Modelling the effect of maintenance strategies and reliability for long-term wind yield assessment

Where a number of onshore wind farm locations are being maintained by a single central Operation and Maintenance Contractor, an effective competition exists between those sites for the use of that maintenance resource. Any differentials between those sites in terms of the costs of repair to the contractor, or the potential return to the contractor for improving the site availability under the Operations and Maintenance Contract, may mean a variance in the level of operational availability achieved by each site. A review of UK contract terms illustrates the potential differentials that may occur. A maintenance optimisation model is created which is used to simulate the potential availabilities of a set of wind farms maintained from a central resource in response to typical published failure rates and restoration times. Monte Carlo methods are applied to this simulation to provide an illustrative set of sensitivities which may be used to adjust availability losses assumed during the energy yield analysis of a potential onshore wind farm location.