From the Carnegie Institution , some lofty ideas. Would you imagine a steady energy supply coming from high altitude kites?
Enough wind to power global energy demand
Washington, D.C.— There is enough energy available in winds to meet all of the world’s demand. Atmospheric turbines that convert steadier and faster high-altitude winds into energy could generate even more power than ground- and ocean-based units. New research from Carnegie’s Ken Caldeira examines the limits of the amount of power that could be harvested from winds, as well as the effects high-altitude wind power could have on the climate as a whole. Their work is published September 9 by Nature Climate Change.
Led by Kate Marvel of Lawrence Livermore National Laboratory, who began this research at Carnegie, the team used models to quantify the amount of power that could be generated from both surface and atmospheric winds. Surface winds were defined as those that can be accessed by turbines supported by towers on land or rising out of the sea. High-altitude winds were defined as those that can be accessed by technology merging turbines and kites. The study looked only at the geophysical limitations of these techniques, not technical or economic factors.
Turbines create drag, or resistance, which removes momentum from the winds and tends to slow them. As the number of wind turbines increase, the amount of energy that is extracted increases. But at some point, the winds would be slowed so much that adding more turbines will not generate more electricity. This study focused on finding the point at which energy extraction is highest.
Using models, the team was able to determine that more than 400 terrawatts of power could be extracted from surface winds and more than 1,800 terrawatts could be generated by winds extracted throughout the atmosphere.
Today, civilization uses about 18 TW of power. Near-surface winds could provide more than 20 times today’s global power demand and wind turbines on kites could potentially capture 100 times the current global power demand.
At maximum levels of power extraction, there would be substantial climate effects to wind harvesting. But the study found that the climate effects of extracting wind energy at the level of current global demand would be small, as long as the turbines were spread out and not clustered in just a few regions. At the level of global energy demand, wind turbines might affect surface temperatures by about 0.1 degree Celsius and affect precipitation by about 1%. Overall, the environmental impacts would not be substantial.
“Looking at the big picture, it is more likely that economic, technological or political factors will determine the growth of wind power around the world, rather than geophysical limitations,” Caldeira said.
Here is a question that no one seems to have ever considered.
The green power activists are all very concerned about CO2 and man’s potential impact on climate.
But what about the potential impact on climate of “green energy” removing so much energy from the climate system?
If we were to truly able to meet our global electrical power needs by wind power and solar power, would this not result in a great deal of energy being removed from the climate system when it is converted instead to electricity?
How important is the role that wind energy plays in the climate system and what impact will removing a large amount of this energy from the climate system?
Also if a large amount of solar energy, which is constantly needed to keep the planet from becoming a cold rock, is converted to electricity instead of heat, and on the scale required, what will happen to the average global temperature?
There seems to be some unstated assumption that solar and wind energy is infinite and removing a large chunk of this energy will have no impact on climate.
Are the green energy activists courting doom for our climate? I do not think their plan is well thought out nor do I think that they understand the climate system well enough to be able to make informed conclusions on these questions.
Regarding SasjaL says: September 10, 2012 at 9:19 am
Check out the definition of satire when the fluids drain out and the internet is up again.
I’m quite astounded by the lack of any intellectual rigor in nearly all the 97 comments I have read so far: willful misreading of the article, simplistic objections, and willful lack of imagination in overcoming them. Only one comment gives a sensible appraisal of what is eminently achievable for producing a proportion, however small of our energy needs. Not one comment has acknowledged what we all know- that if the wind drops, the kite can be reeled in and the speed of that reeling in can ensure its maintaining altitude until it rests on its base. No tangling, crashing into power lines or demolishing buildings. What’s more, being anti warmist doesn’t preclude a desire for pollution-free energy. For this reason, the posting of this article is off-topic with regard to challenging the warmist agenda.
@ur momisugly Scute: Do you have any specific objections to any of the criticisms posted here or just one long ad hom against everyone who posted? I take it also that you will be out lobbying for nuclear power today, since you are so keen on non-polluting energy sources?
Scute says:
September 10, 2012 at 11:17 am
“Not one comment has acknowledged what we all know- that if the wind drops, the kite can be reeled in and the speed of that reeling in can ensure its maintaining altitude until it rests on its base.”
So how far in advance of the squall line do we need to start “safely” reeling in the kites? I see a massive fail during the first bad weather event…
(p.s. For testing purposes, let’s station those kites over your house or place of business…)
First: They used models.
Second: They were not bound by normal rules of physics.
Third: What they propose is pure optimism.
I was trying to decipher where the solutions to the significant technical challenges to this solution are defined. Finally it dawned on me, this is an article out of “Popular Mechanics” and gussied up by imaginary assumptions about just how much power might be possible from a column of air.
Another fantasy for the big AR5 and the future of climate funds.
Other than being a nasty and accusing others of faults you display all so well. Can you answer any of the big tehnical issues?
What happens when:
The wind stops, not slows down, stops? Even if for just a few seconds (not unusual). Even kites, especially kites with turbines are subject to that dratted 32ft per second squared. Most pilots dread an unexpected stall, and that’s with a plane they’re in control of.
