Operation & Maintenance Cost Estimator, OMCE

During the operational phase of an offshore wind farm, operators and owners want to make accurate estimates of the O&M costs for the next coming period of say 1, 2 or 5 years, taking into account the operational experience available at that moment. Having available accurate estimates gives them the opportunity to better control the future O&M costs. Several reasons are present for making such accurate cost estimates:

• ­before the expiration the warrantee period, a wind farm owner needs to decide how to continue with servicing the wind turbines: sign a new contract with the turbine supplier or to take over the total responsibility; 
• to make reservations for future O&M costs (this is especially important for the party who is responsible for the financial management of the maintenance);
• operating experiences may give indications that changing the O&M strategy will be profitable; in that case the costs of the new strategy need to be determined accurately in order to compare the adjusted strategy with the original one;
• if a wind farm is going to be sold to another investor, the new owner wants to have detailed information on what O&M costs he can expect in the future.

Presently, ECN is developing the O&M Cost Estimator, OMCE, to make an accurate estimate of the expected O&M costs for the next 1-5 years.

The OMCE consists of two major parts.

1. The processing of operational data generated by the wind farm by means of so called OMCE Building Blocks which are needed to generate meaningful information for O&M optimisation. In total 4 Building Blocks (BB) have been developed to process each a specific data set. The objective of processing the operational data is in fact two fold:

• To provide information to determine or to update the input values needed for the calculation of the expected O&M effort. It is not expected that the input needed for the calculations can be generated automatically in all cases. The opposite might be true, namely that experts are needed to make the correct interpretations.
• To provide information that gives insight in the health of the wind turbines, for example by means of trend analyses.  

2.     The calculation of the expected O&M effort and costs for the coming period by means of the so called OMCE-Calculator, where all relevant information derived from the operational experience is taken into account. The OMCE Calculator is a time-domain simulation model which calculates the expected O&M costs and downtime for the next 1-5 years. The OMCE Calculator takes three types of maintenance into account:

1. Calendar based maintenance: The effort and cost are usually determined by one or two visits per year. After 3 or 4 years the calendar based maintenance costs can be somewhat higher due to e.g. oil changes in gearboxes. Standstill is only needed during the maintenance actions.
2. Unplanned corrective maintenance: Costs due to random failures are more difficult to predict. They usually lead to immediate standstill and repairs can only be carried out during good weather situations. At the beginning of the wind farm operation the corrective maintenance costs can be somewhat higher than expected due to teething troubles.
3. Condition based maintenance: It might be that major repairs have to be carried out based on the observed degradation of a component. Such replacements generally can be planned in advance, meaning that the turbine does not require immediate shutdown, but only during the repair action itself.