A novel way of recovering energy from flowing water

An enhanced method of extracting power from fluid flow streams has the potential to produce a great deal of carbon free energy.

It relies on having wing shaped hydrofoils that repeatedly go into stall and then recover, which results in massive oscillating forces. While such behaviour is disastrous to aircraft where it is avoided at all costs, it has reached the stage of fairly large, pilot scale marine current demonstrators in a number of countries, the best known in Britain being the 150kW Stingray built by IHC Engineering Business. Sadly, despite very satisfactory performance, and plans for a 5MW version, nothing more seems to have come of this project.

However, Ken Upton, a retired entrepreneur who now lives in Spain, but who started his career in engineering research at Fort Halstead, and who conceived the oscillating foil idea before anyone else that we know of, has come up with a way of enhancing the effect while generating more power. He recently described his latest ideas to us while on a visit to England.

Working with a group of friends who call themselves "4 Paz", he has come up with a new method of extracting the energy from the oscillating motion, which is being seriously considered by a major company.

In order to enhance the oscillating foil idea, Upton has added a Kenape turbine in front of the oscillating foil. A Kenape turbine is an invention of Ken Upton's that essentially consists of a series of tethered kites that are forced to circle. For use in water, the flexible blades of the Kenape rotor are made bat wing shaped. As well as allowing the extraction of some energy from the flow from the rotation, the wakes of the bat wing elements generate considerable amounts of turbulence to enhance the oscillations of the wing.

In addition to this, Upton's foil shape is a delta wing, with a guiding canard wing at the front, so as to adjust the angle of attack and guide the foil into an attitude that generates maximum flutter. For a small device, the canard wings would be fixed, but for a large machine, they could be made so that they could be tilted relative to the foils. As well as enhancing the oscillation of the foils, this arrangement would allow the foil to be turned towards the ground plane so as to shut the machine down.

The power take off from the foil oscillations is at the rear. As the foils interact with the flow, they tend to angle up, trying to somersault, until their angle of attack is so great that they stall. There are two foils in each set, above and below a plate, which enhances the forces they generate through ground effect – a phenomenon used to increase down force in Formula 1 racing cars and to enhance the load carrying capabilities of the Russian Ekronaplan and other sea skimming aircraft.

When they upper foil goes into stall, it is returned to its starting position by gravity, while the lower foil is returned with the help of a buoyancy chamber.

Upton's prototype is only a working model, with the Kenape elements made out of old XRay film, which he says combine the required elements of strength and flexibility. The overall model, which is about 1m long, has so far only been tested in air, although the Kenape rotor has been tested in flowing water in an irrigation canal. It may have potential of its own as a low cost turbine.

Certainly the video reveals the Kenape rotor appears to work really well. Upton has made a number of Kenape rotors that work in air and their main feature is their low cost and very light weight construction, because they are designed to deform with the wind, rather than try to stand rigidly against it. Similarly, lightly constructed rotors, with bat wing shaped, deformable blades, for use in micro hydro projects could also be of benefit.

More information from Ken Upton email: ecofrogtec@terra.es

Author
Tom Shelley

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