The ongoing energy transition towards decarbonisation means that the use of variable renewable energy sources (RES) is increasing significantly, which imposes new requirements on the different components of the system, for example in how they should be planned, sized and controlled to render large-scale grid integration in a sustainable and economically optimal way. The research aims to investigate effects of various factors and future energy scenarios across different sectors to find the optimal combination/interplay of technologies and sizing of system components. The scenarios take into consideration technical and economic aspects and will be utilized to develop novel guidelines and methods for enabling 100% renewable energy system in the Nordic market in a sustainable, reliable and cost-efficient way and enhance security of supply.