Any doubts I once had that wind was a constant thing – like the rising of the sun or the phases of the moon – were dashed one summer on a bicycle. After graduating from university (for the first time) I packed my bike with camping gear and headed west from Toronto. My destination was the West Coast, 3,000 miles (5,000 kilometres) away. To get there, I had to cross the great Canadian Prairies. Under that vast Prairie sky, I pedaled furiously, against tire wind, hour after hour, day after day. It never let up. It would start each morning around 8:30, and be my constant and unwanted companion until early evening. The odd cyclist coming the other way would just fly past, invariably yelling gleefully, “You’re going the wrong way!”
What is the wind, and what makes it so relentless?
We’ve all looked up at the sky and been transfixed by how immense it is – particularly in the Prairies, where clouds dot the sky from one horizon to another, and the majesty of the blue expanse above takes your breath away. Climb a decent-sized mountain, though, and things change – after a few days of climbing, the sky looks darker, as the layer of air that scatters the blue part of the sun’s light starts to thin. The sun starts to appear more white than yellow. Breathing gets harder
Similarly, while the atmosphere looks immense from the ground, from space it’s a different matter. Former shuttle astronaut Vice-Admiral (ret.) Richard Truly, commander of NASA’s Naval Space Command, explains it like this: “When you look at the Earth’s horizon, you see an incredibly beautiful, but very, very thin line. You can see a tiny rainbow of color. That thin line is our atmosphere. And the real fragility of our atmosphere is that there is so little of it.”1
Our atmosphere is a tiny sliver of gas, as thin as a bit of plastic wrapped tightly around a beach ball. Almost all of the atmosphere’s mass sits less than 10 miles (16 kilometres) from the ground. Created by life that happened long before us, it acts like a blanket, trapping the sun’s heat. It’s the atmosphere that makes our sky blue and sun yellow.2
The fact that air actually has mass – that it weighs something – may seem odd. I recall a science teacher telling his very dubious students that a full balloon weighs more than an empty one. “But they weigh the same,” we scorned, “They’re both empty, just shaped differently.” He was right, of course. When we pulled out the scales, the full balloon did weigh more. Thanks to gravity, that thin rainbow of color sticks to the planet – even though stray oxygen molecules are constantly flying off into space.
Razor-thin as it may be, there can be energy in that air when it moves – and lots of it. Friend to sailors on fine days and enemy on foul ones, bane of cyclists and boon to windsurfers, the winds blow, howl and gust. Hurricanes roar, and the jet streams high above us fly past at hundreds of miles an hour. Capturing all that energy can be a huge benefit to mankind.
Wind is really just transformed solar energy – the expansion and contraction of air that has been heated by the sun and then cooled. As gusty and haphazard as wind may appear, large-scale global movements of air currents over land and sea ensure that there are areas where it is quite constant.
Air heats and rises from the equator, shedding moisture as it heads north and south at high altitudes. As it gradually cools, it drops back down to the surface as very dry air. These planet-sized currents are what form deserts, cause trade winds and give us our global weather patterns – patterns that are pretty reliable. That up-across-and-down action at the equator is called a Hadley cell, and a similar process repeats itself two more times between equator and pole.
The planet’s spinning means that some of the pole-bound air at the top of the atmosphere shears off in one direction or another. This “Coriolis effect” is what gives us the trade winds, those highly regular currents sailors rely upon – and which almost broke my knees in the Prairies.
An exotic wind is the jet stream, a high altitude wind that goes fast enough to lengthen or shorten our jet journeys. Jet streams are highly regular, and have been measured at speeds greater than 400 miles per hour ( 640 kilometres per hour). They’re created where two atmospheric zones meet, about six to nine miles (10 to 15 kilometres) up in the subtropics, and about four miles (seven kilometres) up for the polar jet stream. The “troposphere” decreases in temperature with height, but above it is the “stratosphere,” where temperature increases with height. That temperature difference conspires with the Coriolis effect to create the fast-moving jet stream.
