A study of conceptual parallel powertrains for offshore wind turbines focusing on availability

Improving key performance drivers such as availability for offshore wind turbines is imperative for reducing the cost of offshore wind energy. Generally, this paper considers the option of increasing availability of the wind turbine powertrain (generator and power converter) by using N parallel components; a scenario where the wind turbine remains operational (albeit at (N-1)/N capacity) when failure occurs in one element of the powertrain. Although high capital costs are expected for multiple output powertrain topologies, this paper seeks to define how enhanced availability can rather reduce the lifetime cost of energy. This paper explored new strategies of availability enhancement by applying reliability modelling techniques, reliability block diagrams and Markov state space model to multiple output gearboxes with parallel generators and converters. A baseline powertrain was modelled and then the reliability and availability of the proposed strategy evaluated using wind turbine powertrain failure rate and mean time to repair data. Reliability block diagrams were used to optimize the number of parallel systems for producing high availability in the proposed powertrain.