Session: 18-04 HelioCon Heliostat Designs

Paper Number: 141968

141968 - Sunring: Mirror Array Optimization and Prototyping 

Abstract: 

Under a Heliostat Consortium funded project titled “SunRing Advanced Manufacturing and Field Deployment”, Solar Dynamics has improved the optical performance of its SunRing heliostat through a new mirror array design which is accompanied by a new assembly workstation.  The SunRing is a novel, carousel type heliostat, but the mirror array (torque tube plus mirror facets) is a relatively conventional design.  While somewhat conventional, achieving the precise optical performance required of commercial heliostats is not trivial and requires detailed design, analysis, and testing.  This presentation covers the SunRing’s new mirror array, the analysis that lead to the final design, and the prototyping and metrology system used to verify its performance. 

Two main improvements have been incorporated into the SunRing’s mirror array.  First, the SunRing moved to a larger format mirror facet to maximize the mirror’s shipping density within standard shipping containers.  The resulting wider facet reduces the number of facets from six to four on the SunRing.  Secondly, 2-D focusing is added to the mirror array where mirror curvature is added to the originally flat mirrors when placed onto the mirror assembly workstation, and the focused shape is “locked-in” when the mirror array’s support structure is connected to the mirror facets.  The assembly workstation supports the mirror array at designated control points where the height of each control point is independently controlled.  By varying the position of each control point, a 2-D paraboloid shape is imparted into the mirror array where the focal length can be changed based on the heliostat’s position in the solar field. 

Incorporating the larger facets and 2-D focusing led to re-optimizing of the support structure connecting the mirror facets to the SunRing’s torque tube.  The trade-offs between optical performance, material cost, and labor cost were analyzed when selecting the final design.  Optical performance is sensitive to the elevation angle of the heliostat, and elevation angle weighting factors were used to incorporate this sensitivity into the design process.  Weighting factors were based on the annual energy provided to a receiver as a function of the heliostat’s elevation angle.

Lastly, a mirror array prototype will be built in Spring 2024 with results presented at the conference.  The mirror array prototype will be built using the commercial intent assembly workstation to produce a 2-D paraboloid shape.  The mirror array’s optical performance will be verified using Sandia’s SOFAST deflectometry measurement system.  SOFAST will provide a surface slope error map of the mirror array, and this will be used to tune the assembly workstation.  During tuning, the workstation’s control points will be adjusted to minimize slope error.  The resulting slope error of the SunRing will be compared to the FEA predictions where the overall trends are expected to match; however, the magnitude is expected to be larger on the prototype due to real world impacts of slop in joints, manufacturing imperfections, etc… that are idealized in the FEA model.  The presentation will present the overall results of the prototyping effort. 

Presenting Author: Kyle Kattke Solar Dynamics LLC

Presenting Author Biography: Kyle received his Masters in Mechanical Engineering from the Colorado School of Mines. Kyle is a senior engineer and project manager at Solar Dynamics where he manages the development of the SunRing heliostat. Kyle has been in the CSP industry for over 10 years starting at Abengoa Solar before joining Solar Dynamics.

Authors:

Kyle Kattke Solar Dynamics LLC
Nathan Stegall Solar Dynamics LLC