Any mass that moves has kinetic energy, compared to potential energy (like a ball ready to roll down a hill) or chemical energy (like a charged battery). The trick is to grab the kinetic energy in the air and convert it to another form – usually electricity.
Wind turbines all work pretty much the same way: The wind blows, creating enough force to spin a turbine, which in turn powers a generator. There are subtleties (see “Why Do All the Big Ones Look the Same?” lower down), of course, but that’s the thrust of it.
Wind energy has been captured by humans for thousands of years, not just for sailing, but also for grinding corn and wheat (hence windmill), and pumping water. The first practical windmills are thought to have appeared in Persia between 500 and 900 AD, and in northern Europe starting in the 12th century. Before the Industrial Revolution, there were more than 10,000 windmills dotting the British Isles. Throughout the Great Plains of America, windmills pumped water for irrigation, and for locomotives to produce steam on their early journeys across the continent.
Nowadays, wind is big business, and the energy captured is almost always used to create electricity. We’ve applied some of the same principles used to power modern aircraft to building the massive blades – some of which are as big as the wings of a jumbo jet – and these days, a single wind turbine can power a decent-sized town. Turbines three times taller than the Statue of Liberty are to be installed in the harsh conditions of the oceans, and small turbines that look like revolving sculptures are being installed in our urban environments.
Farms of windmills already pepper the landscape, and soon, massive stretches of these farms separated by huge distances will be connected by a supergrid, ensuring that when one region is calm, another can pick up the slack. Eventually, we’ll be able to tap the vast and constant energy resource that is the jet stream, with high altitude generators tethered to the ground miles below.
The fairly easy-to-get stuff can provide five times the total amount of electricity generated worldwide, 10 but if we want to get ambitious, the US Department of Energy reckons that wind could generate 15 times the total world energy use. That’s 15 times all the oil, coal, nuclear, electricity, whatever. The sky’s the limit! That’s not to say there aren’t pitfalls. Getting the power to where it’s needed, storing it so that the lights stay on when the wind doesn’t blow, even the protestations of those who don’t like the way turbines look – these are all obstacles to be overcome.
But even T. Boone Pickens, that irascible American oil magnate, is sold on wind. He has called the United States the “Saudi Arabia of wind.”
Let’s see what that visionary oilman is so excited about.
Denmark is an understated country, not big on grand monuments. One of the most popular tourist sites in the capital, Copenhagen, is a life-sized statue of a mermaid – not exactly showy. We could say the opposite about California. Hollywood, Los Angeles, San Francisco – glamour, color, glitz! Yet, these two unlikely partners ignited the explosion in wind power that continues today.
Back in the 1970s, when OPEC decided to hold the world to ransom by choking off oil supplies, little Denmark felt even more vulnerable than the rest of the world. That’s because the country imported nearly all of its energy. Those oil shocks, if they’d continued, would have brought the economy to its knees. In response, Denmark decided to develop wind power – big-time. In the meantime, half a world away in California, some of the most farsighted economic incentives were being put in place to encourage the generation of power from wind. Denmark made the turbines, and California installed them.
Since then, mainland Europe has taken the lead in wind generation, but the rest of the world is catching up fast. Large-scale wind power is the fastest growing energy source in the world, and 94 gigawatts of capacity was installed in 2007 – enough to replace 90 coal-fired plants or power almost 90 million homes. The current champion is Germany – it has over 20,000 turbines up and running, generating more than 7% of the country’s electricity. But the United States could soon overtake Germany – with Texas leading the pack.
And big industrial players like General Electric are getting into the game, putting considerable resources into developing wind-turbine technology.
