They are also a very expensive substitute, and totally ineffective in reducing, fossil carbon. Germany shut down a good deal of nuclear in favor of wind, and it's a financial and environmental calamity. Note especially that 25 GWe of solar produced 2.4% of total demand, while 12 GWe of nuclear provided 15.3%.
Wind turbines are big, ugly, noisy, unreliable, and puny for their size. The biggest size in service is near the practical limit, at 5 megawatts (5 MW). That's the rated power, for a wind that's rated 7 on the Beaufort scale, one level less than gale force. On the Beaufort Scale, the usable levels of wind are from 4 to 7. Note that at force 3, when a man-o'-war in full sail could make 3 or 4 knots, a 5MW turbine can produce nothing. The capital cost is high, per rated megawatt of power capacity. It's at least four times higher per average megawatt-hour of energy per hour.
Mathematically, wind speed is a random walk. It gets to some strength, and then it may go up or down at almost any rate of change. But the wind power is the cube of the wind speed. So to a first approximation, the rate of change of power is three times as rapid as the rate of change of windspeed. It's a bad bargain, unless you're only interested in the sum over time of the energy provided, which is emphatically NOT the way we want our electricity supplied.
A project proposed for the Thames estuary would have 341 turbines occupying an area of 90 square miles. It is claimed to be a one-gigawatt project. That's probably the nominal capacity, i.e. power available in a very strong, steady wind. Despite subsidies, the oil company Shell had the wisdom to pull out of this project.
You can use wind energy to pump water, and you could in principle store wind energy that way to go with a hydroelectric pumped storage project. The capital costs of a one-gigawatt plant would be enormous, because the average wind power, if you're very lucky, is about a quarter of the peak power for each turbine. So it takes 800 of Germany's behemoth 5 MW wind turbines to provide an average of one gigawatt. It says that
Winds as low as 3.5 m/s will disengage the electromagnetic disc brakes and the turbine should have peak performance during winds of 13 m/s. Winds of 25 m/s or more will cause the turbine to cut-out.13 meters per second is 46.8 km/hour. That's just under 30 mph. This is classified on the Beaufort scale as force 7, a "near gale", producing waves 13 to 20 feet high. If the wind drops to 25 mph, the power drops to a factor of (5/6)3. That's 0.57. The power is now less than 2.9 MW. In a mere 20 mph wind, we get (2/3)3 of the power at 30 mph. That's 1.48 MW
Each of those 5 MW turbines has a peak blade height of 180 metres, almost 600 feet, more than the height of the Statue of Liberty or the Washington Monument, or of Edinburgh Castle above the sea. The difficulty of maintenance is met, at a height of 120 m., where the nacelle and hub of the rotor is, by a platform big enough to land a helicopter. There's a picture of the platform at the aforementioned site. It looks like a job for a very brave and skilled pilot.
Wind turbines are unsightly Wind turbines also break, catch fire in lightning storms, kill lots of bats, also sea eagles and other big birds. Especially rare ones. It takes 200 of the biggest of them and half a gale to produce 1000 MW, the output of one nuclear or heaven forbid, coal-fired generator. If you have 800, you still don't have a reliable one gigawatt supply. The more you have, the more backup, non-wind-turbine, generators you have to keep on spinning reserve.
Some PDF files: