ABSTRACT:
The Ratio of Solid Angles (ROSA) computer code was developed as part of the Crosbyton Solar Power Project (CSPP) for calculation of optical power concentrations due to reflection from a spherical segment mirror. It was developed primarily in support of Department of Energy Contracts DE-AC04-76ET20255 and DE-AC04-83AL21557. This report provides technical information about the ROSA code.

The CSPP is concerned with the development of a technology for producing electric power from steam generated by reflection of the sun's rays from a fixed-mirror solar bowl onto a tracking receiver. In this system, the receiver is cantilevered and pivots about the center of curvature of the mirror. The ROSA code gives optical power concentration ratio profiles at points along the receiver surface.

The ROSA code is written for a spherical segment mirror and the rim angle of the mirror is an input variable. Orientation of the axis of symmetry of the bowl is specified in terms of a vertical-east-north coordinate system. Location of the sun relative to this coordinate system is also an input variable. Shading and rim cutoff effects are automatically included in the computation.

The code permits any convex surface of revolution as a receiver. Normally a cylinder or a cone would be used. For optimum energy capture, the axis of the receiver should lie along the from the center of the sun through the center of the bowl. However, tracking errors can cause misalignment of the receiver axis with this line. The code handles such misalignment in terms of misalignment angle input parameters.

This report consists of two parts, a technical reference manual and a user's guide. The reference manual provides the background material and derivations necessary for the implementation of the code. Computer listings for ROSA are also included in the reference manual.

The user's guide contains an explanation of the input data for the program, special user supplied subroutine requirements, a discussion of the output data, sample output and graphs of sample concentration profiles. Sample BOILER subroutines are given for a right circular cone and a right circular cylinder boiler. A sample RIM subroutine is given for an alternate rim shape.