Clean Power

Published on June 2nd, 2014 | by Michael Barnard


Altaeros BAT Airborne Wind Generation: Behind The Hype

June 2nd, 2014 by  

bat_header_scaledAltaeros and their airborne blimp wind generator have benefited from a reasonable amount of press over the past few weeks. They had asked CleanTechnica to provide coverage as well, but when pressed for more details on the technology, were unwilling to provide them.

The airborne wind energy space was given overview coverage in CleanTechnica a couple of months ago, and Altaeros was included in the mix. The assessment pointed out the five major design choices that airborne wind generation has to make, which companies have made these choices and the serious compromises inherent in each of the choices as well as the common problems.

Altaeros was considered about the most viable of the airborne wind generation technologies, but that isn’t saying much compared to conventional ground-based wind generation. They can take off in still ground winds, land safely and have strong passive safety features. Their solution is most suitable for remote sites that change location relatively frequently or where the only wind resource is at 1000′ (305 m). Stable remote sites are most likely to be better off with straightforward horizontal axis wind turbines that just sit there if there is a wind resource or solar generation otherwise.

When asked for additional details, Altaeros decided that it would be better to not provide them at this point, per an email exchange with Adam Rein, co-founder:

We are reluctant to share incomplete info on our product, and would prefer to engage in this article once the design is finished. In addition, there is concern that a detailed opinion piece could have incomplete information that might impact our FAA permitting process.

It’s likely that the FAA is able to make up their own mind about risks associated with tethered blimps carrying various technologies having had decades of experience with them. That said, the company has every right to withhold information from interested parties who aren’t paying the bills or signing NDAs.

Despite the relatively low amount of information publicly available compared to Makani, there is certainly enough information to make a few initial assessments prior to fuller release of details such as the draft submission to the FAA of their Tethered Aircraft Concept of Operations (TACO).

Altaeros has a handful of challenges which are not well articulated in their literature or in the less critical press coverage they have tended to receive.

1. Helium Prices

They depend on helium which is rapidly getting more expensive with the strategic reserve challenge, leaks out of blimp envelopes rapidly and must be shipped in large and heavy containers to the remote site regularly to keep the device flying. While a wind turbine tower is much heavier and bulkier, it only has to be shipped once then just sits there for 20-25 years. This is a capital expense vs operational expense tradeoff, but claiming Altaeros has an advantage here is a bit disingenuous without showing the math. Per Bloomberg:

The estimated price paid by private buyers has risen 48 percent from as little as $4.15 in 2008 and is up from $1.80 in 1995, according to the U.S. Geological Survey. Production of natural gas was forecast to increase 17 percent during that period to an estimated 23.7 trillion cubic feet last year, according to data from the U.S. Energy Information Administration dated June 2012.

As Altaeros was founded in 2010, their initial numbers were likely not reflective of current realities of their core input. They don’t publish their business case and haven’t shared it, so it’s difficult to say exactly what the dynamic of increasing helium costs does, but up 50% in a handful of years is likely not positive.

nel-p60-electrolyzerIf they were to create their own hydrogen as an alternative by electrolysing water with generated electricity, that would certainly change the situation especially for remote locations, but that’s another relatively complex technology to ship and maintain in remote areas. As the graphic shows, industrial scale hydrogen generation isn’t something which fits into a closet, but into a shipping container. And of course, the FAA and remote communities would undoubtedly be playing clips of the Hindenberg disaster as they contemplated agreeing to this. Hydrogen is likely not a viable alternate to replace increasingly expensive but inert helium.

2. Realities of remote markets

Altaeros states the remote generation market is in the range of $17 billion annually. That’s undoubtedly true, but the question is whether their device is disruptive in these markets. As an example of a significant remote generation challenge, the Nunavik’s Raglan mine is instructive. It requires roughly 35 million litres of diesel fuel annually to run its generators. They plan to install 6 MW of conventional wind turbines to displace roughly 30% of that diesel generation. ~12 million litres of diesel delivered by summer ocean lift to the Northwest Territories costs around a dollar a litre today so there’s a $12 million business case assuming a one year payback. That’s promising.

It’s also instructive to look at the list of communities served by diesel generation today in the Northwest Territories, presumably key target markets for Altaeros. The 28 communities have an average of 2.6 MW of diesel generation with the smallest have 100 KW and the largest having about 28 MW.  This is also promising. That’s a lot of expensive diesel that is shipped during the summer months.

