Up to now, the majority of all scenario studies in the energy sector have been conducted on the basis of country-specific annual balances of conventional and / or renewable energy supply and demand. The long-term scenario analyses of infrastructure integration of RES performed in this thesis additionally take into account the interdependencies between regional and trans-national energy systems and also the needs and costs for corresponding grid infrastructures (for electricity, gas and heat) to enable large-scale RES deployment. The renewable grid integration scenario generation philosophy is based on a storyline approach: two main driving forces are identified, public attitude and technological development, which open a 2-dimensional space with four quadrants. In each of the four quadrants several key, but uncertain parameters influencing RES grid integration (like RES technology cost, electricity demand, fuel-, CO2-prices, etc.) are described in a single storyline. Therefore, there are four different storylines in total: Red, Yellow, Green and Blue. A sequence of models is used to determine the deployment of RES-Electricity / RES-Heating generation technologies and its grid infrastructures needs and costs (based on least-cost principles) in the time period up to 2050. Additionally, a linear optimization algorithm is implemented to analyse interdependencies of neighbouring regions and the importance of bulk electricity storage technologies for integrating large amounts of variable RES-Electricity (incl. mitigation of their effects). Three European countries (regions) are analysed in detail: Austria (Central Western Europe), Serbia (Western Balkan) and Spain (Iberian Peninsula). The analysis of the electricity sector is conducted in the Blue storyline. In Austria the RES-Electricity share increases to about 78% in 2050 due high additional wind, photovoltaic (PV) and hydro generation. With its flexible power plant mix (e.g. pumped-hydro), Austria can significantly contribute to mitigate the variability problem of wind and PV generation in the Central and Eastern European countries in case of transmission grid investments. The Serbian power system has passed a difficult period of underinvestment and also destruction - a lot of rehabilitation is needed in the Serbian grid infrastructure. In Blue, thermal power will remain the main source for electricity generation besides hydropower in Serbia / Western Balkan region until 2050. The main challenges in Spain / the Iberian Peninsula are high levels of RES-Electricity generation surpluses due to variable wind and solar generation already in 2030. Additional backup conventional generation (e.g. gas turbines), electricity storage options (e.g. pumped-hydro, etc.), additional interconnection capacity (e.g. to France) and / or other flexible resources are strongly needed to balance the electricity system. The analysis of the heating / gas sector is conducted in the Yellow storyline. The results show that - regardless which kind of heat grid infrastructure (or stand-alone technology / technology combination) currently exists in a region - a crucial long-term aspect in the further development of the entire portfolio of heating technologies and corresponding grid infrastructures is the future ambition of the implementation of end-use energy efficiency technologies on the demand side. Moreover, end-use energy efficiency implementation on the demand side finally also reacts upon the economics of the different energy carriers in the local / regional heat market and the corresponding network infrastructures. Overall, the analyses in this thesis improve the understanding of grid infrastructure integration of RES technologies in different European regions under various constraints in the long-term.