For wind turbines situated in harsh offshore environments tens of kilometers from the nearest harbour, the O&M strategy has to be considered carefully. When rough sea prevents the maintenance technicians from accessing the turbines for large parts of the year, the choice of vessel fleet and logistics solution for the maintenance activities is also important.
These challenges imply the need for decision support tools. Examples of questions that the offshore wind industry would need to answer:
- Where should the maintenance bases be located?
- What crew transfer vessels should one use? Fast ones or more robust ones, or a combination?
- How much would losses due to downtime be reduced if one improved the condition monitoring system?
- How would it impact the O&M costs if a certain type of failure occurs twice as often as expected?
The NOWIcob model can be used as a tool in investigating and answering such questions.
The model has several possible user groups and applications, depending on one's point of view:
- decision support for developers and operators of offshore wind farms
- evaluating the potential of different vessel concepts for developers and operators of service vessels
- estimating life-cycle operation and maintenance costs for an offshore wind farm
- sensitivity analysis – analysing cost drivers and important parameter for offshore wind power
- evaluating the cost and benefit of introducing new technical concepts in offshore wind farms
Special characteristics and features of the NOWIcob model:
- Markov chain weather model generating synthetic weather time series correctly capturing correlations between weather parameters (wind speed, wave height, wave period...)
- takes into account stochasticity of lead times and repair times, as well as weather and failure times
- detailed modelling of the criteria and time spent for technicians accessing the wind turbines and for jack-up vessel operation
- supports mother vessel / daughter vessel concepts and personnel accommodation/transport vessels that can stay offshore for several days
- modelling of condition-based maintenance
- functionality for automatic sensitivity analysis of important parameters
- user-friendly user interface for input data (Excel) and running simulations
The model is developed by Matthias Hofmann and Iver Bakken Sperstad