Evaluation of solar irradiance in the Vhembe district of the Limpopo province of South Africa using...

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

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 VENDAUNIVERSITY OF VENDAEnergy Postgraduate Conference 2013

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

challengesSTUDY AREA : Limpopo Province; Vhembe district – Makhado,

Musina, , Mutale and Thulamela

VHEMBE DISTRICT

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

* o

H na b

H N

max min* where ro

Hk T T T T

H

*

o

H Ta b

H N

METHODOLOGY - 2

• Measured data– Daily global solar radiation (H) in MJ/(m2 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 (Ho)

– Day lengths in hours(N)• Other parameters

- Regression constants (a, b & kr), where a = 0.186, b = 0.467 and kr = 0.16 for inland.

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.

RESULTS-1

Results-2

Analysis

2010 Average global solar irradiance in MJ/m2

Station

Obser

Temp Angs Gar

Mut 15.273 18.081 21.130 20.746

Mhi14.695 19.361 21.088 19.917

Rab17.510 18.378 21.077 18.671

All17.014 19.129 21.104 19.298

Statistical analysis

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 variationAlldays – 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/(m2 day) for all the models.• Statistical data

– RMSE for each model is very close to zero – the predictive data show good variation trends.

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.

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