Altaeros Energies recently completed tests of a 35-ft scale prototype of its Airborne Wind Turbine (AWT) for remote locations, which will harness energy at altitudes above 1,000 feet.
(Source: Altaeros Energies)
This is very impressive, Ann. Do you know if it needs a babysitter on the ground? Or is it fully automatic? I would imagine this would probably have to be situated in rural areas. But who knows. Maybe it could be situated on a rooftop in Manhattan.
Good questions, Rob. It's described as fully automated and for remote locations. That sounds like it doesn't need a babysitter, although obviously it would need occasional maintenance checks. As far as a rooftop, I don't know--this is a scaled prototype and not full size, so I guess it depends on the size and height of the roof.
At any rate it's a good idea simply because it aims to harvest wind in a location where there is more significant wind than near the ground. I'm also interested to see how things work out with wind harvesting out on the ocean. That's another attempt to get to stronger winds.
The other problem is maintenance. The government funded windmills are largely laying fallow as the grants covered the windmill but not the maintenance. The power generated must not be of much value. Will this happen to these, too?
Warren, the target production model is 100kW, which is on the order of the oil energy output of one of the common stripper wells, which are decidedly non-mobile and require a significant logistical chain from rock to generator. You did observe that the target market is mobile and remote sites?
To Ironhorse- I am afraid I mixed several things together. One was the comment about a 40 ton weight in the air. Second was maintenance cost of a larger commercial device. Third was the value of the output of the large windmills not being adequate to support the maintenance. For small job sites or multiple-family areas the smaller unit refered to in the article could be a real blessing. I assume maintenance would be minimal, although this might not be a reality until the second or third generation.
That could be, Warren. We'll have to see. You're right about the value of the energy. If it's significant, someone will figure out how to fit the maintenance in. Could be these turbines that go to higher altitudes might make the energy harvesting worth the trouble.
Can we assume that statement is twice the power of an equally sized turbine?
The GE 1.5MW turbine has a nacelle / blade assembly weight of 92 tons. Let's say the weight can be cut in half because the power is double at altitude. Call it a nice round 40 tons for discussion sake.
The Air Force has an aerostat based radar system. The aerostat is 186 feet long, 62 feet diameter, and lifts 2200 pounds.
Mr. Glass stated the system would be good for remote sites, and that makes a good deal of sense. Places that need a reasonably portable power source will probably not need a megawatt of power.
But he also implied this system could replace conventional tower turbines. I don't see that; something with the lift capacity of 40 aerostats would be necessary.
Helium is also a non-renewable resource; its price has steadily climbed.
Cell tower? I was thinking Wi-Fi for all..... Don't you love innovation? Well it's nice to look at. I would worry about this project though. I would hate to have this thing land on my roof, because strong winds tore it of the tether.
I guess my question is as a high-altitude lightening rod, can the tether handle the current? Heavy-duty ground wire would be a lot of additional weight. The tether is already handling the power generated. And can the ground power receiver distinguish between the two without catastrophe?
Warren, good questions. I also wonder about the tether material and how it handles different voltage levels, as well as the whole ground system for receiving and distributing power. The company says it is looking for partners for commercialization. Perhaps once it gets past this stage we can learn more details.
Aircraft are regularly struck by lightning.Tethered aircraft have some advantage here over free flying craft.Like church steeples, they may carry grounded lighting protection equipment. The very fact that the turbine is in the wind means it will develop significant static charge (ask Chinook ground crews). I can't imagine why the static discharge and lightning grounding function wouldn't be integrated into the power conductors, Suplimented by any designed-in structural teather metal (reenforcing steel or aluminum). Lightning protection and tolerance is already integral to both power system design and aircraft design and certification.
But aircraft are a flying Faraday shield with no direct connection to ground. Lightning strikes are mega-amps, or at least a gaggle of amps. I wonder, not being a lightning guy, if the cables can carry the mega-load and be light enough at 1000' to keep the system afloat. That's all I'm saying.
The cabling I've seen for 100+ Amp service is on the order of that I've seen for lightning protection. Remember, it is not the instananious amps, it is the integral of I^2Rdt, yes, huge I, but tiny t. -- I'm not concerned.
Aircraft are now being made of composites, so conductors must be integrated into the surface, as is needed with LTAV, too.Even aluminum aircraft have cabling strung internally to guide the strike current.
A point is that aircraft and power system designers both have to know how to deal with lightning.Tethered balloons with conductive lines to the ground go back to the 1860's at least.
When you think about the Wind Farms we've seen – rows and rows of gigantic wind turbines in the Southwestern part of the country – I can imagine these things becoming commonplace in the sky – so much so that pilots would have to have them charted;(that shouldn'tbe too cumbersome of a task, considering NASA is tracking 1000's of pieces of space debris).This concept seems financially lucrative and technologically feasible.Two-Thumbs-Up.
At the end of the press release appears this statement: "In December 2011, the Federal Aviation Administration (FAA) released draft guidelines allowing the new class of airborne wind systems to be sited under existing regulation." After half an hour of web searching, mostly on the FAA site (where I've successfully found draft guidelines and advisories before), I couldn't verify it. Can anyone tell us more about these guidelines and what they cover?
