  In order to meet ever-stricter climate targets and achieve the eventual
decarbonization of the energy supply of German industrial metropolises, the
focus is on gradually phasing out nuclear power, then coal and gas combined
with the increased use of renewable energy sources and employing hydrogen as a
clean energy carrier. While complete electrification of the energy supply of
households and the transportation sector may be the ultimate goal, a
transitional phase is necessary as such massive as well as rapid expansion of
the electrical distribution grid is infeasible. Additionally, German industries
have expressed their plans to use hydrogen as their primary strategy in meeting
carbon targets. This poses challenges to the existing electrical, gas, and
heating distribution grids. It becomes necessary to integrate the planning and
developing procedures for these grids to maximize efficiencies and guarantee
security of supply during the transition. The aim of this paper is thus to
highlight those challenges and present novel concepts for the integrated
planning of the three grids as one multi-energy grid.
