Wind Power Density

Windographer calculates the wind power density, or WPD, from the wind speed and air density using the following equation:

where:
		is the wind power density, or the power per unit area, within the time step [W/m²]
	r	is the air density within the time step [kg/m³]
	U	is the average wind speed within the time step [m/s]

As Calculated Data Column

For each wind speed column in the dataset, Windographer calculates the wind power density in every time step, and adds that time series automatically to the dataset as a calculated data column. It names this calculated column the same as the wind speed sensor name, plus the letters "WPD". For example, if the wind speed column name is "Speed 180m", its associated wind power density column will have the name "Speed 180m WPD".

You can view the wind power density column in all the graphic and tabular formats that Windographer provides for any other data column. Windographer reports the mean WPD for each visible speed measurement in the Wind Speed Sensor summary table, and if the dataset contains wind speed sensors at two or more different measurement heights, Windographer will interpolate or extrapolate as necessary to find the mean wind power density at 50m above ground. It reports that value in the Dataset Summary table and uses it to determine the wind power class. You can explore this process in the Wind Power Class window.

Whenever you change a wind speed data column, or one of the columns that affects the air density column, for example by flagging a segment, deleting a segment, applying a scale factor, or appending more data, Windographer will re-calculate the WPD data column and any other affected calculated columns. The calculated WPD data column inherits the flagged status of its precursor data columns, so if you flag a segment of the speed column with some flag, Windographer will automatically apply that same flag to the corresponding segment of the calculated WPD data column as well. You cannot flag a calculated column directly, so any flags that apply to a calculated WPD column originate from this inheritance mechanism.