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Statistical Assessment of Average Global and Diffuse Solar Radiation on Horizontal Surfaces in Tropical Climate P

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Abstract

The hourly and monthly average global and diffuse solar radiation on horizontal surfaces in Nsukka, a tropical
climate on Lat. 60 52' N, Long. 70 24' E and 397 metres above sea level, were critically evaluated for each month of the year,
starting from November 2009 to October 2010. For each month, the hourly average global and diffuse irradiance obtained were
correlated with local time of the day, using second degree polynomials, while the monthly average values were correlated with
the months of the year, using third degree polynomials. These correlations were performed to facilitate easy prediction of
global and diffuse irradiance at any time and month of the year in Nsukka. The maximum hourly average global irradiance of
773 W/m2 was observed at 12.00 noon for the month of January 2010, while the minimum hourly average value of 426 W/m2
was observed at 2.00 pm for the month of August 2010. The monthly average global radiation varied from 243 W/m2 for the
month of August 2010 to 427 W/m2 for the month of January 2010, while the monthly average diffuse irradiance varied from
28.83 W/m2 in June 2010 to 42.84 W/m2 in January 2010.The hourly and monthly average global and diffuse solar radiation on horizontal surfaces in Nsukka, a tropical
climate on Lat. 60 52' N, Long. 70 24' E and 397 metres above sea level, were critically evaluated for each month of the year,
starting from November 2009 to October 2010. For each month, the hourly average global and diffuse irradiance obtained were
correlated with local time of the day, using second degree polynomials, while the monthly average values were correlated with
the months of the year, using third degree polynomials. These correlations were performed to facilitate easy prediction of
global and diffuse irradiance at any time and month of the year in Nsukka. The maximum hourly average global irradiance of
773 W/m2 was observed at 12.00 noon for the month of January 2010, while the minimum hourly average value of 426 W/m2
was observed at 2.00 pm for the month of August 2010. The monthly average global radiation varied from 243 W/m2 for the
month of August 2010 to 427 W/m2 for the month of January 2010, while the monthly average diffuse irradiance varied from
28.83 W/m2 in June 2010 to 42.84 W/m2 in January 2010.