"All embodiments of the invention may further include measuring stress conditions. Such stress conditions may be measured by measuring temperatures, hydraulic pressures, wind speed, vibrations, acceleration of the wind turbine's tower head, oil level or even by receiving corresponding data from other wind turbines of the same wind farm which are located away from the present wind turbine in a current direction of wind. In such cases determining the rate of wear will be based at least in part on the measured stress conditions.
"The rate of wear may be expressed as a loss of an initial value of the wind turbine over a unit time, for example as USD/hour or /hour. Expressing the rate of wear in such a way simplifies determining a remaining value of the wind turbine and assessing the current rate of wear in the view of the current or expected cost of electricity.
"The method of the invention may further include updating the initial value of the wind turbine. This allows for considering changing costs (usually decreasing costs) for a comparable wind turbine which may, for example, lead to the conclusion that a higher rate of wear is acceptable if the same amount of power produced by the present wind turbine can be produced by a less expensive new wind turbine or if worn out parts of the wind turbine can be replaced for a lower price.
"In some embodiments of the invention a cumulated wear may be calculated from the determined rate of wear. The cumulated wear can then be used to control the load of the wind turbine. E.g. the cumulated wear can be compared to an expected cumulated wear based on the cumulated operating time of the wind turbine. If the result of the comparison yields that the cumulated wear is lower than expected, the power output of the wind turbine can be increased even when the cost of electricity is relatively low. If, on the other hand, the cumulated wear is higher than expected, the power output of the wind turbine can be decreased even more during times when moderate or even high wear rates meet low costs of electricity.
"A second aspect of the invention provides a software storage medium comprising program code which, when executed on a controller of a wind turbine or on a controller of a wind park, causes the controller to execute the method of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
"Further features, properties and advantages of the present invention will be clear from the following description of embodiments of the invention with reference to the accompanying figures.
"FIG. 1 shows a wind turbine adapted for carrying out the method of the present invention.
"FIG. 2 shows an example of a data set comprising typical cost of electricity values as a function of daytime.
"FIG. 3 shows the energy price at the
For more information, see this patent application: Bjerge,
Keywords for this news article include: Patents, Oil & Gas, Wind Energy.
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