Hub Height Time Series
In the hub height time series task you can extrapolate wind speed time series to target heights using shear models defined on their measurement sites in Shear model setup. Extrapolated wind speed time series are generated and saved as calculated series named HHTS(height) on their corresponding measurement sites. These "hub height time series" will all be used by the auto-setup tool in the next task, Calculate wind climate, to generate wind speed and direction frequency distributions and turbulence distributions.
If you need to recalculate the hub height time series after a change to an earlier part of your wind analysis click Recalculate all.
Auto-setup hub height time series
The auto-setup tool will allow you to quickly calculate hub height time series at any measurement site with a shear model defined. A wind speed time series will be calculated for each hub height for each measurement site with a shear model.
The preferred time series defines what type of reconstructed wind speed time series we will extrapolate. The time series for extrapolation to hub height are selected at the primary wind speed measurement height based on the name of the calculated time series:
| Calculated time series name prefix | Meaning |
|---|---|
| PMC | Parallel Measurement Combined wind speeds calculated in the Parallel measurement combination task from two wind speed measurements at the same height above ground. |
| Recon | Reconstructed wind speed time series calculated in the Speed reconstruction task. These wind speed data often contain synthetic records from derived from measurements at other on-site measurement sites. |
In the next task, calculate wind climate, we will use the hub height time series to define the wind speed frequency distribution. Use of reconstructed (Recon) data to define the frequency distribution at a measurement site can increase the uncertainty because there is a higher uncertainty associated with the synthetic records than the measured records. The PMC data do not contain this synthetic data but will generally contain fewer records than the Recon time series. The decision to use Recon or PMC should balance these two uncertainty considerations.
The list of hub heights defines all the heights we will extrapolate to. The default list is populated by the hub heights for any turbine types already loaded into the workbook, but you can add and remove target heights as desired.
Note
In this process we are selecting a preferred time series so that if the chosen time series type does not exist WFA will look for another time series at an earlier stage of the reconstruction process. If you select Recon, a wind speed time series at primary measurement height with a name beginning with Recon is preferred over one beginning with PMC, which is in turn preferred over the primary wind speed measurement.
Manual setup for hub height time series
If you want to extrapolate specific wind speed time series to specific heights use Manual setup. Click Append Row to create further hub height time series.
| Manual-setup option | Description |
|---|---|
| Site | The measurement site containing the wind speeds to extrapolate. The extrapolated series will be saved on this measurement site |
| Wind speed (mean) | The wind speed mean time series to extrapolate |
| Direction (mean) | If you are using a time series shear model with a lookup table binned by direction the wind direction time series here will be used to select alpha values, otherwise it is not used in the hub height time series calculation and can be ignored. |
| Name | Name of the output series, note this is auto-generated by setting the height above ground |
| Height above ground | Height to extrapolate the wind speed time series to |
| Overall speed up | If entered, every record in the extrapolated time series will be multiplied by this speedup value |
Hub height time series results
| Hub height time series table | Description |
|---|---|
| Site | The measurement site containing the wind speeds to extrapolate. The extrapolated series will be saved on this measurement site |
| Speed signal (mean) | The wind speed mean time series to extrapolate |
| Direction signal | If you are using a time series shear model with a lookup table binned by direction the wind direction time series here will be used to select alpha values, otherwise it is not used in the hub height time series calculation and can be ignored. |
| Height above ground | Height to extrapolate the wind speed time series to. Note we do not recommend you edit this in the table here: use manual setup if you need a different height because the hub height time series is not renamed when you change the height here. |
| Name | Name of the calculated series, generally HHTS(height) unless you define your own name in manual setup |
| Annual wind speed [m/s] | The annual wind speed of the extrapolated wind speed time series |
| Overall shear | The overall shear is calculated from the annual wind speed from the extrapolated wind speed series and the input speed signal. A log-law or power law fit is used to match the shear model settings used in Shear model setup. This Overall shear value is used to define the target long term hub height wind speed in the Calculate wind climate task. |
| Optional speed up | If entered, every record in the extrapolated time series will be multiplied by this speedup value |
| Valid data [years] | The number of valid records in the extrapolated time series divided by the number of records in a year. |
| Last calculated date | Updates whenever the time series is recalculated |
| Note | Optional note to record decisions |