  The ambitious energy target to achieve climate-neutrality in the European
Union (EU) energy system raises the feasibility question of using only
renewables across all energy sectors. As one of the EU's leading industrialized
countries, Germany has adopted several climate-action plans for the realistic
implementation and maximum utilization of renewable energies in its energy
system. The literature review shows a clear gap in comprehensive techniques
describing an open modeling approach for analyzing fully renewable and
sector-coupled energy systems. This paper outlines a method for analyzing the
100% renewable-based and sector-coupled energy system's feasibility in Germany.
Based on the open energy modeling framework, an hourly optimization tool
'OSeEM-DE' is developed to investigate the German energy system. The model
results show that a 100% renewable-based and sector-coupled system for
electricity and building heat is feasible in Germany. The investment capacities
and component costs depend on the parametric variations of the developed
scenarios. The annual investment costs vary between 17.6 and 26.6 bn Euro/yr
for volatile generators and between 23.7 and 28.8 bn Euro/yr for heat
generators. The model suggests an investment of a minimum of 2.7-3.9 bn Euro/yr
for electricity and heat storage. Comparison of OSeEM-DE results with recent
studies validates the percentage-wise energy mix composition and the calculated
Levelized Cost of Electricity (LCOE) values from the model. Sensitivity
analyses indicate that storage and grid expansion maximize the system's
flexibility and decrease the investment cost. The study concludes by showing
how the tool can analyze different energy systems in the EU context.
