I'm still a bit confused about how the forces line up for the flight path. If I'm understanding:
- the wing flies in a circle which is perpendicular to the wind (oriented the same way an ordinary wind turbine would be)
- the tether is up-wind from the wing, so the force from the tether pulls the wing into the wind which generates lift, which is used to propel the wing along the circular path
- the propellers are driven by the circular movement of the wing, and generate electricity
So the tether and the wing generate movement, the movement spins the propellers, and the propellers drive the generator. Except for take-off and positioning, where they are used as motors. Am I understanding this?
The tethered airframe converts wind into high-speed lateral motion, sort of like a sailboat would if it were sailing into the wind. These higher speeds can drive the blades faster than if they were simply pointed at a wind source.
Thanks this was my biggest question. I was wondering why it doesn't just stay tethered to the ground in one single position (or as close as possible) flying into the wind.
I guess it makes sense if it rotates perpendicular to the wind - like the tip of a rotor blade, to achieve these higher speeds.
Would be curious to understand more of the math/physics behind that. But at least intuitively it makes some sense now.
I think what they're doing is a milder version of dynamic soaring, which is a popular technique used among RC glider pilots (and some birds).
The speeds attainable are pretty insane, the current RC record is 505 MPH, which in a rather fascinating twist is faster than the fastest POWERED RC aircraft.
This a video that shows a pretty good idea of what it looks like, at compartively slower speeds.
Cool. I never knew that stuff. There's a vid here of a guy getting his glider to 320kph with wind speeds of only 25-30kph before crashing it into a rock face. Reminds me of my own efforts with a RC glider which crashed into a concrete pillar at ~50mph quite promptly due to my lack of pilot skills.
That video helped a lot. I was getting hopelessly lost with the image. In one part the object is moving in still or slow air where the resistance isn't enough to nullify the gain gained at the higher speed upper layer if I'm understanding this correctly.
And finally learned the difference between airspeed vs. groundspeed :D
It's also basically the same idea as used by the people flying trick kites on the beach. Once an aero-astro friend of mine explained that, this whole thing made so much more sense.
My understanding is that dynamic soaring takes advantage of a cliffside or a ridge to provide upward air current. This project seems to be working on flat ground, so as far as I understand, it's not really using dynamic soaring.
I think it works more like regular stunt and power kites, just relying on the "trim" of the airfoil to produce lift and thrust (and the tether's pull) to make it go upwards and then "fall" down.
One way to describe it in words is that it's like a normal wind turbine, but instead of 3 blades, you have one wing that moves in a circle like a blade. And instead of the energy being extracted by a generator where the 3 blades meet, the energy is extracted at the wing itself, by many small turbines.
I think in the last major updated they made it really worse. No horizontal scrolling ever. My father has severe AMD (Age-related Macular Degeneration) and has to zoom very heavily. One day I went to his computer to fix his gmail to be welcomed with a white screen. It was just after they made the shiny new compose popup. It was placed so nicely that only the empty white center was visible. It confused the hell out of me for a moment let alone my father.
I know scaling Gmail is a gigantic effort but I don't really understand this part (can anyone enlighten me). Gmail essentially has two core pages, the inbox (or list) and compose and tens of millions of users. If they can't fix the positioning of one compose popup how will the rest of us manage?
A fair disclaimer in my own work I'm not sure how good we are in handling these issues but we do have a lot more UI and UI changes. It just makes me feel hopeless.
The most prominent, composing a new email. The floating window appears out of bounds and it's impossible to click any buttons on the lower bar, including the send button.
What I do is tabbing all the way down so the floating window reorganizes allowing me to send the email.
I use window 8's built-in scaling to put everything at 125% too because my laptop screen is a 15-inch 1920x1080 and I find with that kind of pixel density I need to make things a little bit bigger. It's ridiculous how many things are broken when doing this.
I'm with you, but I'm a power user. I wonder if anyone has any sentiment analysis showing whether the average web user likes this sort of thing, or finds it annoying.
I'm probably a "power user" as well, but I literally cannot navigate the site. It's like 1/3 of my scrolls don't even register.
