I have been considering effects of parasitic power consumption by wind turbines: power they must use to stay functional even if there is no wind. For the whole of a turbine's working life, a significant amount of the energy it produces will never be seen, for a variety of reasons.
The manufacturers do not give detailed information but we can get some idea of these 'parasitic losses' by using common sense.
Actual figures may vary a little from what I am assuming, but the figures below will not be far from the truth. If you have other ideas I would be pleased to have them.
Below is a representative list of equipment and systems requiring electric power, together with assumed power consumptions. I have assumed a basic 2-megawatt turbine for this study.
Yaw mechanism to turn the rotor into the wind: 20kW
Pitch mechanism to adjust the blade angle to the wind: 15kW
Lights, controllers, communication, sensors, data collection, etc: 10kW
Heating the blades during winter: 250Kw
Heating/cooling and dehumidifying the nacelle: 10kW
Oil heater, pump, cooler and filtering system of the gearbox: 25kW
Hydraulic brake to lock the blades when the wind is too strong: 5kW
Thyristors for power conditioning and connection: 25kW
Magnetizing the stator to keep the rotor speed constant: 25kW
Using the generator as a motor to help blades start to turn when wind speed is low or, as many suspect, to create the illusion the facility is producing electricity when it is not, particularly during site tours. It also spins the rotor shaft and blades to prevent warping when there is no wind. 50kW.
TOTAL drain on the turbine. 435kW.
Not all items will be used at the same time, although this may occur occasionally. However, we can generously assume 50% usage, for a parasitic consumption of approximately 435kW x 0.50, = 215 kW.
Turbine rated wind speed is 12 mps (Metres per second). Rated power is 2 MW.
Power varies as cube of wind speed. So, for a windspeed of 4mps (one third the rated speed):
Power at 4mps is 2,000,000/3x3x3 = 74kW
Nett output is 74 - 215 = –141kW
Similarly, power at 5mps is 144kW
Nett output is -71kW
and power at 6mps is 250kW
Nett output is +35kW
This shows that the machine does not start to produce useful power until wind speeds reach around 6mps, assuming that 35kW from a 2mW machine can be considered useful.
Published figures for average wind speeds locally, at masthead height are 6mps. (1)
There are subsequent losses, such as transformer inefficiencies, and transmission losses to take power from turbine to grid. We can assume approximately 6% to 15%, depending on the type of equipment and transmission line lengths.
What this says is that the turbine is virtually useless even at average wind speeds and that we need considerably more than average in order to get any useful power output.
On average we can expect to power about 12 electric kettles, for an investment of around £2.4 million.
Note that the turbine ‘sells’ its power based on metering at the output unit and thus avoids the effects of transmission losses.
Also, there is no charge made for power that is consumed when there is low or no output. In other words, charges are made based on gross output, not net output.
And we do not even start to save CO2 emissions until we reach average wind speeds. What a huge con job is being foisted on us all.
Footnote..... I hear today on the BBC news that the IPCC recognizes that we can avoid catastrophic climate change by investing even more heavily in renewables and abandoning coal and gas.
Those guys are certainly better at spending money than earning it.
(1) Banbury area. It will vary depending on actual location.