OFFSET is a ray tracing computer code for optical analysis of a solar collector. The code models the flux distributions within the receiver cavity produced by reflections from the solar collector. It was developed to model the offset solar collector of the solar dynamic electric power system being developed for the Space Station. OFFSET has been used to improve the understanding of the collector-receiver interface and to guide the efforts of NASA contractors also researching the optical components of the power system.
The default collector configuration in the code consists of 19 hexagonal panels each containing 24 triangular, reflective facets. Current research is geared toward optimizing flux distribution inside the receiver via changes in collector design and receiver orientation. OFFSET offers many options for experimenting with the design of the system. The offset parabolic collector model configuration is determined by an input file of facet corner coordinates. The user may choose other configurations by changing this file, but to simulate collectors that have other than 19 groups of 24 triangular facets would require modification of the FORTRAN code. Each of the roughly 500 facets in the assembled collector may be independently aimed to smooth out, or tailor, the flux distribution on the receiver's wall. OFFSET simulates the effects of design changes such as in receiver aperture location, tilt angle, and collector facet contour.
Unique features of OFFSET include:
- Equations developed to pseudorandomly select ray originating sources on the Sun which appear evenly distributed and include solar limb darkening;
- Cone-optics technique used to add surface specular error to the ray originating sources to determine the apparent ray sources of the reflected sun;
- Choice of facet reflective surface contour -- spherical, ideal parabolic, or toroidal;
- Gaussian distributions of radial and tangential components of surface slope error added to the surface normals at the ten nodal points on each facet; and
- Color contour plots of receiver incident flux distribution generated by PATRAN 2.5 processing of FORTRAN computer code output.
OFFSET output includes a file of input data for confirmation, a PATRAN 2.5 results file containing the values necessary to plot the flux distribution at the receiver surface, a PATRAN 2.5 results file containing the intensity distribution on a 40 x 40 cm area of the receiver aperture plane, a data file containing calculated information on the system configuration, and a file including the X-Y coordinates of the target points of each collector facet on the aperture opening. Other output consists of several files that allow for a number of different PATRAN 2.5 plots, and P/PLOT input data files to allow X-Y plotting of various data results.
OFFSET carries the NASA case number LEW-14778. It was originally released as part of the COSMIC collection.
SOURCE CODE AVAILABLE