However, the Altaeros BAT has a nameplate capacity of 30 KW and a likely capacity factor after weather groundings, maintenance and other challenges of 30%. Assuming that the diesel generation runs at 60% capacity factors, the smallest community would require 3 of them to displace half of the diesel, the average would require about 80 and the largest would require about 850. If the BAT capacity factor is higher, then the numbers are a bit better.

The Altaeros device just doesn’t deliver sufficient electricity to be a substantial contributor to real electrical demands in remote areas unless it scales well and cheaply without significant downsides. So how does it scale?

3. Scaling Challenges

Press_Release_Header_02Altaeros’ elongated donut (toroidal) approach won’t scale well as an individual device. Scaling the BAT device would rapidly run into structural rigidity problems as the toroid increased in diameter. Countering the rigidity challenge would rapidly increase weight. Rotational torque gets harder to counter as scale increases as well, also increasing weight. This is why blimps are airbags with stuff suspended beneath them, not toroids. Scaling this up to any reasonable size won’t be particularly effective.

Their device won’t scale well as a farm of devices either. None of the airborne wind generation players are studying multiple device interactions yet because they can’t make a single device that is cost effective. But when you have the Altaeros 2000′ (610 m) tethers in winds of different velocity and direction at different altitudes going up and down at different times, you will have tether crossing interactions and tangles unless you spread the devices a long way apart. To be sure, Altaeros’ problems are lower in this regard than cross-wind approaches such as Makani.

For context on the current level of thinking on multiple device wind farms, there are exactly three references in the 600 pages of the recent Springer book on multiple devices, and they have to do with balancing power among the class of devices that generates power by pulling cable off of a regenerative winch, not with tether entanglement and safe spacing. It’s likely that they’ll have to be closer to tether length apart than not, so 2000′ or 610 meters, mostly in areas with relatively low shrub and other ground obstacles that might tangle tethers under edge conditions of higher winds, lower buoyancy and ice/snow buildup.

4. Aerial hazards

Long thin tethers create aerial hazards that are hard to spot, and a bunch of them would make an area a no-fly zone. The tethers will vary substantially in location too as the wind changes direction, covering an inverted cone with a diameter of roughly 2000′ (610 m) at the top. A bit of safety margin and you have a one kilometre diameter and height no fly zone. The average Northwest Territories town would need 80 of them and require roughly a roughly 80 square kilometre area one kilometre in altitude above ground level as a no-fly zone.

For context, Tuktoyaktuk is roughly average in terms of generation with 2.5 MW and covers 11 square kilometres, so you would need close to eight times the surface area of the town as a flight exclusion area. Or you could install a single modern 2 MW conventional wind turbine to achieve the same result. Given the prevalence of bush planes and helicopters in northern areas as well as most or all airports being under visual flight rules, this represents a significant additional flight risk for the average community or remote resource extraction site compared to alternatives. It’s unclear why they would bother.

5. WiFi Platform

Reports indicate that Altaeros is investigating being a WiFi platform for the community in question. It’s a good idea to make the blimp a multi-platform vehicle for remote areas instead of just a power generation unit, but it’s unclear that WiFi is the killer app. WiFi standard IEEE 802.11n has an outdoor range of around 660′ (200 m), but the device is supposed to fly at 1000′ (305 m). Beyond that you start needing specialized antenna on receiving devices. This isn’t necessarily a showstopper, but it indicates the lack of attention to the numbers most press is providing to Altaeros.

Other higher altitude potential applications might be more useful, such as radar or other sensors. It’s hard to say if the Altaeros platform is sufficiently robust to support them however.


So the device won’t scale up or out well and doesn’t generate much electricity to displace the primary diesel generation. And real wind turbines are being put in place with significant generation capacity at fixed sites because they can displace sufficient very expensive diesel to be worthwhile. As a result, the potential remote niches where this technology can play are much smaller than the total $17 billion. So where are they useful?

  1. Regularly moving remote sites. Small geological exploration or research teams that move every few weeks or months might find this valuable.
  2. Small Frigid Zone settlements in a big clearing in a forest or among hills, or anywhere the wind resource at 100 meters is otherwise inadequate. In those sites, it’s not possible to put a normal tower in to get a wind turbine into clean air, but the Altaeros device could get into clear air. Anything in the Temperate or Torrid zones in this situation would probably be much better off with solar power.

