Back to light entertainment, new Makani site, new companies, conference news

So after that painful exposuse to some math, here is something nice to look at, Makani's rather fetching new website . There's a new video I hadn't seen:



Which is nice to see, not sure what the wing area is, but you can see the power output and windspeed in the plot, if you managed to keep watching after that stomach churning on-board cam bit. I might do a post on the content of the new site at a later date.

Also here's a new company: Kitemill. I know not alot about this project but given the name I would expect ground generation with a kite? And another one : Altaeros Energies, who don't have a site yet but this article
shows a logo and the scheme of operation which is basically a windturbine elevated with a buoyant & lift generating, passively stable enclosure/fairing like this:

Final exciting news is that Jianjun Zhang of the snappily titled: Guangdong High-Altitude Wind Power Technology Ltd. will be at the AWE conference. I'm sure everyone is keen to hear about that project. Registration is open for the conference and I would definately recommend going. The list of speakers looks fantastic.

Ok ok, here's the last bit: Flygen vs Groundgen the finale

Has it really been 2 months? Sorry for the lack of updates, I have been desperately trying to bring my work together for my Dphil thesis which is due to be submitted in 53 days exactly and I'm still, hmm about 25k words and about 10 flight tests short!

Here is some of the ground gen/ flygen comparison brutally culled from my post on the awe list and from Loyd's wonderful paper.

Ok, some pros and cons. This is assuming that for a flygen you would have a hard wing and for a groundgen a soft wing. Uwe at TU Delft pointed out quite correctly that you can have a hard wing groundgen like that at Ampyx that will have some of the advantages  (and disadvantages!) of both approaches.

Soft	Hard
Harder to get high L/d	Easier to get high L/d
Lighter	Heavier - inertial loss?
Less prone to weight penalties on scaleup	More prone to weight penalties on scaleup
Cheap	Expensive
Subject to wear, esp when fluttering	Excellent wear characteristics
Under-actuated	Excellent control authority
Difficult and comp expensive to model- Multibody approach?	Can be modeled through conventional techniques, i.e.Neuton/Euler or Lagrangian in real time
Pack down small	Don't pack down
Could deform to match conditions	Must operate in all conditions
Can do ground gen	Must run power down cable
Severe cable wear from repetetive bending - if doing groundgen	Cable bending frequency is low - if doing flygen

After that, here are some gems from Loyd:

Basically this is saying that the power scales linearly with air density but with the cube of the apparent windspeed. Translation: Going fast is dispropotionately rewarded, when going high air will be thinner but this should be more than cancelled out by faster wind.

Next....Speed, and hence apparent wind speed is going to be affected by the lift/drag (glide) ratio of the wing, less drag meaning more speed. According to Loyds analysis this is another exponential effect - check it out here for the drag(flygen) mode, where:

This graph shows the exponential scaling showing how important efficient wings are. It looks linear but the scales are logarithmic ok!

This next graph shows that the peak power of the lift(groundgen,Fc) and drag(flygen,Fd) modes are pretty much the same. Groundgen reelspeed wants to be about 1/3 of windspeed, and there is a broad peak for the flygens in terms of the ammount of drag you put on the wing, which gives a fair bit of operational leeway.

Now, Loyd does miss some things out for that comparison graph: tether drag: assuming that you have an unfaired ( a normal) tether, it will begin to dominate the drag of the system as your l/d on the wing gets higher and higher, so you won't see anything like the advantage shown by the graph.
Also Loyd assumed weightless wings.... why does this matter? Because during steering you are pulling the wing away from the direction it's is going, you will be using some of the energy from the wind for fighting the wings inertia. The heavier the wing the greater the loss.

Ok there ares a load of other things that could be incorporated to a model but that's enough for one day. So.. the conclusion is..... There is no clear winner, each approach has advantages and disadvantages, the 'best' solution won't neccesarily win the market, it will be a balance based on capital cost, performance, durability, safety, public acceptance, and more. In short, there's no free lunch.

Groundgen/Flygen Comparison Weekend - 2

Ok, as promised, here is the second part, Flygen or 'Drag Mode' machines, here is a video that Corey of SwissKitePower pointed me to (thanks Corey!), featuring one of Makani Power's wings in much more detail than I had seen previously. Let get straight to it.



As you can see, they have moved well away from the fabric kite, groundgen approach they took at the start and the system now much more closely resembles a UAV. There is a strong dihedral, (the wings point up) on the horizontal stabilisers at the back there, and a lighter diherdral on the main wings. The 'fuselage' for want of a better word seems to be a large composite pole, I don't know if it really takes two people to lift it or if they are just being careful.

