Optimal renovation of Swiss buildings including photovoltaic potential and considering the uncertain future

Abstract

Buildings bear a great potential of electricity production through the installation of PV on their hull. Additionally, energy-related retrofits offer an essential tool to lower the CO2 emissions of the building stock, which in Switzerland currently account for 33%. This work identifies the optimal PV configuration for existing MFH in Switzerland on the one hand and the optimal overall renovation strategy including PV potential on the other hand. It addresses the previously unexplored research area of combining a life cycle analysis in terms of emissions and cost with considering uncertainties of parameter assumptions. The analysis is conducted on two case study buildings using a Monte Carlo simulation.
The optimal PV configuration consistently includes a full coverage of the roof with PV. The Mono-Si modules lead to minimal life cycle cost and the CIS modules to minimal life cycle emissions under application of the FAB LCA allocation method. The coverage of the facades with PV as well as the battery size varies across the renovation scenarios and assumptions, with south oriented surfaces consistently prioritized over north oriented ones. The optimal renovation strategy remains unchanged when including PV potential: Leaving the building at status quo is the optimal strategy for minimizing life cycle cost, while replacing the heating system with a heat pump and adding biobased insulation is the optimal renovation strategy for minimizing life cycle emissions.
The optimal PV configuration is minimally affected by the consideration of Swiss governmental subsidies. However, assuming the increased electricity tariffs from 2023, the GD LCA allocation method or the tariffs of a Swiss electricity provider with a significantly high feed-in tariff and low electricity tariff, changes the optimal PV configuration to full coverage of the building hull, no battery and Mono-Si modules. In other words, these assumptions lead to a prioritization of feeding as much electricity into the grid as possible.
To conclude, the optimal PV configuration for both minimizing life cycle emissions and cost involves expansive coverage of the building hull with PV. By reducing the cost associated with biobased insulation material, the renovation strategy including a replacement of the heating system with a heat pump and adding biobased insulation emerges as the leading approach to both achieve minimal life cycle emissions and cost.