<br />
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