Saturday, 6 February 2010

Kitegen/Deep Green wind and tidal power

A while back I did a post entitled Power kites, Kitegen and oodles of green energy (click this link for post).This was about the astonishingly large amounts of wind energy that can be captured using power kites flown by computer in a figure of eight pattern. These appeal to me because they bridge two of my great loves – flying wings (hang gliders/paragliders) and environmentalism. This “8” flight path is, of course, familiar to anyone who kitesurfs - they won’t be surprised at all about the amazing forces that these airfoils harness, having experienced them first hand.power kite  Kilowatts of power are available from these devices.

They are better than conventional wind turbines because, for their size, they “sweep” a much larger area of the sky and also they “sweep” at a higher altitude than a wind turbine of similar size.

A power kite can access the faster moving winds aloft – a 100 square foot kite (which would fold up into a suitcase) can operate in the same, or better, regime of wind flow as a 100 metre tall wind turbine – even better, the conventional horizontal axis wind turbine’s blades obviously spend  half of their time in the lower speed winds nearer the ground which induce powerful engineering stresses on the structure that the kite simply does not have.

Here’s a link to Kitegen

Here’s a Youtube video that combines animation with live field tests – these things work! Smaller versions could conceivably power individual houses without having to have a big tower for the turbine to sit on. There are other videos of a 100 sq ft kite generating 10 kw!

From their website: “Kite Gen’s vision is a new type of electric generation plant, based on a renewable source, suitable for any territory, at costs lower than fossil fuel generation plants, in direct competition with today’s conventional production (coal, oil or nuclear), in the GigaWatt class.”


As if that wasn’t revolutionary enough, here is effectively the same idea but in water instead. is a Swedish company, originally an offshoot of Saab, that has developed a concept called “Deep Green”.

Deep Green

It consists of a tethered “wing” which is “flown” underwater in a figure of eight pattern. Unlike the Kitegen concept, which generates power as the kite is pulled out from the base station where the generators are, the Deep Green hydro plane actually incorporates a generator within the “flying” bit itself.

Here’s a promotional video from Minesto showing the concept in an experimental tank.

Because of the power kite like action, the Deep Green generators are moving through the water flow so fast that they do not need gearboxes, as conventionally designed tidal mills do. That cuts down on the cost, weight and maintenance required and the increased flow means that the power obtainable from the Deep Green is much greater - moving water contains far more energy than wind of the same speed as it is around 800 times denser than air.

Even our Jersey States has a special group looking at exploiting the tidal stream resources off our Channel Islands, but what they are looking at is conventional “propellers on the sea bed” type generators. Tidal stream energy is of course reliable and totally predictable. This Deep Green concept is still at the experimental water tank stage but it’s almost entirely a matter of engineering the devices and scaling them up, not a matter of any further invention.

The most significant thing about this idea is that it can operate in much slower or deeper tidal streams than conventional  tidal stream generators.  There are only relatively few areas around the British Isles which have sufficiently fast tidal flows to render ordinarily designed tidal mills worthwhile – however, even so, the amount of energy in these limited areas is colossal. One of the best of these is around Alderney and this is where investigations are taking place for a commercial company to install generators in the next year or so.

The “Deep Green” concept promises to allow much bigger areas of tidal flow around the British Isles, and also many other places around the world, to be used to harvest reliable abundant renewable energy. Here’s a pic of some of the better areas.

world tidal stream resources

Following a successful demonstration, development of the technology is continuing to the next stage - deployment of a prototype off the coast of Northern Ireland in 2011.

Animation of Deep Green concept

Ideas like this remove one irritating objection that anti-sustainability nit-pickers bring up about most renewables –that they are intermittent and unpredictable.


No comments: