Wind turbines look like airplane propellers running
on the spot—spinning round but going nowhere. They're serving a very useful purpose, however.
There's energy locked in wind and their giant rotors can capture some of it and turn it instantly into electricity. Have you ever stopped to wonder how wind turbines work? Let's take a
Photo: A small wind farm in Colorado, United States. These are relatively small turbines: each one produces about 700kW of energy (enough to supply about 400 homes). The turbines are 79m (260ft) high (from the ground to the very top of the rotors) and the rotors themselves are 48.5m (159ft) in diameter. The top part of each turbine (called the nacelle) rotates on the tower beneath so the spinning blades are always facing directly into the wind.
Photo by Warren Gretz courtesy of US Department of Energy/NREL (DoE/NREL).
A turbine, like the ones in a wind farm, is a machine that spins around
in a moving fluid (liquid or gas) and catches some of the energy passing by.
All sorts of machines use turbines, from jet engines to
hydroelectric power plants and from diesel railroad locomotives to windmills. Even a child's toy windmill is a simple form of turbine.
The huge rotor blades on the front of a wind turbine are the "turbine" part. The blades have a special curved shape, similar to the airfoil wings on a plane. When wind blows past a plane's wings, it moves them upward with a force we call lift; when it blows past a turbine's blades, it spins them around instead. The wind loses some of its kinetic energy (energy of movement) and the turbine gains just as much. As you might expect, the amount of energy that a turbine makes is
proportional to the area that its rotor blades sweep out; in other words, the longer the rotor blades, the more energy a turbine will generate. Obviously, faster winds help too: if the wind blows twice as quickly, there's potentially eight times more energy available for a turbine to harvest. That's because the energy in wind is proportional to the cube of its speed.
Wind varies all the time so the electricity produced by a single wind turbine varies as well. Linking many wind turbines together into a large farm, and linking many wind farms in different areas into a national power grid, produces a much more steady supply overall.
Photo: Head for heights! You can see just how big a wind turbine is compared to this
engineer, who's standing right inside the nacelle (main unit) carrying out maintenance. Notice how
the white blades at the front connect via an axle (gray—under the engineer's feet) to the gearbox and generator
behind (blue). This is a 900kW turbine with a 55m (182ft) diameter rotor mounted on a tower 33m (110ft) off the ground. Photo by Lance Cheung courtesy of US Air Force.
Key parts of a wind turbine?
Although we talk about "wind turbines," the turbine is only one of
the parts inside these machines. For most (but not all) turbines,
another key part is a gearbox whose gears convert the
relatively slow rotation of the spinning blades into higher-speed motion—turning the drive shaft quickly enough to power the electricity generator.
The generator is an essential part of all
turbines and you can think of it as being a bit like an enormous, scaled-up version of the dynamo on a bicycle.
When you ride a bicycle, the dynamo touching the back wheel spins around and
generates enough electricity to make a lamp light up. The same thing
happens in a wind turbine, only the "dynamo" generator is driven
by the turbine's rotor blades instead of by a bicycle wheel, and
the "lamp" is a light in someone's home miles away.
In practice, wind turbines use different types of generators that aren't very much like
dynamos at all. (You can read about how they work, more generally, in our main article about
How does a wind turbine work?
Wind (moving air that contains kinetic energy) blows toward the turbine's rotor blades.
The rotors spin around, capturing some of the kinetic energy from the wind, and turning the central drive shaft that supports them. Although the outer edges of the rotor blades move very fast, the central axle (drive shaft) they're connected to turns quite slowly.
In most large modern turbines, the rotor blades can swivel on the hub at the front so they meet the wind at the best angle (or "pitch") for harvesting energy. This is called the pitch control mechanism. On big turbines, small electric motors or
hydraulic rams swivel the blades back and forth under precise electronic control. On smaller turbines, the pitch control is often completely mechanical. However, many turbines have fixed rotors and no pitch control at all.
Photo: A 3MW wind turbine with its rotor blades removed, showing the pitch
control mechanism. The tower is on the right and notice the engineer perched on top
(for scale). Photo by Werner Slocum courtesy of NREL.
Inside the nacelle (the main body of the turbine sitting on top of the tower and behind the blades), the gearbox converts the low-speed rotation of the drive shaft (perhaps, 16 revolutions per minute, rpm) into high-speed (perhaps, 1600 rpm) rotation fast enough to drive the generator efficiently.
The generator, immediately behind the gearbox, takes kinetic energy from the spinning drive shaft and turns it into electrical energy. Running at maximum capacity, a typical 2MW turbine generator will produce 2 million watts of power at about 700 volts.
Anemometers (automatic speed measuring devices) and wind vanes on the back of the nacelle provide measurements of the wind speed and direction.
Using these measurements, the entire top part of the turbine (the rotors and nacelle) can be rotated by a yaw motor, mounted between the nacelle and the tower, so it faces directly into the oncoming wind and captures the maximum amount of energy. If it's too windy or turbulent, brakes are applied to stop the rotors from turning (for safety reasons). The brakes are also applied during routine maintenance.
The electric current produced by the generator flows through a cable running down through the inside of the turbine tower.
A step-up transformer converts the electricity to about 50 times higher voltage so it can be transmitted efficiently to the power grid (or to nearby buildings or communities). If the electricity is flowing to the grid, it's converted to an even higher voltage (130,000 volts or more) by a substation nearby, which services many turbines.
Homes enjoy clean, green energy: the turbine has produced no greenhouse gas emissions or pollution as it operates.
Wind carries on blowing past the turbine, but with less speed and energy (for reasons explained below) and more
turbulence (since the turbine has disrupted its flow).
How turbines harvest maximum energy
If you've ever stood beneath a large wind turbine, you'll know that they are
absolutely gigantic and mounted on incredibly high towers. The longer
the rotor blades, the more energy they can capture from the wind. The
giant blades (typically 70m or 230 feet in diameter, which is about 30
times the wingspan of an eagle) multiply the wind's force like
a wheel and axle, so
a gentle breeze is often enough to make the blades turn around.
Even so, typical wind turbines stand idle about 14 percent of the
time, and most of the time they don't generate maximum power.
This is not a drawback, however, but a deliberate feature of their design
that allows them to work very efficiently in ever-changing winds.
Think of it like this. Cars don't drive around at top speed
all the time: a car's engine and gearbox power the wheels as quickly or slowly as we need
to go according to the speed of the traffic. Wind turbines are analogous:
like cars, they're designed to work efficiently at a range of different speeds.
A typical wind turbine nacelle is 85 meters (280 feet) off the
ground—that's like 50 tall adults standing on one another's shoulders! There's
a good reason for this. If you've ever stood on a hill that's the
tallest point for miles around, you'll know that wind travels
much faster when it's clear of the buildings, trees, hills, and other
obstructions at ground level. So if you put a turbine's rotor
blades high in the air, they capture considerably more wind energy
than they would lower down. (If you mount a wind turbine's rotor twice as high,
it will usually make about a third more power.) And capturing energy is what wind turbines
are all about.
Photo: In theory, wind is still at ground level and blows faster the higher from the ground you go, in a region
that's known as the boundary layer. Generally, the taller a wind turbine, the better, although there are practical limits and
diminishing returns from going ever higher.
Since the blades of a wind turbine are rotating, they must have
kinetic energy, which they "steal" from the wind. Now
it's a basic law of physics (known as the conservation
of energy) that you can't make energy out of nothing, so the wind
must actually slow down slightly when it passes around a wind
turbine. That's not really a problem, because there's usually
plenty more wind following on behind! It is a problem if you want to
build a wind farm: unless you're in a really windy place, you have
to make sure each turbine is a good distance from the ones around it so it's not affected by them.
Photo: This unusual Darrieus
"egg-beater" wind turbine rotates about a vertical axis, unlike a
normal turbine with a horizontal rotor. Its main advantage is that it can be mounted nearer to the ground,
without a tower, which makes it cheaper to construct. It can also capture
wind coming from any direction without using things like pitch and yaw motors,
which makes it simpler and cheaper. Even so, turbines like this suffer from a variety of
other problems and are quite inefficient at capturing energy, so they're very rare.
This one is 17m (56ft) high and produces ~150 kilowatts of power.
Photo by courtesy of US National Archives.
Advantages and disadvantages of wind turbines
At first sight, it's hard to imagine why anyone would object to clean and green wind turbines—especially
when you compare them to dirty coal-fired plants and risky nuclear ones, but they do have some disadvantages.
One of the characteristics of a wind turbine is that it doesn't generate
anything like as much power as a conventional coal, gas, or nuclear plant. A typical
modern turbine has a maximum power output of about 2 megawatts (MW), which is enough to run
1000 2kW electric toasters simultaneously—and
enough to supply about 1000 homes, if it produces energy about 30 percent of the time.
biggest offshore wind turbines can now make 13 megawatts, since they can be built much taller and winds are stronger
and more persistent out at sea.
If a 2MW turbine can power 1000 homes, simply scaling up the numbers, you'd expect a 13MW turbine
to be able to power about 6500 homes.
In practice, however, because new turbines are more efficient and operate more of the time, a 13MW offshore turbine can actually
make enough power for about 12,000 homes.
In theory, you'd need 1000 2MW turbines to make as much power as a
really sizable (2000 MW or 2GW) coal-fired power plant or
a nuclear power station
(either of which can generate enough power to run a million 2kW toasters at the same time);
in practice, because coal and nuclear power stations produce energy fairly consistently
and wind energy is variable, you'd need rather more.
(If a good nuclear power plant operates at maximum capacity 90 percent of the time, and a good, brand new, offshore wind farm manages to do the same 45 percent of the time, you'd need twice as many wind turbines to make up for that, or three times as many for a wind farm working at 30 percent capacity.
Ultimately, wind power is variable and an efficient power grid needs a predictable supply
of power to meet varying demand. In practice, that means it needs a mixture of different
types of energy so supply can be almost 100 percent guaranteed.
Some of these will operate almost continually (like nuclear),
some will produce power at peak times (like hydroelectric plants),
some will raise or lower the power they make at short notice (like natural gas),
and some will make power whenever they can (like wind). Wind power can't be the only form of supply—and no-one has
ever pretended that.
Photo: You can put lots of turbines together
to make a wind farm, but you need to space them out to harvest the
energy effectively. Combining the output from many wind farms
in many different areas produces a smoother and more predictable power supply.
This is the Ponnequin Wind Farm in Colorado, United States.
Photo by Warren Gretz courtesy of NREL.
As we've just seen, you can't jam a couple of thousand wind turbines tightly together and expect them
to work effectively; they have to be spaced some distance apart
(typically 3–5 rotor diameters in the "crosswind" direction, between each turbine and the ones
either side, and 8–10 diameters in the "downwind" direction, between each turbine and the ones
in front and behind).
Put these two things together and you arrive at the biggest and most
obvious disadvantage of wind power: it takes up a lot of space.
If you wanted to power an entire country with wind alone (which no-one has ever seriously suggested),
you'd need to cover an absolutely vast land area with turbines.
You could still use almost all the land between the turbines for farming; a typical wind farm removes less than 5 percent
of land from production (for the turbine bases, access roads, and grid connections).
You could mount turbines out at sea instead, but that raises other problems and costs more. Even onshore, connecting arrays of wind turbines to the power grid is obviously a bigger hurdle than wiring up a single, equivalent power plant. Some farmers and landowners have objections to new power lines, though many earn handsome profits from renting out their land
(potentially with a guaranteed income for a quarter of a century), most of which they can continue to use as before.
On the plus side, wind turbines are clean and green: unlike coal stations, once they're constructed, they don't make the carbon dioxide emissions that are causing global warming or the
sulfur dioxide emissions that cause acid rain (a type of air pollution).
Once you've built them, the energy they make is limitless and (except for spare parts and maintenance) free
over a typical lifetime of 20–25 years.
That's even more of an advantage than it sounds, because the cost of running conventional power plants is heavily geared to risky things like wholesale oil and gas prices and the volatility of world energy markets.