The next obvious video to post would be of Joby Energy's prototypes, but there are no embeddable videos up on youtube so you'll have to look here instead. There's a couple of nice video's of really agile free flight and self powered VTOL which I would assume is more scaleable than being shot into the air with compressed air, but what do I know?!....(edit 02/aug/10, makani's site now shows a full vtol concept with landing cradle, so clearly they are not planning on relying on the current scheme indefinitely!)

I'll do some basic comparison between the 2 approaches tomorrow, with a bit of reference to Loyd to bring it all together.

Groundgen/Flygen Comparison Weekend - 1

Ground-generating Configuration Videos

This weekend being a holiday here in the UK, I'm going to take some brief breaks from a hectic programming schedule to post some video links. Part of the reason I'm doing this is to highlight the difference between generating on the ground, and generating in the sky, what Loyd called the 'Lift mode' and 'Drag mode' respectively.

Airborne wind energy is still in its infancy but I get the feeling that this difference is quite crucial and it will be really interesting to see how each stream matures over the next few years. Both schemes have some common benefits and challenges but also some very definate advantages and disadvantages. After I've shown both sets, I'll list a few of these as I see them and it would be really great to get some feedback from the surprisingly ever increasing number of readers.

The first video is Stefano Milanese from KitEnergy talking about some tests performed with their generator on a boat.

and here is a recent test from the laddermill team at TUdelft, they have a new website by the way at www.kitepower.eu. It shows them maxing out their generator at 20kW with a 25m SLE kite, there is also load of other interesting videos on the Laddermill Youtube channel so check them out.

Hopefully you readers will get impression of a growing maturity of kite energy, both in hardware and also operationally. Please note that TUDelft have air space authority for their testing at such altitudes - don't try that at home!

2010 International Conference

Details of this year's Airborne Wind Energy conference, new consortium anounced

Sorry everyone for the terribly long wait since the last post, it has been all hands to the decks since February, having said that, there will be some exciting footage coming up soon.


The news today though is the details of the 2010 Airborne Wind Energy Conference (Let's not dwell on the retreat from high altitude shall we!) are out. Here is the link to the site: http://www.awec2010.com .
Key details:

• Conference Dates: Sept 29-30, 2010
• Conference Location: Stanford University, CA
• Submit speaker request by: (not explicit) ASAP

And also there is a new international Industry Organisation, the Airborne Wind Energy Consortium : http://www.aweconsortium.org . It's about time this happened, it makes sense for those kind of advocacy and communications activities to be done collectively for the whole industry.

CMNA power, new startup

Another US stealth startup, another marine kite company

Only a quick note today, but in one of my sporadic googling sessions I found a new start-up. And I also found out about another marine propulsion startup. It looks like I'm going to have to update that graph sooner rather than later!

The power producer is called CMNA power, their site is amazingly tight-lipped ( boring!) but their incubator at the University of Texas is less shy (hooray!). As this is all I can find, we'll have to wait to see if they have flying or ground based generators.

Much more informative is the site of AirplayKitesailing, who are developing kite systems for catamaran racing, but with an eye on the yacht market later down the line. They were founded by a couple of TUDelft graduates. I'm hoping to meet up with some of these guys later in the month when I'm in Delft, I want a a ride on one of those cats!

Here's a video:

Festo Cyberkite

Kite Energy in Brushed Aluminum

As the day here is wet and gloomy (but windy!). I thought I'd write a post about my current favorite kite energy project. It was done by a company called Aeroix for the German industrial automation giant Festo, using Festo hardware to construct the groundstation.

As a development system it is almost perfect in that it is not really intended as a generator, but rather as a platform to test the control and tracking system, and on which to trial new kite designs. That is the level where the key development questions can be asked without spending unneccesary money.

Aeroix worked with the technical fabrics that they provide to German kite/paraglider company Flysurfer/Skywalk amongst others, so as to have a buoyant helium filled kite as well as standard ram-air twin-skin bridled foil kite.

Another interesting thing about this project is the is the shape of the kite which echos the bio-mimetic wings Festo have had built for other projects. The bridle is definately complex as you can see in the video. I'd like to see lift and drag curves for the kite but obviously they aren't giving anything away!

Before you get bored, here's the video:



One thing you might be wondering about is why 4 line control from the ground? Well, I guess it wouldn't be much of a showcase for festo's automation gear if all the fancy hardware was 50m+ away from you up in the sky. Aeroix are pushing forward with the project with a more specific generating system called Enerkite, and are sensibly avoiding all talk of MW and planning incremental scaleup. Finally someone with patience! Good luck to the Aeroix team, I can't wait to see their progress.