Influence of Canting Mechanism and Facet Profile on Heliostat Field Performance

1. Influence of Canting Mechanism and Facet Profile on Heliostat Field Performance Stellenbosch University Energy Postgraduate Conference 2013

2. 2 ATS 150 Heliostat • (4th generation) Carpe Diem Solar: HelioCa 16

3. 3 Total Beam Dispersion Error

4. 4 Canting and Facet Curvature z x (x >> z)

5. 5 Analytical and Numerical Analysis Geometric Optics Ray Tracing

6. 6 1 Validation 0.9 Yearly Performance Model Validation Ray Tracer: SolTrace Validation Geometric Optics Validation Case: Off-axis Canting 0.8 <0.7% 0.7 AIPWI 0.6 Ray Tracer: Experimental Validation 0.5 q on-axis canting ( = 30) q on-axis canting ( = 90) 0.4 (Buck, 2009) (Noone, 2011) HFCAL 6% q on-axis canting ( = 30) (Buck,et al. 2009) q on-axis canting ( = 90) (Buck,et al. 2009) 0.5 1 1.5 2 2.5 3 0 R

7. 7 Parameter Variation Incidence Angle Toroid Misalignment Angle AZ Tracking FHA Tracking

8. 8 Profile Optical Performance 14 12 10 Flat Parabolic 8 Spherical Abr-Free 6 Aligned Toroid CDF Toroid COA 4 2 0 90 80 70 60 50 40 30 20 10 0 

9. 9 Toroidal Profile

10. 10 Conclusions • An analytical and numerical tools have been developed to analyse the optical behaviour of a profiled heliostat. • Both tools have been validated and show good correlation to experimental and commercial software packages. • An aligned toroid provides the best optical performance • During profile misalignment performance tends toward a spherical profile at 45 and performance degrades further up to 90 We gratefully acknowledge: National Research Fund Solar Thermal Energy Research Group Department of Science and Technology Stellenbosch University Hope Project