The insolation on vertical surface having different directions in the Kingdom of Bahrain

The daily total global (HT) and diffuse (HDIF) solar radiation, measured at Bahrain International Airport, Kingdom of Bahrain, (latitude 26° 13″N and longitude 50° 39″E), had been recorded, analyzed, and studied. The mean hourly values of HT and HDIF on horizontal and vertical surfaces (facing North, South, East and West) have been averaged to daily and monthly radiation. The monthly average global solar radiation on a horizontal, vertical north, vertical east, vertical south and vertical west was 22.5, 4.0, 9.4, 11.9 and 11.3MJ/m2, respectively. The monthly average of the diffuse (HDIF) and direct (HDIR) insolation was found 6.9 and 15.4MJ/m2, respectively. The direct radiation represents, on average, 69.4% of the total insolation while the diffuse represents 30.6% of it. In comparing these values with previously measured total direct and diffuse in 1996 at the University of Bahrain, Isa Town campus, Kingdom of Bahrain (latitude 26° 20″N and longitude 50° 5″E), we found that the previous records give less percentage of HDIR/H than the recent ones by 10.7%, while the opposite is true for HDIF/H, as the recent is larger by 24.5%. This might be attributed either to the difference in the accuracy of the sensors or to the reduction in the atmospheric pollution, bearing in mind that the distance between the two places does not exceed 50 km. The total insolation incident on vertical west-facing surface was found to, on average, be larger than east facing by 20.2%, and as much as by 50.8% in January and larger by only 11.9% in July.

Fig. 4 shows that HT,W is different, and larger, than HT,E by nearly 20.2% in average, and as much as by 50.8% in January, and by 11.9% in July. This maybe attributed that insolation is affected by haze, humidity, and aerosols in the early hours of the day in Bahrain, which cause it to reflect back to space and to diffuse. Fig. 5 shows the total insolation on vertical South facing surface (HT,S). It exhibits a classical behavior for regions at the northern hemisphere at middle latitude (23° to 44° N). The maximum insolation was in winter sessions (18 MJ/m2 > HT,S > 14.3 MJ/m2) which is expected since the sun is at low altitude, while the least insolation in summer session (8 MJ/m2 > HT,S > 4.7 MJ/m2) as Average monthly irradiation 35.0 30.0 MJ/m 25.0 The recorded HT, HT,E, HT,W, HT,S, HT,W, HDIF and HDIF show normal pattern. No anomaly is noticed except the slight non-symmetrical shape of HT,W and HT,E (vertical West and East total solar irradiation) where HT,W was found slightly larger than HT,E. The data listed in the literature [8] for countries having similar latitude to Bahrain (f = 26°N, H = 22.5 MJ/m2) such as Karachi, Pakistan (f = 24.8°N, H = 19.86 MJ/m2), Miami, USA(f = 25.8°N, H = 16.72 MJ/m2) and West Palm Beach, USA, strongly supports our actual measurement—taking into consideration the differences in longitude, elevation from sea level and sky quality. Further use of this data for modeling the incident solar irradiation on vertical surfaces facing North, East, South, and West in Bahrain and nearby regions, will be published shortly. This will allow architects and engineers to build more environmentally friendly houses and premises (sustainable buildings), i.e. less electricity and energy consumption and environmentally friendly.