The turbines themselves just keep getting bigger. Back in 1980, a decent-sized wind turbine stood 50 feet high (15 metres) and could generate enough power for a few homes. Clipper, a California-based company is now developing a turbine that will be rated somewhere between 7.5 and 10 megawatts- that’s 200 times more power than the older model, or enough to supply a decent-sized town – with a rotor diameter twice the wingspan of a jumbo jet. One large Clipper can provide enough electricity for more than 6,000 North American homes.11
Not to be outdone, the European Union is funding research into a 20-megawatt turbine that will stand almost three times the height of the Statue of Liberty – and they’re looking at ways to attach these turbines to the seabed or to floating platforms. They’re even working on “smart blades” that change their shape depending on the wind conditions.
Canada is contributing to the evolution of these massive machines. A Canadian company called WhalePower has come up with something called Tubercle Technology. The leading edge of its blades are modeled on – you guessed it – the flipper of a humpback whale, making movement through the air more efficient. The technology is sort of like the dimples on a golf ball, creating just the “right kind of turbulence” to minimize drag.
These big turbines are not normally installed one at a time, but in huge wind farms that extend to the horizon. Now that’s a power plant! These expansive farms can be found on land, on shallow coasts – and soon the deep sea.
Most of the world’s existing wind farms are on land. Obviously, that’s the easiest place to start, and it’s certainly the most cost-effective. The world’s largest wind farm (as of mid-2009) is the Horse Hollow Wind Energy Center in Texas, with more than 400 huge turbines rated between 1.5 and 2.3 megawatts, and covering 47,000 acres. Even this massive farm will soon be overtaken, and right in Texas.
A project big enough to power three million homes, 13 owned in part by Shell, will blow the Horse Hollow project away, and not only in size. It will try to solve the problem of what to do when the wind doesn’t blow, by using underground compressed air to store power and act as a kind of battery. Pump up the reservoir when it’s windy, and release the pressure to drive a turbine when it’s not.
How much wind is there on land? More than enough to power the US – “North Dakota alone is theoretically capable (if there was adequate transmission capacity) of producing enough wind-generated power to meet more than one-third of US electricity demand,” according to the American Wind Energy Association.14
T. Boone Pickens certainly views the American Great Plains as a resource ready to exploit, and he’s putting his money where his mouth is. The legendary oilman is gearing up to build wind farms all the way from the Texas panhandle to North Dakota, and figures we could generate one-fifth of the US electrical production for $1 trillion. 15 (Oh – and throw in another $200 billion to transmit that energy to where it’s needed most.)
Land may be the easiest place to put up a wind farm, but it’s open water that’s got the really good wind. Today, lots of wind farms sit in water shallow enough to attach the turbines right to the sea floor. It’s not hard to do – just drive a massive steel stake into the seabed and attach the turbine.
In the shallow harbor outside Copenhagen sits the Middelgrunden project, where 20 two-megawatt turbines, each more than 330 feet (100 metres) tall, stand in a gentle curve. They provide some serious competition for that understated little mermaid – they’re a tourist attraction in their own right. Generating enough power for 30,000 homes, they stand as a testament to Denmark’s early lead in big wind.
However, it’s the UK that’s emerging as the offshore champ, with a number of existing projects and more in the works. Any wonder for an island nation? The London Array in the Thames Estuary will be a 1,000-megawatt monster, generating enough power to feed 750,000 London homes. A slightly smaller farm has been approved for North Wales. Siemens expects Britain to account for half of the company’s worldwide offshore turbine sales. 16
If you’ve ever gone sailing, you’ll know that the wind on open water is far stronger than on land. Compare the winds in the Gulf of Maine, for instance, to those in the American Midwest, and you’ll find that they’re about one-third more powerful. That may not seem like much, but the extra bit more than doubles the amount of energy generated. University of Maine professor Habib Dagher calls it “the largest renewable resource that the US has.” And it’s a resource that’s crying out to be developed.
But turbines on the open water must be able to withstand the vagaries of the ocean: strong gales, massive ocean waves and swells, and saltwater spray. Not only is the sea hard on the turbines themselves, but the horrendous conditions make it all the harder to service them. Plus, there’s the added hurdle of getting all that power to land.