This isn't "design for the masses," it's just plain broken.
Edit: I don't know why I'm being downvoted, it must be working for some people. Here is a video of me trying to scroll (in Chrome) https://www.youtube.com/watch?v=ulAw0P2geRE
My scrolling seems to work, but it is annoying. The embedded video does not work at all for me. I had to copy link location and paste it another window for it to work.
Google is in the position to have done exactly this kind of analysis, and apparently the majority likes this crap. I'm glad I am not alone in hating it though.
Google, and to a certain extent Facebook, LinkedIn, and all other large web companies are in positions to make data driven design decision, and every time it's done I hear lots of complaining. I'm wondering how great data driven design really is.
On the flip side, how often do you hear that Apple's software design is driven by data analysis, and how often do you hear complaints about their designs?
I hate Apple design, but I just don't use their products. All Apple products have a good alternative...not necessarily true for Google, Facebook, Linkedin, etc.
Is it? What does it achieve? I think anyone browsing HN knows the opinion of the average HN user on scrolljacking. If they're still doing it it's because either they don't read HN or they have data that proves it works.
Honestly, I think it might help. I design websites sometimes and I'm on here. At first I was kind of into it, but HN helped me see the error in my initial excitement.
This implementation especially is incredibly obnoxious.
Not sure why this was downvoted. I agree, after the 10th discussion on how designers are breaking scrolling, I'm not sure what is achieved apart from "yeah, that still pisses me off too!"
I agree, the scrolling experience made me exit that page quicker than I should have. This is also a good time to remind folks of Mike Bostock's excellent writeup on scrolling: http://bost.ocks.org/mike/scroll/
That's something worth mentioning as an addendum to a more substantive comment. Making it the sole basis of your comment is the epitome of short-sightedness. As the proverb has it, when a finger points at the moon, only the fool looks at the finger.
This is actually the best scrolling I've encountered in one of these glorified-slideshow types of sites, especially for those who (like me) like to scroll with the arrow keys.
I think this is pretty cool, but several questions spring to mind which I haven't found good answers for.
The first is what sort of density can you get out of these? How many per acre/hectare? 1? 3? California has a number of wind installations and some of them are pretty dense [1].
The second is what sort of radar signature does this thing have? Probably not a navigation hazard but should be interesting on the weather doppler display.
They do mention density in terms of kw / sqm as being slightly higher than conventional turbines, but don't give a lot of details beyond that. I can only hope it's not based on parking them all right next to each other and hoping they don't get tangled up :p
My friend worked for Makani for quite some time. I remember at the time, they were in financial difficulty and, in his words, laid off all the people who viewed it only as a science project in order to get lean. Not enough people were focused on what would be necessary to bring the tech to market. He ended up finally leaving after some time, but I think before Google took them. A Google X type of environment probably is perfect for people who like working on science projects and can't be hindered by financial constraints that would hold back innovation at this scale. Would be interesting if Google ends up being able to turn this into something used by many parties worldwide.
I guess they did very well to lay off the people who thought of it as a science project, because it's obviously an engineering project! All the science needed to make it work already exists, it's just a question of hammering it together. Disclaimer: engineer here.
The 60% load factor seems a dream come true... well above offshore wind levels (c. 50%). Having said that, I'm very curious to know the capex per MW, and the ongoing O&M costs for each of the kites. Onshore wind has experienced a considerable decline both in the cost of the turbine and O&M... my impression is that this technology is not going to be cheap to run. Anyone has any insight?
I fly stunt kites and power kites, and what is not immediately apparent to someone who doesn't is that the movement of the kite itself will generate apparent wind (and lift) on the sail/airfoil. Flying in a circle or a figure eight pattern will add a lot of "pull" on the tether. Ie. the load factor of a moving kite is far greater than a stationary kite or propeller.
Here's another kite related technology that uses this to their advantage, they have built a giant computer controlled power kite that is used to power cargo ships (they claim 50% fuel savings in favorable conditions). They're also prototyping for electrical power generation.
