Assessing the costs and benefits of dynamically positioned floating wind turbines to enable expanded deployment

Abstract

In addition to technical and economic challenges, the offshore wind industry must also contend with environmental and socio-political concerns that constrain development. Here, the viability of dynamically positioned floating offshore wind platforms that could ameliorate these constraints is analyzed. Such a design can unlock deeper, less-contentious waters that are farther from shore and reduce environmental interactions in the ocean, thus expanding and improving deployment opportunities. While prior studies on this application only focused on energy performance, the resulting cost of energy and benefits have not yet been quantified. Although prior studies found that the energy-performance of this strategy does not show promise, it is possible that a full understanding of the costs and benefits will reveal a decision space where it makes sense. To address this gap in the literature, the cost penalty of this application compared to moored turbines is estimated here. A physical engineering model is used to compute the environmental loads on a floating offshore wind turbine to estimate the expected energy needed by the station-keeping thrusters and one potential environmental benefit—eliminated mooring chains. The models were validated using marine engineering simulation software. Dynamic positioning realizes a cost penalty of at least 30 U.S. dollars/megawatt-hour while eliminating up to 900 km of mooring chains for a 1-gigawatt array. Up to 3 megawatt-hours of stored energy are needed to station-keep during continuous low winds. Furthermore, dynamic positioning is more viable for turbines of intermediate size (8–10 MW) rather than larger turbines (15 MW). The results show that aerodynamic loads on the turbine fall sharply beyond the rated wind speed, operational and design improvements may further improve the viability of this application, and the energy performance of this application continually improves with added thrusters although the cost of energy does not.