Once construction is completed, commissioning will begin. The definition of ‘commissioning’ is not standardised, but generally covers all activities after all components of the wind turbine are installed. Commissioning of an individual turbine can take little more than two days with experienced staff.
Commissioning tests will usually involve standard electrical tests for the electrical infrastructure as well as the turbine, and inspection of routine civil engineering quality records. Careful testing at this stage is vital if a good quality wind farm is to be delivered and maintained.
The long-term availability of a commercial wind turbine is usually in excess of 97 per cent. This value means that for 97 per cent of the time, the turbine will be available to work if there is adequate wind. This value is superior to values quoted for conventional power stations. It will usually take a period of some six months for the wind farm to reach full, mature, commercial operation and hence, during that period, the availability will increase from a level of about 80-90 per cent after commissioning to the long-term level of 97 per cent or more.
It is normal practice for the supplier of the wind farm to provide a warranty for between two and five years. This warranty will often cover lost revenue, including downtime to correct faults, and a test of the power curve of the turbine. If the power curve is found to be defective then reimbursement will be made through the payment of liquidated damages. For modern wind farms, there is rarely any problem in meeting the warranted power curves, but availability, particularly for new models, can be lower than expected in the early years of operation. During the first year of operation of a turbine some ‘teething’ problems are usually experienced. For a new model this effect is more marked. As model use increases, these problems are resolved and availability rises.
After commissioning, the wind farm will be handed over to the operations and maintenance crew. A typical crew will consist of two people for every 20 to 30 wind turbines in a wind farm. For smaller wind farms there may not be a dedicated O&M crew but arrangements will be made for regular visits from a regional team. Typical routine maintenance time for a modern wind turbine is 40 hours per year. Non-routine maintenance may be of a similar order.
There is now much commercial experience with modern wind turbines and high levels of availability are regularly achieved. Third party operations companies are well-established in all of the major markets, and it is likely that this element of the industry will develop very much along the lines associated with other rotating plant and mechanical/electrical equipment.
The building permits obtained in order to allow the construction of the wind farm may have some ongoing environmental reporting requirements, for example the monitoring of noise, avian activity or other flora or fauna interest. Similarly there may, depending on the local regulations, be regulatory duties to perform in connection with the local electricity network operator. Therefore, in addition to the obvious operations and maintenance activity, there is often a management role to perform in parallel. Many wind farms are the subject of project finance and hence regular reporting activities to the lenders will also be required.