1. Evaluation of solar irradiance in the Vhembe district of the Limpopo province of South Africa using different theoretical models. BY T.S. MULAUDZI, E.N. MALUTA AND V.SANKARAN UNIVERSITY OF VENDA Energy Postgraduate Conference 2013

2. OUTLINE OF THE PRESENTATION Introduction, Study Area, Methodology, Results and discussions & Conclusions INTRODUCTION Importance of solar energy Availability of weather stations in Vhembe Availability of the ground measured solar irradiance Challenges and Ways of addressing these challenges STUDY AREA : Limpopo Province; Vhembe district – Makhado, Musina,, Mutale and Thulamela

3. VHEMBE DISTRICT

4. METHODOLOGY -1 Selected models: –Angstrom (clearness index (CI) and relative sunshine hours (RSSH)) –Hargreaves and Samani model (temperature based model) (maximum and minimum temperature data) –Garcia model (CI, daylength (N) and temperature

5. METHODOLOGY - 2 Measured data –Daily global solar radiation (H) in MJ/(m 2 day) – from Agricultural Research Council (ARC) –Actual sunshine hours (n) in hours - from South African Weather Services (SAWS) –Maximum and minimum temperature data in degrees (ARC) Computed data –Extraterrestrial global solar radiation (H o ) –Day lengths in hours(N) Other parameters - Regression constants (a, b & k r ), where a = 0.186, b = 0.467 and k r = 0.16 for inland.

6. METHODOLOGY-3 Estimate of H for the years 2007, 2008, 2009 and 2010. Compare some of these data with the measured data. Graphical representation of the estimated and measured data (2010). Tabulate the average annual data. Accuracy tests of the estimated data.

7. RESULTS-1

8. Results-2

9. Analysis 2010 Average global solar irradiance in MJ/m 2 StationObserTempAngsGar Mut 15.27318.08121.13020.746 Mhi 14.69519.36121.08819.917 Rab 17.51018.37821.07718.671 All 17.01419.12921.10419.298 Statistical analysis MutMhiRabAll RMSE T0.0140.0160.0300.011 A0.0250.0240.0300.018 G0.0150.0170.0370.011 MBE T0.0070.0120.0300.006 A0.0160.0180.0270.011 G0.0090.0140.0340.006 MPE T0.7691.2153.0270.579 A1.5901.7512.7351.121 G0.9311.4313.3940.626

10. DISCUSSIONS Comparison of the observed and the estimated H using different models : Mutale & Rabali - Temperature based model and Angstrom model predictions are the best. Garcia model data shows some variations. Mhinga - Both the temperature and Garcia models overestimated the global solar irradiance in this area. The Angstrom model exhibits a good variation Alldays – Good variation for all the models. Average global solar irradiance –The difference between the observed and the estimated data is less than 7.0 MJ/(m 2 day) for all the models. Statistical data –RMSE for each model is very close to zero – the predictive data show good variation trends.

11. CONCLUSIONS The estimated global solar radiation for the stations studied are comparable with the observed data from ARC. The best suitable models for this area are the temperature based and Angstrom model. THANK YOU