Being able to take advantage of tidal power around the coast of the U.K. has been limited so far by the cost of dams and other obstacles, as well as extremely variable results.
A company in England, however, has partnered with Oxford University and is suggesting that it has figured out how to bypass some of the obstacles, creating a new horizontal axis turbine that is usable in shallower, slower tidal waters less than 30 meters, or about 98 feet, deep at a reasonable cost.
Conventional water turbines are limited in where they can be used because of the size of their blades, meaning that they have to be used in water around 30 meters deep to be effective. This new technology, called THAWT, or Transverse Horizontal Axis Water Turbine, however, is intended to be deployed in much shallower water, which might have water flowing at a slower rate.
As water flows past the fence leading to the turbine, the current backs up and this "blockage" creates a head of water that increases the efficiency of the turbine. This "blockage" basically gets bigger as the turbine gets larger in proportion to the length of the fenced area around the turbine, so the longer the fence, the greater the output by each turbine.
"The re-design that we've done changes the blades so that they form this triangulated structure, and that's a very stiff and very strong structural form. And that means that the loads in the blades are principally carried by axial forces and that means that the stresses are much lower," said Guy Houlsby, professor of civil engineering at Oxford, in an interview with Reuters.
The turbines have been proposed for installation in the Bristol Channel, with a 1 kilometer, or 0.6 mile, long tidal fence being able to generate 30 megawatts of power at its peak. The project will total £143 million pounds, or $224 million, and is set to be operational by 2021. Experts suggest that if properly implemented, the turbine could produce up to 5 percent of the energy requirements of the whole U.K. The Bristol Channel, which is more than 30 miles wide at its widest point, separates South Wales from Devon and Somerset in southwest England.
Being able to produce that much power isn't the only advantage to THAWT, however. Each rotor on the turbine can last up to 25 years, and the electricity connectors and columns can last 100 years. Kepler Energy, the company proposing the installation, notes its generator and other electrical equipment are installed in dry columns, which increases their reliability and efficiency. The generating units consist of two sets of blades sitting on three columns with a single generator in between.
Kepler is seeking funding for the project as it moves into the development and planning phases, which includes an environmental assessment.
The project could significantly reduce the carbon footprint of the U.K. The proposed turbine could produce as much power as a nuclear plant if the fence length is increased to up to 10 kilometers, or about 6.2 miles. The blades also move relatively slowly so the energy company says there's little risk to the fish and plant life around the turbines. The developers of THAWT say that similar installations could also be used in the waters off the coasts of a number of Asian countries as well as France.
Via: Reuters
