Hacker News Reader

Comment by Grustaf | Hacker News Reader

We're building a new type of wind turbine that generates energy using significantly less material, making it much cheaper to install. We do this using huge fixed wing kites made of carbon fibre, and drone technology.

View on HN

Interesting area to work in.

There's huge interest in renewables here in China and a great deal of windy Himalayan mountain peaks that have been covered with wind generators here in Yunnan province (far southwest China) in the recent past. Also solar and hydro is everywhere. Lots of e-vehicles too, everything from golf buggies to cop cars to buses to taxis to bicycles to cars to old-person mobiles to tractors.

Also coming from Australia with Scottish heritage, I wonder if you could use this to power long distance autonomous e-vehicular trucking through remote high wind land areas?

We also have awesome high altitude lakes for kite surfing (Fuxian in particular), I used to sail Weta trimarans there, but sold them last year. Motor boats are banned. You guys should come visit!

+Wiener's Eighth and Final Law: You can never be too careful about what you put into a digital flight-guidance system.

We're actually in talks with a fellow Scandinavian that lives in Yunnan right now!

When I lived in Shaolin a long time ago I did spend some time exploring Yunnan, the mountains are amazing, some of the most stunning views I've ever seen. This was more than 15 years ago and there seemed to be very little interest in electrical vehicles or renewable energy, I'm happy to hear things have improved!

SkySails have been exploring pulling large ships with kites, but I don't think it's very practical for trucks, then it makes more sense to go via electricity. Apart from the impracticality, there are also pretty subtle reasons of efficiency. They did use kites to pull vehicles in Ancient China though!

This is an awesome idea. I remember reading about kite-based propulsion systems for large ships a few years ago, do you see any overlap with that area?

How do you deal with the possibility of the kite breaking free of the tether, or breaking up in the air? I guess it could be quite dangerous if there's a populated area downwind.

There is definitely some overlap with SkySails (as that project was called), particularly in the control software part.

But as far as kite power goes the principles are quite different. They use the pull (or "lift") of the kite to directly help propel the ship, while we have generators installed on the kite and harvest energy that way. This is called "drag mode" kite energy, vs "lift mode" where you let the kite pull on the tether and let it reel out and thereby generate power (or pull a ship).

We haven't looked into it but I have a feeling it would be more efficient to use drag mode even on a ship and generate electricity that would be fed into a hybrid engine system.

The scenario you mention is not really a major concern, for several reasons:

First of all the tether is of course designed to withstand all reasonable situations, with a wide margin of safety.

Secondly, the way the kite normally lands and launches itself as the wind drops and returns is by flying as a drone using the rotors-generators (see the website), so as long as the kite isn't completely broken it would just return to earth in a controlled manner.

Furthermore, in a worst case scenario, an untethered kite is actually much _less_ dangerous as it can't travel faster than the wind, whereas while tethered it can go 10 times faster or more. (As a kite surfer the first thing you learn is that if something goes wrong you should release the kite.)

While in use the kite will be some 200 m up, but several kilometres from land, so it will not be able to get very far in the time it takes to fall to earth.

This is cool ! How does it compare in size and power generation to a modern upgright wind turbine ?

Thanks! The size we're targeting now is a system of two kites on one tether, each with a wing span of 20 m and weighing 1650 kg. This would generate around 1 MW.

The largest off-shore wind turbines right now have 80 m blades and generate 8 MW at a weight of 1300 tonnes (excluding foundation), but the main reason they are so large is economies of scale, off-shore wind turbines are expensive.

Kite wind turbines do not have to be as large to be economical.

But with a traditional wind turbine with 80 meter long blades, the total "footprint" for each one is roughly a 160 meter wide circle. In principle you don't need much space between those circles in a bigger wind farm (but because of turbulence and the wind shadow there usually is).

What is your "wind farm" model? Reserving a kilometer wide circle for each kite pair does not really seem feasible even off-shore.

The wind shadow from a traditional wind turbine is actually very significant. For example, at the London Array, a very modern wind farm, they have 175 wind 3.6 MW rated turbines over 90 square kilometres, so about two per square kilometre.

Some scholars believe that kite energy can best this by a wide margin. For example, you can put the kite systems at alternating heights to combat the problem with wind shadow, and there is no reason why you wouldn't be able to have a significant overlap in the circles, since the wind will be blowing in close to the same direction throughout the wind farm.

wow, that's really cool. Why is it cheaper than normal wind turbines ? Maintaining drones that take off and land autonomously sounds expensive

I really like the idea of low environmental impact

They are cheaper to build because they require about two orders of magnitude less material for the upper parts, and at least one order of magnitude less foundation (for the same power generation). This saves on both building and setting it up and I would say there is pretty strong consensus on this part.

You are correct however that it is less obvious that it makes sense when maintenance is factored in, but we are convinced it does. For perspective, large modern wind turbines are much more sophisticated than one might think.

How is this different from GoogleX's project?

I'm glad you asked ;)! The short answer is that we are going to become the first company to succeed in putting two kites on one line, which is much more efficient but of course more complex to pull off. We will achieve this by iterating much faster, learning from the community and taking advantage of the explosion in drone technology.

Makani is a very cool project but we think we can improve on it further!

Reply on news.ycombinator.com