The European energy transition policies aim to mitigate the effects of climate change by moving away from fossils and promoting both onshore and offshore renewable energy technologies. Although onshore renewables are driving the transition so far, policymakers believe that in order to achieve the targets, the power grid must have access to the theoretically abundant energy present in the oceans. More specifically, these targets suggest that by 2050, around the continent there should be at least 340 GW of marine and offshore renewables for EU member-states, in addition with 125 GW for the UK.

The present study investigates the role of marine and offshore renewable technologies in 100\% renewable energy scenarios, inspired by the European targets of 2030, 2040 and 2050. The assessment of their role is based on he upgraded version of the open-source PyPSA-Eur (Python for Power System Analysis - European Sector, v0.25.1) energy system modelling tool developed within the Marine Renewable Energies Lab (MREL) of TU Delft, the PyPSA-MREL-TUD. This version is designed to have access on wave and farshore wind resources. The PyPSA framework utilizes an extract of the entire ENTSO-e transmission network and ERA5 climate data. By using time-series of 2018 for both the energy demand and weather data, this energy system model attempts to find cost-optimal solutions for the configuration of the different components of the power system. The developments include the addition of three wave energy converters and two types of floating offshore wind turbines to the existing generators and their associated costs, as well as the upgrade of the spatial resolution of the GEBCO bathymetry dataset of the model. For wave power, the model can access shallow water, nearshore and farshore wave resources, while for wind power both bottom fixed and floating generators are sub-categorized according to their distance from shore. Two significant constraints of the model include minimum generator capacity constraints for wind and wave power, and 70 \% energy equity per country.

The analysis of the results focuses mainly on the generator and storage system configuration of the system. An emphasis was also given on the required expansion of the transmission grid, and the objective's investment and operational costs. What is initially observed is the impact of the spatial resolution of the ERA5 dataset on wave energy converter installations, which underestimated the energy potential profiles. Capacity constrained versions of the scenarios showed that wave energy has a higher average hourly market value, but is highly susceptible to seasonal patterns. Although the performance is better during colder periods, wave converters suffer the most during the warmer periods and are also the first generator type to be curtailed. While offshore wind turbines were installed all around the continent, with the best candidates being France, Baltic and Scandinavian countries, Greece and Romania, wave converters were installed mostly in Portugal, Ireland and Italy. However, the accessibility of every country to the sea basins varies. Country-specific analysis of the model implies that, for the 2050 horizon scenario, there is still a high level of dependability of landlocked countries on solar energy, on their neighbours and on storage systems. The overall line capacity must increase by a factor of two.