Open Access Open Access  Restricted Access Subscription Access

Impact of Solar Flux Ratios on Sky Condition Over Regional Climate of Nigeria

Samuel Olu Ojo, J.B. Tawose

Abstract


Solar flux ratios measure the optical effects of the atmospheric constituents on the radiation interacting with them. The common solar flux ratios investigated in this work include Clearness index, Cloudiness index, and Cleanness index. The NCEP/NCAR Reanalysis derived data were used in this work which comprises 6-synoptic hourly daily surface data. The data obtained at the resolution of 0.25km × 0.25km were direct and diffused solar radiation. The data covered a period of 10 years (2005–2014) for four climate zones in Nigeria which are Sahel, Guinea Savannah, Derived Savannah and Coastal regions. These data were analysed to obtain the global solar radiation and other solar ratios. The analyses showed that time of the day, seasons and sky conditions greatly affect the variation of solar flux ratios. The clearness and cleanness indices were observed to be higher during the daytime and dry season than the night time and wet season in all the regions. For instance, in the Sahel region, the values of clearness and cleanness indices were 0.70 and 0.61 during the daytime and 0.04 and 0.16 during the night-time, respectively. Conversely, the cloudiness was observed to be higher in the night time and the wet season than the daytime and the dry season. The values of Cloudiness index for the daytime and the night time were 0.42 and 0.68 in the Sahel. Those of other regions and seasons were equally analysed and studied. Finally, the results of the characterization of sky condition showed that the global irradiance has the high proportion of the diffused component in Nigeria. Hence, the sky condition was predominantly partial cloudy.

Full Text:

PDF

References


A.L. Ali, S.S.D. Atsu, J.A. Jervase. Monthly average daily solar radiation and clearness index contour maps over Oman, Energy Convers Manage. 2003; 44: 691–705p.

S. Coppolino. A new correlation between clearness index and relative sunshine, Renew Energy. 1994; 4(4): 417–23p.

J.A. Duffie, W.A. Beckman. Solar Engineering of Thermal Processes. John Wiley and Sons: New York; 1991.

M. Iqbal. An Introduction to Solar Radiation. Academic Press: New York; 1983; 59–67p.

M.G. Iziomon, T.O. Aro. On the annual and monthly mean diurnal variations of diffuse solar radiation at a meteorological station in West Africa, Meteorol Atmosph Phys. 1999; 69: 223–30p.

F.J.K. Ideriah, S.O. Suleman. Sky conditions at Ibadan during 1975–1980, Solar Energy. 1989; 43(6): 325–30p.

A. Kuye, S.S. Jagtap. Analysis of solar radiation data for Port Harcourt, Nigeria, Solar Energy. 1992; 49(2): 139–45p.

E.C. Okogbue, J. Adedokun. On the estimation of solar radiation at Ondo, Nigeria, J Phys. 2002; 14: 97–9p.

T.C. Chineke, E.C. Igwiro. Urban and rural electrification: enhancing the energy sector in Nigeria using photovoltaic technology, UNESCO/ANSTI, Afr J Sci Technol. 2008; 9(1): 102–8p.

L. Akpabio, S. Udo, S. Etuk. Empirical correlation of global solar radiation with meteorological data for Onne, Nigeria, Turk J Phys. 2002; 26: 301–7p.

E.B. Babatunde, T.O. Aro. Relationship between clearness index and cloudiness index at a tropical station (Ilorin, Nigeria), Renew Energy. 1999; 6(7): 801–5p.

S.O. Udoh. Sky conditions at Ilorin as characterized by clearness index and relative sunshine, Solar Energy. 2000; 69: 45–53p.

G. Montero, J.M. Escobar, E. Rodríguez, R. Montenegro. Solar radiation and shadow modelling with adaptive triangular meshes, Solar Energy. 2009; 83(7): 998–1012p.

K.Y. Kondratyev. Radiation in the Atmosphere. Academic Press: New York; 1969, 277–80p.

S. Jeff. Oxford Atlas of History Sahel Region. New York: Oxford University Press; 2010, 22–3p.

Canuk. 2011. About the country Nigeria. Retrieved 27 May 2011.

L. Awosika, R. Folorunso. (2014). Nigeria. The Ocean Data and Information for Africa (ODINAFRICA) Project. Retrieved from www.odinafrica.org.

E.B. Babatunde. Some solar radiation ratios and their interpretations with regards to radiation transfer in the atmosphere, Nigeria J Pure Appl Phys. 2005; 4: 41–5p.

E.C. Okogbue, J.A. Adedokun, B. Holmgren. Hourly and daily clearness index and diffuse fraction at a tropical station, Ile-Ife, Nigeria, Int J Climatol. 2009; 29: 1035–47p. http://doi.org/10.1002/joc.

Z.D. Adeyefa, B. Holmgren, J.A. Adedokun. Spectral solar irradiance under harmattan conditions, Renew Energy. 1995; 6(8): 989–96p.

O.S. Ojo, B. Adeyemi. Estimation of solar radiation using air temperature and geographical coordinates over Nigeria, Pac J Sci Technol. 2014; 15(2): 78–88p.

E.C. Okogbue, J.A. Adedokun. Characterization of sky conditions over Ile-Ife, Nigeria based on 1992–1998 solar radiation observations, Meteorogische Zeitschrift, Germany. 2002b; 11(6): 419–23p.


Refbacks

  • There are currently no refbacks.