The underlying technology for the Makani kites and a standard turbine are the same. In the Makani case you have one kite with eight turbines, and like a standard wind turbine, all turbines need to be serviced. If you have to service 1 turbine, the other 7 stop operating. Hence, on a per turbine basis, I believe availability won't be around the 98-99% level (the industry standard), but lower.
Additionally you have the tether, a new variable, which is another moving piece, and will also need to be serviced.
I've done some back of the envelope numbers, and without assuming a higher capex (which I'm fairly certain it is), on an recurrent basis, an increase in production doesn't really lead to cheaper $/MWh on an O&M basis.
Standard Turbine Makani
Capacity (MW) 1.5 0.6
Load factor 23% 60%
Production (MWh) 3,022 3,154
Availability 98% 95%[1]
Net Production 2,962 2,996
O&M $/turbine/yr 20,000 20,000[2]
$/MWh/year $6.75 $6.68
[1] I think I'm being generous at a 95% availability, but I haven't got enough data to make another assumption.
[2] O&M can be contracted on a turbine or MW basis. Still, given the "complexity" of Makani, the price of this could be higher than the standard cost.
This is a new technology, and not much info is available e.g. how big can these get, what's the investment cost per MW, what are the potential maintenance issues, how does availability look like, etc. My above argument is an educated guess, but I'd really like to know more about it. I really like the idea and I would like the economics to work out.
After they get going, I don't see how the capex could possibly be higher than for a traditional tower wind turbine. Everything is smaller, and closer to the ground. Less site preparation, and you don't need to rent giant cranes. You're also not shipping giant blades and pylons with special trucks.
Also, using smaller generators means that you've got a higher production volume, which can mean significant cost savings. You're also not dealing with giant bearings, gearboxes, etc. which are expensive to produce.
And if you're taking a kite offline, you might as well replace all the motor-generators at the same time. I assume they'll be designed to easily detach and replace. Then, back at the shop, you can check them out on your test bench, and see which ones can return to service in the spares stock.
Thank you for the link, I was wanting to read that article but had forgotten about it.
I met Don on a return flight from SJC to OGG. He seemed very kind and passionate about the Makani Power project at the time. The idea, as he explained it, originated from plans to build a self powered kite boat [1] that could circumnavigate the world. The "self powered" part interested his friends at Google and they started funding him. He confessed that he had accidentally become an engineer in the process, but his real passion was wind surfing and kite surfing and he was eager to get back to that.
This looks a lot like a project being developed by Bryan Roberts (IIRC) in Australia, that New Scientist covered about fifteen years ago. He was using a gyrocopter-like structure (he called it a gyromill) to keep the devices up in the air, and with an intent to be much higher up than these things seem to be aimed at, but the principle remains the same (tethered, high enough to gain some consistency of wind).
> The energy kite simulates the tip of a wind turbine blade, which is the part of a turbine that makes most of the energy. The kite is launched from the ground station by the rotors, which act like propellers on a helicopter. Once in the air, the kite generates power by flying in large circles where the wind is strong and consistent. Air moving across rotors mounted on the kite forces them to rotate, driving a generator to produce electricity, which travels down the tether to the grid.
Are the rotors that launch the kite the same as the ones that generate the electricity?
Please correct me if I'm wrong, but I was under the impression that wind turbines were effectively unsustainable due to the materials they are made of and their actual lifespan not offsetting the initial financial and environmental costs.
Now, I understand that this project is supposed to provide greater versatility and efficiency using cheaper materials, but it seems to me (by no means an expert on the subject) that these kites are considerably more prone to damage by their very nature too.
Honest question, is this really solving a problem?
P.S.: this website is absolutely horrible to navigate.
I've never heard the argument that current wind turbine are unsustainable before. I don't see why that would be so. The base is concrete, the tower is steel, neither of which is exotic. The generator is pretty standard. All of that is industrial tech we invented a century ago, and we know how to maintain it for the long haul.
The blades themselves are composite, that may have some longevity issues (you typically need to paint carbon fiber to prevent UV degradation every view years), but I don't know, they can last for a long time. Fiberglass boats last 50+ years.
