ANALYSIS AND MITIGATION OF THERMAL EFFECTS ON A LARGE FACADE-MOUNTED PV ARRAY

摘要

A 20 kW grid-connected PV array, one of the larger systems in Canada, was installed on the Queen's University campus in Kingston during the first quarter of 2003. Planning for the array began more than 18 months earlier with the identification of an appropriate façade. The initial design consisted of 330 panels mounted as awnings above the windows of the upper 4 levels of a 7-storey building. This design was intended to provide an additional benefit of summer shading and reduced heat gains in the non-air-conditioned offices. A risk was identified early on, however, that the combined geometries of the façade, operable windows, and proposed awnings could significantly reduce the effectiveness of the building’s passive window ventilation. This problem was increased by the fact that the dark collector surfaces would increase the total solar radiation absorbed on the building façade. To assess this risk, the design team installed and instrumented a small section of solar array in a similar orientation. The measurements obtained, together with the results of numerical modelling, permitted the team to conclude that, although unlikely to frequently occur, increased heat gain to the offices was nevertheless a real possibility. Consequently, a number of design changes were proposed to mitigate the undesired effects and were incorporated into the final design. These included reducing the panel density, repositioning the arrays and improving the airflow behind the arrays. This paper presents the results of the experimental and numerical analysis performed and discusses the design changes made as a consequence of this study.