# Hydrogen Production from Offshore Wind Parks: Current Situation and Future Perspectives
## 2 System Components
### Offshore Wind  
When analysing fixed bottom wind turbines or floating turbines the main differences are cost and the locations where each technology can be implemented. The fixed bottom is the most used technology by a significant margin, with 24,952 MW installed in Europe, compared to only 62 MW of floating wind installed in Europe at the end of 2020 [4]; thus, it is the most cost-effective solution in offshore wind farms. However, floating wind prices are expected to lower rapidly in the next few years and allow access to much deeper waters; this will be useful in countries that do not have shallow water far from shore. The water depth around Europe is assessed in [5]; only the North Sea, Irish Sea, and a few other areas have a somewhat shallow depth where fixed bottom foundations can be installed. On the other hand, the water around the Iberian Peninsula and southern Europe can get be much deeper not too distant from the shore.  
The report in [6] shows a projection of the Levelized Cost Of Energy (LCOE) of both bottom fixed and floating wind until 2050. The report indicates a current LCOE of 175 \(\upcels\)/MWh for floating and 90 \(\upcels\)/MWh for fixed bottom technologies. In 2050, these two figures are estimated to converge to 35 \(\upcels\)/MWh.  
The installation of fixed bottom wind turbines involves the use of a specialized boat capable of burying the foundations deep in the seabed, along with a crane to assemble the tower, nacelle, and individual blades. Comparing with floating wind, this newer approach can be fully assembled on land or dry dock and afterward be towed by a regular tugboat to the project's location. This much simpler installation can be another factor in lowering the costs; when more floating substructures are built, economies of scale have their effect. Europe is the leader in offshore wind power, and most of the installed power is in the North Sea (79%, according to WindEurope [4]), a location with high wind speed [5] and relatively shallow water and thus a good candidate for fixed bottom installations.  
Around 80% of offshore wind resources are located in waters deeper than 60 m (where fixed bottom installations are not feasible), and average wind speeds increase further from shore [7]. To access this potential, floating wind currently represents the best approach; with the number of installations planned in the coming years, the future of floating wind is looking bright.  
The first floating wind farm ever built on a commercial level is Hywind Scotland [8; 9], composed of 5 turbines of 6 MW each, supported by a spar buoy. It has been producing energy since 2017. The buoys are 78 m in length and are attached to the seabed by 3 mooring lines. Although this is a simple design, added installation problems can arise from the dimensions of the buoy, such as the inability to be assembled on a simple port. More specifically, for hydrogen production, the individual electrolyzer approach is not as straightforward due to the cylindrical shape of a spar buoy, which limits the amount of space available to install an electrolyzer and the remaining infrastructure. Consequently, this structure requires more substantial modifications when compared to a semi-submersible platform, making the latter the most cost-competitive floating platform for an individual electrolyzer project [10].  
One of the first wind farms deployed on a commercial level using a semi-submersible platform is WindFloat Atlantic in Viana do Castelo, Portugal. It was commissioned in 2020 [4] and is composed of 3 turbines of 8.4 MW each, supported by a semi-submersible structure made of 3 cylindrical buoys 30 m high and 50 m apart. Some advantages of this design are the simple assembly of the wind turbine on the structure in port and, due to hydrogen production by individual electrolyzers, the unobstructed area of 1082 m\({}^{2}\), with some modifications. Several other projects using similar platform designs are planned in the coming years [4].