Kite turbines that harness wind energy

While turbines present one solution to harness wind energy and transform it into electricity, they are not the only structures to do this. A company in Spain has created the Vortex Bladeless, a six foot tall tower fan-like structure, which wobbles from side to side to produce power. Their lack of huge blades means these can be popped up in more locations and may prove less harmful to birds on land. There is also something else which catches the wind, which could be revolutionary in this technology -  kites. Chris Smith spoke to engineer Rod Reed, from Windswept and Interesting, who's designed a kite turbine, which might take wind energy to new heights...

Rod - There's a lifting kite up in the sky that normally would carry a camera. But instead of the camera, this time on the line, we've got this spinning set of kites that are flying around the line and those lines they're turning a generator on the ground. It's like a set of model aeroplane wings tied around in a circle and they're really efficient and fast as they go around. The parachute one, it stays up on the top and adds a little bit of tension into the system so that we can transmit torque down to the ground. Because we hold the tethers apart, and because they're in tension, and the kite blades are out at a distance, we can transmit that torque to ground safely.

Chris - So how much force are they generating then? How much twist is coming down the cables?

Rod - So we get about a kilowatt and a half out of a small model that I'm able to launch myself, but in the next automated one that we're going to work on, there's going to be a robot doing my job in the field. And we'll be taking that one up to 10 kilowatts. But we can stack them in networks, so we're hoping to make really giant ones in the future.

Chris - And how do you avoid having a hideous tangle, which seems to be the outcome whenever I try and fly my kids' kites?

Rod - If you think of putting a single fishing line out, there's a hundred of you trying to fish in the same place, you'll get those tangled very quickly. But instead you could have a few thousand lines in a fishing net, but it doesn't tangle because of the way it's tied together. So we have very stretched out lines.

Chris - And is your view then that you would have, instead of a field full of wind turbines, we could have a field full of kites? And you're basically flying just an array of kites at perhaps a range of heights as well? And in that way, you're just generating all the time.

Rod - We already fly at a range of heights. We stack rotors one on top of the other. So we've got multiple kites on each layer on the turbines that we have.

Chris - What about the environmental impacts of this? Is this noisy?

Rod - Anything moving in wind, anything going fast through wind, is going to make noise. We have a fairly low tip speed ratio as compared to a normal turbine, so it's slightly less noisy. If there was a season that you wanted to be rid of these things, if you had to get them down and you knew there was a flock coming by or something like that, they're very quick. In Norway, there's a kite company that takes their systems down for any given event like coast guard emergencies, and such. We can bring them down within minutes if need to be.

Chris - And what's the ground footprint like?

Rod - Well, I've got systems that at the moment they fit in the back of my car. So I've got an electric car; I can take a turbine with me and recharge. But in the next version, these automated ones, I'm going to be putting on a back line handling system. Having a back line just gives you this safety, this extra line in case anything goes wrong. So that will want to drive at about a radius of 15 metres out from the ground station.

Chris - And the P word always has to come along at some point, what's the price? Is this going to be cheap or is this going to be very expensive?

Rod - You've got about a tenth of the material that standard wind turbine has because the materials are following the forces in this, we're working in tensile systems. So it should be very capital light as we go forward.