Abstract
A simple formula to predict the received global solar irradiance q(t), W/m2 for clear days is suggested on pure theoretical basis. It is expressed in terms of the length of the local day time td which is well defined in literatures on meteorological basis. The introduced distribution is also a function of the maximum value of the daily received irradiance qmax. which in turn is expressed in term of the solar constant. This renders the trial to be a closed system. Thus the obtained distribution is not a semi empirical one. Both cases of symmetrical and asymmetrical distributions for q(t) are considered. For its simplicity it can be easily integrated along the length of the day to get the daily totals of solar energy received by unit horizontal area. This is important for practical applications. Comparison between computed according to the present model and published experimental meteorological data in Barcelona (Spain), Hong Kong (China), Jeddah and Makkah (Saudi Arabia) is given as illustrative examples. Better fitting relative to the published trials for the same locations are obtained. The introduced model itself gives good fitting for the intermediate intervals points of the local day time which is the more effective region. The estimated relative error is 12% for Hong Kong, and it is 7% for Barcelona, Jeddah and Makah.
Highlights
A simple formula to predict the received global solar irradiance q(t), W/m2 for clear days is suggested on pure theoretical basis
The present trial represents a new approach to introduce a suggested formula based on well-established solar data such as the length of the solar day “td” in hours, which is well defined in [15], and is expressed through the maximum value of the daily solar irradiance qmax W/m2
While for asymmetrical distribution the obtained value is: 0.4715qmaxtd [4]. This shows that the daily totals of the global solar irradiance on a horizontal surface depends on the degree of symmetry about the point t = tmax, at which the received solar irradiance attains its maximum value [4]
Summary
The prediction of the diurnal global solar radiation q(t) W/m2 is needed as one important input parameter to study theoretically the design and performance es-. Other trials expressed the required distribution in the form of polynomial [in(t − tmax)] [16] with relative maximum error 16%, or in. The present trial represents a new approach to introduce a suggested formula based on well-established solar data such as the length of the solar day “td” in hours, which is well defined in [15], and is expressed through the maximum value of the daily solar irradiance qmax W/m2. Data of the received global solar irradiance in different locations [7] [9] [12] [13] and that computed using the present suggested model is given.
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