A high-resolution determination of the technical potential for residential-roof-mounted photovoltaic systems in Germany

In Germany the introduction of a feed-in tariff for renewable energies in the year 2000 led to a massive increase in newly constructed photovoltaic (PV) plants reaching a total installed capacity of 35 GWp as of November 30th, 2013. The distribution of these plants shows a large disparity between regions, which motivates investigations of regional potentials which earlier studies of Germany have not addressed in detail. This study presents a high-resolution calculation for the technical potential of residential-roof-mounted photovoltaic systems for each municipality in Germany. Electricity load curves for municipalities were generated based on the socio-economic structure and used to draw generalized conclusions about the relationship between the (potential) supply from PV and the local demand. The total German residential-roof-mounted technical PV potential was determined as 148 TWh/a with an installable capacity of 208 GWp. About 30% of municipalities could become autonomous based on a yearly balance of PV electricity generation. If the daily and seasonal variations in demand and PV electricity generation were considered, only 53 of the 11,593 German municipalities could become autonomous, provided they installed a short-term storage system which would have to be sized around 57% of their daily electricity demand. Imposing the restriction that no feedback of electricity into the distribution network outside the municipality should occur, and assuming that no local storage exists, around 49% of the total technical potential, i.e. 103 GWp could be installed (i.e. 90 GWp additional potential since some municipalities already experience feedbacks into the distribution network). A validation of the results with municipal solar cadastres has shown that the discrepancy between them and the technical potential calculated in this study is quite consistently about 30%, which is assumed to be due to non-residential buildings not being considered here. The calculated technical potential is most sensitive to the assumptions on the module efficiency and the usable area of (slanted) roofs. A validation of building data assumptions as well as a comparison with other studies both show a good agreement.