ISSUES IN SOLAR TRACKING FOR SUB-SAHARA AFRICA

1. ISSUES IN SOLAR TRACKING FOR SUB-SAHARA AFRICA Slide 19 Kant Eliab Kanyarusoke – (Presenter) Jasson Gryzagoridis & Graeme Oliver 21st May 2012

2. PURPOSE:RPD • ReportAPHELION & PERIHELION EFFECTS on TROPICAL areas’ incident solar radiation • Propose changes in ‘rule of thumb’ fixed panel installations in ALL TROPICAL areas • Demystify 2 - axes tracking in high diffuse radiation areas

3. CONTENTS • INTRODUCTION – WHY THE STUDY? • METHODOLOGY • RESULTS • CONCLUSIONS & WAY FORWARD • APPENDICES

4. INTRODUCTION • FACT 1: Solar tracking increases energy yields • FACT 2: Limited to No tracking in Tropical Africa’s domestic systems. WHY?? • Functional issues • Technical issues • Economic issues ISSUES WHAT TO DO?? • Design, construct & test suitable tracker

5. DESIGN APPROACH • CONTINENTAL RESOURCE SURVEY • TRACKING CHOICES • PRELIMINARY DESIGN • DETAILED DESIGN • MANUFACTURING • TESTING • THIS PAPER REPORTS ON 1ST TWO

6. METHODOLOGY ANALYTICAL • Reviewed ASHRAE irradiancy data at 80 stations • Deduced Beam & Diffuse components • Made Excel spread sheets for daily components • Wrote & ran Matlab scripts for 15 min. interval incident energy

7. METHODOLOGY contd. • Derived total incident irradiancy on inclined plane (Perez et al. 1990 model) • Wrote & ran Matlab scripts to: • Optimise fixed panel slopes • Re-optimise for two slope design in TROPICS • Determine and graph daily incident energy across year for different fixed and tracking mountings PEREZ et al. 1990

8. RESULTS (I)- AP/PERI HELION EFFECTS • NORTH TROPICAL ‘SUMMER’ YIELDS LESS THAN SOUTH TROPICAL ‘SUMMER’ • SOUTH TROPICAL ‘WINTER’ GIVES LESS THAN NORTH TROPICAL ‘WINTER’ BUT • SUN ‘CROSSES’ LATITUDE TWICE A YEAR SO,------ • ASYMMETRIC YIELDS WITH CALENDAR

9. RESULTS (Ia)- Horizontal plane radiation THE APHELION EFFECT IN NORTHERN TROPICAL LATITUDES DIFFUSE RADIATION INFLUENCE AT ALL LATITUDES APHELION

10. RESULTS (2)- Fixed slope panels • Best slope is different from conventional • Even the best is NOT good enough • Mandatory 180o turn twice a year • NEW BEST is TWO slope –: • turning twice if • turning 4 times if • The two slopes are: ZERO and • Up to 10 % increase on conventional fixed • Up to 15%increase during ‘winter’ months

12. RESULTS (3)- Solar tracking panels • 2 Axes continuous tracking: • 30 to 52% increment on conventional fixed (20 to 45% on proposed NEW 2 – SLOPE) • Single polar axis continuous tracking: • Generally differs by 4-5%age points from 2 axes continuous tracking • Yields slightly higher than 2 axes in high diffuse radiation areas • Single polar axis 6-step tracking: • Differs by 7-10 %age points from continuous version

14. CONCLUSIONS • Ap/Peri-helion effects in tropics is a major factor in energy distribution across latitudes • Dominant practice of fixed slope installation is NOT justifiable from incident energy yield or cost of intervention points of view • Geography is an important factor (perhaps more than Astronomy?) in incident energy yields • 2 Axes tracking IS NOT always a panacea to maximum energy gains

15. NEXT ----- • Actual yields computations from PV & ST systems • 2 SLOPE fixed systems design • Tracking flat ST systems design • Polar tracking system design • --------- ---------- ------------ THANK YOU; DANKIE; ENKOOSI; ASANTE

16. ISSUES INTRODUCTION

17. PEREZ et al. 1990 METHODOLOGY contd.

18. APHELION JAN 3rd JULY 4th 181 DAYS JUNE 21st 184 DAYS DEC 23rd RESULTS (I)- Horizontal plane radiation Adopted & Modified by Kanyarusoke from: http://www.universetoday.com/61202/earths-orbit-around-the-sun/

19. ISSUES IN SOLAR TRACKING FOR SUB-SAHARA AFRICA