Within the projects of this working area, scenarios studies are carried out, to evaluate the impact of various factors on the development of the future energy system. The tool to carry out these scenario analysis, various energy system models are being used. They have been built using the The Integrated MARKAL-EFOM System (TIMES), a model generator developed by the Energy Technology System, Analysis Programme (ETSAP) of the International Energy Agency (IEA). Currently the focus of the work is to study the boundary conditions under which fusion power plants might enter the energy market in the second half of this century. Another issue is the analysis of the impact of different methodological approaches for the treatment of technological progress on the model results. Two different global models are being used for these analysis, the single-regional TUG-IPP-Model, and the 15-regional EFDA-TIMES-Model.