Altaeros is suitable for a market that is a fraction of the total $17 billion total market. If it displaces a bunch of diesel in a few dozen or a hundred sites, that’s probably pretty good. But it’s not a suitable solution for the majority of the $17 billion niche market. I’d be surprised if it were able to service even $500 million of the opportunity, never mind actually sell that many devices. Once again, this is supposition as Altaeros isn’t sharing their math.

Altaeros is the most viable of the airborne wind generation technologies and it is highly constrained in terms of where it will likely be worth putting into operation. You can start to see why the airborne wind space is riddled with decades of abandoned prototypes. It’s a fascinating space for academic research, but commercial potential is low.

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About the Author

For the past several years Michael has been analyzing and publishing reports and articles on decarbonization technologies, business models and policies. His pieces on electrical generation transformation and electrification of transportation have been published in CleanTechnica, Newsweek, Slate, Forbes, Huffington Post, Quartz, RenewEconomy, RenewablesInternational and Gizmag, as well as included in textbooks. Third-party articles on his analyses and interviews with Mike have been published in dozens of news sites globally and have reached #1 on Reddit Science. Much of his work originates on, where Mike has been a Top Writer annually since 2012. He also has published a climate-fiction novel, Guangzhou Future Tense.

  • Ronald Brakels

    To be fair, if they were to use hydrogen no one would bother to lug around an industrial hydrogen generator. Not when the less efficient bucket method has a much lower capital cost. What’s the gas bag volume of one of these things? A couple hundred square meters? That would require around 20 kilograms of hydrogen that could be obained from about 200 liters of water, a very large bucket, some salt, a DC generator, and about 200 liters of diesel. Of course once one gasbag was up electricity from it could be used to generate hydrogen to fill another. It would take a while, though.

    • I’ll defer to your judgment on the tiny generator shown, but in context of any significant generation they would need something industrial. It would likely be clearer that this was my intent if the helium/ hydrogen item was after the economics and scaling discussions.

      • Ronald Brakels

        Oh, please don’t defer to my judgement. I could easily be off by an order of magnitude. Of course, if they were to use a Hindenburg sized quantity of hydrogen or helium then they would need to generate/get plenty more gas to make up for leakage, which will be particularly bad because of their blimps’ large surface area.

  • loebner

    They should use hydrogen instead of helium. True, it’s inflammable (*not* explosive) , but so is gasoline. Hydrogen is cheap, plentiful, and more buoyant than helium.

    The danger of fire is very small, and if the blimp burns, so what? It is unmanned.

    • Ronald Brakels

      It would seem that hydrogen wouldn’t have result in a much higher fail rate, but even a small increase might might it uneconomical. And presumably the chance of one splatting someone would be small but perhaps even a small increase in splat chance is unacceptable. But it almost certainly makes sense to user safer helium during the prototype stage. Once the bugs are worked out (if ever) it could be changed to hydrogen. Of course hydrogen’s greater leak rate would be a problem. But a small quanity of water could be carried onboard and slowly electrolysed by a little current to replace lost hydrogen. Amusingly, it would almost certainly be easier to have this done by a some lightweight solar cells rather than the wind generator.

  • Devil

    Well, I am just a fresh graduate of Civil Engineering and have been experimenting with wind turbines, since Bangladesh [where I am currently at] has no wind tunnel whatsoever, or the required facilities to test smaller prototypes, I have been using tinkered household devices to get a better idea about the efficiency of various designs.

    On point: I tried to launch a small turbine into the air, infact I used 2 large hydrogen[8% or so lighter than helium and cheaaap], it did not seem at all logical to me to spend so much on the lifting on a regular basis, generators are heavy, whats the point of getting cleaner air if you cant throw a 1 MW turbine up there at the very least?

    The people behind the project are talented I am sure, however this device seemed a bit too far fetched imo.

  • Omega Centauri

    If the goal is to displace some fraction of annual deisel gen, PV should also be considered. PV will do little to nothing during the long winters, but it could cover a lot of summer demand. Some mixture of PV + horizontal axis turbines would probably displace the most fuel demand.

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