This paper describes the Horizon 2020 project Space@Sea (www.spaceatseaproject.eu) which started in November 2017. This project aims to provide a concept of affordable and flexible floating islands. With increasing population and rising sea level there is a scarcity for space on land for the people to live, grow food and harvest renewable energy. Moreover, a large number of people live in areas that are exposed to the risk of flooding in case of sea level rise. These trends call for a solution at sea that creates a new perspective. Previous projects on floating habitation such as the TROPOS project (www.Troposplatform.eu) have delivered artist impressions. Technical solutions are yet to be provided. In the Space@Sea project a conceptual study is done to develop a standardized floating solution for offshore space. Four applications focusing on energy hub, living, aquaculture and maritime transport will be demonstrated. For two locations a business case of a combination of these applications will be examined. The present paper discusses the Space@Sea project background and approach of the collaborative research. First results regarding the basic design and societal acceptance are discussed at a high level. Throughout the Space@Sea project results will be published on Frontiers in Marine Science.

Recent years have shown an increasing interest in low frequency response of offshore floaters in current. Spar VIM behavior and Semi Submersible flow induced behavior is known from calm water tow tests. Recent tow test projects have also shown low frequency TLP response in steady current. The motions from the model tests are used in the global analysis of the mooring systems and risers for these platforms. This paper discusses the dynamic behavior in current of multi column floaters and the associated complex flow patterns. Shielding between columns is addressed as well as the effect of mass ratio (i.e. floater mass divided by displacement). It is shown that lower mass ratios such as for conventional TLP’s may result in larger sway response than for deep draft semi submersibles. The motion behavior is discussed as well as the increase in total mean current loads due to transverse motions.

About 70% of the earth’s surface area is covered with water. Due to the sea level rise and increasing population in coastal areas we need to use our oceans more for energy production, food production, working and living. In the present paper we discuss the results of a model test for a floating mega island in large waves up to 15.5 m significant wave height. The objective of this study is to investigate the motion response and loads on the island. These results may then be used to support further innovation of these islands. The proposed island comprises 87 large floating triangles that are connected to one another. Together they form a flexible floating island of 1.5 by 2 km in cross-section at scale 1:250. The results are presented for the motion response of the island as well as the forces between the islands triangular modules and the mooring loads. These were measured using forces transducers and motion sensors. The present work is part of a conceptual test carried out at MARIN. The island modules are interconnected with springs and fenders. This method is much similar to what is used in side by side offshore operations in the oil and gas industry. Due to the flexibility in the connections the island will follow the waves in high seas. The forward two rows of the island will move in phase with the sea and therefore the amount of green water is much smaller than for a rigid island.

The HAWAI JIP originated from the observed differences between model tests and numerical simulations in shallow water. These differences were identified as being caused by spurious free waves and reflected waves in the model basin. Identifying these waves and incorporating them in the numerical simulations greatly improved the agreement between the model test results and the simulation results. Although the effect of spurious waves is also present in deep water, the effect is most profound in shallow water. The research therefore focused on shallow water, further refinement of wave identification, the background and theory behind spurious free waves, the effect of these waves on the motions of a LNG carrier and the occurrence of free waves in reality. In order to identify the different types of wave systems in a model basin a wave splitting (or separation) technique has been developed. This paper describes the current state-of-the-art of wave splitting and its limitations. Results are presented in the form of motion statistics of an LNG carrier that is moored in 15 m and 30 m water depth. The model tests results are compared with simulation results with and without the wave splitting methodology.

Time domain simulations are used extensively to assess the availability of turret moored terminals for offloading operations. The availability analysis provides a key input when assessing the economical viability of a project. In this context, it was deemed important to perform a benchmark study. Three programs have been used: AQWA-DRIFT - an ANSYS product maintained by Century Dynamics and used at SBM, LIFSIM and aNySIM both developed in MARIN. Five environments including wind, waves and current have been selected one of which with all components in-line and the remaining four with oblique wind and current. Simulations have been performed with identical input for the three programs. Results are compared statistically, but also in the time domain. Lessons learned will be discussed and areas of improvement identified.