Ground measurements of Global Horizontal Irradiation in Doha, Qatar

The present work shows an analysis of ground measurements of Global Horizontal Irradiation (GHI) taken at the Doha International Airport for the period 2008-2012. Inter-annual variability and monthly averages of GHI values were calculated from the available records of daily total irradiation values, analysed and discussed along with the daily averages. The average daily GHI value in Doha for the whole 5-year period is 5.61 kWh/m2/day, a total of 2048 kWh/m2/year. The highest monthly average is 6.97 kWh/m2/day during the month of June, followed by May with 6.92 kWh/m2/day. Day 149 of the year, which corresponds to the 29th of May, shows the highest daily average for this period, with 7.49 kWh/m2/day. In addition to global solar radiation, the daily and monthly average clearness indices along with three meteorological parameters (air temperature, relative humidity and air pressure) are presented and analysed. The annual average of clearness index for Doha obtained from ground measurements is 0.62, somewhat higher than the 22-year averaged value provided by the NASA-SSE database, 0.57. GHI and clearness index values are important parameters for solar-related projects; GHI assessment, for instance, is vital for PV applications. Even though the measurements were taken in Doha, a coastal and an expanding city, the values found in this study indicate that Doha has a good potential for this kind of applications and better conditions could be expected in other areas of Qatar.