Wind turbine towers and nacelles contain quite a bit of metal, and
concrete foundations to stop them falling over (a typical turbine has
in total), so constructing them does have some environmental impact. Even so, looking at their entire operating lifespan, it turns out that they have among the lowest carbon dioxide emissions of any form of power generation, significantly lower than fossil-fueled plants, most solar installations, or biomass plants. Now nuclear power plants also have relatively low carbon dioxide emissions, but wind turbines don't have the security, pollution, and waste-disposal problems many people associate with nuclear energy, and they're much quicker and easier to construct. They're also much cheaper, per kilowatt hour of power they produce: half the price of nuclear and two thirds the price of coal (according to 2009 figures quoted by
Milligan et al). According to the Global Wind Energy Council, a turbine can produce enough power in 3–6 months to recover the energy used throughout its lifetime (constructing, operating, and recycling it).
Artwork: Wind turbines are much bigger and more powerful than they
were just a few decades ago. Each one of these turbines shows how the state of the art
has improved dramatically every five years since the mid 1980s. The numbers on top are the
rotor diameter and maximum power. Artwork by Joshua Bauer courtesy of NREL.
Very low carbon dioxide emissions (effectively zero once constructed).
No air or water pollution.
No environmental impacts from mining or drilling.
No fuel to pay for—ever!
Completely sustainable—unlike fossil fuels, wind will never run out.
Turbines work almost anywhere in the world where it's reliably windy, unlike fossil-fuel deposits that are concentrated only in certain regions.
Unlike fossil-fueled power, wind energy operating costs are predictable years in advance.
Freedom from energy prices and political volatility of oil and gas supplies from other countries.
Wind energy prices will become increasingly competitive as fossil fuel prices rise and wind technology matures.
New jobs in construction, operation, and manufacture of turbines.
High up-front cost (just as for large nuclear or fossil-fueled plants).
Economic subsidies needed to make wind energy viable (though other power forms are subsidised too, either economically or because they don't pay the economic and social cost of the pollution they make).
Extra cost and complexity of balancing variable wind power with other forms of power.
Extra cost of upgrading the power grid and transmission lines, though the whole system often benefits.
Variable output—though that problem is reduced by operating wind farms in different areas and (in the case of Europe) using interconnectors between neighboring countries.
Large overall land take—though at least 95 percent of wind farm land can still be used for farming, and offshore turbines can be built at sea.
Can't supply 100 percent of a country's power all year round, the way fossil fuels, nuclear, hydroelectric, and biomass power can.
Loss of jobs for people working in mining and drilling.
But what if the wind doesn't blow?
Some people worry that because wind is very variable, we might suddenly lose all our electricity and find
ourselves plunged into a "blackout" (a major power outage) if we rely on it too much.
The reality of wind is quite different. "Variable" does not mean unreliable or unpredictable. Wherever you live, your power comes from a complex grid (network) of intricately interconnected power-generating units (ranging from giant power plants to individual wind turbines). Utility companies are highly adept at balancing power generated in many different places, in many different ways, to match the load (the total power demand) as it varies from hour to hour and day to day. The power from any one wind turbine will fluctuate as the wind rises and falls, but the total power produced by thousands of turbines, widely dispersed across an entire country, is much more regular and predictable. For a country like the UK, it's pretty much always windy somewhere. As Graham Sinden of Oxford University's Environmental Change Institute has shown, low wind speeds affect more than half the country for only 10 percent of the time; for 60 percent of the time, only 20 percent of the UK suffers from low wind speeds; and only for one hour per year is 90 percent of the UK suffering low speeds (Sinden 2007, figure 7). In other words, having many wind turbines spread across many different places guarantees a reasonably steady supply of wind energy virtually all year round.
Photo: One way to overcome some of the drawbacks of wind turbines is to site them out at sea where they take up less room and generate more energy. This is Block Island Wind Farm, the first offshore farm in the United States, near Rhode Island.
Photo by Dennis Schroeder courtesy of NREL.
