High-altitude wind power

September 24, 2012 11:08 PM

In honor of the opening of Shepherds Flat Wind Farm in Oregon this week, the largest wind farm in the United States, let's take look at 'high-altitude wind power', HAWP:

A recent Nature analysis of potential wind power found that wind turbines placed on Earth's surface could extract kinetic energy at a rate of at least 400 TW, whereas high-altitude wind power could extract more than 1,800 TW. At these rates there would be pronounced climate impacts, but since the world currently uses 18 TW, effectively unlimited.

Accessing HAWP wind is pretty tricky but a number of start-ups are trying. They say it's cheaper and easier to deploy than ground wind technology. The technologies are all different but have the same premise, something like a kite or blimp in the air tethered to the ground.

* Makani Power (California) is the furthest along to deployment with $20 million backing from Google and ARPA. Makani hopes to build a 92-foot ridged wingspan rated at 600 kilowatts (150 households) (video), but in the future they want to build a 5-megawatt version with a 213-foot wingspan for offshore.

*Ampyx PowerPlane (Netherlands) is also close to deployment. The kite pulls on the tether on the ground which rotates a turbine. They expect to be operational within a few years.

*Magenn Power (California), a helium-filled, blimp-like structure floats 1,000 feet up and the entire balloon spins as the wind blows. It has undergone successful test flights.

*Altaeros (Boston), another a helium-filled device but it basically lifts a standard turbine into the air (video).

*WindLift (California), a soft-wing kite design noted for ease of transport and quick set-up for use in temporary situations (funding from U.S. Marine Corps).

*EnerKite (Germany), uses a similar system as the WindLift.

On the down side, without help from the government, these technologies could take 20 years or more to overcome reliability problems in large scale operation. It's estimated that a $100 million government program could bring that down to 5 years. All of the above fly within a few thousand feet of the ground, the HAWP Holy Grail is the Jet Stream 5 or 6 miles up.

[This post derived from Yale360]

posted by stbalbach (35 comments total)

Yes! I remember reading about this in Pournelle's A Step Further Out, and it was exciting even way back then. Thanks for this intriguing update on the state of the art, stalbach!

(Although out of all of them, only Altaeros looks anything like I imagined.)
posted by Kevin Street at 11:57 PM on September 24, 2012

I kinda like the Windstalk concept.
posted by the man of twists and turns at 12:56 AM on September 25, 2012 [2 favorites]

Cracking post, really like your links and the super cool blimp turbine thing - keeping an eye on this in the future.
posted by Cogentesque at 1:28 AM on September 25, 2012

This is fascinating, but it got me wondering: if energy is being taken out of the wind, the wind is less powerful further on. What effect would that have on local wind patterns, and by extension, on global climate?
posted by Petrot at 4:31 AM on September 25, 2012

Oh for flying fuck's sake, no.
posted by scruss at 4:40 AM on September 25, 2012

That wasn't directed at you, Petrot. It was directed at this fringe, perennially “alternative” gullible investor energy collection scheme.

Yes, wind turbines extract energy from the wind. But it can't extract all the energy from the rotor disc, otherwise flow would stop. If a rotor is about 100m in diameter, and the atmosphere is about 10-11km deep, you're extracting some of the energy from less than 1% of the height of the atmosphere, and that from a not particularly energetic bit of the atmosphere, too.

The oft-quoted paper is The influence of large-scale wind-power on global climate [PDF]. This note is a good intro and caveat to the paper.
posted by scruss at 4:55 AM on September 25, 2012 [1 favorite]

makani has a lot of videos on youtube...

also, see this minidocumentary by KQED on high altitude windpower
posted by ennui.bz at 6:20 AM on September 25, 2012

If its so great, why aren't airplanes wind-powered?
posted by blue_beetle at 6:45 AM on September 25, 2012 [2 favorites]

I've had dreams about giant, colorful kites filling the skies over a futuristic skyline, day and night, tethered to spires and towers...

...and now that's apparently how we're going to power our cities.

Goddamn, I love living in the future sometimes.
posted by Slap*Happy at 7:05 AM on September 25, 2012 [1 favorite]

I would also think that, at these altitudes, there would be less bird kill than with ground-mounted turbines. I hope so, at least.
posted by Danf at 7:46 AM on September 25, 2012 [1 favorite]

I don't like that the process for most of these is using a kite to pull on a cable, then wind the cable back up. That seems highly inefficiency - they're generating in bursts rather than continuous. And the power generation seems to be incredible low as well. Look at the chart on the bottom of this one's page.

Magenn Power Inc.

