Big Tidal Power Turbine - Dick LaRosa

The Orkney Islands lie to the north of Scotland. These land masses separate the Atlantic Ocean from the North Sea. There is a strong tidal flow through the Pentland Firth, a channel that separates the Orkneys from the Scottish mainland. This is the location of the European Marine Energy Centre, which provides power transmission access for turbines anchored to the sea floor. The 1.0 Megawatt Atlantis Resources  AK1000 was deployed here in late August at a 35-m-deep location. The turbine has twin three-blade rotors 18 m in diameter. Photographs indicate that the two rotors are rigidly atached at opposite ends of the same shaft with the blades aligned in the flow direction. That is, if the rotors were not turning, a downstream blade would be in the shadow of its upstream counterpart. The blades are fixed-pitch and have little twist. The turbine is rigidly attached to its mount, and the rotation direction reverses when the tidal flow reverses. Unlike most blade airfoils, the leading edge is exactly the same as the trailing edge.

Most wind and underwater rotors have husky hubs and large-diameter cylindrical blade roots, probably because most have adjustable pitch. The large diameter plus a blade twist near the root afford adequate stiffness to withstand the axial thrust . The AK1000 is designed to produce 1.0 MW at a stream velocity of 2.65 m/s, but the waterway is very complicated because there are many islands, and there are surges of much higher velocity. The turbine design was tested by tugboats towing it (probably mounted on pontoons) in open sea. The towing tests may not have duplicated the impacts of the nasty Pentland Firth. Atlantis Resources has reported a blade failure and has blamed it on a "manufacturing defect" for which the blade fabricator has taken responsibility. However, I expect they will correct it with a huskier, less graceful blade root design. No great loss. The inner part of the rotor doesn't contribute much to the performance.

Pentland Firth is considered to be more than a test site. Atlantis Resources has proposed a computer data center in the area to use the power produced by a large array of turbines. This avoids the problem of exporting electric power from this remote location. The power depends on the cube of the stream velocity, so little power is produced for a considerable time when the tidal flow is reversing. A data center requires a lot of cooling, so perhaps the turbine array can be large enough to power refrigeration equipment to freeze water when the tide is running. Then the ice can be used to cool the computers when the tide is reversing.

Comments

[Carl Schwab]

Dick,
Could you give me via email, a website that will detail the
AK1000 head/prop unit? Thanks.
Carl

[Dick LaRosa]

For info on AK1000 go to www.atlantisresourcescorporation.com
This has photos. Click on link to 24-08-2010 news release.
This has a list of links with useful information.

[power transmission equipment]

Trees that block roadways, the destruction of roadbeds or the destruction of primary bridges can hamper the movement of heavy equipment. The destruction of power transmission equipment
towers, transformer sub-stations and fuel delivery systems to power plants can disrupt power transmission to large areas.