While it's true that you might need 1000 wind turbines to produce as much power as a giant coal or nuclear plant, it's also true that if a single wind turbine fails or stops turning, it causes only 1/1000th (0.1 percent) of the disruption you get when a coal or nuclear plant fails or goes offline for maintenance
more often than you might think). It's also worth bearing in mind that wind is relatively predictable several days in advance so it's easy for power planners to take account of its variability as they figure out how to make enough power to meet expected demands.
Opponents of wind power have even suggested that it might be counter-productive, because we'd need to build extra backup coal, nuclear, biomass, or hydro plants (or some way of storing wind-generated electricity) for those times when there's not enough wind blowing. That would certainly be true if we made all our energy from one, single mega-sized wind turbine—but we don't! In reality, even countries that have large supplies of wind energy have plenty of other sources of power too; as long as wind power is making less than half of a country's total energy, the variability of the wind is not a problem. (Denmark, for example, makes 20 percent of its electricity—and meets 43 percent of its peak load—with wind; Eric Martinot's article
"How is Denmark Integrating and Balancing Renewable Energy Today?" [PDF] gives an excellent overview of how that country has managed to integrate huge amounts of wind power into its grid.) In practice, every country's electricity has always come from a mixture of different energy sources, and the ideal mix varies from one country to another for geographical, practical,
and political reasons.
How can we store the power of the wind?
Wind could play a bigger part in the future if we could find cost-effective ways of storing electricity produced
on windy days for times when there's little or no wind to harvest. One tried and tested possibility is pumped storage: low-price electricity is used to pump huge amounts of water up a mountain to a high-level lake, ready to be drained back down the mountain, through a hydroelectric turbine, at times of high demand when the electricity is more valuable. (In effect, we store electricity as gravitational potential energy, which we can do indefinitely, and turn it back to electricity when it suits us.)
Photo: How pumped storage works: When there's lots of cheap electricity about (at night or when the wind is blowing), water is pumped up the mountain to the high-level lake at low cost. When electricity is more expensive and valuable (in the day, at peak times), the water drains from the high lake to the low one, powering a hydroelectric turbine.
Batteries could also be a contender—if we had enough of them. There have been suggestions about using a fleet of electric cars as a giant collective battery, for exactly this purpose, but even large-scale batteries hooked up to individual wind farms could be very helpful. Statoil, for example, plans to install a huge wind-powered battery called BatWind in Scotland. Flywheels (heavy, low-friction wheels that store energy as they spin) are another possibility.
Is wind the energy of the future?
It certainly has a part to play, but how big a part depends on where in the world you are and whether there are better alternatives suited to your local geography. In sunny Australia, for example, solar would probably be cheaper.
In countries that have windy winters (when electricity demand is at its highest), wind turbines could be a
strong contender; on August 11, 2016, for example, wind turbines in (windy) Scotland produced
enough energy to power the whole country,
while in May 2021, wind energy provided
almost two thirds of Britain's entire electricity.
Countries with lots of fossil-fueled plants and no plans to retire them soon might find investments in carbon capture and storage (scrubbing the carbon dioxide from the emissions of coal and other fossil plants) a wise option, though that remains a largely unproven technology. Ultimately, it's a political choice as well as a scientific one. In Germany, where people have strong opposition to nuclear power, there have been huge investments in wind energy. Denmark, another European country, plans to move to 100 percent renewable energy with a massive commitment to wind. Although China is investing heavily in wind power, it still makes about
of its electricity from coal. In short, while the growth of wind power is impressive, it still plays a relatively small part, overall, in providing the world's electricity.
Which countries have most wind power?
It's no surprise to find the biggest countries (China, the United States, and India among them) topping the list of countries with the most installed wind capacity, measured in gigawatts. But if we measure installed capacity per capita, we get this very different chart. Now European countries such as Denmark, Sweden, Ireland, and Germany lead the pack, the United States is 13th, the UK isn't much better, China manages only 16th place, and India (not even on the chart) comes in at number 33.
Chart: Wind energy per capita (top-20 countries).
