Floating offshore wind turbine (FOWT) has the characteristics of easy installation and disassembly, more stable and stronger wind resources, and less visual and noise pollution. Compared with the traditional offshore engineering floating platform in oil& gas industry, the lower limit of the possible water depth for FOWT operation is much smaller, and there is FOWT application case with a water depth of around 30 meters in China. When designing a FOWT in shallow water, its mooring system will encounter significant safety and economic challenges. For example, the catenary mooring system requires a huge mooring footprint radius, while the tensioned mooring will withstand great dynamic tension. The above two mooring methods will greatly increase the mooring cost and seriously hinder the commercial development of shallow-water floating wind. In this paper, a "low-tension hybrid mooring (LTHM)" system is proposed. By arranging buoys and weight at intervals on the mooring line, a flexible mooring system with load buffering characteristics is formed, so that it has a designable horizontal stiffness. The natural frequency of the system is far away from the wave frequency, which greatly reduces the dynamic loads from the order of wave frequency (WF) magnitude to the low frequency (LF) load, thereby reducing the whole mooring system cost. It should be pointed out that the LTHM system proposed in this paper can also be applied to other floating structures, especially in shallow water conditions. Two demonstration cases of different floater types are presented in the paper to show its favorable feature in shallow water.
As the source of power for the industrial and economic development of human society, the development and utilization of energy has always been the most important research section. In recent decades, the excessive development and use of fossil energy that cannot be regenerated by human beings has caused significant environmental pollution and climate change problems, which are becoming more and more serious. Therefore, the development and utilization technology of clean renewable energy has attracted more and more attention from domestic and foreign industry and academia. The International Energy Agency predicts that if the world gets on track for net zero emissions by 2050, then the annual market opportunity for manufacturers of wind turbines with other clean energy type grows tenfold to USD 1.2 trillion by 2050(IEA,2021).Wind energy, as the most commercialized renewable energy source, has correspondingly shown great appeal.