The wind goes into a tight circle? Think tornado, but even a storm front can cause this.
Sudden wind direction changes? Downright common.
High altitude dust? Volcanoes and sand storms do more than play havoc with planes that can avoid them.
Wing span necessary for high altitude flight? Without power the wings must do all of the work holding that turbine. That needs significant wing area, even if you’re only putting a miniscule turbine up. The bigger the turbine, the more massive the wings and supporting superstructure.
These are just the quick ones off the top of my head as I was wondering how they were deciding they could shade so much of the land below. I am also curious how much electricity must be available to reel those suckers in, just in case or for any reason.
Now about the intellectual rigor of your comment…
rogerknights wrote:
“This seems a lot more practical than offshore. Fewer maintenance problems, and lower construction costs.”
I’ve got to go with Roger and against the naysayers on this one. I think the idea has promise.
Kites would be a lot more versatile than turbines: you can vary the height to catch the strongest wind; you could even move them from place to place to take advantage of seasonal variations or follow the jetstream and they would be much easier to remove if they don’t work out. It is worth some further research at least.
Leave it to private industry. If it’s economically viable, they’ll do it. And if some corporation just wants to green their image by sponsoring it, that’s fine with me too.
Bill Illis wrote:
“I missed the part where they actually generate electricity.”
Watch the video linked to by banjo (although he appears to be dismissive). The energy is gained when the kite is being pulled up and along by the wind, turning the cable drum. There is not the same resistance when reeling the cable in, if you tweak the aerodynamics of the kite. If you had several kites aloft in the jetstream some can be being let out (generating electricity) as others are being reeled in.
But keep your kite aloft in a thunderstorm and you’ll have more energy than you bargained for coming down that cable.
Thallstd says:
“tty… if you watch the video of their test flight (http://www.makanipower.com/category/flights/) it seems that a lot of what you indicate is needed either isn’t (maybe because it’s tethered and not free-flying?) or has already been accomplished (not to say it doesn’t need improvement) or the entire video is a fake. As for landing, once in operation it is housed on a small tower and never touches the ground so traditional landing gear and auto-logic is not needed.”
Actually in that video you will note that the test aircraft has a (fixed) landing gear, it has ailerons and rudder (and apparently a separate elevator, which I thought might have been eliminted by using the ailerons as elevons, but apparently not).
Also note that it apparently took five years development work to get the the autopilot to the point where it can make one autonomous crosswind turn.
As for the autopilot not having any capability to make untethered landings, sure it will work in a way, but it means that every time the tether breaks or the wind strength goes below stalling speed an aircraft will be lost.
And I can assure you that there is a world of difference between brief test-hops in perfect conditions to continuous operations in all weathers. Going from one to the other took rather more than a generation for ordinary aircraft.
Replying to many:
Not sure about icing, but can’t see how it would be a problem. Not a problem for cable due to resistive heat, and can’t see how heating systems would be problematic on wings. Could also just change altitude or land.
Cable weight is a relatively minor issue, a 15km long IM10 Carbon Fibre cable that can support 1000 tonnes with factor of safety of 2 weighs 100 tonnes and is about 80mm diameter Weight is proportional to length. And the conductor embedded in the cable doesn’t add much weight or size at high voltages. Line drag is a problem (will generally fair the line) – but scales up with kite size, so if works at 600m with a 5MW kite then it will work just fine at 10km with a 1GW kite.
The Makani system isn’t the only way of doing things (or even necessarily the best in the opinion of myself and some other people in the know) – can also use lighter than air to support some or all of the kite and line weight. at higher altitudes, or use many kites distributed over the length of the line. Again something that works best in GW sizes.
Carbon fibre is very strong over the long term as long as it is not subjected to changing stresses (fatigue), for proof of this look at energy storage flywheels. The nature of the loading on a kite on a long line is such that the tension remains very consistent due to elasticity of the line and light weight of the kite+line compared to lift – so not much fatigue.
In article they state worldwide wind power 1800TW, extracting a few TW is not going to be a problem for climate, and at 10km altitude won’t even notice it at ground level – whereas thermal power stations do produce noticeable local effects.
A lot of posters on this thread seem to be arguing at cross purposes.
The article is about a parachute type kite that generates electricity at ground level by turning a cable drum.
Makani Power of Almeda, which so many commenters seem to be referring to, propose an aircraft type kite with a turbine that would generate electricity at altitude that would then have to be transmitted down the cable.
The first idea is the simpler of the two and I think potentially feasible.
Here is a funny calculation. found a claim “http://www.ecomagination.com/the-power-above” claim up to 10kW per sq meter in the jetstream.
Umm … At 30,000 feet and -40 centigrade the density of air is about 0,45 kgm-3. To produce 10 kW per square meter would require a wind strength of about 210 m/s or about 450 mph, that is nearly twice the highest wind speed ever recorded in the jet stream and therefore about three times the maximum energy density (since energy is proportional to the square of the wind velocity).
Incidentally it is physically impossible to extract more than about half the energy from wind.
