Modelling and Performance Study of a Building Integrated Photovoltaic. Facade in Northern Canadian Climate

V. Delisle

CANMET Energy Technology Centre-Varennes, Natural Resources Canada
Varennes, Quebec, Canada J3X 1S6, veronique. delisle@nrcan. gc. ca


A model was developed to predict the electrical and thermal performance of different configurations of double-glazed and triple-glazed BIPV fenestration systems. Simulations showed that using a PV laminate as the middle pane as opposed to the outer pane reduced the amount of electricity generated by more than 22%, but led to slightly warmer inner pane temperature. This last characteristic can be beneficial in artic climates since it can contribute to reduce perimeter heating requirements. The multi-glazing BIPV systems modelled were also compared with non-vision sections of a curtainwall faqade in three different Canadian cities. These substitutions had little effect on the space cooling load, but increased the space heating energy requirements by 8.9-10.6% and 4.6-5.3% for double-glazed and triple-glazed curtainwall assemblies, respectively.

Keywords: Curtainwall, Photovoltaics, BIPV

1. Introduction

Over the past years, building-integrated photovoltaics (BIPVs) have witnessed a significant increase in interest as a technology approach for incorporating PV electricity production in buildings. One of the reasons to explain this gain in popularity is that BIPV are more architecturally pleasing than rack-mounted PV systems. Furthermore, they can be considered to have lower installation cost when used to replace expensive cladding or roofing materials [1].

Recently, designs have begun integrating PV semi-transparent laminates into curtainwall constructions [2] and skylights [3]. These laminates consist of opaque PV cells encapsulated with EVA in between two layers of transparent glass sheet. The level of transparency is determined by the PV density, which is the portion of the PV laminate area covered by PV cells, and has a direct influence on the building solar heat gain, natural daylighting, and the amount of electricity generated. Research on the integration of PV into windows has mainly focused on the impact of the different fenestration parameters on buildings energy consumption. Wong et al. [4] studied numerically and experimentally the roof integration of a double-glazed semi-transparent PV window in a residential building. For a PV density of 50%, reductions in overall energy consumption in the order of 3% and 8.7% were observed compared to a standard BIPV roof for the hottest and coldest climate studied, respectively. When the PV density was increased to 80%, the cells were found to heat up more, decreasing the electrical conversion efficiency of crystalline cells. For both 50% and 80% PV density scenarios, replacing a BIPV roof by BIPV semi­transparent windows reduced the annual heating energy requirements but increased the cooling load during the summer. Fung et al. [5] developed and validated a one-dimensional transient model of a semi-transparent BIPV laminate in Hong Kong. Compared to clear glass, BIPV laminates with

cell densities of 20% and 80% were found to reduce the annual total heat gain by approximately 30% and 70%, respectively.

This paper aims at evaluating the performance of five curtainwall constructions in Canada with multi-glazed BIPV assemblies used as the non-vision sections of a building fa9ade. To achieve this objective, an analytical model was first developed to estimate the BIPV systems thermal resistance and electricity production. Then, simulations were performed to assess their impact on a building space heating and cooling loads when combined with curtainwall vision sections to form a fa9ade.