visventis.org

A visualization of the carousel in action.

Recently we met another kite power enthusiast, Phil Anderson, here in Cambridge. We asked him to write about his own ideas. So here he is:

“The “Carousel” is a semi-physical model of a small scale vertical axis kite generator. The image above shows five kites tracking around a prescribed path as the legs of carousel turn beneath them. Each  kite rotates on its tether to face into the apparent wind, that is, the vector addition of the wind and the kite velocity. Within the model, the tension on each tether is calculated from the kite’s apparent wind and the kite pointing vector, assuming a realistic function for lift, drag and slew.

“Two aspects of the schematic should be noted. Firstly the kites appear to make a complete revolution on their tether during each cycle. This is important because it exactly counters the rotation  of the carousel which would otherwise cause the tether to become increasingly twisted. Although a design incorporating a swivel on the tether is possible, adding control lines (i.e. having a three- or four-line tether), makes swivel-decoupling unwieldy.

“Secondly, the flight orbit generates torque on the carousel by a combination of alternating between the power-zone and window-edge feather (as for other designs) coupled to the phase of the orbit to the phase of the carousel: the kites are acting at an angle to the arm of carousel for most of the orbit.

“The physical basis of the model provides an estimate of the total power per kite integrated over a revolution of the carousel for any given orbit. This power estimate can be used as a metric for the efficiency of the orbit; the orbit itself is a parametric function and the power metric is used to optimise the function for a given wind speed.”

Thanks, Phil!

Credits: cmogle

If you are around next Wednesday (20th July 2011) and you want to have a glimpse of power-kites and how powerful and fun they are, just come over in Midsummer Common, around 18:30 to take part or take a look. It will be fun.

More info about the event on the groupspace page.

P.S.: If you’ve got a kite, just bring it alone. More kites, more fun.

Credits: Opensourceway

Here at VisVentis.org we would like to approach the development of high
altitude wind in a collaborative way. We are very interested in the
field, and we thought we could try to build something to have a bit of
fun and do something useful.

We are also interested in exploring new ways to do research in the AWE
field and, inspired by the Opensource Way, we want to try to do it in a
distributed way, sharing and collaborating with people who are
interested in the project.

To that end we have set up an account on groupspace, called visventis
(surprisingly). We are going to start building our first prototype in
the following months, so anybody who is interested in developing ideas
or building airborne systems to capture wind energy please join us
there. We will use this to set up meetings to do the actual hardware
work, which will happen in Cambridge, UK, as well as share ideas through
our wiki and mailing list. We’ve already had encouraging support and an
offer of collaboration from the SwissKitePower team, which is great.

We are really excited by the idea of developing Airborne Wind
technologies using a collaborative and open approach. If you are too,
keep in touch with us by subscribing to this blog, or if you’re keen to
participate and to get your hands dirty, join the visventis group.

One of us, Oliver Woodford, was lucky enough to attend the second annual (hopefully!) Airborne Wind Energy Conference in Leuven, Belgium last month. It was great to see so many different airborne approaches to generating power from wind being developed. I’ve categorized these into 3 groups: static approaches, which hover in the air, like the buoyant-shroud turbine of Altaeros and gyro-copter turbines of SkyWindPower; vertical approaches, whose motion is perpendicular to the ground, such as the A-frame system of the Worcester Polytechnic Institute, and the buoyant cylinders of Omnidea; finally crosswind approaches, such as the drag-based system of Makani and Joby (recently merged), and the lift-based systems of the majority of other players, including Ampyx, TU Delft and KU Leuven.

Three groups were especially inspiring from our perspective: the SwissKitePower team, headed by Corey Houle, who custom-built a complete test system themselves, including winch and kite control pod; David Olinger’s group at Worcester Polytechnic Institute, who are looking to design cheap systems for developing countries; last, but by no means least, the three TU Munich undergraduates (Simon Bolten, Patrick Lauffs and Michael Schölkopf) who founded Windward Energy and built a kite control pod and winch system for virtually nothing.

The feeling at the conference was very much that the field has a long way (possibly more than a decade) to go before any of these technologies reach commercial scale and economy, and only then will the winning technologies be known. In the meantime it will be very exciting to be a part of.

A final note – next year’s conference returns to Stanford, California. Hopefully see you there!

VisVentis has been formed to first make extremely simple kite wind energy systems that can be made on a low budget by people who presently have inadequate access to electricity. There are something like 2 billion such people in the world and the boom in mobile phone ownership, the desire to study after sunset, and the need to pump water has created a huge demand for cheap power. We believe a manually controlled kite system can supply that demand.