The potential payoff is huge, though, so that pretty much guarantees the engineering problems will be solved. Another incentive lies in the fact that almost 80% of the electricity in the US is consumed by people living along the coasts of the Atlantic, Pacific and Great Lakes. “With all due respect to North Dakota and South Dakota, which have also been labeled the Saudi Arabia of wind, people live along our coastlines,” 17 says Raymond Dackerman, general manager of Blue H, a Boston-based company.
Deep-sea test projects are underway in Norway, Denmark and France, and a full-scale wind farm is planned for 2013 in the North Sea. It will be a while before they’re commercially ready, though, so it looks like Mr. Pickens might win this race on land.
Ever wonder why all large turbines look similar? To be sure, there are almost as many types of turbines as there are cars – one blade, two blades, many blades that form a wheel, wild-looking vertical egg-beaters, and even lovely twirling statues that look like a jazz riff on the helix shape of our DNA (more on that in the next section). But the big ones – the massive turbines that make up the utility-scale wind farms – all look similar, with the same kind of blades, and nearly always three of them. Why? It’s all physics.
Intuitively, it seems like the wind pushes those blades around to generate power, but that’s not the case. Just like a puffed-out sail or the wing of a jet in flight, a different force is at play.
When a jet flies through the air, it uses lift – an upward force that counteracts gravity. That lift comes from something called Bernoulli’s principle,18 and it’s the same thing that turns the turbine blade, except the wind is slower and the blade is vertical. But it’s lift, or suction, that pulls the blade, just like the wing of a jet. That’s why the blades all look roughly the same – they’ve been designed to maximize lift and minimize drag (friction) of the blade passing through the air.
Sure, but why always three blades? It’s all a matter of efficiency.
To get the most energy out of the passing air, the rotating blades need to interact with as much of that air as possible. Lots of blades may seem more efficient, since there’s more surface area to interact with the wind. But as they rotate, they also interact with each other, by disturbing the airflow. That’s a bad thing. So, how about fewer blades? They’d have to rotate faster to interact with all the passing air, creating too much drag. It’s a balance: The blades have to turn fast enough to interact with all the air, slow enough that drag isn’t an issue, and with few enough of them to ensure they don’t interact with each other. It turns out that three blades is pretty much optimal.
There are other shapes and ideas for different purposes, of course. One novel idea was created by a German company: SkySails, a great big sail that’s attached to an ocean-going freighter. It helps to pull the boat, and can reduce fuel use by 10% to 35%, according to the company. 19
As puzzling as it seems, some people just don’t find wind turbines beautiful. Though most of our industrial trappings – vehicles, roads, factories, telephone poles – aren’t exactly easy on the eyes, wind is often singled out for aesthetic criticism. One solution is to plant wind farms away from urban areas or in the open sea.
Another solution is to make them smaller and more beautiful, designed to integrate right into coastal, mountainous or urban environments.
Micro-wind designs are normally used to provide power in remote locations. They differ only from their larger counterparts in size. Helix Wind has added a twist – literally. Helix, based in San Diego, California, started with a vertical design. The spinning part extends straight upward from a vertical shaft. Vertical designs have been around for a while, and there are advantages: They spin equally well whatever the wind direction, and they stand up to much stronger gusts than their larger, horizontal cousins.
Helix’s breakthrough is to develop a visually stunning design, made from an aluminum alloy, that looks like a pulsing piece of modern art. CEO Ian Gardner says: “Why do early-stage technologists become enamored with engineering and forget the aesthetics? The people buying and using their inventions care about what it looks like and how their neighbors might react.”
Based on a double-helix shape similar to our DNA, and producing enough power for several homes, Helix’s turbines are designed to please the eye. Also used in isolated environments (like cell towers or remote facilities), they are meant to integrate into the modern urban landscape. The first Helix installation, by the side of a highway in urban California, is often mistaken for art.