I would imagine the designed lifecycle of a wind turbine is 25+ years, and I also imagine that the bases will last long beyond that. In 50 years we may have to go around and replace the blades on these things, but that's it.
My understanding is that, among other things, the generators come under extreme stress during exceptionally windy occasions, causing a lot of wear and tear that happens way up at the top of these giant windmills.
These require a lot of manual maintenance, which is dangerous and expensive due to the nature (and location) of the work.
Additionally (and as a demonstration of just how much stress they come under), while coming under said strain, they've been known to burst into flames https://www.youtube.com/watch?v=C_oFPF6Anwo
As for their lifespan, the government agencies that build them claim 25 years, but there's controversy about this. Searching online will find you conflicting studies, including this one http://www.ref.org.uk/publications/280-analysis-of-wind-farm..., which states
"Analysis of site-specific performance reveals that the average normalised load factor of new UK onshore wind farms at age 1 (the peak year of operation) declined significantly from 2000 to 2011" indicating that they may wear out more on the order of ten years.
Now that was a cursory search but in any case the argument that the wind farms cost so much to maintain that they're nonviable is not new.
Wind turbines aren't exotic tech, but it is a giant turbine that is placed way up on a pole, and fundamentally a turbine will need maintenance, so someone has to go up and do that maintenance, and that's expensive.
> Additionally (and as a demonstration of just how much stress they come under), while coming under said strain, they've been known to burst into flames
I thought all wind turbines were built with brakes now exactly to prevent this and other more spectacular failure modes, like the blades fragmenting. They have a defined operating range, and if the wind isn't in that range the brakes engage and the blades don't move.
Not quite, if the wind is too strong the blades feather (edge on to the wind) brakes exist but are puny and are only for maintenance use. Some blades have a tip that the rotates and causes high drag in the event of feathering failing and going into an overspeed.
What government agencies are out there mass-building wind? In terms of America at least, that's not how our generation system is set up.
Also, the recently-published Wind Vision[1] runs with an expected 20-year lifetime, and starts digging into system reliability specifics on page 70. Wind Vision was a lengthy collaborative process with industry, the labs, and DOE HQ. Good news is that there have been significant reliability gains in the gearboxes, generators, and electrical systems.
Current designs are not standardized, so the worst case is fairly poor. However, economically on average wind is fairly close to Coal Power and in some cases actually cheaper even without subsidies. So, there is no way for it to be a net loss energy wise because electricity is vary cheap energy.
PS: For scale wind is on target to hit ~8% of total electricity generation in 2018.
Note, wind has gotten much better over time so 2013 numbers look much better than 2006 numbers.
Germany levelized cost of electricity generation in 2013 (EUR/MWh)
Onshore wind farms 45–107
Coal-fired power plants (brown coal) 38–53
Coal-fired power plant (hard coal) 63–80
Though I may have undersold things for new generation:
Regional Variation in Levelized Costs of New Generation Resources
Conventional Coal Minimum 87.0, Average 95.6, Maximum 114.4
Wind Minimum 71.3, Average 80.3, Maximum 90.3
IMO one of the more interesting numbers was Wind, onshore Operating Cost (USD/kW) Min 10.95 Max 60.00. That's a wide gap.
PS: Granted, these don't seem to account for time value of money but that's often overstated in terms of economic impact. Basically, if you turn 1oz of gold into 2oz of gold for free it's a net gain even if it takes 50 years, time value really just means there might be better uses of your personal money not that something is a net loss.
I think last year I read about an experimental setup that uses lidars to measure incoming wind allowing angle to be adjusted, ideally before the gusts hit. No conclusion at that time though.
(The offshore ones are huge and I guess changing the angle can't be done anywhere near fast atm.)
Thank you for your reply. I used to live in Scotland where there are a lot of wind turbines and I remember controversy in the news about the fact that while the expected lifespan of a wind turbine should be around 20 years, the actual lifespan ended up being in the region of 12 years, and the long-term maintenance costs ended up being higher than expected. There was also controversy about the environmental damage done to forests and birds, as well as noise pollution, though I guess this isn't directly related to the subject at hand.