Global warming supposedly produces more wind , so we should therefore keep burning fossil fuels. Alternatively we could cover the planet with black plastic “cling film” in order to absorb all that extra “back radiation” for power production !
“Umm … At 30,000 feet and -40 centigrade the density of air is about 0,45 kgm-3. To produce 10 kW per square meter would require a wind strength of about 210 m/s or about 450 mph, that is nearly twice the highest wind speed ever recorded in the jet stream and therefore about three times the maximum energy density (since energy is proportional to the square of the wind velocity).
Incidentally it is physically impossible to extract more than about half the energy from wind.”
you forgot that the amount of mass flowing through that square meter is proportional to the velocity too. So velocity is more like 35-40m/s = 70-80kts, 125-144km/hr ie about right for the jet stream.
I agree with the concept. But, as usual, when the rubber hits the road, the concept evaporates.
What is the EROEI for this wind power proposal? In absence of an answer, assume < 1. It is unsustainable.
“High as a kite with a buzz” is the slogan for soliciting stoner funding.
Ask anyone who has operated sailplanes in a winch launch operation about the practicalities. There’s a reason towplanes and motor gliders are desirable!
Maybe we could harvest all the Ch’i energy found in Feng Shui in our homes! Wind mills could be placed in sharp angles in hall ways, and the Ch’i extracted in that way. First computer models should be run to determine the maximum level of power extraction.
As for harvesting energy from high altitude winds, we could just hang the wind turbines from clouds.
“Today, civilization uses about 18 TW of power … ”
Whoa. That’s *primary* power power – all the energy including heat energy going in the front end of power plants, combustion transportation, etc. Wind electric power does not have to play that game. That is, a coal plant producing 1GW thermal can be replaced with 300-400 MWe average wind, intermittent output issues aside for a moment. Space heat and the like use direct heating, but I think the total worldwide *secondary* power load is more like 11-12 TW, with room for less still to the extent space heat is accomplished with heat pumps instead of direct heat.
“It is weather. You stick kites 5-10 miles up, by the thousands, you will alter weather patterns.”
During any given daylight hour in the US there are some three thousand large body jet aircraft 3-5 miles up. Has this altered the weather?
I don’t mind pie in the sky brain-storming coming up with completely useless and unworkable ideas – except when I have to pay for it. The House needs to hold hearings on who authorized funding for this study and who permitted Federal resources at Livermore to be devoted to this “work”.
“””””……M Courtney says:
September 10, 2012 at 12:35 am
The point about high-altitude winds is that they always blow.
No-one has yet built a kite that can get up there and then work reliably but that is a technical problem; it is not a fundamental flaw in the concept.
Don’t mix up the low level wind turbines (which do need the winds to be “just right”) with the jet stream.
These kites aren’t (yet) proven to be able unworkable……”””””
So If you tether one of these “kites” (what a thought), and then you start extracting gigajoules from it, something in my Primer 1 Physics book, says there is going to be a reaction on the kite, like a big shove. I suppose that eventually the kite string will lay out in a catenary shape.
My schoolboy experience with flying kites, to some whacking great heights; well into the illegal aircraft inhabited range, says that catenaries are pretty damn big and horizontical for a long way, when the kite is that high. I seem to recall dropping such kites on the farm house way down the road. But in those days we didn’t fly a 10 megaWatt turbine on our kite; well we were too poor to afford one; otherwise, I’d a done it.
It’s also good that the wind direction doesn’t change. We used to tether our kites to the barbed wire fence, and go home for the night. Quite often, the next morning it would have crashed on the farm house up the road, instead of the one down the road. Who knows what it would take out while rotating during the night.
At least when you anchor a boat, you can put out two anchors to stop the boat from sailing up onto the beach.
They did say there were some bugs to work out didn’t they.
Personally, I’m much more a fan of the tethered geo-synchronous satellite that holds itself up without wind, and pipes down a lot of solar electricity.
“””””…..Rob L says:
September 10, 2012 at 1:36 pm
“Umm … At 30,000 feet and -40 centigrade the density of air is about 0,45 kgm-3. To produce 10 kW per square meter would require a wind strength of about 210 m/s or about 450 mph, that is nearly twice the highest wind speed ever recorded in the jet stream and therefore about three times the maximum energy density (since energy is proportional to the square of the wind velocity)……”””””
Well not exactly. The wind drag force goes as the square of the wind speed, but the power goes as the cube so the energy would go about at least the cube of the wind speed. That is in fact the beauty of wind power. If the wind speed drops to half of your design operating wind speed, you lose 87 1/2 percent of your generating capacity.
But if the wind speed doubles, you get eight times the power but the whole thing blows up anyway, so you actually end up with zero.
Wind is an ideal energy source, you can get winds from zero to 150 mph or even 250 in a tornado, whereas with hydro power, you just control how much water you let out of the lake to match your load at the time.
Stopped reading after ” ….. the team used models to quantify the amount of power that could be generated”. May as well say “I made a bunch of stuff up to fit my version of reality”. Most computer models simply reflect the biases of their creators and are about as realistic as the imaginary worlds of Half Life, Doom and Quake.