Yes, you would need a lot of wind turbines to have a significant, noticeable effect on the weather. There are three potential impacts:
- Wind turbines will change the pattern of turbulence downwind from them.
- Wind turbines will take some energy out of the wind
- Wind turbines will typically displace thermal plant generation, which means that less heat and less steam / water vapour is released from thermal plants: this may have an effect on the local weather in the immediate vicinity of the thermal plant.
As far as I know, point 3 hasn't been studied yet. Points one and two have been looked at in various forms, with different types of micro, meso and macro modelling. The difficulty, as ever, is that we are modelling turbulence, with uncertain boundary conditions. Those who do meso and macro scale modelling are aware of the problems that this causes, but publish nevertheless. There are those who do do bottom-up modelling, starting with the micro modelling of individual turbines, and building up from there, either with processor-intensive area-wide micro-modelling, or through parameterisation. Professor Mark Z Jacobson of Stanford has published quite a lot in the field, and also contributes comments on others work in the field.
At the moment, the bottom line is that deployment is so low, as to give virtually no significant results, with one notable exception: wind turbines can increase the turbulence immediately above ground, in their wake, and this can be quite effective in preventing ground frost. This has been used by farmers, who put turbines on the edge of their field to help protect their winter crops from frosts.
From reference 1 (parameterisation of micro results):
Should wind supply the world’s energy needs, this parameterization
estimates energy loss in the lowest 1 km of the atmosphere to be
~0.007%. This is an order of magnitude smaller than atmospheric energy
loss from aerosol pollution and urbanization, and orders of magnitude
less than the energy added to the atmosphere from doubling CO2. Also,
the net heat added to the environment due to wind dissipation is much
less than that added by thermal plants that the turbines displace.
There are various works in the field, and it can be helpful to do a quick sanity check on a paper's assumptions, to assess it:
- Does the paper account for all vertical mixing within reasonable range of the turbine (good), or does it impose some arbitrary ceiling close to turbine height, and assume no mixing above it (bad)?
- Does it take account of a mix of onshore and offshore wind ?
- Do any extrapolations of deployed wind copy existing patterns (bad), or model deployment based on realistic forecasts of planned deployment (good)?
References:
- Investigating the Effect of Large Wind Farms on Energy in the Atmosphere
Magdalena R. V. Sta. Maria and Mark Z. Jacobson, DOI:10.3390/en20400816
While I'm not willing to spend the money to get access the paper, one issue jumps out at a casual reading of the abstract - turbine design. Honeste_vivere's answer mentions the possibility of destroying a farm, and the abstract includes "The reduction in wind speed due to large arrays increases the probability of survival of even present turbine designs." What seems to be missing at this level is the need to produce turbines which will work effectively at hurricane-force winds. Current devices are simply incapable of doing this, and since any turbine has a limited operating range for efficient operation anything capable of working when a hurricane hits will be useless most of the time.
This seems possible in principle, but among other things it would require a very large investment in R&D, the turbines would need to be far more robust than current designs (and therefore more expensive), and testing of operational units would obviously be problematic.
Also not mentioned, and not explored in honeste_vivere's answer, is just how one would dissipate the extracted power. If the power is not dissipated, the turbines can't extract it. Giant heaters out to sea which dump heat into sea water? For any heaters less than 100's of square kilometers, I suspect a successful hurricane amelioration would have catastrophic ecological consequences.
Between the need for dedicated hurricane turbines and the need for power dissipation structures, the cost would seem very high.
But then again, I didn't read the article, so I might be wrong.
Best Answer
The principle of conservation of energy is your friend.
The wind turbine generates electricity.
That energy has to come from somewhere.
The other energy in the system is the kinetic energy of the wind.
Therefore, the wind turbines convert the kinetic energy of the wind into electricity, and the kinetic energy of the air downwind of the rotor is less than the kinetic energy upwind of the rotor. Your "perfect" wind turbine would be useless.
The lift generated by the wind over the blade moves the blade around. That takes energy from the wind to achieve. The energy is delivered into the generator.
There's a comprehensive book called "Wind Energy - The Facts", and the technology chapter covers the specific aerodynamics. Your closest decent library should have a copy.
See also "Wind Turbine Blade Design", Peter J. Schubel and Richard J. Crossley, Energies 2012, 5, 3425-3449; doi:10.3390/en5093425