Environmental assessment of building-integrated photovoltaics
Abstrakt
According to the latest report of the United Nations, the buildings and construction sector combined are responsible for 30% of total global final energy consumption and 27% of total energy sector emissions. Therefore, decarbonizing the built environment is crucial to fulfill the Paris Agreement goals and mitigate climate change. On-site electricity production via sustainable technologies could enable existing and new buildings to minimize their environmental impact. More specifically, building-integrated photovoltaics (BIPV) are well positioned to accelerate the decarbonization of the building stock, while increasing the share of renewable electricity.
Several life cycle assessment (LCA) studies have already investigated the environmental impacts of buildings and PV systems. Nonetheless, the life-cycle impacts of building-integrated photovoltaics are poorly known.
This master thesis aims at identifying the most environmentally friendly BIPV (façade-integrated). Therefore, all required life cycle inventory data are collected in order to assess and compare the embodied emissions of BIPV. The results show that the emissions of the mounting system are 40.43 kg CO2-eq/m2 (mean value). As for the PV modules, amorphous silicon (a-Si) proves to have the lowest impact with 26.59 kg CO2-eq/m2, and monocrystalline silicon (single-Si) the highest one with 119.61 kg CO2-eq/m2. The emissions of the inverter start from 491.05 kg CO2-eq/unit (2.5 kW output) to 2019.43 kg CO2-eq/unit (20 kW output) and for the electric installation, emissions start from 37.57 kg CO2-eq/unit according to the system’s capacity. Lastly, the emissions of a lithium-ion battery are estimated to be 16.25 kg CO2-eq/kg.
In addition, the carbon payback time is calculated for the potential integration of a PV system in each façade of a certain building in Zurich. This is realized by implementing computational design. Overall, it appears that PV have the highest share of greenhouse gas emissions, followed by the mounting system, the inverter and the electric installation. As for the carbon payback time, BIPV systems with a-Si modules have the shortest carbon payback period, starting from 16 years, and BIPV systems with multi-Si modules have the longest one, starting from 21 years. The location and orientation of the building but also the local grid mix have a great influence in the carbon payback time.