Nice that Kitex understood that “overspeed protection is not the main thing, it’s the ONLY thing”. ESPECIALLY for a turbine designed for low wind speeds! 
Completely agree for a horizontal axis wind turbine - then it’s one of the main things. For very light structures I may add controlling unwanted vibration modes is the second thing.
I’m uncertain how much of a challenge this will be for AWE. Most airborne concepts has a method of modifying the L/D ratio of the wing. The main question is how much margin you need to stay within limits when depowered - and if the kite can remain stable a very low lift values.
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These types of issues are what we who actually have the acumen to build wind turbines from scratch end up dealing with. Your average wannabe innovator who makes a few sketches and posts future-promises on the internet has no idea what they would be getting into if they had to develop real machinery. That is when you deal with real issues, that never get mentioned by the armchair-innovators because they don’t even know about them!
Wow, nice rendering - give that kid a cigar!
My Girl has a Red Dot, Your Girl ain’t Doodley-Squat:
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Looks like the overspeed protection works pretty well.
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It’s unusual to see an AWE company produce anything remotely resembling a regular wind turbine. For this model I will note some pros and cons:
PROS:
- This design represents a known design direction for small wind turbines: maximizing the “capacity factor”, which ends up being synonymous with “low wind speed turbine”. In other words, a disproportionately large swept area compared to the size of the generator, aimed toward coming as close as possible to max output of the generator, as much of the time as possible.
I’ve had my own name for this approach, for a long time: “generator worship”, where a shrine is constructed around the generator, to maximize the usage of the generator, whatever it takes. This design would seem to embody this approach of maximizing energy production relative to rated peak output.
(An alternative design direction is ducted turbines, which I call “rotor worship” - building a shrine to the rotor itself in the form of a duct, as a sacrificial offering to “the rotor god”.)
Either approach is a deviation from what is known and proven optimal.
- They started with limiting peak output, relative to swept area, using pitch control. This is a good sign that they comprehended the known fact, seldom understood by perpetual newbies, that overspeed protection is the most important thing in wind energy design.
CONS:
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Rather than building upon what is known to work well, and inventing forward from that point, it seems to start from a fantasy of kite-supported turbines, then “inventing” in a backward direction, to add a central steel pole as a support against gravity, all the while pretending in mere words (“kite”, “tether”) that they’ve take “the standard kite-supported turbine”, and come up with a “new revelation” that the actual weight-supporting aspect of the kite COULD be replaced by a novel concept of adding a stiff central member which removes the “normal” burden of a kite carrying the weight of the turbine, while still pretending all the standard guy wires are called “tethers”, as though they have come up with something new in turbine support, still using kite-ish words to describe it. It’s like they still have one foot in their previous fantasy-world of AWE, expecting everyone else to go along with their private fantasy-world outlook.
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As I’ve pointed out before, the Kite-X design is a near duplicate of one of the very first electric windmill designs from what - 70 years ago? Also from Denmark? It’s called the Gedser turbine. Anyone who knows the history of wind energy is familiar with this hard-to-forget design, with the guy-wire-stiffened rotor, and a chain or belt drive to increase the RPM from a slow rotor to a better speed to spin a smaller generator.
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While the effort toward a low windspeed turbine, using less material, is admirable, the appearance is somewhat frail and spindly, with visible wobbles of both the rotor and guy wires during operation. Wobbles are never a good sign, indicative of wear taking place in real time. This would imply a short lifetime before catastrophic failure.
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The resulting turbine design is still large, heavy, and expensive.
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With all that swept area, and all those visible wobbles, will it survive a strong wind or storm?
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They are using a belt drive. Belts and chains are a natural “go-to” “solution” for newbies, often warned against by the veterans. Personally, I’ve seen quite a few tries at belt and chain drives - even tried a chain drive myself and found it noisy and prone to rust as the veterans had warned - never seen any belt or chain turbine remain after the early press-release stage has passed.
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The stated business model, only customers in Denmark, the manufacturer doing all their own installs and service, is unusual for a small wind company, and may be problematic.
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The use of screw anchors to “replace” concrete anchors to reduce global warming CO2 emissions from the hardening concrete is a choice any turbine with guy wires could make, depending on soil conditions and how long they want it to remain stable before requiring new anchors. This seems like maybe an example of a “greenwashing”, excuse-driven, “innovation” that is really only a known design choice for any small turbine, or any guyed tower of structure, for that matter.
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In AWE (even AWE “cheating”, by using a pole) all true accomplishments remain “in the future” - in this case a track record of reliable operation over at least a couple of years in various locations and wind environments is a necessary step which can only take place “in the future”.
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Any small wind company is automatically in a challenging position - most do not survive, and since solar has gotten so cheap, there are few legitimate small wind manufacturers still in business. One way they die is when their turbines start failing in the field, and they can’t keep up with accumulated warranty repairs and service.
Despite the noted possible problems, I admire the effort and thinking that has gone into this Kite-X experimental design direction. It’s not the worst example in the history of wind energy or anything. There is a lot to like about it, however innovative wind energy is not easy to get right…
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We will see. I think we are in a great spot.
We have more than two years of operation experience with our small wind catchers. Consider the scaling factors this is a quite significant amount of load cycles.
A structure made of glass fiber will naturally move more than one out of steel. Perhaps it can actually help reduce loads…!
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A very impressive project overall. I admire the care that has gone into the design. But my early impression, based on many years in the field of small wind turbines, was it represents a “fair weather turbine”, meaning it may seem fine, as long as it is not placed in a challenging wind resource. I’ve noticed over the years, most new turbine models are tested in optimal conditions, and when bad conditions predominate, the problems magically emerge.
Since the “windcatcher” represents itself as a low windspeed turbine, so far, so good. The idea of it providing power for a campsite was clever and cute. But in my experience, it’s when any model is placed in a windfarm-class wind resource that sustained high winds, and even brief very high winds, will reveal the weak points of a design or model. Any location can have a storm! Looks like the belts and even the pulleys wear out fairly quickly? A good turbine should be able to go for many years without replacing parts, or really any service whatsoever, once mounted. Well at least you are having fun! That’s one thing that separates wind from solar. Solar is boring, whereas wind is an action-sport adventure!
For permanent installations in the case of high winds, action must be taken to prevent generator overspeed, causing overheating and burnout. In the case of Kitex, a temporary installation, perhaps it would be better to lower the mast when high or turbulent winds occur. In this way, they can eliminate pitch control which simplifies the design of the turbine. This operation can be fully or semi autonomous.
Hello Gordon. My impression is their new version costs something like well over $20,000, and is more of a permanent installation for home or farms. Over 5 kW I think? With a diameter over 30 feet? Anyway, planning to “just take 'er down” whenever the predicted winds look like they could be trouble, is a textbook newbie response to any mention of concept of overspeed protection. It doesn’t take into account the fact that predicted average winds overnight can instead turn out to be high winds, or a predicted gentle rain can turn out to be a storm. There’s a lot of experience out there to be learned from, if you talk to the people who have been through it and burned out many generators. And taking turbines up and down sounds great in theory, but usually takes a lot more concerted effort than one would assume. And it can be a bit dangerous. You really don’t want to go through it very often. The only way the “just take 'er down” approach works out, is if it is just an experimental machine that you don’t plan on leaving unattended for mother nature to have her way with.
Still, at least they DID start out with addressing overspeed protection, so that is a good sign. Hope for the best!