Please don't get me wrong, I'm all in favor of clean energy, I'm genuinely trying to inform myself about the pros and cons of each solution.
It's a bit odd to be attempting to inform yourself of pros and cons you don't know, but also make a very strong opening statement about wind power. I work in the energy industry and I can honestly say I've never heard someone refer to wind turbines as "effectively unsustainable." Maybe, as a joke? But certainly not in any serious way.
If you want to learn more about wind in general you can cherry pick sections from the recently released Wind Vision[1]. It should be able to answer most anything you'd wonder about.
I honestly wasn't trying to make a strong statement, but given the reactions and the downvotes, it does seem like I didn't come across as intended, my apologies for that.
And thank you for the reference, I will make sure to read through it as soon as I get more time.
controversy in the news about the fact that while the expected lifespan of a wind turbine should be around 20 years, the actual lifespan ended up being in the region of 12 years
There certainly was controversy. An initial study did indicate the lifespan was likely to be 12 years[1], but that was immediately questioned because Scotland already had 16 yo windfarms with no maintenance issues.
That initial study led to additional research, which showed that:
the UK's earliest turbines, built in the 1990s, are still producing three-quarters of their original output after 19 years of operation, nearly twice the amount previously claimed, and will operate effectively up to 25 years. This is comparable to the performance of gas turbines used in power stations.
The study also found that more recent turbines are performing even better than the earliest models, suggesting they could have a longer lifespan.[2]
Also, there's no real controversy about "damage done to forests and birds, as well as noise pollution". There's no damage at all to forests, bird deaths are in the order of 0.1% and noise pollution is what it is: they can be noisy if they are built near you, but there is no mystical "subsonics" or something that some people claim.
Well if you are talking about damage done to forests & noise pollution, then you are trying to capture the externalities of power production into its "true cost".
I'm all for that, but if you decide to do that you also have to use the same methodology for coal, oil, nuclear, etc. Sorry birds, but I feel like the cost of every bird killed by a wind turbine pales in comparison to what a few mountain top removal coal mines do to an area.
In terms of economic ROI for the corporations owning wind turbines, I think it works out even w/o tax credits. Obviously the tax credits help, but the credits are not generous enough to justify all of this investing on their own. I believe the companies have done the analysis and believe it is profitable.
I was thinking about starting the anti-windows party to campaign for banning glass in architecture, just to see how dedicated people are to the premise of reducing bird deaths caused by human structures.
Motor assemblies and the hub likely take the brunt of the stress and would require the most maintenance. Servicing them in the long term is a problem in that there simply not enough qualified people to do that job. Figure part electrician, part mechanic, and more, just to be able to work on one. Then throw in that candidates for this work must be very physically fit and mentally agile to be able to do the two hundred foot or more climbs.
So besides the material costs of building and maintaining we may run up against one that isn't fixable as quickly, getting the people to do the work.
Me neither, I'd be interested to hear more. I understand that 25 years is their lifespan. There was an interesting HN submission recently that discussed the problem of what to do with the blades once they reach EOL. Obviously they are very large and very hard to recycle due to the materials they are made from - a problem that increases with scale of course.
Like everything, I'm sure turbine blade tech will iterate. I recall hearing once that solar panels weren't viable because they didn't last long enough to recoup the energy cost it took to build them. I don't believe this is the case any more though?
I'm fairly certain you're wrong about that. A quick googling suggests that a commercial wind turbine produces about 1M kWh/year, more or less. That's a great deal more energy than it would require to manufacture and install.
By comparison, it takes about a pound of coal to produce 1 kWh of electricity, more or less. So a single wind turbine produces the equivalent energy of a MILLION pounds of coal every year! How much does it cost to mine and transport that coal, not to mention the construction and operating costs of the plant?
That said, what problem is this solving? Well, the core solution is converting to wind-based power. The kites are just a cost reduction for the conversion process. They presumably cost less to make than standard towers, and are easier and cheaper to install. They probably have long-term cost/kWh benefits as well.
