Below there's an example of a wind report generated by WINDTRACKER, let's look at the wind speed frequency distribution first:
If we want to convert this information on generated electricity [kWh] from any wind turbine, we need to have at hand the power curve of these wind turbines. Let's look at the wind profile:
0-3m/s (meters per second) had 1,623 hours of wind.
4m/s had 1,111 hours of wind
5m/s had 963 hours of wind and so on....
When we look at a wind turbine power curve, we will see that the manufacturer gives you a certain power at a certain wind speed, for example at 6m/s could have a power rating of 10kW. Keep in mind that power rating is an instant rating and it does not imply energy generation. For energy generation we need to look at the amount of power being generated during a period of time, in this case over an hour. An this is where the kWatt / hour comes from [kWh].
Now that we know the power rating at difference wind speeds from our wind turbine, we just need to multiply these by the amount of hours on the report:
|Wind Speed [m/s]||Hours [h]||Power curve [kW]||Energy generated [kWh]|
|0 - 3 m/s||1,623.7 h||0 kW||0 kWh|
|4 m/s||1,111.3 h||0.4 kW||444.5 kWh|
|5 m/s||963.7 h||1.5 kW||1,445.6 kWh|
|6 m/s||737.8 h||3.1 kW||2,287.2 kWh|
|7 m/s||563.2 h||5.6 kW||3,153.9 kWh|
|8 m/s||443.8 h||7.4 kW||3,284.1 kWh|
|9 m/s||309 h||9.1 kW||2,811.9 kWh|
|10 m/s||211.2 h||11.2 kW||2,365.4 kWh|
|11 m/s||126.2 h||13.6 kW||1,716.3 kWh|
|12 m/s||96.8 h||16.4 kW||1,587.5 kWh|
|+13 m/s||198.8 h||16.0 kW||3,180.8 kWh|
The good thing about using this method of calculating energy generation from a wind turbine is that it is based on real data collected from your own land, there're no predictions or extrapolations from other sites. It is just what it is at your own site.
The Wind rose intensity will give you an idea of where the wind is most strong but also which wind direction is more frequent with the winds at which the wind turbine is more efficient. This part of the report is very valuable when deciding where exactly to sit the wind turbine and also for wind turbine manufacturers.
The values above tell you what was the average wind speed per wind direction and also how much time (%) was in comparison to the rest of the data gathered.
It is good practice to do this Power/Energy calculation for every wind turbine you are serious about so you can find which one is going to give the best output results. Also make sure you check with the wind turbine manufacturer in order to get an up to date power curve.