If you mean power, visit How much power could I generate from a wind turbine?
If you mean wind generated energy (which is what you sell), read on.
Energy is everything; you can sell energy, but you can’t sell power (at least not in the context of wind power!) People often get obsessed with wanting the highest possible power output from a wind turbine, but this is really quite irrelevant. When you sell electricity you are paid depending on the number of kWh (kilowatt-hours) you sell (i.e. based on the energy) and not for the power you produce. Energy is the capacity to do work, while power is the rate at which work can be done. It is a bit like miles and miles-per-hour; the two are clearly related, but are fundamentally different.
The amount of wind energy that can be generated depends mainly on the size of wind turbine and the annual average wind speed at the site. There are some other factors that affect energy capture such as nearby hills, trees and buildings (or other wind turbines) that could obstruct the wind, and the efficiency of the wind turbine itself. Assuming your turbine has been well sited and is from a good quality manufacturer the most important factor will be the annual average wind speed.
The table and chart below shows the annual energy production in MWh for a range of turbines from 50 kW to 2.5 MW. For the ‘derated 500 kW’ turbine it assumes that a derated version of a standard 800 kW turbine is used, so the energy production figures look high, but this is accurate because the wind turbine has an ‘oversize’ rotor because it is derated from a standard 800 kW model.
|Maximum Power Output||Example Turbine||Annual Energy Capture (MWh) for the following Annual Average Wind speeds:|
|50 kW||Northern Power NP50||158||183||205||224||241||254||n/a||n/a||n/a|
|100 kW||Norvento nED-100||203||252||300||346||388||425||n/a||n/a||n/a|
|225 kW||Endurance X-35||335||428||523||614||701||782||n/a||n/a||n/a|
|900 kW||EWT DW61||1,437||1,800||2,168||2,530||2,878||3,207||n/a||n/a||n/a|
|1.5 MW||ENO 82||2,516||3,139||3,768||4,383||4,972||5,524||6,036||6,505||n/a|
|3 MW2||Enercon E82||2,940||3,788||4,698||5,646||6,610||7,569||8,506||9,406||10,256|
- Some of turbines in the table are not suitable for ‘class 1’ sites with annual average wind speeds above 8.5 m/s, hence are shown as n/a. Where there is a figure provided for 9 m/s, this will be a special ‘class 1 variant’ which generally has a smaller rotor and shorter tower to limit the extreme loads on the turbine.
- The Enercon E82 comes in three variants with maximum power outputs of 2, 2.3 and 3 MW depending on the average wind speed at the site. In the table we have selected the most appropriate variant.
The estimates are based on real manufacturers’ power curves, assume a Rayleigh wind speed distribution and include an availability factor of 0.95 (i.e. we have allowed for 5% of the time for maintenance downtime, which is conservative).
Note that for multiple-turbine sites just multiply the figures above by the number of wind turbines you are considering. For your site there may well be turbines from other manufacturers that we would consider, so please don’t assume that these are the only turbines that we work with (though they are all very good quality machines).
Note that really accurate wind energy production estimates require accurate wind data measured at the site and a lot of modeling on specialist wind software (we use Windfarm), but the figures above are a good starting point for initial site appraisal estimates.
You’ll notice that the annual wind energy production from the wind turbines increases disproportionately compared to the increase in annual mean wind speed; for example an increase in annual mean wind speed from 6.5 to 7.0 m/s is an 8% increase in wind speed, but the corresponding increase in annual energy production is around 14%. This is because the power output of a wind turbine is proportional to the cube of the wind speed and demonstrates how fundamentally important it is that wind turbines are located where the local wind speed is at its maximum.
Want to install a wind turbine?
If you are in the UK then take our Wind Site Self-Assessment - Step 1 of our modular Windpower Feasibility Study. It takes about 20 minutes to work through the basic checks to see if your site might be suitable, including:
- Estimating wind speed
- Checking proximity of nearby properties
- Checking site access and approach roads
- Investigating connection with the grid