A MILLION pounds (which really should be said in a "Dr Evil" voice :-)) is 500 tons.
A rail car carries 120 tons of coal.
A typical 2 GWe thermal plant burns a rail car of coal every ~20 minutes (coal has ~30 MJ/kg, and there are ~1000 kg/ton, so 120100030E6 = 3.6E12 J/rail car, and 2 GWe ~ 4 GWth, which over 1000 seconds = 4E12 J)
So by your figures, a windmill's yearly output is equivalent to a little over an hour's operation of a typical coal-fired plant.
EDIT: 1 kWhr = 3.6 MJ, so a pound of coal produces closer to 10 kWhr than 1 (~20 kWhr thermal => 10 kWhr electric after efficiency correction), but the argument still stands. 9000 changed to 900 below.
Windmills are great, and tech like this that increases load factor, lowers costs and extends their reach into more marginal areas is good, but it'll take almost 900 windmills to replace one coal plant, plus oodles of energy storage for when the wind isn't blowing.
One coal plant, on the other hand, can be replaced by one nuclear plant, or a dozen-odd small nuclear plants of modern, modular, passively-safe design.
People who believe anthropogenic climate change has a very significant chance of ending civilization should be pushing as hard as they possibly can in favour of nuclear power for this reason. If we had invested heavily in nuclear in the 70's and 80's we wouldn't be in this mess now.
Nuclear is not without its costs, of course, but all industrial-scale power sources have costs, and no one is seriously proposing we end industrial civilization, so we need to decide which tradeoffs are acceptable. Solar capacity and wind both have roles to play, but it is very hard to escape a role for nuclear in replacing base-load coal.
I don't understand the focus on how many windmills it takes to replace one coal plant. It's not like there's some limit to how many you can build. If the costs are comparable, that's what matters, no?
At a certain level it actually does matter. The sustainability of a power resource is measured in many ways, even if CO_2 emissions is the most widely touted. Measures like water use, construction cost/emissions, and land use are significant. The number of windmills being built _does_ have an upper bound, dictated by some combination of land requirement and material availability. Of late, for example, the desire for high-output synchronous turbines has been held back by the limited availability of the rare earth magnets that make them just so effective.
EROEI of wind turbines is about 20:1. That is, you recover 20x the energy that goes into constructing and maintaining the turbines over their lifespan.
The argument that some of the materials used in turbine manufacture presently rely on fossil fuels (e.g., coal used for coking steel) doesn't mean that other options for such processes aren't possible. Though shortages of fuelwood were among the key reasons for switching from fuelwood to coal in the first place in the 1600s-1700s.
Metallurgical coal is going to be the very hardest thing to get away from. Improvements in the coking process (carbon capture) are plausible, but the chemistry basically demands burning a butt-load of carbon.
Thermal coal is replaceable by conservation, nuclear power, and to some extent wind/solar plus storage, and if I were in charge I'd be pushing to ban new thermal coal development. But metallurgical coal is going to be almost physically (or chemically) impossible to replace.
It's a a big use, 14% of global coal use from memory based on a recent query.
BP's annual energy review 2014 gives total global coal use as 3,881.4 Mtoe (million tons of oil equivalent), which works out to 5.54 billion tonnes of coal. 14% of that is still a large number, 776 million tons.
I happened to look up total forestry production in the US recently, let's see if I can't find that ....
Total US lumber production is equivalent to 928 Mboe. So, yeah, applying 84% of US timber production to coking activities would supply the world with steel.
US steel production is just under 100 megatonnes (2007). Global production is 1,600 megatonnes. So US production is 6.25% of global. The US could provide for its own steel manufacture somewhat more feasibly.
Incidentally, energy use in producing construction materials is among the reasons I see a possible future not for biofuels but for biomaterials -- utilizing plants or organic processes to directly provide structural materials (or replacements for them) that we use.
Carbon separation from seawater seems another possible approach, though I haven't specced out that for coking purposes:
The materials you're probably talking about are rare earth magnets used in their bearings -- the jury is kind of out on their sustainability since they're rare and depletable but highly likely to be recycled at the end of a turbine's life.