It is art, of course. It just happens to make electricity, too.
Where might wind power go from here? While some companies are eyeing the deep oceans, others are looking up – waaay up.
The jet stream never stops. Based on the Earth’s rotation and some basic atmospheric physics, you can count on it day or night, summer or winter. The problem, of course, is the height. The jet stream sits somewhere between 20,000 and 40,000 feet (6,000 and 12,000 metres) up, running east in the northern hemisphere, at speeds that average from 125 to 160 miles per hour (200 to 260 kilometres per hour).
Mining the jet stream could deliver enormous amounts of power. According to atmospheric scientist Ken Caldeira, at the Carnegie Institution’s Department of Global Ecology at Stanford University, “My calculations show that if we could just tap into 1% of the energy in high-altitude winds, it would be enough to power all civilization. The whole planet.” We’re hunting really big game here. So who’s on the prowl?
An American company called Sky WindPower has developed functional prototypes designed to fly in the jet stream, generate power and send it back to Earth through the cables to which they are tethered. Since these sky-high turbines are portable, they can be packed up and moved when the jet stream shifts around, as it sometimes does.
The folks at Sky WindPower reckon that if these high-flying turbines were deployed en masse, they could generate power at two cents per kilowatt hour – that’s way less than coal. Time Magazine thinks enough of the company’s take on things that it recently named the company’s flying electric generator as one of the top 50 inventions of 2008.
This isn’t pie-in-the-sky stuff – it’s real, it’s possible, it’s large-scale, and it’s on the way.
A slightly less lofty vision comes from a Canadian company called Magenn. Its vision is to enable small-scale, reliable generation by using a helium balloon to get a small turbine up above the unstable winds found at lower heights. They’re simple but effective, particularly for areas where the good winds are found above surrounding treetops or buildings. Hoist the balloon and turn the switch!
We’ve seen the potential of wind. There’s enough harvestable wind out there to provide five times the world’s electrical consumption. And that’s without any of the futuristic stuff, like mining the jet stream, which I’ll ignore for now.
As you might suspect, it’s not quite that easy. Sometimes, the wind doesn’t blow, and it’s often far from the cities where it’s needed. The distance issue is simple: Build a big grid. The intermittency problem is a bit harder to solve. When we flip a light switch, we want the light to come on, regardless of whether the wind is blowing. It’s that simple.
Generally speaking, if the proportion of wind is less than 20% of the total electrical supply, it’s not much of a problem. Only Denmark is close to reaching that point; even Germany and Britain have a long way to go. The US is at around 1 %, as is the rest of world. So there is lots of wind yet to harvest, without any fancy tricks.
And as far as fancy tricks go, there are really just two. First trick: Store the energy. One way to do that is with giant storage – like the compressed air concept they’re going to use in Texas – or hydrostorage. Hydrostorage means using wind power to pump water up a hill into a giant reservoir, then using that water for hydroelectricity when the wind stops. There’s another way. When the Energy Internet arrives, storage could take place in millions of small batteries – like the ones that will run our electric cars. They could store energy when they’re not being used, but that story will have to wait until The Energy Internet page.
Second trick: Connect lots of wind farms (and other renewable sources) from faraway places to the same grid. When one place is calm, another is windy. Studies from the University of Kassel in Germany show that so called large-scale grid balancing can increase the percentage of wind’s contribution in Europe to 70%.20 A similar figure could probably be reached in the United States.
What’s the potential of wind? Easily 20% of our energy needs, and probably more like 40%, with storage and grid balancing. How fast can we get to 40%? We’d need to install around 1.5 million two-megawatt turbines over the next 10 years or so.21 That’s a massive job, but as Lester Brown of the Earth Policy Institute says: “We build 65 million cars every year, so it’s not a big deal. We could produce these wind turbines for the entire world simply by opening the closed automobile assembly plants in the United States.”22