Drawn by Explainthatstuff.com using 2021 wind capacity data courtesy of [PDF] Renewable Capacity Statistics 2021, International Renewable Energy Agency (IRENA), Abu Dhabi, 2021, and 2020 population data compiled by the
These are the most recent publicly available datasets available at the time this article was last updated in January 2022.
If you're interested in how things have moved on, compare this chart with the one I drew a few years ago using
courtesy of the Global Wind Energy Council and World Bank.
I think another interesting thing about this chart is not how much wind energy we're making, but perhaps how
little. Most countries here are making about 300–400 watts of power for each person, which
is fine as long we don't all want our 300–400 watts at exactly the same time. But think for a moment how much power you use—a kettle,
vacuum cleaner can easily gobble over 2000 watts, for example—and you'll see just how much more renewable energy needs to grow to provide anything like the power we all need.
Photo: Micro power to the people! This small, mast-mounted Rutland Windcharger is designed to trickle-charge 12V and 24V batteries, such as those used in small boats, far from the grid. At a wind speed of 40–55 km/h (20–30 knots), it will produce a handsome 140–240 watts of power. At 20 km/h (10 knots), it produces a rather more modest 27 watts.
If small is beautiful, micro-wind turbines—tiny
power generators of about 50–150 W capacity, perched on a roof or mast—should be the most attractive
form of renewable energy by far. They're certainly very widely used for all kinds of portable
power, typically for recharging batteries in things like yachts and canal boats,
and for powering temporary traffic lights and road signs.
Some manufacturers have pushed micro-wind technology aggressively, hinting that people
could make big savings on electricity bills, and benefit the environment,
by putting a little turbine on their roof to feed energy into the national power grid.
The reality is a bit different: micro-turbines linked to the grid do indeed bring economic and
environmental benefits if they're sited in reliably windy areas, but
they're less helpful in towns and cities where buildings
make "energy harvesting" more of a challenge and there's much more turbulence from obstructions.
So are micro-wind turbines really worth the investment? How do they compare with their big brothers?
How micro-wind turbines compare
These figures are simply designed to give a rough comparison of the differences between
large-scale and micro-wind turbines. Bear in mind that there's a huge variety of micro-turbines.
Tower roughly 80–100m (260–344ft) high.
Roof, or mast typically ~10m (30ft) high.
Up to 90m (300ft).
1–8 megawatts (1000–8000 kilowatts).
50–40,000 watts (0.05–40 kilowatts).
Operates in wind speeds
10–55mph (16–90 km/h).
10–40mph (16–64 km/h).
$1–2 million per MW.
Provides power to
1 home (or single site).
How to set up your own micro-wind turbine
If you want to build your own micro-wind turbine, what do you need?
The first thing to bear in mind is that small wind turbines spin
at dangerously high speeds, so technical skill and safety are paramount: ideally, get your turbine
installed by a professional. Apart from the turbine itself, you also typically need a piece
of electrical equipment called an inverter (which converts the
direct-current electricity produced by the turbine's generator into
alternating current you can use in your home) and appropriate
electrical cabling. Your turbine will also need either a connection
into the grid supply or batteries to store the energy it produces.
Photo: Although micro-wind turbines on homes have proved controversial, they definitely have their place. Here's the Rutland Windcharger from our top photo helping to charge the batteries in a go-anywhere, portable highway construction sign. It's getting help from the large flat solar panel mounted on top. This is a great example of how micro-wind turbines can be useful if you put them in the right place, at the right time.
Aside from the equipment, here are a few pointers worth bearing in mind:
The best place to start is with a professional assessment of
your site's wind potential, which involves a series of measurements
with an anemometer. Remember that wind turbines generally work far better in
open, rural areas than mounted on rooftops in cities.
Don't assume it will automatically be windy enough to make
the investment in a microturbine worthwhile: a recent UK study of
microturbines by Encraft found a mixed picture, with good
performance from the best-located turbines and the very worst
performing model (embarrassingly) not even producing enough
electricity to power its own electronics—in other words, using more
electricity overall than it produced. Some contribution to the environment!
