Assessing implementation feasibility of energy transition pathways: The case of solar PV in Switzerland

Cost-optimization energy system models have been widely used to generate technically and economically feasible pathways to reach energy and climate targets for policy guidance. Yet, the complex socio-technical nature of transitions leads to very large uncertainties, requiring an assessment of real-world implementation feasibility of these modeled pathways. In this study, a novel approach is developed to empirically quantify the implementation feasibility of achieving modeled solar PV targets in 143 sub-national districts in Switzerland in 2035 and 2050, by combining a spatially-explicit cost-optimization electricity system model with a hindcasting-based probabilistic technology growth model. It shows that national-level PV deployment targets are likely to be achieved at 20.9 GW (73% probability) in 2050 from the modeled pathways with current trends, and unlikely to be reached in ambitious pathways with 42.6 GW of PV in 2050 (17% probability). At the district level, feasibility is geographically uneven, with the greatest uncertainty of reaching targets across four pathways in south-western and western Swiss districts. Economic policies and accounted context drivers that impact net present value calculation of PV projects do not appear to substantially alter the feasibility of results, indicating that either support beyond economic incentives for PV is needed, or modeled transition pathways should scale down their PV ambition to remain feasible.