A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1984

The global solar radiation on a HORIAONTAL SURFACE AT BANDKOK has been analysed with the objective of comparing it with the work done by LIU and JORDAN and subsequent workers on the long term performance of solar thermal collectors by the 'utilizability' methods. It was observed that the 'generalised K curves' are not applicable to Bangkok. The first part of this study analyses various correlations for the density (and cumulative) frequency curves applicable to both tropical and temperate regions. A 'quadratic' modified beta function distribution has been proposed. It has been found that the density function is not a unique function of K , as can be interred from LIU and JORDAN, but also depends on a another parameter, Kmax, which probably depends on climatic and geographical factor. The second part of the study analyses the hourly cumulative frequency curves at Bangkok for all the hours of the month. It was found that they are all linear and very close to each other, an observation which is probably equally valid for the temperate regions. Based on the above observation, a very simple functional form for daily utilizability is derived and validated for Bangkok. The final part of this study has the objective of finding the hourly utilizability correlation for Bangkok by using the modified beta distribution. A procedure of grouping the cumulative frequency curves of each particular hour based on dry and rainy months has been found to give satisfactory results for predicting utilizability values. This procedure can be extended for other locations as well. As the main prerequisite for the widespread use of solar thermal applications is a detailed analysis of radiation data for determining the long term performance of solar thermal collectors, such analysis should be extended for other locations.