Table 3 presents the electricity production obtained with TRNSYS for the three BIPV curtainwall constructions (scenarios 2, 3 and 4). As it can be observed, systems in Yellowknife and Iqaluit generate approximately the same amount of electricity, whereas the ones in Montreal produce between 4 and 7% less electricity. This can be explained by Yellowknife and Iqaluit greater annual south-facing vertical radiation and lower ambient temperature throughout the year. This table also indicates that scenario 4 is the worst in terms of electricity generation with a production reduced by more than 22% compared to scenarios 2 and 3. The building heating and cooling loads for each one of the 5 scenarios and 3 cities considered are shown in Fig. 6. From this graph, it can be seen that for every city, the lowest heating loads are obtained in scenarios where spandrel is used as the non­vision section, with a difference of only 2 to 3% between the double-glazed and triple-glazed cases (scenario 1 and 5). This variation is small considering that the triple-glazed curtainwall construction of scenario 5 has greater thermal resistance, but this assembly also has a lower solar heat gain coefficient and thus, provide less passive solar heating. The influence of changing from a double-glazed to a triple-glazed system on the space cooling energy requirements is only noticeable for Montreal, but is more important than for space heating with a difference between the two scenarios in the order of 6%. When comparing the substitution of spandrel panels with BIPV curtainwalls, it can be observed that it affects more significantly the space heating load than the cooling load, and the double-glazed systems than the triple-glazed systems. In fact, the heating load increases by 8.9-10.6% when going from scenario 1 to 2 and only by 4.6-5.3% and 5.6-6.3% when going from scenario 5 to 3 and 5 to 4, respectively.

2. Conclusion

This study showed that double-glazed and triple-glazed BIPV curtainwalls with a PV laminate used as the outer pane have similar electrical performance. When a PV laminate is used as the middle pane in a naturally ventilated triple-glazed fenestration system, however, a reduction in electricity generation in the order of 22% can be expected due to the smaller amount or radiation reaching the cells and the heating up of the PV. A possible benefit of this last configuration was found to be the reduction of perimeter heating in the winter caused by greater inner glazing temperature. In locations with important cooling load, however, this temperature could potentially create discomfort in the summer. When using BIPV curtainwalls for the non-vision sections of a south­facing curtainwall facade of a small office building, the heating load was found to increase by 8.9­10.6% for the double-glazed systems and 4.6-5.3% for the triple-glazed ones.

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Nomenclature