Spar-buoy and semi-submersible size comparison over design range.

Spar-buoy and semi-submersible size comparison over design range.

Sandia and the University of Maine recently published a Sandia technical report on floating-platform options for deep-water vertical-axis wind turbines (VAWTs). This analysis uses a 5 MW VAWT topside design envelope created by Sandia to compare floating platform options for each turbine in the design space. The platform designs are based on two existing designs, the OC3 Hywind spar-buoy and Principal Power’s WindFloat semisubmersible. The designs were scaled using Froude-scaling relationships to determine an appropriately sized spar-buoy and semisubmersible design for each topside. Both the physical size of the required platform as well as mooring configurations were considered.

Hypothetical deployment site off the coast of Maine and location of the NBDC buoy used for wave characterization.

Hypothetical deployment site off the coast of Maine and location of the NBDC buoy used for wave characterization.

Results were compared with a comparable 5 MW horizontal-axis wind turbine (HAWT) in order to identify potential differences in the platform and mooring sizing between the VAWT and HAWT. Our study shows a potential for cost savings due to the VAWT’s reduced platform size requirements.