12 years ago we had already doubled the output of their blimp with a ground based generator. And current models are producing 5 times as much as they expect to peak at.

They also are either designed to move around a lot or have the potential to, which means each one needs significantly more space in order to keep from crashing in to each other, which means you can't pack them in as densely as a ground based generator.

High altitude wind power seems like a great idea, I just don't think any of these designs are it.
posted by LoudMusic at 8:06 AM on September 25, 2012

I've wondered what this would look like fully implemented. When you go to the beach, would your view of the ocean be blighted by a bunch of these hovering over the horizon? Or would they be farther out, where you can't see them?

Right now I spend a lot of time driving back and forth across Eastern Washington and Oregon, which in the past few years has seen an incredible increase in the number of wind farms. And everyone, when they first saw one of the modern white wind turbines, thought "Oh, how cool, and even kind of beautiful." But now that the landscape is cluttered up with hundreds and hundreds of them, they look ugly and menacing.
posted by HotToddy at 9:04 AM on September 25, 2012

blue_beetle: If its so great, why aren't airplanes wind-powered?

Apparently there was a problem with one of the early models.
posted by IAmBroom at 9:07 AM on September 25, 2012

HotToddy: I've wondered what this would look like fully implemented. When you go to the beach, would your view of the ocean be blighted by a bunch of these hovering over the horizon? Or would they be farther out, where you can't see them?

Right now I spend a lot of time driving back and forth across Eastern Washington and Oregon, which in the past few years has seen an incredible increase in the number of wind farms. And everyone, when they first saw one of the modern white wind turbines, thought "Oh, how cool, and even kind of beautiful." But now that the landscape is cluttered up with hundreds and hundreds of them, they look ugly and menacing.

I'll take wind turbines over oil rigs and on-shore oil derricks and pumps, any day.

Bonus: if the turbine spills some of its fuel and it washes ashore, I don't have to clean wind off my feet.
posted by IAmBroom at 9:09 AM on September 25, 2012 [1 favorite]

Danf: I would also think that, at these altitudes, there would be less bird kill than with ground-mounted turbines. I hope so, at least.

That's the GREAT part - with the balloon-as-wind-wheel model, there shouldn't be any significant risk to flying animals.
posted by IAmBroom at 9:13 AM on September 25, 2012

scruss: But it can't extract all the energy from the rotor disc, otherwise flow would stop.

So, if I'm following you, water wheel technology won't work, because you can never extract all the energy from the river?
posted by IAmBroom at 9:17 AM on September 25, 2012

HotToddy: "they look ugly and menacing."

Ever driven by a coal plant?
posted by the_artificer at 9:39 AM on September 25, 2012 [4 favorites]

But now that the landscape is cluttered up with hundreds and hundreds of them, they look ugly and menacing.

You should see what mountain removal for coal does to the landscape.

My only comment is as others have said, there is no choice, it's either this, or that. Pick your poison. I'll take wind over mercury poisoning. Seen that way, they are beautiful. Literal life savers, like Ronnie Reagan in his youth, heroic. Hardly menacing, just the opposite. All in the mind. Windmills are the symbol of our generation's break from the past, not unlike the steam engine a symbol of a break from the past of the horse and carriage. Sky-scrappers. Ugly! Cars took a while to be accepted on streets, cities banned them in certain areas. Etc. Nothing forever, one day we will have nuclear fussion or some other miracle energy source and the windmills come down and everything returns to how it was.
posted by stbalbach at 10:04 AM on September 25, 2012 [2 favorites]

> there would be less bird kill than with ground-mounted turbines

Well, there's still the cables that go vertically from the ground, and power cables off a lot of birds. Wind turbines killing lots of birds isn't really a thing, certainly not compared to cats, tall building and powerlines.
posted by scruss at 10:13 AM on September 25, 2012 [1 favorite]

I'll take wind turbines over oil rigs and on-shore oil derricks and pumps, any day.
Ever driven by a coal plant?
You should see what mountain removal for coal does to the landscape.

Yes, yes, I fully agree, other extraction technologies are ugly as well. What I'm saying is that at first, wind turbines seemed like they would look "clean" as well as being "clean," but they turn out to be nearly as ugly as anything else. And I'm wondering if HAWP will be an improvement, or just as bad.
posted by HotToddy at 10:22 AM on September 25, 2012

> So, if I'm following you, water wheel technology won't work, because you can never extract all the energy from the river?

