THE DEVELOPMENT OF A PROTO-TYPE PV DECK-SHADING SYSTEM AS THERMAL BUFFER AND ELECTRICITY GENERATOR

摘要

A Copper Indium Diselenide (CIS) technology photovoltaic deck-shading system has been designed for the sub-tropical climate to generate electricity, act as a thermal buffer and provide naturally lit shaded recreation or teaching-space at deck level. The system has been designed for pre-wiring and pre-fabrication techniques to allow the increased quality control of factory production plus reduced site installation costs. The system has a wider range of applications but is customized to the 7.5m x 9.6m planning grid of Hong Kong (HK) Schools. The system is suited to 330x 1300mm dimensioned modules, and particularly the ST40 CIS module manufactured by Siemens Solar. The robust, lightweight and low-maintenance system is particularly designed for latitude 22°where high altitude sun permits close-spacing of the modules that can, with 33% increased module area, maximise summer electricity yield. Performance under high wind-load has been a critical factor in the design necessitating wind tunnel measurements and module wind-loading tests. The module supporting system consists of factory pre-fabricated stainless steel trusses supporting paired strings of modules. Each truss interlocks to the preceding truss through the hub containing the customized electrics junction box. The system and its electrical components are intended as starters to the development of a local PV components industry. Simulation studies for the new 36 class Ma Wa School, to be completed in 2003, indicate that a 6-bay system provides a modest 2.8% saving on the annual cooling load and the electricity yield contributes 9.79% to the estimated annual classroom electricity demand. Tendered costs indicate the total system construction at approximately US$681/m~2 with module costs representing about 61% of the system costs.