This report was produced as part of the THINK project. The existing transmission grid in Europe is located mainly onshore. Nonetheless, there are also grid developments offshore that should not be neglected. Indeed, there is also part of the transmission grid located offshore, which includes both the connection of distinct onshore grids and the connection between offshore generation sites and onshore transmission grids. Considering the EU climate and energy policy objectives as binding, the grid will continue its development offshore through the following decades to enable the achievement of the objectives regarding the EU electricity generation mix. Indeed, a significant increase of offshore wind power capacity is expected in several member states (including Germany, France, the Netherlands and the UK) and, consequently, also an increase in electricity grid located into the sea. Furthermore, the intended share increase in renewable energy technologies in the overall generation mix will lead to an increase in the variability and intermittency of electricity production. This variability can be tempered with a stronger transmission grid, since the latter would allow for the unrestricted transfer of electricity between the supply and demand sites, even when very distant from each other. Thus, it means that, besides the capacity increase in the existing lines, it will also be necessary to invest in new lines; and part of this transmission will inevitably be offshore. Thus, grids are already developing offshore, and this development will continue even though at what pace and how they will develop is still uncertain. Indeed, there are different possible configurations for a future offshore grid: it can be a simple multiplication of standalone lines that provide each a single service (either connection of generation, or connection between transmission grids) ; or it can be a more integrated infrastructure like an offshore meshed grid that combines and interconnects dozens of offshore lines and generation units (hereafter combined solution). A combined solution can usually bring some advantages compared to the multiplication of individual lines. Indeed, it typically requires fewer physical components, but has higher power capacity, which is commonly beneficial due to the economies of scale present in transmission systems. This has also been the case onshore with the development of the transmission grid, where a combined solution approach has been favored for a long time now, especially since the introduction of both technology and operational standards in the previous century. However, the development of a combined solution offshore is still unpredictable due to the existing uncertainties regarding necessary technological developments. In fact, most developments offshore use a less-known technological system for which standards do not yet exist, i.e. it is based on Direct Current (DC) instead of Alternating Current (AC) systems ; and an integrated solution offshore would require some technology components that are still not available today. Moreover, there are also strong costs uncertainties, not only due to the referenced uncertainties in technology development, but also due to the unclear role of a future offshore grid. Indeed, there are different visions on the possible role of an offshore grid in the future ; while some envisioned a regional grid whose main role is to integrate offshore wind from Northern Europe, others envisioned an infrastructure which is integrated into a more global grid (covering EU and neighboring countries). The aim of our report is to formulate policy recommendations to the European Commission (DG Energy) on offshore grids and their future development.
