Small wind / Buyer questions
Energy and economics
Can I insert annual average wind speed into a turbine power curve to calculate annual energy?
The short answer
In general, applying annual mean wind speed to one point on a turbine power curve does not establish annual energy. Power varies nonlinearly with speed and operating state. An energy estimate needs the time spent under relevant conditions, interpreted through an applicable curve and explicit loss assumptions.
Keep the order of operations clear
For a time-series method, evaluate the supported generation for each represented interval and integrate over its duration. For a distribution method, weight the curve response by the hours or probabilities in the corresponding speed ranges. These approaches retain information lost when all speeds become one mean.
The average of curve outputs need not equal the curve output at average speed. This remains true even when the mean wind value itself has been calculated correctly.
Use an illustrative comparison to expose the issue
Suppose two equally long intervals have speeds of 2 m/s and 8 m/s. Their mean is 5 m/s. For a purely illustrative curve giving 0 kW at 2 m/s, 1 kW at 5 m/s and 4 kW at 8 m/s, the mean output is 2 kW, while the curve value at the mean speed is 1 kW.
Those invented curve values explain the calculation only. They are not MARSTON product data and should not be used to size equipment.
Request the information that the decision requires
Ask for the resource distribution or time series, curve identity, reference conditions, availability and loss treatment. If only an annual mean is available, label any resulting estimate as a model-based screening case with distribution assumptions.
When timing affects self-consumption or off-grid service, even an annual distribution may be insufficient; chronological overlap with demand matters. The assessment should explain which question its inputs can answer before a single annual kWh figure is used to compare quotations or justify an order.
Sources
- System Advisor Model documentation: wind-resource inputs and time-series limitations
- System Advisor Model documentation: turbine curves, hub height and shear
Examples are illustrative. Confirm product-specific performance, compatibility and supply scope in the applicable documents.