You're basically replacing oil with oil in plastic form. Where is the gain?
Ok so we got this reply.
Not sure if you're trolling but the point is that the windmill makes power as long as it exists and functions. So if it generates more power in its lifetime than the oil that took to make it, that's the gain. Is this not obvious? Its the same with solar cells
So, a wind turbine weighs a thousand tons (or whatever). That's 10 gwh of oil. Does it produce that much energy?
I'll try to do a very naive (napkin) calculation. (The way the question is formed does not warranty -IMHO- a more detailed/diligent calculation).
(Also, apologies in advance, but it's been over a decade since I worked for a wind farm so my numbers and estimates might be outdated).
For a 1.5-MW turbine, typical blades should measure 110 ft to 124 ft (34m to 38m) in length, typically weigh about 5000 kg each source: Composites world.
That means that the total mass of the blades is about 15000kg. (although approximately 75% of it is by weight glass, but let's assume that all of it is from PE - it won't matter in the end).
Let's assume that the wind blade is made from PP (usually a thermosetting epoxy system is used, but I don't have access to reliable data regarding this, and PP is a good thermoplastic alternative).
For each kg of PP, about 0.54 to 0.68 lit of petrol is required. (Let's take the worst case 0.54). For each lt of petrol 0.9 kg of crude oil is required. (source: THE USE OF CRUDE OIL IN PLASTIC MAKING CONTRIBUTES TO GLOBAL WARMING)
This means that for each kg or crude oil about 0.6 kg of PP is made.
So this means that for the 15000kg of the blades about 25000 kg of crude oil are required.
Additionally 1kg of crude oil produces about 44 MJ. Therefore the energy in the crude oil required to make the plastic of the blades is about $1.1\cdot 10^{12}J $ or (the less impressive) 0.3056 GWh. (UPDATE: I found on the following article, for the wind blade system, the estimated energy per metric ton is about 170GJ/t)
Again please make a note that there are gross simplifications/assumptions:
All things considered, the assumptions should even out, given the accepted worst case values, they might even be overly conservative.
A properly placed wind generator has a capacity factor of about .25 to 0.5. Assuming the lowest $C_F =0.25$, a 1.5 MW wind generator in a year would produce about:
$$E_{WG} = 1.5 [MW]\cdot 365[days]\cdot 24[hr]\cdot C_F = 3.285 [GWh]$$
So the 1.5MW turbine would produce over 10 times more energy annually.
Not burning the Oil has the added benefit that greenhouse gases are not produced. This is a significant environmental benefit, and if you add the benefit from the reduced carbon taxes, it adds an economic incentive.
Every once in a while questions like this come out of the woodworks, usually with a tone similar to other key-board warriors we have heard before. you don't know if it's a tease or a genuine deep misunderstanding.
In the spirit of improving my gravely lacking skills in being entertaining, I take a stab at this question.
If we compare burning a windmill to burning oil, burning the oil is a lot more efficient.
Also, the industry has many provisions to burn the oil as cleanly as possible whereas there have not been any attempts at burning the windmills efficiently!
