Analysis of solar heat gain factors using sky clearness index and energy implications

For sizing air-conditioning equipment, maximum solar heat gain factors (SHG Fs) are used for estimating the design peak load, Recently, SHGF data repre senting the prevailing weather conditions have become important and practic al for part load performance design. We have developed an approach for calc ulating SHGFs for the horizontal and vertical surfaces at the peak and othe r significant levels based on solar angles and clearness index (K-t). An an alysis of the SHGF data has shown that the proposed model performs better t han the ASHRAE clear sky approach, particularly at high significant levels (ASHRAE, American Society of Heating, Refrigerating and Air Conditioning En gineers). The findings provide information for the determination of total a ir conditioning plant capacity at both the peak load operation and the mult iple equipment sizing under part load condition. This has implications for the management of energy use in the commercial sector as air conditioning i s a major energy end user in commercial premises in subtropical climates. ( C) 2000 Elsevier Science Ltd. All rights reserved.