You're not following me, no. If you remove all of the kinetic energy from the wind in a rotor disc, the wind stops (y'know, the old ½mv² thing; you can't make the m=0 'cos it's a constant, so the v has to be zero if all the KE has been removed). If the wind stops, the rotor stops. So there has to be a limit on the theoretical amount of energy that a rotor can take out of a wind stream, and this is defined by Betz' law.
posted by scruss at 10:34 AM on September 25, 2012 [1 favorite]

The Makani kite design is really intense. It's much more like an airplane than a kite; the propeller running in reverse is how it extracts its power, so it's continuous and it's also usable as a power source. Take a look at the second presentation page to see how each kite takes off and lands like a VTOL aircraft. In case it needs maintenance or there's a storm, the thing lands itself gently on its ground station. That blows my mind every time. Another video, this one of a real live kite. This is an essential feature because their target deployments have hundreds of kites, too many to have a manual process for putting them up or bringing them down. So rad!
posted by breath at 10:55 AM on September 25, 2012

Petrot: "This is fascinating, but it got me wondering: if energy is being taken out of the wind, the wind is less powerful further on."

Other human structures (for example, cities) also absorb and/or redirect wind energy and make it less powerful further on, but no one asks "what about the effect on wind?" when people builds buildings or plants trees (while the question does come up in other discussions of wind turbines). It's interesting how we become more aware of the energy being "taken" when that energy is actually used constructively instead of silently wasted.

My own naive intuition is that, since the atmosphere is so many kilometers deep, adding some resistance just at or near the bottom of it won't have very noticeable effects on the overall flow of energy. It seems like asking whether gravel on the ocean floor would change global ocean currents.

The Nature Climate Change paper linked in the original post talks about the global climate effects of very large scale wind power extraction, using actual models. They estimate that wind turbines to supply 100% of current world power demand would be "unlikely to substantially affect the Earth’s climate" although they would have measurable effects:

We find that civilization-scale reliance on wind power, if uniformly distributed, might change zonal mean temperature by ~ 0.1 K and zonal mean precipitation by ~ 1%. Consistent with previous literature, we find that large-scale near-surface KEE [kinetic energy extraction] has a small surface warming effect, whereas whole-atmosphere KEE has a cooling effect. In both cases we observe a decrease in global average precipitation.

posted by mbrubeck at 11:09 AM on September 25, 2012 [1 favorite]

scruss: "If you remove all of the kinetic energy from the wind in a rotor disc, the wind stops. If the wind stops, the rotor stops"

Sure, but doesn't the Nature paper acknowledge that right in its first paragraph? "However, in the limit of infinite drag, the atmosphere is motionless and there is no kinetic energy to extract."
posted by mbrubeck at 11:19 AM on September 25, 2012

The Makani kite design is really intense.

Looks very cold war.. It is the only one I skipped on first look at this post, but it is actually really interesting!

It's much more like an airplane than a kite; the propeller running in reverse is how it extracts its power, so it's continuous and it's also usable as a power source.

The props would be next to useless as generators at normal wind speeds. But in this design the wing surface area is used to accelerate the airplane into high speed circles, thus increasing the wind velocity across the props, which allows the small props to generate useful power. At least I assume that's what I'm seeing. Very nice.

I'd like to see the video of the tether breaking. This design might even be able to recover gracefully. It is moving very fast toward the ground for part of the circle though, so maybe not :)
posted by Chuckles at 11:28 AM on September 25, 2012

Yes, yes, I fully agree, other extraction technologies are ugly as well. What I'm saying is that at first, wind turbines seemed like they would look "clean" as well as being "clean," but they turn out to be nearly as ugly as anything else. And I'm wondering if HAWP will be an improvement, or just as bad.

The launch vehicles should have minor visual impact; about as much as a plane flying over head. The tethers will be hard to see especially against sky. The launch platforms will be more like oil rigs. They could minimise even that impact by building the platforms behind berms of some sort or by taking advantage of the lee of ridge lines in land that isn't pancake flat. Or even a row of trees. One of the disadvantages is the launch platforms are going to take up a lot more land than a ground based windmill tower. And it seems unlikely we'll ever see tethered power generation in populated areas; the risk of something catastrophic happening with the tether and having the tethered object crash to the ground would make that a non starter.
posted by Mitheral at 12:23 PM on September 25, 2012

> The tethers will be hard to see especially against sky.

The FAA will have something to say about that. If I have to bloody light my wind turbines, these things have to be lit up like christmas trees.
posted by scruss at 12:27 PM on September 25, 2012

> Sure, but doesn't the Nature paper acknowledge that right in its first paragraph?