Depending on where you live, you will almost certainly need
planning consent for a wind turbine, so check that out carefully with your
local authority first.
Sound out your neighbors before you start spending any money:
instead of turning your "local friends" into bitter enemies with your rooftop propeller, maybe you could persuade them to join you in a community green-energy venture?
Remember that roof-mounted wind turbines could prove noisy
and cause problems with vibration.
Don't forget that there are all kinds of other energy
technologies that might give a quicker and better return on your
investment and make more difference to the planet. Energy efficiency
measures (such as improved heat insulation) generally give the
quickest payback for least cost and make the most difference in the
short-term, and solar hot water systems work very well
almost anywhere. Ground-source heat pumps are also worth a look.
For useful comments and suggestions on this article, I'm extremely grateful to Dr John Twidell (author, with Tony Weir, of the
excellent Renewable Energy Resources);
Robert Norris of RenewableUK; and Robert Preus of NREL. Needless to say, any errors and inaccuracies are entirely my responsibility.
This article uses a number of wonderful photos and artworks sourced from NREL and elsewhere—and I'm very grateful to the photographers and artists.
Little Limit to the Amount of Wind Energy by Dave Levitan. IEEE Spectrum, September 2012. How much wind energy is there on Earth? Is there an upper limit? How much of humankind's energy could we really make from the wind?
Three steps to build a wind farm by David Shukman. BBC News, 15 August 2011. How do you build an offshore wind farm? This great interactive feature from the BBC explains all you need to know.
Renewable Energy Resources by John Twidell and Tony Weir. Routledge, 2015. Covers all kinds of renewable energy. Chapters 7 and 8 focus on wind.
Wind Power Myths Debunked by Michael Milligan et al, IEEE Power & Energy Magazine, November/December 2009. A clear, easy-to-understand explanation of how wind power can be integrated into a grid network.
Wind: Physicist David MacKay looks at how much of a contribution wind power can realistically make to the UK's total energy needs in his book Sustainable Energy Without the Hot Air, 2009.
[PDF] Society's Cost of Electricity by Siemens Wind Power, 2014. A detailed comparison of wind and other forms of power generation, which attempts to take into account the full range of their costs and benefits (not just simple economic costs). [Archived via the Wayback Machine]
Flickr: Wind turbines: Some Flickr photos are published under Creative Commons licences (allowing limited reuse under certain conditions); others are copyright images.
Inside a wind turbine: A fascinating seven-minute tour of a turbine at Crystal Rig Wind Farm in Scotland by Fred Olsen Renewables.
A reality check on renewables by Professor Sir David MacKay, YouTube, June 26, 2013. An eloquent introduction to renewable energy: if you want to use solar or wind, you need an awful lot of it to make any difference, and you can expect it to take up a vast land area. Wind is discussed at
8m 6s, where David concludes that if the UK wanted to produce all its energy from wind, it would need to cover half the country with wind farms.
↑ Estimates like this are obviously very rough, because
homes use different amounts of electricity and the electrical energy a single wind turbine makes can vary.
But if we average over many homes and study the output of turbines over a long period, we can come up with
a reasonable figure. I take this particular estimate from the British green energy company Ecotricity in a 2013 web page titled
Where Our Numbers Come From [Archived via the Wayback Machine,
retrieved in January 2022]. This calculates that a 2.3MW turbine can supply about 1,345 homes based on a
capacity factor (effectively, how much of the time the turbine is working at maximum capacity) of 27.7 percent. Offshore wind farms now achieve much higher capacity factors than this, though it's still a decent figure for onshore wind (see note 3 below).
↑ The "capacity factor" of wind farms varies quite a bit, but
30–50 percent is a decent, working range. A blog called Energy Numbers suggests that typical UK offshore farms vary between about 33 percent and 50 percent for 2021. For the United States, Walt Musial of NREL quotes [PDF] capacity factors of 40–50 percent for offshore wind in a document dated March 2018. The capacity factor for onshore wind farms is significantly lower.
For 2021, RenewableUK quotes
UK government figures of 26.46 percent for onshore wind farms and 39.94 percent for offshore.
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