I really dislike the idea of a tethered balloon a few thousand feet in the sky. It's pretty easy to see the balloon and avoid it as another aircraft, but the tether would be another problem all together. Radio towers are stationary, well lit, and rarely exceed 1000' AGL. The article suggested "thousands of feet" of altitude, making for a difficult to see tether extending into the normal cruising altitude of of General Aviation aircraft. Imagine a balloon at 3000' with a ceiling of 2500' putting the balloon out of sight. You have VFR conditions and the only indication of a plane shredding barrage balloon in the area being the tether. It sounds darn scary to me.
True, I have to agree with that "Pilot's Perspective" ,,,, Giant wind balloon in the sky – Easy to see, no problem.Giant wind balloon in the sky, 10,000's of feet over-head tethered by a fine, thin cable, sounds like a trip-wire hazard.Maybe they need to limited to 2,000 feet with a red-beacon cable (like on current radio aerial towers) for example-?
I had found some relevant FAA regulations last week. 14 CFR Part 101 covers such issues as model rocketry, kites, and balloons. Not very lengthy, but it seems that while the present discussion calls the application "tethered", the FAA calls it "moored" because it carries no intended passengers. As such, the FAA is mostly concerned about flight hazards or obstructions the balloons present. The "Barrage Balloon" concerns, again, are matters of generations of operational experience:
"Any balloon not designated to carry people is not regarded by FAA as an aircraft and is regulated under 14 CFR Part 101 only insofar as it might become a hazard or obstruction to flight. It must be more than six feet in diameter or have a gas capacity of more than 115 cubic feet, must be flown no higher than 500 feet above the ground and no less than 500 feet below the base of any cloud, must be flown no closer than five miles from the boundary of any airport, and must not be flown when the visibility is less than three miles. When operated between sunrise and sunset the balloon and its mooring lines must have colored pennants or streamers attached at 50 foot intervals beginning at 150 feet AGL and visible for at least one mile. When operated between sunset and sunrise the balloon and its mooring lines must be lighted to give a visual warning regardless of its altitude. To prevent runaway accidents, an automatic rapid deflation device must be attached so that it will activate if the mooring lines fail. This device must function independently from any crew or other human input."
Obviously, operating over 500 feet should involve FAA concern. I'm guessing, but owing to the temporary nature of the installation, operation over 500 feet I would think would involve normal channels of ATC NOTAMs "Notices To Airmen":
Thanks for that info, ironhorse. Since 14 CFR Part 101 gives over 500 feet as a limit, I wonder if this is the regulation (mentioned at the end of the press release) that was amended to increase height, or if another regulation that allows objects above 500 feet was amended to include balloons and wind turbines. I'm not sure what you mean in your last comment by "the temporary nature of the installation"? I don't believe these are designed to be temporary.
Surveillence radar and cameras have been regularly flying on balloons up to 15,000 feet (e.g., USAF Tethered Aerostat Radar System)
I seems to me that 14CFR Part 101 mostly defines what people can do with out FAA oversight (or ATC corrdination, flight cetificaiton, or licencing), e.g., defining what actions do not infringe on airspace.
re: "temporary", let's just call it a portable installation, but yes, I could see their design in use in a permanant installation.
cf., the proposed San Luis downdraft towers are around 3000ft.
Definitely a lot of considerations in this design. I think it's a pretty clever bit of engineering - however I'm willing to bet that between regulatory requirements, safety hazards and other usage issues (maintenance, lightning, etc.), that the road to market for this technology will be significantly higher than for other alternative energy approaches I've seen. It might even prove fatal for this approach . I think it's a brave vision nonetheless.
I have a sneaking suspicion that this new innovative device will cause the FAA rules, as currently drafted, to consider some updating.Obviously, this type of craft was not in the thoughts of the authors at the time of its writing. Ah, Change is Good !
So many of the FARs are interrelated. The 500' altitude limit on the balloon is probably there because that is the lowest cruising altitude over an uncongested area. In that way an aircraft can't possibly stumble into the balloon. The same goes for the 500' below any cloud restriction, which is the same restriction that VFR pilots fly by. I really think the only way to permit the balloons to fly higher, safely, would be to create a restricted airspace for them. With so much risk and so much cost, I'm not sure it's a better solution than a ground based windmill.
One thing that fascinates me about wind power its intrinsic multi-purpose impact.Like oil well fields, most of the ground is unoccupied by the wind turbines (but with much more power per tower than per well).Oil production, wind production, beef production*, grain production*, and wildlife habit*, may all occupy the same space. Additionally a wind tower or balloon may provide other services that such structures perform (elevation of communication tranceivers, cameras, and radar)
The aerostat turbines bring two additional factors to this: greater power density (if not greater efficiency) and transience. For all of the expense of building a tower, you have to repeat the expense if you need to move it – Tethered balloon turbines may be relocated seasonally, annually, or contingently in response to seasonal, climatic, or other variations in demand or wind.
*(Presuming complementary modern intensive grazing management and no-till practices)
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