The lifespan questions are different -- wind and constant mechanical motion put a lot of stress on turbines and I believe as some other commenters pointed out that the actual lifespans often haven't measured up to the predicted ones.
Makani's capex for a kite should be pretty low; as I recall, talking to Saul like 8 years ago, the difficulty was in stable control of the tethers, not in the economics if control was achieved. But who knows where they're at now (or even exactly how good my recall is).
They estimated the lifetime of the farm they studied, and estimated the maintenance and decommissioning costs. Those estimates are probably going to be reasonable, but they are estimates.
All numbers regarding things that will happen in the future tend to be estimates, no matter which long term engineering project you care to pick. For fairly obvious reasons.
Your point seemed to be that the first of the studies you picked was based on estimates for things like total lifetime and decommissioning.
But the fact that the first thing you picked relied on estimates for those things tells us nothing at all about the quality of the data, just that estimates were used for something where estimates are always used.
I suppose my point was that it is unfortunate that so much context is lost by the time a chart ends up in Wikipedia. At a minimum, they should probably get rid of some of the decimal places in their table.
I was not trying to paint it as likely that the other studies would be similar to the one I looked at (I see why my phrasing doesn't necessarily communicate that, but I was simply trying to say that I hadn't done more than look at the 1 study).
> effectively unsustainable due to the materials they are made of and their actual lifespan not offsetting the initial financial and environmental costs
I don't know where you got the information from, but I can assure you that that is not the case. Wind is extremely sustainable, even if we factor in the carbon footprint of the production and construction of the wind farm.
I think in comparison to existing fossil fuels (price/ROI), in this WIki article they talk about how the drop of oil price meant funding for these types of projects went away:
One of the bigger issues with wind energy (solar also) that this solution doesn't address is the distribution. These energy sources don't have consistent output, and definitely do not match peak requirements. In other words, at times they will produce far more than needed and others far less. The solution to this could be smart grids and energy storage, neither of which are really at a feasible point at scale yet. But we're getting there.
Baseline + peak load grids is a much more complex problem. But that said, it doesn't mean wind isn't helpful or useful - it just means some grid design change.
Consider this - any energy captured from wind can be stored, at some known percentage of loss due to thermal and other inefficiencies. Heck, wind a spring with it! This is going to be less efficient, but not orders of magnitude so - and it still keeps us on clean and relatively inexpensive wind, as opposed to dirty and increasingly expensive fossil fuels.
I live in the land of many wind turbines, the Øresund region of southern sweden, and I know that they can break down or even catch fire from time to time. Who is going to service this aeroplane when it breaks down?
It just seems to me that this idea has too many possible problems that could go horribly wrong from trying to fly a plane around on a teather in strong winds.
To be honest, before I saw the G+ page and read the top HN comments, my first thought was that april 1st is right around the corner. ;)
At the altitude these will be flying at, the wind is pretty consistent compared to the wind at ground level we're used to. However, I would imagine that the on-board controller could kick on it's propellers or something if the altitude changes too much.
Stunt kite flyer here. Flying (both powered and unpowered) is about managing the mechanical energy in the kite/aircraft. If you have kinetic or potential energy available, you can always trade one for the other. If you have neither, you've almost landed.
This kite will always be doing quite significant movement, so the "apparent wind" on the airfoil surfaces should keep it moving even when the wind is dying down. Additionally, you can reel in the tether to give a little bit of movement to the kite. Typical kites can be flown by walking backwards at a normal walking speed (4-5 m/s or less).
This looks like a very controllable kite, I'm sure their control programs can land it in pretty adverse conditions safely.
I don't know. It works for RC helicopters of 500 size or so. I haven't seen autorotation performed with multicopters, though, so not sure how it maps to this application. I'm guessing these are fixed-blade machines. RC heli's manage autorotation via their collective pitch, which RC quadcopters (or hexacopters) don't have (collective). So it might not be relevant. But on the other hand, if the value of avoiding a crash is high enough, they could make the blades collective just for that purpose. Or maybe make one or two of the multiple props collective... I'd assume they already have a working solution to avoid falling out of the sky, but then, it isn't mentioned in the copy.
