Abstract: Offshore wind farms in China are moving into deep and open sea. The offshore distance and water depth have significant impact on the technology selection and cost of key equipment for offshore wind farms, subsequently influencing the unit power cost of wind farm investment. This paper analyzes the key equipment for offshore wind farms such as foundation structure and submarine cables in terms of the cost variation with different offshore distance and water depth, discusses the influence of technologies such as foundation structure, high voltage power collection and power transmission on project cost. It is concluded that by adopting flexible DC and high voltage power collection technologies, the unit power cost of key equipment for wind farms in open sea may be lower than that for the offshore wind farms under construction. For the wind farms in deep and open sea with 8 MW wind turbines, the unit power cost of key equipment will decrease by 2 200RMB/kW if advanced technologies for foundation structure and transmission system are adopted, remarkably lowering the project cost of wind farms in deep and open sea.

Key words: deep and open sea, offshore wind power, key equipment, techno-economics, electrical system, foundation structure