BiPV system performance and efficiency drops: overview on PV module temperature conditions of different module types

A typical problem of BiPV systems (Building Integrated Photovoltaic) is the power loss due to temperature increase, because modules often operate close to the building envelope with low ventilation. It is thus essential to properly evaluate and compare the PV temperature conditions of different PV module categories (in terms of PV technology and material type). Several explicit correlations exist for the evaluation of the PV module temperature, among which the simplest and most handy is a linear expression (i.e. T-mod = T-amb+k G) which links T-mod with the ambient temperature (T-amb) and the incident solar radiation flux (G). Within this expression the value of the dimensional parameter k, known as the Ross coefficient, depends on several aspects (i.e. module type, wind velocity and integration characteristics). However, dispersed values for this parameter can be found in literature (in the range of 0.02-0.06 K m(2)/W) according to different module types, while more information are provided regarding different integration characteristics. This paper aims at giving an overview of the value of k for different module types according to monitored data registered over one year time period at the ABD-PV plant in Bolzano (Italy). The highest values of k, which means the highest module temperature at a certain G, are registered for the three glass-glass (G-G) module types (k(Tmod, c) from 0.033 K m(2)/W to 0.037 K m(2)/W). The glass-tedlar (G-T) module types operate at slight lower temperature values (k(Tmod, c) ranging from 0.029 K m(2)/W to 0.032 K m(2)/W). (C) 2014 The Authors. Published by Elsevier Ltd.