EDIT: There are quadcopters that can fly inverted, but I think they use powered servos with a reverse polarity. The value of autorotation is that it works when your main power source dies. So it all depends on the context and parameters (is there a backup battery of lower capacity available for emergency situations, say).
I'm happy to see experimentation in new wind technologies, but it makes me sad to see things like this grabbing headlines when floating offshore is such a strong contender that just needs some more funding for the engineering effort (mostly because it's pushing the currently tested limits of carbon composites).
It seems like if there were a "farm" of these kites, they would have to be very widely spaced out, or else they would crash into each other or get their tethers tangled up.
I'm worried about the noise. The blades spin many times faster than a regular windmill. I imagine it will sound similar to a small plane flying very close to the ground. Of course a plane flies over once and it's gone; this thing will produce a constant droning noise that fluctuates in pitch and volume every few seconds as the kite goes up and down. If you put them far offshore this wouldn't be a problem, but I wouldn't want one of these near my house.
I'm sceptical that that's true. We can put mufflers on gas engines to make them quieter. The prop, though, is moving a lot of air, and there's no way to get around that and have it still work.
A 300hp hub, spinning a 9ft diameter propeller at 1584 RPM should be roughly 72dB as measured from 1,000 feet. From a mile away, it will be more like 57dB or about TV volume from 6 feet away. -- Then again, these are spinning far faster than you'd expect from a wind turbine.
Makani seems ideal for their needs: "Alaska’s electricity infrastructure differs from that of the lower 48 states in that most consumers are not linked to large interconnected grids through transmission and distribution lines; rural communities in Alaska rely primarily on diesel electric generators for power. "
-- http://www.eia.gov/state/?sid=AK
Commercial planes don't fly below 250m at all, expect when taking off and landing at airfields.
The structure of these "turbines" are that of planes which look like large birds to real birds, so they would stay away from the area with them.
I'd assume that these would be installed in large open fields, so it shouldn't affect migration patterns or bird localities.
I have seen eagles attack quadcopters thinking they were birds, but those are usually of similar sizes to what eagles' prey would look like, but obviously this shouldn't be a problem as well.
Looks kind of cool. I just looked up the cost of regular turbines are "about $1.3 million to $2.2 million per MW of nameplate capacity installed." So I guess for a 600kw kite to be economic you'd have to build them for about $1 - 3m given the kite produces more constant power. Dunno what happens when the wind drops and all your kites have to land.
For a second a tried to imagine a satellite view of the earth with many of these flying. It'd look mesmerizing. I really applaud Google for funding research on affordable renewable energy. It's unfortunate that the scrolling doesn't work, but hey the prototype does!
The research I've seen says bats are mostly affected by low frequency pressure waves from conventional turbines, so these won't have that problem.
They may also spin fast enough to make enough noise to scare birds away, but they are also moving pretty fast, so could pose a problem for birds at the low end of their loop, which is somewhat under 150 m.
Putting them on a migration route would be a very bad thing for birds.
Off topic but I have been toying with building a small catamaran powered by a Darrieus turbine or a kite setup such as depicted. The point is wind powered navigation of busy rivers and the east coast intracostal waterway. Obviously this makes zero sense on the open sea or in wide bays, where long tacks are easy and more efficient. Tacking on the intracoastal is practically infeasible in today's world, yet there is loads of wind. Can anyone refer me to to prior art on this?
- the wing flies in a circle which is perpendicular to the wind (oriented the same way an ordinary wind turbine would be)
- the tether is up-wind from the wing, so the force from the tether pulls the wing into the wind which generates lift, which is used to propel the wing along the circular path
- the propellers are driven by the circular movement of the wing, and generate electricity
So the tether and the wing generate movement, the movement spins the propellers, and the propellers drive the generator. Except for take-off and positioning, where they are used as motors. Am I understanding this?