No, that refers to the kinetic energy in the whole atmosphere. I was referring to the flow within the turbine.
posted by scruss at 12:30 PM on September 25, 2012

at first, wind turbines seemed like they would look "clean" as well as being "clean," but they turn out to be nearly as ugly as anything else

Speak for yourself. I'd take a view of a bunch of wind turbines -- which are artificial but ultimately, innocuous (unless you're a bird) -- over a view of a coal power plant, which is a constant visual reminder of the poisonous, climate-changing, and mildly radioactive waste products it's belching, and the nonrenewable fossil fuels it's consuming. The two don't seem equal at all.

I think the only reason there's any significant opposition to wind power at all is because it's being put in the view of rich folks, and in particular off the shores that are taken up exclusively by their vacation palaces, while coal power plants are typically located in the poorest parts of town (and the biggest ones are in "flyover" states anyway).
posted by Kadin2048 at 12:48 PM on September 25, 2012 [1 favorite]

People fly planes that run on wind all the time.

There are plenty of birds at 2000' AGL: hawks, buzzards, swifts, and so on. I've seen them at 6,000'.

The FAA would likely create areas of restricted airspace to accommodate power generation tethers, just like they do for tethered balloons and so forth. See the map excerpted in this article. I'd regret losing the sections of sky, but I'm still all for it.

I think the rows of wind turbines on the Pennsylvania ridges are beautiful---certainly more beautiful than a stripped mountaintop or the natural gas well flares that dot the hills around here.
posted by tss at 4:59 PM on September 25, 2012

What I'm saying is that at first, wind turbines seemed like they would look "clean" as well as being "clean," but they turn out to be nearly as ugly as anything else.

wat?

OK, look. There's a power plant in Sommerset, MA, right at the apex of beautiful Narragansett Bay. Coal. It was pure 1960's utilitarianism, a large, corrugated tin building, painted industrial pale green. It was murdering the fish spawn at a very sensitive part of the bay with the hot-water output from cooling the turbines, and that was causing some important fisheries to crash. The correct course of action would be to modernize the turbines. No, the power company said, "Everyone? Everyone? Can we have your attention? OK. We would just like to say, FUCK. YOU."

So, not only do we have the grandfathered-in smoke stack emitting smog, now we have two gigantic cooling towers, I mean Three Mile Island nuke-you-lar big cooling towers. They dwarf anything else on the bay, and are visible from almost anywhere on the water, completely wrecking the view as they belch steam all day and flash ultra-bright warning strobes all night. You can see them from Newport. Ugly grey concrete monsters, sullen and ominous.

Now, there are some people who may take exception to the tall, silent and graceful white-winged wind turbines on aesthetic value...

...and after the cooling tower debacle, they may now go take a hike.
posted by Slap*Happy at 9:05 PM on September 25, 2012 [3 favorites]

scruss: > So, if I'm following you, water wheel technology won't work, because you can never extract all the energy from the river?

You're not following me, no. If you remove all of the kinetic energy from the wind in a rotor disc, the wind stops (y'know, the old ½mv² thing; you can't make the m=0 'cos it's a constant, so the v has to be zero if all the KE has been removed). If the wind stops, the rotor stops. So there has to be a limit on the theoretical amount of energy that a rotor can take out of a wind stream, and this is defined by Betz' law.

And you're not distinguishing this in any way from waterpower. In both cases, there is a limit to how much energy may be extracted, and, yes, they both follow Betz' Law (which deals with a "fluid", BTW - both water and air are fluids in this context).

But this is simply a design consideration. We don't design engines so that they can just barely overcome static friction on a steep incline, even though (theoretically) the car could still accelerate from that point. And wind turbines will be designed with Betz' Law as an engineering guidance. So, I'm not sure what your point is. You might as well be saying, "There's a limit on how fast bearings can turn".
posted by IAmBroom at 1:16 PM on September 26, 2012

(Also, your link seems to be broken, so I redirected it to a Wikipedia site that works.)
posted by IAmBroom at 1:21 PM on September 26, 2012

I don't know what point you're trying to make, IAmBroom. I never even touched on your point about waterpower. I was responding to Petrot's question, and trying to explain that there was a relatively small amount of the atmosphere's total kinetic energy extracted by a wind turbine, so while there may be small, measurable, local effects, the macro effect is negligible.

(My link works fine; it's from the Windpower Guided Tour from the Danish Wind Industry Association. Maybe it's you? The Wikipedia link has some dubious stuff with possibly fake citations to support the article's claim that ducted turbines can operate above the Betz limit.)
posted by scruss at 6:14 PM on September 26, 2012

I suppose we're talking past each other then.
posted by IAmBroom at 11:10 AM on September 27, 2012